Ice core - Knowledge

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506.9 m in April 1970; by 1973 a depth of 952 m had been reached. A subsequent hole, Vostok 2, drilled from 1971 to 1976, reached 450 m, and Vostok 3 reached 2202 m in 1985 after six drilling seasons. Vostok 3 was the first core to retrieve ice from the previous glacial period, 150,000 years ago. Drilling was interrupted by a fire at the camp in 1982, but further drilling began in 1984, eventually reaching 2546 m in 1989. A fifth Vostok core was begun in 1990, reached 3661 m in 2007, and was later extended to 3769 m. The estimated age of the ice is 420,000 years at 3310 m depth; below that point it is difficult to interpret the data reliably because of mixing of the ice.

2727:(GISP), a multinational investigation into the Greenland ice sheet that lasted until 1981. Years of field work were required to determine the ideal location for a deep core; the field work included several intermediate-depth cores, at Dye 3 (372 m in 1971), Milcent (398 m in 1973) and Crete (405 m in 1974), among others. A location in north-central Greenland was selected as ideal, but financial constraints forced the group to drill at Dye 3 instead, beginning in 1979. The hole reached bedrock at 2037 m, in 1981. Two holes, 30 km apart, were eventually drilled at the north-central location in the early 1990s by two groups: 555:

fluid. In mineral drilling, special machinery can bring core samples to the surface at bottom-hole pressure, but this is too expensive for the inaccessible locations of most drilling sites. Keeping the processing facilities at very low temperatures limits thermal shocks. Cores are most brittle at the surface, so another approach is to break them into 1 m lengths in the hole. Extruding the core from the drill barrel into a net helps keep it together if it shatters. Brittle cores are also often allowed to rest in storage at the drill site for some time, up to a full year between drilling seasons, to let the ice gradually relax.

514: 2316: 1412: 761: 1872:, show strong seasonal variation. In some cases there are contributions from more than one source to a given species: for example, Ca comes from dust as well as from marine sources; the marine input is much greater than the dust input and so although the two sources peak at different times of the year, the overall signal shows a peak in the winter, when the marine input is at a maximum. Seasonal signals can be erased at sites where the accumulation is low, by surface winds; in these cases it is not possible to date individual layers of ice between two reference layers. 2494: 774:

the alternating layers remain visible, which makes it possible to count down a core and determine the age of each layer. As the depth increases to the point where the ice structure changes to a clathrate, the bubbles are no longer visible, and the layers can no longer be seen. Dust layers may now become visible. Ice from Greenland cores contains dust carried by wind; the dust appears most strongly in late winter, and appears as cloudy grey layers. These layers are stronger and easier to see at times in the past when the Earth's climate was cold, dry, and windy.

526: 1428: 367: 157: 2619: 2458:, ice in a well is melted to provide a water supply, leaving micrometeorites behind. These have been collected by a robotic "vacuum cleaner" and examined, leading to improved estimates of their flux and mass distribution. The well is not an ice core, but the age of the ice that was melted is known, so the age of the recovered particles can be determined. The well becomes about 10 m deeper each year, so micrometeorites collected in a given year are about 100 years older than those from the previous year. 584:, there has to be a way to determine the relationship between depth and age of the ice. The simplest approach is to count layers of ice that correspond to the original annual layers of snow, but this is not always possible. An alternative is to model the ice accumulation and flow to predict how long it takes a given snowfall to reach a particular depth. Another method is to correlate radionuclides or trace atmospheric gases with other timescales such as periodicities in the earth's 255: 177:. Firn is not dense enough to prevent air from escaping; but at a density of about 830 kg/m it turns to ice, and the air within is sealed into bubbles that capture the composition of the atmosphere at the time the ice formed. The depth at which this occurs varies with location, but in Greenland and the Antarctic it ranges from 64 m to 115 m. Because the rate of snowfall varies from site to site, the age of the firn when it turns to ice varies a great deal. At 2654: 22: 465: 2735:, was launched as an international consortium led by Denmark. Drilling began in 1996; the first hole had to be abandoned at 1400 m in 1997, and a new hole was begun in 1999, reaching 3085 m in 2003. The hole did not reach bedrock, but terminated at a subglacial river. The core provided climatic data back to 123,000 years ago, which covered part of the last interglacial period. The subsequent North Greenland Eemian ( 2731:, a European consortium, and GISP-2, a group of US universities. GRIP reached bedrock at 3029 m in 1992, and GISP-2 reached bedrock at 3053 m the following year. Both cores were limited to about 100,000 years of climatic information, and since this was thought to be connected to the topography of the rock underlying the ice sheet at the drill sites, a new site was selected 200 km north of GRIP, and a new project, 384:

drills, designed for use without drilling fluid, were limited in depth as a result; later versions were modified to work in fluid-filled holes but this slowed down trip times, and these drills retained the problems of the earlier models. In addition, thermal drills are typically bulky and can be impractical to use in areas where there are logistical difficulties. More recent modifications include the use of

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reference layer. This was done, for example, in an analysis of the climate for the period from 535 to 550 AD, which was thought to be influenced by an otherwise unknown tropical eruption in about 533 AD; but which turned out to be caused by two eruptions, one in 535 or early 536 AD, and a second one in 539 or 540 AD. There are also more ancient reference points, such as the eruption of

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the calculation of a melt-feature percentage (MF): an MF of 100% would mean that every year's deposit of snow showed evidence of melting. MF calculations are averaged over multiple sites or long time periods in order to smooth the data. Plots of MF data over time reveal variations in the climate, and have shown that since the late 20th century melting rates have been increasing.

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above the core. When the core is retrieved, the cuttings chamber is emptied for the next run. Some drills have been designed to retrieve a second annular core outside the central core, and in these drills the space between the two cores can be used for circulation. Cable-suspended drills have proved to be the most reliable design for deep ice drilling.

1154: 388:, which eliminates the need for heating the drill assembly and hence reduces the power needs of the drill. Hot-water drills use jets of hot water at the drill head to melt the water around the core. The drawbacks are that it is difficult to accurately control the dimensions of the borehole, the core cannot easily be kept sterile, and the heat may cause 741:, about 11,700 years ago, is now formally defined with reference to data on Greenland ice cores. Formal definitions of stratigraphic boundaries allow scientists in different locations to correlate their findings. These often involve fossil records, which are not present in ice cores, but cores have extremely precise 5910:

Souney, Joseph M.; Twickler, Mark S.; Hargreaves, Geoffrey M.; Bencivengo, Brian M.; Kippenhan, Matthew J.; Johnson, Jay A.; Cravens, Eric D.; Neff, Peter D.; Nunn, Richard M.; Orsi, Anais J.; Popp, Trevor J.; Rhoades, John F.; Vaughn, Bruce H.; Voigt, Donald E.; Wong, Gifford J.; Taylor, Kendrick C.

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within the firn layer causes other changes that can be measured. Gravity causes heavier molecules to be enriched at the bottom of a gas column, with the amount of enrichment depending on the difference in mass between the molecules. Colder temperatures cause heavier molecules to be more enriched at

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The density and size of the bubbles trapped in ice provide an indication of crystal size at the time they formed. The size of a crystal is related to its growth rate, which in turn depends on the temperature, so the properties of the bubbles can be combined with information on accumulation rates and

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through firn, so the ice at a given depth may be substantially older than the gases trapped in it. As a result, there are two chronologies for a given ice core: one for the ice, and one for the trapped gases. To determine the relationship between the two, models have been developed for the depth at

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A log is kept with information about the core, including its length and the depth it was retrieved from, and the core may be marked to show its orientation. It is usually cut into shorter sections, the standard length in the US being one metre. The cores are then stored on site, usually in a space

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drills allow the removal of the core barrel from the drill assembly while it is still at the bottom of the borehole. The core barrel is hoisted to the surface, and the core removed; the barrel is lowered again and reconnected to the drill assembly. Another alternative is flexible drill-stem rigs, in

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When there is summer melting, the melted snow refreezes lower in the snow and firn, and the resulting layer of ice has very few bubbles so is easy to recognise in a visual examination of a core. Identification of these layers, both visually and by measuring density of the core against depth, allows

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The brittle ice zone typically returns poorer quality samples than for the rest of the core. Some steps can be taken to alleviate the problem. Liners can be placed inside the drill barrel to enclose the core before it is brought to the surface, but this makes it difficult to clean off the drilling

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The drill removes an annulus of ice around the core but does not cut under it. A spring-loaded lever arm called a core dog can break off the core and hold it in place while it is brought to the surface. The core is then extracted from the drill barrel, usually by laying it out flat so that the core

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that press against the borehole, to prevent the drill assembly rotating around the drillhead as it cuts the core. The drilling fluid is usually circulated down around the outside of the drill and back up between the core and core barrel; the cuttings are stored in the downhole assembly, in a chamber

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in Antarctica in an area where old ice lay near the surface. The cores were dated by potassium-argon dating; traditional ice core dating is not possible as not all layers were present. The oldest core was found to include ice from 2.7 million years ago—by far the oldest ice yet dated from a core.

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with a high voltage between them on the surface of the ice core gives a measurement of the conductivity at that point. Dragging them down the length of the core, and recording the conductivity at each point, gives a graph that shows an annual periodicity. Such graphs also identify chemical changes

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Any method of counting layers eventually runs into difficulties as the flow of the ice causes the layers to become thinner and harder to see with increasing depth. The problem is more acute at locations where accumulation is high; low accumulation sites, such as central Antarctica, must be dated by

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Cores show visible layers, which correspond to annual snowfall at the core site. If a pair of pits is dug in fresh snow with a thin wall between them and one of the pits is roofed over, an observer in the roofed pit will see the layers revealed by sunlight shining through. A six-foot pit may show

227:. The lowest layer of a glacier, called basal ice, is frequently formed of subglacial meltwater that has refrozen. It can be up to about 20 m thick, and though it has scientific value (for example, it may contain subglacial microbial populations), it often does not retain stratigraphic information. 4730:

Sigl, M.; Winstrup, M.; McConnell, J. R.; Welten, K. C.; Plunkett, G.; Ludlow, F.; Büntgen, U.; Caffee, M.; Chellman, N.; Dahl-Jensen, D.; Fischer, H.; Kipfstuhl, S.; Kostick, C.; Maselli, O. J.; Mekhaldi, F.; Mulvaney, R.; Muscheler, R.; Pasteris, D. R.; Pilcher, J. R.; Salzer, M.; Schüpbach, S.;

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as "the father of modern snow surveying". In the winter of 1908–1909, Church constructed steel tubes with slots and cutting heads to retrieve cores of snow up to 3 m long. Similar devices are in use today, modified to allow sampling to a depth of about 9 m. They are simply pushed into

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In central Greenland a typical year might produce two or three feet of winter snow, plus a few inches of summer snow. When this turns to ice, the two layers will make up no more than a foot of ice. The layers corresponding to the summer snow will contain bigger bubbles than the winter layers, so

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The need for a string of drillpipe that extends from the surface to the bottom of the borehole can be eliminated by suspending the entire downhole assembly on an armoured cable that conveys power to the downhole motor. These cable-suspended drills can be used for both shallow and deep holes; they

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time (the time taken to pull the drilling equipment out of the hole and return it to the bottom of the hole). Since retrieval of each segment of core requires tripping, a slower speed of travel through the drilling fluid could add significant time to a project—a year or more for a deep hole. The

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and Vostok in the Antarctic; not all these early holes retrieved cores. Over the following decades work continued at multiple locations in Asia. Drilling in the Antarctic focused mostly on Mirny and Vostok, with a series of deep holes at Vostok begun in 1970. The first deep hole at Vostok reached

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Meteorites and micrometeorites that land on polar ice are sometimes concentrated by local environmental processes. For example, there are places in Antarctica where winds evaporate surface ice, concentrating the solids that are left behind, including meteorites. Meltwater ponds can also contain

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When drilling in temperate ice, thermal drills have an advantage over electromechanical (EM) drills: ice melted by pressure can refreeze on EM drill bits, reducing cutting efficiency, and can clog other parts of the mechanism. EM drills are also more likely to fracture ice cores where the ice is

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Cores are often drilled in areas such as Antarctica and central Greenland where the temperature is almost never warm enough to cause melting, but the summer sunlight can still alter the snow. In polar areas, the Sun is visible day and night during the local summer and invisible all winter. It can

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coring project, a vacuuming system was set up to facilitate this. The surface that receives the core should be aligned as accurately as possible with the drill barrel to minimise mechanical stress on the core, which can easily break. The ambient temperature is kept well below freezing to avoid

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Thermal drills, which cut ice by electrically heating the drill head, can also be used, but they have some disadvantages. Some have been designed for working in cold ice; they have high power consumption and the heat they produce can degrade the quality of the retrieved ice core. Early thermal

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rotated from the top, and drilling fluid is pumped down through the pipe and back up around it. The cuttings are removed from the fluid at the top of the hole and the fluid is then pumped back down. This approach requires long trip times, since the entire drill string must be hoisted out of the

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in Indonesia injected material into the stratosphere, and can be identified in both Greenland and Antarctic ice cores. If the date of the eruption is not known, but it can be identified in multiple cores, then dating the ice can in turn give a date for the eruption, which can then be used as a

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project at Camp Century, where in the early 1960s three holes were drilled, the deepest reaching the base of the ice sheet at 1387 m in July 1966. The drill used at Camp Century then went to Byrd Station, where a 2164 m hole was drilled to bedrock before the drill was frozen into the

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Bazin, L.; Landais, A.; Lemieux-Dudon, B.; Toyé Mahamadou Kele, H.; Veres, D.; Parrenin, F.; Martinerie, P.; Ritz, C.; Capron, E.; Lipenkov, V.; Loutre, M.-F.; Raynaud, D.; Vinther, B.; Svensson, A.; Rasmussen, S. O.; Severi, M.; Blunier, T.; Leuenberger, M.; Fischer, H.; Masson-Delmotte, V.;

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Ice cores from different depths are not all equally in demand by scientific investigators, which can lead to a shortage of ice cores at certain depths. To address this, work has been done on technology to drill replicate cores: additional cores, retrieved by drilling into the sidewall of the

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research around the world, with one of the high priority research targets being deep cores in polar regions. SIPRE conducted pilot drilling trials in 1956 (to 305 m) and 1957 (to 411 m) at Site 2 in Greenland; the second core, with the benefit of the previous year's drilling experience, was

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anything from less than a year of snow to several years of snow, depending on the location. Poles left in the snow from year to year show the amount of accumulated snow each year, and this can be used to verify that the visible layer in a snow pit corresponds to a single year's snowfall.

493:, and stored for shipment. Additional packing, including padding material, is added. When the cores are flown from the drilling site, the aircraft's flight deck is unheated to help maintain a low temperature; when they are transported by ship they must be kept in a refrigeration unit. 2533:

Expedition to central Greenland in 1930–1931. Sorge dug a 15 m pit to examine the snow layers, and his results were later formalized into Sorge's Law of Densification by Henri Bader, who went on to do additional coring work in northwest Greenland in 1933. In the early 1950s, a

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hole, and each length of pipe must be separately disconnected, and then reconnected when the drill string is reinserted. Along with the logistical difficulties associated with bringing heavy equipment to ice sheets, this makes traditional rotary drills unattractive. In contrast,

294:(chips of ice cut away by the drill) must be drawn up the hole and disposed of or they will reduce the cutting efficiency of the drill. They can be removed by compacting them into the walls of the hole or into the core, by air circulation (dry drilling), or by the use of a 200:, or to summer melting, and the overall shape of the glacier does not change much with time. The outward flow can distort the layers, so it is desirable to drill deep ice cores at places where there is very little flow. These can be located using maps of the flow lines. 489:

below snow level to simplify temperature maintenance, though additional refrigeration can be used. If more drilling fluid must be removed, air may be blown over the cores. Any samples needed for preliminary analysis are taken. The core is then bagged, often in

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Retrieve ice cores that reach back over 1.2 million years, in order to obtain multiple iterations of ice core record for the 40,000-year long climate cycles known to have operated at that time. Current cores reach back over 800,000 years, and show 100,000-year

407:(expanded) until it is wide enough to accept the casing; a large diameter auger can also be used, avoiding the need for reaming. An alternative to casing is to use water in the borehole to saturate the porous snow and firn; the water eventually turns to ice. 2664:, a European ice coring collaboration, was formed in the 1990s, and two holes were drilled in East Antarctica: one at Dome C, which reached 2871 m in only two seasons of drilling, but which took another four years to reach bedrock at 3260 m; and one at 419:

The logistics of any coring project are complex because the locations are usually difficult to reach, and may be at high altitude. The largest projects require years of planning and years to execute, and are usually run as international consortiums. The

403:(fitted with a cylindrical lining), since otherwise the drilling fluid will be absorbed by the snow and firn. The casing has to reach down to the impermeable ice layers. To install casing a shallow auger can be used to create a pilot hole, which is then 1736:

in Iceland in 1783, can be identified in the ice core record, it provides a cross-check on the age determined by layer counting. Material from Laki can be identified in Greenland ice cores, but did not spread as far as Antarctica; the 1815 eruption of

2691:(WAIS) project, completed in 2011, reached 3405 m; the site has high snow accumulation so the ice only extends back 62,000 years, but as a consequence, the core provides high resolution data for the period it covers. A 948 m core was drilled at 785:

In addition to manual inspection and logging of features identified in a visual inspection, cores can be optically scanned so that a digital visual record is available. This requires the core to be cut lengthwise, so that a flat surface is created.

314:, for safety and to minimize the effect on the environment; it must be available at a reasonable cost; and it must be relatively easy to transport. Historically, there have been three main types of ice drilling fluids: two-component fluids based on 286:

for lowering and raising the auger, cores up to 50 m deep can be retrieved, but the practical limit is about 30 m for engine-powered augers, and less for hand augers. Below this depth, electromechanical or thermal drills are used.

2675:, which reached 2503 m in 1996, with an estimated age of 330,000 years for the bottom of the core; and a subsequent hole at the same site which reached 3035 m in 2006, estimated to reach ice 720,000 years old. US teams drilled at 1896:. Another complication is that in areas with low accumulation rates, deposition from fog can increase the concentration in the snow, sometimes to the point where the atmospheric concentration could be overestimated by a factor of two. 239:

forms on the top layer. Buried under the snow of following years, the coarse-grained hoar frost compresses into lighter layers than the winter snow. As a result, alternating bands of lighter and darker ice can be seen in an ice core.

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19 cm long section of GISP 2 ice core from 1855 m showing annual layer structure illuminated from below by a fibre optic source. Section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter

2668:, which reached bedrock at 2760 m in 2006. The Dome C core had very low accumulation rates, which mean that the climate record extended a long way; by the end of the project the usable data extended to 800,000 years ago. 172:

An ice core is a vertical column through a glacier, sampling the layers that formed through an annual cycle of snowfall and melt. As snow accumulates, each layer presses on lower layers, making them denser until they turn into

103:, can be used to date the layers of ice. Some volcanic events that were sufficiently powerful to send material around the globe have left a signature in many different cores that can be used to synchronise their time scales. 1338: 440:, and includes representatives from 12 countries on its steering committee. Over the course of a drilling season, scores of people work at the camp, and logistics support includes airlift capabilities provided by the 689:

Timescales for ice cores from the same hemisphere can usually be synchronised using layers that include material from volcanic events. It is more difficult to connect the timescales in different hemispheres. The

1149:{\displaystyle \mathrm {\delta ^{18}O} ={\Biggl (}\mathrm {\frac {{\bigl (}{\frac {^{18}O}{^{16}O}}{\bigr )}_{sample}}{{\bigl (}{\frac {^{18}O}{^{16}O}}{\bigr )}_{SMOW}}} -1{\Biggr )}\times 1000\ ^{o}\!/\!_{oo},} 1216:

measurements of an ice core sample with the borehole temperature at the depth it came from provides additional information, in some cases leading to significant corrections to the temperatures deduced from the

2517:'s Antarctic expedition in 1902 and 1903, 30 m holes were drilled in an iceberg south of the Kerguelen Islands and temperature readings were taken. The first scientist to create a snow sampling tool was 546:

zone, bubbles of air are trapped in the ice under great pressure. When the core is brought to the surface, the bubbles can exert a stress that exceeds the tensile strength of the ice, resulting in cracks and

2786:(International Partnerships in Ice Core Sciences) has produced a series of white papers outlining future challenges and scientific goals for the ice core science community. These include plans to: 4732: 752:, "In many ways, ice cores are the 'rosetta stones' that allow development of a global network of accurately dated paleoclimatic records using the best ages determined anywhere on the planet". 2555: 453: 4938:

Arienzo, M. M.; McConnell, J. R.; Chellman, N.; Criscitiello, A. S.; Curran, M.; Fritzsche, D.; Kipfstuhl, S.; Mulvaney, R.; Nolan, M.; Opel, T.; Sigl, M.; Steffensen, J.P. (5 July 2016).

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Bauska, Thomas K.; Baggenstos, Daniel; Brook, Edward J.; Mix, Alan C.; Marcott, Shaun A.; Petrenko, Vasilii V.; Schaefer, Hinrich; Severinghaus, Jeffrey P.; Lee, James E. (29 March 2016).

45:. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores are 1346:

showed that the deuterium excess reflects the temperature, relative humidity, and wind speed of the ocean where the moisture originated. Since then it has been customary to measure both.

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The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen

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data. Not all boreholes can be used in these analyses. If the site has experienced significant melting in the past, the borehole will no longer preserve an accurate temperature record.

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components of dust. The very small quantities typically found require at least 300 g of ice to be used, limiting the ability of the technique to precisely assign an age to core depths.

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Summer snow in Greenland contains some sea salt, blown from the surrounding waters; there is less of it in winter, when much of the sea surface is covered by pack ice. Similarly,

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can be isolated by subliming the ice in a vacuum, keeping the temperature low enough to avoid the loess giving up any carbon. The results have to be corrected for the presence of

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expedition took pit samples over much of the Greenland ice sheet, obtaining early oxygen isotope ratio data. Three other expeditions in the 1950s began ice coring work: a joint

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Some of the deposited chemical species may interact with the ice, so what is detected in an ice core is not necessarily what was originally deposited. Examples include HCHO and

551:. At greater depths, the air disappears into clathrates and the ice becomes stable again. At the WAIS Divide site, the brittle ice zone was from 520 m to 1340 m depth. 4044:"Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records" 196:

Two or three feet of snow may turn into less than a foot of ice. The weight above makes deeper layers of ice thin and flow outwards. Ice is lost at the edges of the glacier to

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is found to create glacial meltwater that washes away temporally ordered layers of trapped aerosols that researchers use as an historical record of environmental events. The

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Landais, A.; Dreyfus, G.; Capron, E.; Pol, K.; Loutre, M.F.; Raynaud, D.; Lipenkov, V.Y.; Arnaud, L.; Masson-Delmotte, V.; Paillard, D.; Jouzel, J.; Leuenberger, M. (2012).

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is slightly more likely to condense from vapour into rain or snow crystals. At lower temperatures, the difference is more pronounced. The standard method of recording the

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techniques to find the optimal combination of multiple independent records. This approach was developed in 2010 and has since been turned into a software tool, DatIce.

1831:) is produced in the atmosphere by marine organisms, so ice core records of MSA provide information on the history of the oceanic environment. Both hydrogen peroxide ( 266:

and they are still used for short holes. A design for ice core augers was patented in 1932 and they have changed little since. An auger is essentially a cylinder with

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In addition to the impurities in a core and the isotopic composition of the water, the physical properties of the ice are examined. Features such as crystal size and

5475: 298:(wet drilling). Dry drilling is limited to about 400 m depth, since below that point a hole would close up as the ice deforms from the weight of the ice above. 5973: 1753:

levels in Greenland ice had increased by a factor of over 200 since pre-industrial times, and increases in other elements produced by industrial processes, such as

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appears only in summer snow because its production in the atmosphere requires sunlight. These seasonal changes can be detected because they lead to changes in the

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borehole, at depths of particular interest. Replicate cores were successfully retrieved at WAIS divide in the 2012–2013 drilling season, at four different depths.

2747:. EastGRIP reopened for field work in 2022, where the CryoEgg reached new depths in the ice, under pressures in excess of 200 bar and temperatures of around -30c. 1680:, have been used to infer the thickness of the firn layer, and determine other palaeoclimatic information such as past mean ocean temperatures. Some gases such as 4042:; Cwynar, Les C.; Hughen, Konrad; Kershaw, Peter; Kromer, Bernd; Litt, Thomas; Lowe, David J.; Nakagawa, Takeshi; Newnham, Rewi; Schwander, Jakob (January 2009). 3654: 2743:, which began in 2015 in east Greenland and was planned to be completed in 2020. In March 2020, the 2020 EGRIP field campaign was cancelled due to the ongoing 2474:

orientation can reveal the history of ice flow patterns in the ice sheet. The crystal size can also be used to determine dates, though only in shallow cores.

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can rapidly diffuse through ice, so it may be necessary to test for these "fugitive gases" within minutes of the core being retrieved to obtain accurate data.

1391:. Combining this information with records of carbon dioxide levels, also obtained from ice cores, provides information about the mechanisms behind changes in 262:

Ice cores are collected by cutting around a cylinder of ice in a way that enables it to be brought to the surface. Early cores were often collected with hand

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Martinerie, P.; Nourtier-Mazauric, E.; Barnola, J.-M.; Sturges, W. T.; Worton, D. R.; Atlas, E.; Gohar, L. K.; Shine, K. P.; Brasseur, G. P. (17 June 2009).

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have been found in ice cores in Antarctica and Greenland. Chlorine-36, which has a half-life of 301,000 years, has been used to date cores, as have krypton (

4866:"High-resolution records of the beryllium-10 solar activity proxy in ice from Law Dome, East Antarctica: measurement, reproducibility and principal trends" 1342:

where d is the deuterium excess. It was once thought that this meant it was unnecessary to measure both ratios in a given core, but in 1979 Merlivat and

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Impurities in the ice provide information on the environment from when they were deposited. These include soot, ash, and other types of particle from

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Walker, Mike; Johnsen, Sigfus; Rasmussen, Sune Olander; Popp, Trevor; Steffensen, Jørgen-Peder; Gibbard, Phil; Hoek, Wim; Lowe, John; Andrews, John;

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in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. These data can be combined to find the

2739:) project retrieved a 2537 m core in 2010 from a site further north, extending the climatic record to 128,500 years ago; NEEM was followed by 794:

The isotopic composition of the oxygen in a core can be used to model the temperature history of the ice sheet. Oxygen has three stable isotopes,

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which gases are trapped for a given location, but their predictions have not always proved reliable. At locations with very low snowfall, such as

4092: 2582:, the following year. The success of the IGY core drilling led to increased interest in improving ice coring capabilities, and was followed by a 5389: 2539: 4004: 6016: 5811: 667:

produced directly in the ice by cosmic rays, and the amount of correction depends strongly on the location of the ice core. Corrections for

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Uglietti, Chiara; Zapf, Alexander; Jenk, Theo Manuel; Sigl, Michael; Szidat, Sönke; Salazar, Gary; Schwikowski, Margit (21 December 2016).

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The cutting apparatus of a drill is on the bottom end of a drill barrel, the tube that surrounds the core as the drill cuts downward. The

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Schilt, Adrian; Baumgartner, Matthias; Blunierc, Thomas; Schwander, Jakob; Spahni, Renato; Fischer, Hubertus; Stocker, Thomas F. (2009).

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metal ribs (known as flights) wrapped around the outside, at the lower end of which are cutting blades. Hand augers can be rotated by a

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in Antarctica the depth is 95 m and the age 2500 years. As further layers build up, the pressure increases, and at about 1500 m the

1439:, but it was not until the late 1970s that a reliable extraction method was developed. Early results included a demonstration that the 122:, with the deepest core reaching 3769 m. Numerous other deep cores in the Antarctic have been completed over the years, including the 53:(for shallow holes) or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old. 83:

Impurities in ice cores may depend on location. Coastal areas are more likely to include material of marine origin, such as sea salt

500:

in the US. These locations make samples available for testing. A substantial fraction of each core is archived for future analyses.

3002: 5834: 4541:"Glacial-interglacial and millennial-scale variations in the atmospheric nitrous oxide concentration during the last 800,000 years" 2812:

Come up with a standardised lightweight drill capable of drilling both wet and dry holes, and able to reach depths of up to 1000 m.

363:

is flexible enough to be coiled when at the surface. This eliminates the need to disconnect and reconnect the pipes during a trip.

5476:"Surviving Harsh Operating Conditions: How Protronix EMS is Powering Cutting-Edge Research in East Greenland | Protronix EMS" 1635:, a record of the summer insolation, and hence combining this data with orbital cycle data establishes an ice core dating scheme. 5043: 3139: 2783: 569: 2800:

Drill additional cores to provide high-resolution data for the last 2,000 years, to use as input for detailed climate modelling.

2340:

in the atmosphere at a rate that depends on the solar magnetic field. The strength of the field is related to the intensity of

2462:, an important component of sediment cores, can also be found in ice cores. It provides information on changes in vegetation. 1527:(nitrous oxide) levels are also correlated with glacial cycles, though at low temperatures the graph differs somewhat from the 5070:"An ice-core pollen record showing vegetation response to Late-glacial and Holocene climate changes at Nevado Sajama, Bolivia" 5955: 5883: 5630: 4615: 3667: 3311: 3043: 2985: 2942: 6053: 4633:"Long-lived halocarbon trends and budgets from atmospheric chemistry modelling constrained with measurements in polar firn" 1732:

caused by non-seasonal events such as forest fires and major volcanic eruptions. When a known volcanic event, such as the

456:, a previous Greenland ice core drilling site, to the EastGRIP site. Drilling is expected to continue until at least 2020. 2865: 714:) can be used to connect the chronology of a Greenland core (for example) with an Antarctic core. In cases where volcanic 3511: 2374:

in ice cores, about 10,000 atoms in a gram of ice, and these can be used to provide long-term records of solar activity.

476:

With some variation between projects, the following steps must occur between drilling and final storage of the ice core.

301:

Drilling fluids are chosen to balance the pressure so that the hole remains stable. The fluid must have a low kinematic

235:, leaving the top inch or so less dense. When the Sun approaches its lowest point in the sky, the temperature drops and 6910: 6400: 3034:

Gabrielli, Paolo; Vallelonga, Paul (2015). "Contaminant Records in Ice Cores". In Blais, Jules M.; et al. (eds.).

2483: 6601: 6197: 3953: 3782: 3673: 2797:

Identify additional proxies from ice cores, for example for sea ice, marine biological productivity, or forest fires.

748:

The dating of ice sheets has proved to be a key element in providing dates for palaeoclimatic records. According to

1455:

than just before the start of the industrial age. Further research has demonstrated a reliable correlation between

7515: 6237: 2732: 1700:, can be detected in ice cores after about 1950; almost all CFCs in the atmosphere were created by human activity. 1611:

correlates with the strength of local summer insolation. This means that the trapped air retains, in the ratio of

1435:

It was understood in the 1960s that analyzing the air trapped in ice cores would provide useful information on the

5595: 3867: 349:

Rotary drilling is the main method of drilling for minerals and it has also been used for ice drilling. It uses a

5103:"Physical properties of the P96 ice core from Penny Ice Cap, Baffin Island, Canada, and derived climatic records" 2740: 421: 139: 5428: 7165: 2562: 232: 107: 1575:(oxygen) can be used to date ice cores: as air is gradually trapped by the snow turning to firn and then ice, 189:

of the ice changes from hexagonal to cubic, allowing air molecules to move into the cubic crystals and form a

6647: 6395: 4939: 4905:

Wagenhach, D.; Graf, W.; Minikin, A.; Trefzer, U.; Kipfstuhl, J.; Oerter, H.; Blindow, N. (20 January 2017).

2513:; these were drilled with iron rods and did not produce cores. The deepest hole achieved was 60 m. On 2360: 480:

can slide out onto a prepared surface. The core must be cleaned of drilling fluid as it is slid out; for the

5712:"Field season 2016: East GReenland Ice core Project (EGRIP) 2015–2020: Establishing the EGRIP drilling camp" 5009: 106:

Ice cores have been studied since the early 20th century, and several cores were drilled as a result of the

6390: 3396: 1358: 497: 7536: 7145: 6580: 6450: 4502: 2724: 2389:), created by nuclear weapons testing in the 1950s and 1960s, has been identified in ice cores, and both 734: 449: 135: 6021: 4394: 3439: 2763:. Some of these cores reach back to the last glacial period, but they are more important as records of 2558:, in central Greenland. Core quality was poor, but some scientific work was done on the retrieved ice. 698:

about 40,000 years ago, can be identified in cores; away from that point, measurements of gases such as

568:

Many different kinds of analysis are performed on ice cores, including visual layer counting, tests for

7084: 6790: 6770: 5765: 4445:"Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation" 2728: 778:

other methods. For example, at Vostok, layer counting is only possible down to an age of 55,000 years.

469: 110:(1957–1958). Depths of over 400 m were reached, a record which was extended in the 1960s to 2164 m at 4245: 4191: 4096: 3693:"An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120–800 ka" 1365:, followed by slower cooling. Other isotopic ratios have been studied, for example, the ratio between 6780: 6752: 6585: 6364: 3036:

Environmental Contaminants: Using Natural Archives to Track Sources and Long-Term Trends of Pollution

2570:

retrieved in much better condition, with fewer gaps. In Antarctica, a 307 m core was drilled at

2375: 922: 3482: 513: 7120: 6847: 6046: 4013: 2696: 2688: 1749:

Many other elements and molecules have been detected in ice cores. In 1969, it was discovered that

433: 127: 123: 5822: 3304:

Exploration of Antarctic Subglacial Aquatic Environments: Environmental and Scientific Stewardship

3271:"Thermal electric ice-core drills: history and new design options for intermediate-depth drilling" 258:

Ice auger patented in 1932; the design is very similar to modern augers used for shallow drilling.

254: 7170: 6785: 6735: 6522: 6369: 6026: 2866:"Coronavirus Already Hindering Climate Science, But the Worst Disruptions Are Likely Yet to Come" 1724: 1420: 445: 100: 5718: 5454: 3359:

Anonymous (30 June 2017), Ice Drilling Design and Operations: Long Range Technology Plan, p. 24.

7430: 7079: 6903: 6685: 6486: 6232: 6131: 5710:

Dahl-Jensen, Dorthe; Kirk, Marie; Larsen, Lars.B.; Sheldon, Simon G.; Steffensen, J.P. (2016).

4563: 3868:"An extremely brief reversal of the geomagnetic field, climate variability and a super volcano" 2590:

French, Australian and Canadian projects from the 1960s and 1970s include a 905 m core at

719: 5675:

Blunier, T.; Spahni, R.; Barnola, J.-M.; Chappellaz, J.; Loulergue, L.; Schwander, J. (2007).

5569: 4907:"Reconnaissance of chemical and isotopic firn properties on top of Berkner Island, Antarctica" 4287: 3161:

Sheldon, Simon G.; Popp, Trevor J.; Hansen, Steffen B.; Steffensen, Jørgen P. (26 July 2017).

7453: 7160: 6287: 3970: 2824: 723: 142:, originally expected to complete a deep core in east Greenland in 2020 but since postponed. 95:

that correlate with cold, dry periods in the past, when cold deserts were scoured by wind.

68:

trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as

7196: 6720: 6661: 6637: 6632: 5924: 5846: 5788: 5742: 5688: 5653: 5338: 5114: 4954: 4877: 4744: 4689: 4644: 4456: 4206: 4055: 3839: 3798: 3704: 3569: 2806:

Improve the ability to handle brittle ice, both while drilling and in transport and storage

2529:

The first systematic study of snow and firn layers was by Ernst Sorge, who was part of the

2326: 1452: 727: 695: 429: 338:. Newer fluids have been proposed, including new ester-based fluids, low-molecular weight 8: 7546: 7390: 7217: 7135: 6747: 6642: 6560: 6550: 6325: 6242: 6222: 6212: 6039: 3163:"Promising new borehole liquids for ice-core drilling on the East Antarctic high plateau" 3009: 2514: 1499: 600:, the uncertainty in the difference between ages of ice and gas can be over 1,000 years. 65: 5928: 5850: 5792: 5746: 5692: 5657: 5342: 5118: 4958: 4881: 4748: 4648: 4460: 4210: 4059: 3843: 3802: 3783:"AMS radiocarbon dating of ice: validity of the technique and the problem of cosmogenic 3708: 3573: 3558:"International ice core community meets to discuss best practices for ice core curation" 2977: 2971: 2775:, in the Alps, and in Indonesia, New Zealand, Iceland, Scandinavia, Canada, and the US. 525: 7541: 7222: 7019: 6872: 6852: 6730: 6715: 6700: 6622: 6421: 6385: 6187: 5862: 5036: 4978: 4768: 4479: 4444: 4073: 2455: 1685: 1159: 607: 441: 424:

project, for example, which as of 2017 is drilling in eastern Greenland, is run by the

355: 151: 7317: 5042:(Report). Cold Regions Research and Engineering Lab, Hanover, NH. pp. 1–2. 97–1. 4218: 3327:

Schwikowski, Margit; Jenk, Theo M.; Stampfli, Dieter; Stampfli, Felix (26 July 2017).

3001:

Tulaczyk, S.; Elliot, D.; Vogel, S.W.; Powell, R.D.; Priscu, J.C.; Clow, G.D. (2002).

2815:

Improve core handling to maximise the information that can be obtained from each core.

2687:(1004 m in 1999), with both cores reaching ice from the last glacial period. The 7505: 7468: 7292: 7009: 6896: 6680: 6476: 6471: 6315: 6151: 5951: 5898: 5879: 5626: 4982: 4970: 4760: 4611: 4484: 3949: 3828:"Radiocarbon dating of glacier ice: overview, optimisation, validation and potential" 3663: 3307: 3039: 2981: 2938: 2840: 2772: 2744: 2506: 1833: 1720: 1689: 683: 585: 400: 186: 5866: 4559: 4260: 4077: 3617:

Uchida, Tsutomu; Duval, P.; Lipenkov, V.Ya.; Hondoh, T.; Mae, S.; Shoji, H. (1994).

7510: 7410: 7307: 7237: 7099: 6978: 6877: 6826: 6742: 6690: 6466: 6444: 6310: 6207: 5932: 5854: 5796: 5750: 5696: 5661: 5346: 5122: 5081: 4962: 4918: 4885: 4772: 4752: 4685: 4652: 4555: 4474: 4464: 4256: 4214: 4063: 3847: 3806: 3722: 3712: 3577: 3340: 3301: 3282: 3174: 2794:

Improve ice core chronologies, including connecting chronologies of multiple cores.

2634: 2575: 2177: 1495: 742: 581: 577: 343: 339: 61: 5101:

Okuyama, Junichi; Narita, Hideki; Hondoh, Takeo; Koerner, Roy M. (February 2003).

4039: 2699:

from 2002 to 2005, extending into the last glacial period; and an Italian-managed

1333:{\displaystyle \mathrm {\delta D} =8\times \mathrm {\delta ^{18}O} +\mathrm {d} ,} 134:. In Greenland, a sequence of collaborative projects began in the 1970s with the 7405: 7380: 7262: 7175: 7064: 6810: 6775: 6762: 6725: 6672: 6530: 6425: 6359: 6320: 6157: 4246:"Recent melt rates of Canadian arctic ice caps are the highest in four millennia" 3138:. Niels Bohr Institute Centre for Ice and Climate. 2 October 2008. Archived from 2676: 2543: 2518: 2356: 2341: 2315: 2046: 1693: 1436: 622:. In the polar ice sheets there is about 15–20 μg of carbon in the form of 366: 335: 323: 306: 156: 1864:

that are linked to vegetation emissions and forest fires. Some species, such as

7347: 7297: 7282: 7155: 7140: 7069: 7054: 6988: 6973: 6710: 6508: 6496: 6440: 6435: 6429: 6354: 6277: 6202: 5966: 5666: 5641: 5390:"Record-shattering 2.7-million-year-old ice core reveals start of the ice ages" 5351: 5326: 5008:. US Geological Survey Central Region Research. 14 January 2005. Archived from 4923: 4906: 4449:

Proceedings of the National Academy of Sciences of the United States of America

2820: 2768: 2692: 2665: 2579: 2530: 691: 597: 496:

There are several locations around the world that store ice cores, such as the

295: 291: 279: 220: 119: 69: 6006: 5996: 5967:

Fifty Years of Soviet and Russian Drilling Activity in Polar and Non-Polar Ice

3811: 3515: 760: 7530: 7478: 7420: 7400: 7395: 7342: 7337: 7322: 7267: 7150: 7125: 7004: 6627: 6545: 6540: 6491: 6481: 6121: 6001: 5997:

US National Ice Core Laboratory video showing storage and processing of cores

5902: 4940:"A Method for Continuous Pu Determinations in Arctic and Antarctic Ice Cores" 2755:

Ice cores have been drilled at locations away from the poles, notably in the

2646: 2642: 2607: 2522: 2502: 2395: 1781: 1738: 1643: 749: 389: 263: 96: 77: 73: 50: 7212: 4966: 4657: 4632: 4469: 3852: 3827: 3689: 3003:

FASTDRILL: Interdisciplinary Polar Research Based on Fast Ice-Sheet Drilling

2493: 678:

produced by nuclear testing have much less impact on the results. Carbon in

7358: 7287: 7044: 7039: 6983: 6705: 6503: 6217: 6192: 6177: 6143: 6103: 5755: 5730: 5035:

Taylor, Susan; Lever, James H.; Harvey, Ralph P.; Govoni, John (May 1997).

4974: 4764: 4733:"Timing and climate forcing of volcanic eruptions for the past 2,500 years" 4488: 3717: 3692: 2845: 2630: 2571: 2471: 1861: 1856: 1697: 1388: 1362: 1350: 1253:) and makes water more likely to condense and less likely to evaporate. A 679: 573: 360: 350: 319: 275: 249: 212: 161: 115: 111: 46: 5937: 5912: 5801: 5701: 5676: 5327:"Drilling to the beds of the Greenland and Antarctic ice sheets: a review" 5086: 5069: 4890: 4865: 3345: 3328: 3287: 3270: 3179: 3162: 2618: 7473: 7352: 7332: 7327: 7312: 7272: 7130: 7014: 6405: 6302: 6264: 6247: 6182: 6163: 6096: 6076: 5127: 5102: 4630: 3582: 3557: 2711: 2680: 2626:

levels (ppm) going back nearly 800,000 years, and related glacial cycles.

2390: 2129: 1767: 1733: 1343: 481: 399:

When drilling deep holes, which require drilling fluid, the hole must be

376: 178: 138:; there have been multiple follow-up projects, with the most recent, the 34: 5367: 4756: 1703:

Greenland cores, during times of climatic transition, may show excess CO

580:. For the results of these tests to be useful in the reconstruction of 7500: 7483: 7463: 7415: 7049: 6963: 6172: 6167: 6062: 3727: 3329:"A new thermal drilling system for high-altitude or temperate glaciers" 2704: 2684: 2566: 2434: 2408: 2133: 1803: 1514:

can be used to determine the relationship between core depth and age.

572:

and physical properties, and assays for inclusion of gases, particles,

385: 310:

fluid must contaminate the ice as little as possible; it must have low

236: 216: 5858: 4672:

Delmas, Robert J. (1993). "A natural artefact in Greenland ice-core CO

2764: 1427: 7089: 7029: 6958: 6953: 6948: 6862: 6842: 6575: 6535: 6272: 6081: 6012:

A misleading graph has been circling the internet since at least 2010

6007:

Byrd Polar Research Center – Ice Core Paleoclimatology Research Group

5432: 4068: 4043: 3618: 2828: 2756: 2736: 2653: 1765:, have also been recorded. The presence of nitric and sulfuric acid ( 1743: 1728: 1638: 1228: 1227:

Hydrogen ratios can also be used to calculate a temperature history.

822: 809: 796: 655: 635: 592: 490: 302: 190: 88: 38: 4937: 1411: 519:

Bubbles in an Antarctic ice sample. Illuminated with polarised light

7443: 7438: 7115: 7024: 6857: 6339: 6252: 5913:"Core handling and processing for the WAIS Divide ice-core project" 2599: 2421: 2319: 1869: 1807: 738: 315: 311: 271: 204: 197: 7252: 5766:"Towards orbital dating of the EPICA Dome C ice core using δO 4731:

Steffensen, J. P.; Vinther, B. M.; Woodruff, T. E. (8 July 2015).

4538: 2809:

Find a way to handle cores which have pressurised water at bedrock

1802:) in precipitation can be shown to correlate with increasing fuel 1486:, the amount in the atmosphere is correlated with the strength of 1419:(green), reconstructed temperature (blue) and dust (red) from the 888:

is slightly more likely to turn into vapour, and water containing

7385: 7375: 7302: 7074: 7059: 6968: 6943: 6919: 6867: 6091: 6086: 3971:"Toward a radiometric ice clock: U-series of the Dome C ice core" 3944:

Elias, Scott; Mock, Cary, eds. (2013). "Volcanic Tephra Layers".

1865: 1758: 1673: 1491: 1487: 1483: 726:

has also been used to date ice cores. Another approach is to use

711: 437: 404: 327: 208: 181:

in Greenland, the depth is 77 m and the ice is 230 years old; at

57: 42: 3404: 682:

can also be dated by separating and testing the water-insoluble

604:

firn density to calculate the temperature when the firn formed.

7257: 6938: 6933: 3326: 2672: 2591: 2551: 2459: 1754: 1681: 1646:

processes in trapped air, determined by the measurement of the

745:

information that can be correlated with other climate proxies.

715: 283: 224: 182: 118:

ice drilling projects in Antarctica include decades of work at

4370:. Centre for Ice and Climate. 8 September 2009. Archived from 346:, and kerosene-based fluids mixed with foam-expansion agents. 193:. The bubbles disappear and the ice becomes more transparent. 7448: 7277: 7094: 6292: 6031: 5717:. Ice and Climate Group, Niels Bohr Institute. Archived from 3447: 2760: 2700: 2661: 2638: 2583: 2535: 1677: 1467:

levels and the temperature calculated from ice isotope data.

1354: 639: 548: 532: 531:

Sliver of Antarctic ice showing trapped bubbles. Images from

331: 267: 131: 92: 5709: 5596:"The race to save glacial ice records before they melt away" 4012:. EGU General Assembly 2012. Vienna, Austria. Archived from 3619:"Brittle zone and air-hydrate formation in polar ice sheets" 3468: 3425: 3302:

National Research Council of the National Academies (2007).

3008:(Report). 2002 FASTDRILL Workshop. p. 9. Archived from 2723:

In 1970, scientific discussions began which resulted in the

1254: 21: 7458: 7227: 7034: 6888: 6226: 6108: 5677:"Synchronization of ice core records via atmospheric gases" 4904: 4729: 3306:. Washington DC: National Academies Press. pp. 82–84. 3160: 2935:

Paleoclimatology: Reconstructing Climates of the Quaternary

2510: 1762: 1750: 1669: 452:. In 2015 the EastGRIP team moved the camp facilities from 174: 165: 5100: 4037: 2671:

Other deep Antarctic cores included a Japanese project at

1860:) have been studied, along with organic molecules such as 464: 322:

to increase density; alcohol compounds, including aqueous

6126: 5731:"A brief history of ice core science over the last 50 yr" 5037:

Collecting micrometeorites from the South Pole Water Well

4006:

Toward unified ice core chronologies with the DatIce tool

3616: 3000: 2831:

in Antarctica in advance of this impending loss of data.

1502:, for which a timescale is available from other sources, 84: 4442: 4395:"How are past temperatures determined from an ice core?" 5763: 5068:

Reese, C.A.; Liu, K.B.; Thompson, L.G. (26 July 2017).

5034: 4587: 3931: 3904: 3370: 2587:

borehole by sub-ice meltwater and had to be abandoned.

5897:. Washington DC: World Data Center A for Glaciology . 5642:"Reliability of ice-core science: historical insights" 4003:

Toyé Mahamadou Kele, H.; et al. (22 April 2012).

921:

ratio is to subtract the ratio in a standard known as

855:

indicates the temperature when the snow fell. Because

5625:. Princeton, New Jersey: Princeton University Press. 1286: 933: 5965:

Ueda, Herbert T.; Talalay, Pavel G. (October 2007).

4610:. Cambridge: Cambridge University Press. p. 9. 4505:. National Weather Service Climate Prediction Center 3825: 1490:, which are in turn correlated with the strength of 1357:

in Greenland, were instrumental in the discovery of

145: 6607:

Global Boundary Stratotype Section and Point (GSSP)

5589: 5587: 4002: 3033: 722:and hence provide fixed points for dating the ice. 132:

International Trans-Antarctic Scientific Expedition

3662:. Chichester: John Wiley & Sons. p. 150. 3268: 1387:can provide information about past changes in the 1332: 1148: 591:A difficulty in ice core dating is that gases can 5431:. East Greenland Ice Core Project. Archived from 5308: 5306: 5304: 5302: 5289: 5287: 5285: 5224: 5222: 4823: 4821: 4784: 4782: 4713: 4711: 3204: 3202: 3118: 3116: 3088: 3086: 3084: 3082: 3069: 3067: 3038:. Dordrecht, Netherlands: Springer. p. 395. 2610:cores recovered by a Canadian team in the 1970s. 1133: 1126: 1105: 954: 99:elements, either of natural origin or created by 7528: 5584: 5067: 4522: 4520: 4503:"Climate Prediction Center – Expert Assessments" 4414: 4412: 4338: 4336: 4190:Ruddiman, William F.; Raymo, Maureen E. (2003). 4170: 4168: 4166: 4164: 4162: 4160: 4158: 4156: 4154: 3600: 3598: 3596: 3594: 3539: 3537: 3535: 3533: 3371:"EastGrip – The East Greenland Ice-core Project" 2916: 2914: 718:is interspersed with ice, it can be dated using 5832: 4851: 4839: 4827: 4812: 4800: 4788: 4717: 3927: 3925: 3623:Memoirs of National Institute of Polar Research 3269:Zagorodnov, V.; Thompson, L.G. (26 July 2017). 3103: 3101: 2771:in south Asia. Cores have also been drilled on 2606:, starting in 1969 with a 382 m core; and 634:in each kilogram of ice, and there may also be 5835:"Glaciochemistry of polar ice cores: A review" 5674: 5299: 5282: 5219: 4818: 4779: 4708: 4598: 4596: 3916: 3892: 3514:. National Ice Core Laboratory. Archived from 3199: 3113: 3079: 3064: 2884: 2882: 2657:The EPICA Dome C and Vostok ice cores compared 2540:Norwegian-British-Swedish Antarctic Expedition 1711:production by acidic and alkaline impurities. 1349:Water isotope records, analyzed in cores from 6904: 6047: 5909: 5568:. PAGES – Past Global Changes. Archived from 4517: 4409: 4333: 4273: 4189: 4151: 3780: 3764: 3762: 3604: 3591: 3543: 3530: 2911: 2633:ice drilling projects began in the 1950s, in 2322:from 1960s nuclear testing in US glacier ice. 1406: 1074: 1034: 1004: 964: 5325:Bentley, Charles R.; Koci, Bruce R. (2007). 5107:Journal of Geophysical Research: Solid Earth 4311: 4309: 4307: 4305: 3922: 3512:"About Ice Cores :: Drilling Ice Cores" 3098: 2901: 2899: 2897: 370:Mechanical drill head, showing cutting teeth 16:Cylindrical sample drilled from an ice sheet 5964: 5324: 5276: 5264: 5252: 5240: 4593: 4192:"A methane-based time scale for Vostok ice" 4185: 4183: 3691:Chappellaz, J.; Wolff, E. (1 August 2013). 2976:. Cheltenham, UK: Stanley Thornes. p. 2879: 6911: 6897: 6054: 6040: 5873: 4315: 3990: 3759: 3136:"Deep drilling with the Hans Tausen drill" 2937:. Amsterdam: Academic Press. p. 138. 282:to power the rotation. With the aid of a 168:between surface snow and blue glacier ice. 5936: 5892: 5878:(3rd ed.). Abingdon, UK: Routledge. 5800: 5754: 5700: 5665: 5552: 5540: 5528: 5516: 5504: 5492: 5350: 5126: 5085: 4922: 4889: 4656: 4478: 4468: 4302: 4067: 3969:Aciego, S.; et al. (15 April 2010). 3943: 3851: 3810: 3726: 3716: 3581: 3344: 3286: 3178: 2894: 1267:. There is a linear relationship between 6602:Global Standard Stratigraphic Age (GSSA) 5427:Madsen, Martin Vindbæk (15 March 2016). 4392: 4288:"Periodic Table of Elements: O – Oxygen" 4180: 3437: 3395:Madsen, Martin Vindbæk (14 April 2016). 3368: 2703:project completed a 1620 m core at 2652: 2617: 2613: 2492: 2314: 1431:Ozone-depleting gases in Greenland firn. 1426: 1410: 1260:ratio can be defined in the same way as 759: 463: 414: 365: 253: 164:in Alaska. There is increasingly dense 155: 20: 5945: 5809: 5414: 5213: 5201: 5189: 5177: 5165: 5153: 5141: 3640: 3555: 3480: 3256: 3244: 3232: 3220: 3208: 3193: 3122: 3107: 3092: 3073: 2932: 2920: 2718: 2710:In 2016, cores were retrieved from the 2574:in 1957–1958, and a 264 m core at 2419:, with a half-life of 11 years), lead ( 1707:in air bubbles when analysed, due to CO 375:require an anti-torque device, such as 278:, and some can be attached to handheld 80:that best fits all the available data. 7529: 5876:Reconstructing Quaternary Environments 5812:"The history of early polar ice cores" 5728: 5426: 5312: 5293: 5228: 4947:Environmental Science & Technology 4690:10.1034/j.1600-0889.1993.t01-3-00006.x 4671: 4602: 4526: 4430: 4418: 4393:Mulvaney, Robert (20 September 2004). 4342: 4243: 4231: 4174: 3968: 3753: 3741: 3652: 3505: 3503: 3481:Kolbert, Elizabeth (24 October 2016). 3394: 2969: 2863: 2465: 1900:Soluble impurities found in ice cores 6892: 6035: 5893:MacKinnon, P.K. (1980). "Ice Cores". 5639: 5620: 5593: 5365: 5022: 4863: 4702: 4354: 4327: 4285: 4145: 4133: 4121: 4109: 3768: 3438:Petersen, Sandra (23 February 2016). 3369:Petersen, Sandra (23 February 2016). 3058: 2957: 2905: 2888: 2857: 1551:graphs. Similarly, the ratio between 610:can be used on the carbon in trapped 5874:Lowe, J. John; Walker, Mike (2014). 5810:Langway, Chester C. (January 2008). 5049:from the original on 11 October 2017 3781:Wilson, A.T.; Donahue, D.J. (1992). 2053:Human and biological gas emissions: 1191:of 0‰; a sample that is depleted in 789: 4608:Climate Change and Climate Modeling 4253:Global and Planetary Climate Change 4090: 3874:. ScienceX network. 16 October 2012 3500: 2803:Identify an improved drilling fluid 2448: 1482:(methane) is produced in lakes and 13: 6401:Adoption of the Gregorian calendar 5976:from the original on 20 April 2017 5948:Mechanical Ice Drilling Technology 5833:Legrand, M.; Mayewski, P. (1997). 5606:from the original on 16 July 2024. 4995:Delmas et al. (2004), pp. 494–496. 3946:Encyclopedia of Quaternary Science 2750: 2484:History of scientific ice drilling 1714: 1451:concentration was 30% less at the 1361:—rapid warming at the onset of an 1323: 1315: 1291: 1242:, or D) is heavier than hydrogen ( 1089: 1086: 1083: 1080: 1065: 1051: 1025: 1022: 1019: 1016: 1013: 1010: 995: 981: 945: 755: 459: 126:project, and cores managed by the 37:that is typically removed from an 14: 7558: 5990: 4637:Atmospheric Chemistry and Physics 4368:"Isotopes and the delta notation" 3556:Hinkley, Todd (9 December 2003). 2548:Juneau Ice Field Research Project 146:Structure of ice sheets and cores 7516:Template:Periglacial environment 5972:(Report). ERDC/CRREL. TR-07-02. 5558: 5546: 5534: 5522: 5510: 5498: 5486: 5468: 5447: 5420: 5408: 5382: 5359: 5318: 5270: 5258: 5246: 5234: 5207: 5195: 5183: 5171: 5159: 5147: 5135: 5094: 4091:Gow, Anthony (12 October 2001). 2310: 1688:(CFCs), which contribute to the 638:particles from wind-blown dust ( 558: 542:Over a depth range known as the 524: 512: 25:Ice core sample taken from drill 6283:English and British regnal year 6022:Beyond EPICA-Oldest Ice mission 5821:(TR-08-1): 1–47. Archived from 5368:"TALos Dome Ice CorE – TALDICE" 5061: 5028: 5016: 4998: 4989: 4931: 4898: 4857: 4845: 4833: 4806: 4794: 4723: 4696: 4665: 4624: 4581: 4560:10.1016/j.quascirev.2009.03.011 4532: 4495: 4436: 4424: 4386: 4360: 4348: 4321: 4279: 4267: 4261:10.1016/j.gloplacha.2011.06.005 4237: 4225: 4139: 4127: 4115: 4103: 4093:"Summer and winter core layers" 4084: 4031: 3996: 3984: 3962: 3937: 3910: 3898: 3886: 3860: 3819: 3774: 3747: 3735: 3683: 3646: 3634: 3610: 3549: 3509: 3474: 3462: 3444:East Greenland Ice Core Project 3431: 3419: 3401:East Greenland Ice Core Project 3388: 3375:East Greenland Ice Core Project 3362: 3353: 3320: 3295: 3262: 3250: 3238: 3226: 3214: 3187: 3154: 3128: 3052: 2778: 2556:Expéditions Polaires Françaises 1642:the bottom of a column. These 1498:. Since insolation depends on 140:East Greenland Ice-Core Project 6061: 5594:Jones, Nicola (14 July 2024). 3787:production in polar ice cores" 3027: 2994: 2963: 2951: 2926: 2563:International Geophysical Year 2526:the snow and rotated by hand. 2488: 503: 108:International Geophysical Year 1: 6396:Old Style and New Style dates 4219:10.1016/S0277-3791(02)00082-3 4048:Journal of Quaternary Science 3978:TALDICE-EPICA Science Meeting 2864:Berwyn, Bob (27 March 2020). 2851: 2622:Composite data for Dome C, CO 2363:can detect the low levels of 2361:Accelerator mass spectrometry 1599:, and the relative amount of 6918: 6348:Pre-Julian / Julian 4290:. EnvironmentalChemistry.com 2933:Bradley, Raymond S. (2015). 2695:by a project managed by the 498:National Ice Core Laboratory 91:ice cores contain layers of 7: 6581:Geological history of Earth 6451:Astronomical year numbering 6017:A 2.7 million year old core 4852:Legrand & Mayewski 1997 4840:Legrand & Mayewski 1997 4828:Legrand & Mayewski 1997 4813:Legrand & Mayewski 1997 4801:Legrand & Mayewski 1997 4789:Legrand & Mayewski 1997 4718:Legrand & Mayewski 1997 2834: 2725:Greenland Ice Sheet Project 1158:where the ‰ sign indicates 450:National Science Foundation 136:Greenland Ice Sheet Project 10: 7563: 5946:Talalay, Pavel G. (2016). 5667:10.3189/002214311796406130 5640:Alley, Richard B. (2010). 5621:Alley, Richard B. (2000). 5613: 5455:"Finally, put in at EGRIP" 5352:10.3189/172756407786857695 4924:10.3189/172756494794587401 4548:Quaternary Science Reviews 4199:Quaternary Science Reviews 2827:plans to store additional 2594:in Antarctica, drilled by 2565:(1957–1958) saw increased 2481: 2477: 2432:, 22 years), and silicon ( 2304:, other organic compounds 1423:for the past 420,000 years 1407:Palaeoatmospheric sampling 426:Centre for Ice and Climate 318:-like products mixed with 247: 149: 60:provide information about 7496: 7429: 7368: 7245: 7236: 7205: 7184: 7108: 6997: 6926: 6835: 6819: 6803: 6761: 6753:Thermoluminescence dating 6671: 6660: 6648:Samarium–neodymium dating 6615: 6594: 6568: 6559: 6521: 6459: 6414: 6378: 6347: 6338: 6301: 6263: 6142: 6117: 6069: 5623:The Two-Mile Time Machine 3812:10.1017/S0033822200063657 3656:Quaternary Dating Methods 2970:Knight, Peter G. (1999). 2683:(554 m in 1994) and 1727:of the ice. Placing two 1587:is lost more easily than 1359:Dansgaard-Oeschger events 1162:. A sample with the same 923:standard mean ocean water 733:The boundary between the 563: 446:Hercules transport planes 243: 6467:Chinese sexagenary cycle 2697:British Antarctic Survey 2689:West Antarctic Ice Sheet 1746:about 72,000 years ago. 576:, and various molecular 434:University of Copenhagen 160:Sampling the surface of 128:British Antarctic Survey 124:West Antarctic Ice Sheet 6681:Amino acid racemisation 5277:Ueda & Talalay 2007 5265:Ueda & Talalay 2007 5253:Ueda & Talalay 2007 5241:Ueda & Talalay 2007 4967:10.1021/acs.est.6b01108 4658:10.5194/acp-9-3911-2009 4470:10.1073/pnas.1513868113 3948:. Amsterdam: Elsevier. 3853:10.5194/tc-10-3091-2016 3469:Dahl-Jensen et al. 2016 3426:Dahl-Jensen et al. 2016 2497:A store of core samples 2355:in the atmosphere is a 2138:Atmospheric chemistry: 1725:electrical conductivity 570:electrical conductivity 6686:Archaeomagnetic dating 6198:Era of Caesar (Iberia) 5756:10.5194/cp-9-2525-2013 5396:. AAAS. 14 August 2017 4316:Lowe & Walker 2014 4286:Barbalace, Kenneth L. 4244:Fisher, David (2011). 4095:. NOAA. Archived from 3991:Lowe & Walker 2014 3718:10.5194/cp-9-1715-2013 3483:"When a Country Melts" 2658: 2627: 2498: 2323: 1911:Measured in polar ice 1432: 1424: 1334: 1150: 766: 473: 371: 259: 169: 26: 7454:Giant current ripples 6586:Geological time units 5950:. Beijing: Springer. 5938:10.3189/2014AoG68A008 5839:Reviews of Geophysics 5802:10.5194/cp-8-191-2012 5702:10.5194/cp-3-325-2007 5646:Journal of Glaciology 5370:. Talos Dome Ice Core 5087:10.3189/2013AoG63A375 5012:on 13 September 2005. 4891:10.5194/cp-7-707-2011 4397:. Scientific American 3653:Walker, Mike (2005). 3346:10.3189/2014AoG68A024 3288:10.3189/2014AoG68A012 3180:10.3189/2014AoG68A043 2825:Ice Memory Foundation 2679:in the 1990s, and at 2656: 2621: 2614:Antarctica deep cores 2505:drilled holes in the 2496: 2318: 1430: 1414: 1335: 1151: 763: 467: 442:US Air National Guard 415:Large coring projects 369: 257: 159: 24: 6638:Law of superposition 6633:Isotope geochemistry 5917:Annals of Glaciology 5911:(31 December 2014). 5828:on 18 November 2016. 5566:"IPICS White Papers" 5331:Annals of Glaciology 5128:10.1029/2001JB001707 5074:Annals of Glaciology 4911:Annals of Glaciology 4864:Pedro, J.B. (2011). 4099:on 13 February 2010. 3583:10.1029/2003EO490006 3333:Annals of Glaciology 3275:Annals of Glaciology 3167:Annals of Glaciology 2719:Greenland deep cores 2454:meteorites. At the 2327:Galactic cosmic rays 1854:) and formaldehyde ( 1453:last glacial maximum 1284: 1184:ratio as SMOW has a 931: 833:. The ratio between 728:Bayesian probability 696:geomagnetic reversal 430:Niels Bohr Institute 351:string of drill pipe 62:ancient temperatures 7391:Moraine-dammed lake 7218:Subglacial eruption 6771:Fluorine absorption 6748:Luminescence dating 6643:Luminescence dating 6551:Milankovitch cycles 6391:Proleptic Gregorian 6223:Hindu units of time 5929:2014AnGla..55...15S 5851:1997RvGeo..35..219L 5793:2012CliPa...8..191L 5781:Climate of the Past 5747:2013CliPa...9.2525J 5735:Climate of the Past 5729:Jouzel, J. (2013). 5693:2007CliPa...3..325B 5681:Climate of the Past 5658:2010JGlac..56.1095A 5343:2007AnGla..47....1B 5119:2003JGRB..108.2090O 4959:2016EnST...50.7066A 4882:2011CliPa...7..707P 4870:Climate of the Past 4757:10.1038/nature14565 4749:2015Natur.523..543S 4649:2009ACP.....9.3911M 4588:Landais et al. 2012 4461:2016PNAS..113.3465B 4211:2003QSRv...22..141R 4060:2009JQS....24....3W 4019:on 5 September 2017 3932:Landais et al. 2012 3917:Blunier et al. 2007 3905:Landais et al. 2012 3893:Blunier et al. 2007 3844:2016TCry...10.3091U 3803:1992Radcb..34..431W 3709:2013CliPa...9.1715B 3697:Climate of the Past 3574:2003EOSTr..84..549H 3142:on 3 September 2017 3015:on 4 September 2017 2546:in Antarctica; the 2515:Erich von Drygalski 2466:Physical properties 1999:Terrestrial salts: 1901: 1686:Chlorofluorocarbons 877:, water containing 396:under high stress. 211:; isotopes such as 41:or a high mountain 7537:Incremental dating 7223:Subglacial volcano 7206:Volcanic relations 6873:Terminus post quem 6853:Synchronoptic view 6820:Linguistic methods 6781:Obsidian hydration 6716:Radiometric dating 6701:Incremental dating 6623:Chronostratigraphy 5895:Glaciological Data 5652:(200): 1095–1103. 5572:on 11 October 2017 4274:Souney et al. 2014 3605:Souney et al. 2014 3544:Souney et al. 2014 2659: 2628: 2501:In 1841 and 1842, 2499: 2456:South Pole Station 2344:, so the level of 2324: 1899: 1433: 1425: 1330: 1160:parts per thousand 1146: 767: 720:argon/argon dating 608:Radiocarbon dating 586:orbital parameters 582:palaeoenvironments 474: 372: 260: 170: 152:Ice-sheet dynamics 27: 7524: 7523: 7492: 7491: 7010:Accumulation zone 6886: 6885: 6799: 6798: 6656: 6655: 6517: 6516: 6472:Geologic Calendar 6334: 6333: 5957:978-7-116-09172-6 5885:978-0-415-74075-3 5859:10.1029/96RG03527 5632:978-0-691-10296-2 5366:Iaccarino, Tony. 4953:(13): 7066–7073. 4743:(7562): 543–549. 4643:(12): 3911–3934. 4617:978-0-521-84157-3 4455:(13): 3465–3470. 3669:978-0-470-86927-7 3510:UNH, Joe Souney. 3313:978-0-309-10635-1 3045:978-94-017-9540-1 2987:978-0-7487-4000-0 2944:978-0-12-386913-5 2841:List of ice cores 2773:Mount Kilimanjaro 2745:COVID-19 pandemic 2507:Unteraargletscher 2308: 2307: 1996:Aridity and wind 1721:hydrogen peroxide 1690:greenhouse effect 1119: 1095: 1069: 999: 790:Isotopic analysis 344:fatty-acid esters 340:dimethyl siloxane 187:crystal structure 7554: 7411:Terminal moraine 7243: 7242: 6979:Piedmont glacier 6913: 6906: 6899: 6890: 6889: 6878:ASPRO chronology 6827:Glottochronology 6743:Tephrochronology 6691:Dendrochronology 6669: 6668: 6566: 6565: 6365:Proleptic Julian 6355:Pre-Julian Roman 6345: 6344: 6140: 6139: 6056: 6049: 6042: 6033: 6032: 6002:Ice Core Gateway 5985: 5983: 5981: 5971: 5961: 5942: 5940: 5906: 5889: 5870: 5829: 5827: 5816: 5806: 5804: 5778: 5760: 5758: 5741:(6): 2525–2547. 5725: 5724:on 9 April 2017. 5723: 5716: 5706: 5704: 5671: 5669: 5636: 5608: 5607: 5591: 5582: 5581: 5579: 5577: 5562: 5556: 5550: 5544: 5538: 5532: 5526: 5520: 5514: 5508: 5502: 5496: 5490: 5484: 5483: 5480:protronix.co.uk/ 5472: 5466: 5465: 5463: 5461: 5451: 5445: 5444: 5442: 5440: 5435:on 18 March 2017 5424: 5418: 5412: 5406: 5405: 5403: 5401: 5386: 5380: 5379: 5377: 5375: 5363: 5357: 5356: 5354: 5322: 5316: 5310: 5297: 5291: 5280: 5274: 5268: 5262: 5256: 5250: 5244: 5238: 5232: 5226: 5217: 5211: 5205: 5199: 5193: 5187: 5181: 5175: 5169: 5163: 5157: 5151: 5145: 5139: 5133: 5132: 5130: 5098: 5092: 5091: 5089: 5065: 5059: 5058: 5056: 5054: 5048: 5041: 5032: 5026: 5020: 5014: 5013: 5002: 4996: 4993: 4987: 4986: 4944: 4935: 4929: 4928: 4926: 4902: 4896: 4895: 4893: 4861: 4855: 4849: 4843: 4837: 4831: 4825: 4816: 4810: 4804: 4798: 4792: 4786: 4777: 4776: 4727: 4721: 4715: 4706: 4700: 4694: 4693: 4669: 4663: 4662: 4660: 4628: 4622: 4621: 4604:Neelin, J. David 4600: 4591: 4585: 4579: 4578: 4576: 4574: 4569:on 8 August 2017 4568: 4562:. Archived from 4554:(1–2): 182–192. 4545: 4536: 4530: 4524: 4515: 4514: 4512: 4510: 4499: 4493: 4492: 4482: 4472: 4440: 4434: 4428: 4422: 4421:, pp. 2533–2534. 4416: 4407: 4406: 4404: 4402: 4390: 4384: 4383: 4381: 4379: 4364: 4358: 4352: 4346: 4340: 4331: 4325: 4319: 4313: 4300: 4299: 4297: 4295: 4283: 4277: 4271: 4265: 4264: 4250: 4241: 4235: 4229: 4223: 4222: 4196: 4187: 4178: 4172: 4149: 4143: 4137: 4131: 4125: 4119: 4113: 4107: 4101: 4100: 4088: 4082: 4081: 4071: 4069:10.1002/jqs.1227 4035: 4029: 4028: 4026: 4024: 4018: 4011: 4000: 3994: 3988: 3982: 3981: 3975: 3966: 3960: 3959: 3941: 3935: 3929: 3920: 3914: 3908: 3902: 3896: 3890: 3884: 3883: 3881: 3879: 3864: 3858: 3857: 3855: 3838:(6): 3091–3105. 3823: 3817: 3816: 3814: 3778: 3772: 3766: 3757: 3751: 3745: 3744:, pp. 2530–2531. 3739: 3733: 3732: 3730: 3720: 3703:(4): 1715–1731. 3687: 3681: 3680: 3679:on 14 July 2014. 3678: 3672:. Archived from 3661: 3650: 3644: 3638: 3632: 3630: 3614: 3608: 3602: 3589: 3587: 3585: 3553: 3547: 3541: 3528: 3527: 3525: 3523: 3507: 3498: 3497: 3495: 3493: 3478: 3472: 3466: 3460: 3459: 3457: 3455: 3446:. Archived from 3440:"About EastGRIP" 3435: 3429: 3423: 3417: 3416: 3414: 3412: 3403:. Archived from 3392: 3386: 3385: 3383: 3381: 3366: 3360: 3357: 3351: 3350: 3348: 3324: 3318: 3317: 3299: 3293: 3292: 3290: 3266: 3260: 3254: 3248: 3242: 3236: 3230: 3224: 3218: 3212: 3206: 3197: 3191: 3185: 3184: 3182: 3158: 3152: 3151: 3149: 3147: 3132: 3126: 3120: 3111: 3105: 3096: 3090: 3077: 3071: 3062: 3056: 3050: 3049: 3031: 3025: 3024: 3022: 3020: 3014: 3007: 2998: 2992: 2991: 2967: 2961: 2955: 2949: 2948: 2930: 2924: 2918: 2909: 2903: 2892: 2886: 2877: 2876: 2874: 2872: 2861: 2635:Franz Josef Land 2576:Little America V 2449:Other inclusions 2444: 2441: 2440: 2431: 2428: 2427: 2418: 2415: 2414: 2405: 2402: 2401: 2388: 2386: 2385: 2373: 2371: 2370: 2354: 2352: 2351: 2339: 2337: 2336: 2303: 2302: 2301: 2292: 2291: 2290: 2281: 2280: 2279: 2271: 2270: 2260: 2259: 2258: 2248: 2247: 2246: 2236: 2235: 2234: 2225: 2224: 2223: 2213: 2212: 2211: 2200: 2199: 2198: 2188: 2186: 2185: 2174: 2170: 2169: 2168: 2160: 2159: 2149: 2148: 2147: 2127: 2126: 2125: 2115: 2114: 2113: 2103: 2099: 2097: 2096: 2086: 2084: 2083: 2075: 2074: 2064: 2063: 2062: 2047:aluminosilicates 2044: 2043: 2042: 2032: 2031: 2030: 2020: 2019: 2018: 2009: 2008: 2007: 1988: 1987: 1986: 1977: 1976: 1975: 1965: 1964: 1963: 1954: 1953: 1952: 1943: 1942: 1941: 1932: 1931: 1930: 1902: 1898: 1895: 1894: 1893: 1885: 1884: 1859: 1853: 1851: 1850: 1842: 1841: 1830: 1829: 1828: 1820: 1819: 1808:Methanesulfonate 1801: 1799: 1798: 1790: 1789: 1778: 1776: 1775: 1734:eruption of Laki 1667: 1665: 1664: 1656: 1654: 1653: 1634: 1633: 1632: 1622: 1621: 1620: 1610: 1609: 1608: 1598: 1597: 1596: 1586: 1585: 1584: 1574: 1573: 1572: 1562: 1561: 1560: 1550: 1549: 1548: 1538: 1537: 1536: 1526: 1524: 1523: 1513: 1512: 1511: 1481: 1480: 1479: 1466: 1465: 1464: 1450: 1449: 1448: 1402: 1401: 1400: 1386: 1384: 1383: 1375: 1373: 1372: 1339: 1337: 1336: 1331: 1326: 1318: 1314: 1313: 1294: 1277: 1270: 1263: 1257: 1252: 1250: 1249: 1241: 1239: 1238: 1220: 1212: 1209:. Combining the 1205: 1201: 1199: 1198: 1187: 1183: 1181: 1180: 1172: 1170: 1169: 1155: 1153: 1152: 1147: 1142: 1141: 1131: 1125: 1124: 1117: 1109: 1108: 1096: 1094: 1093: 1092: 1078: 1077: 1070: 1068: 1064: 1063: 1054: 1050: 1049: 1040: 1038: 1037: 1030: 1029: 1028: 1008: 1007: 1000: 998: 994: 993: 984: 980: 979: 970: 968: 967: 960: 958: 957: 948: 944: 943: 920: 918: 917: 909: 907: 906: 898: 896: 895: 887: 885: 884: 876: 874: 873: 866:is lighter than 865: 863: 862: 854: 852: 851: 843: 841: 840: 832: 829: 828: 819: 816: 815: 806: 803: 802: 709: 708: 707: 677: 675: 674: 665: 663: 662: 653: 652: 651: 633: 632: 631: 621: 620: 619: 528: 516: 114:in Antarctica. 7562: 7561: 7557: 7556: 7555: 7553: 7552: 7551: 7527: 7526: 7525: 7520: 7488: 7425: 7406:Sevetti moraine 7364: 7318:Roche moutonnée 7263:Cirque stairway 7232: 7201: 7180: 7104: 7065:Lateral moraine 6993: 6922: 6917: 6887: 6882: 6831: 6815: 6811:Molecular clock 6804:Genetic methods 6795: 6776:Nitrogen dating 6763:Relative dating 6757: 6726:Potassium–argon 6673:Absolute dating 6663: 6652: 6611: 6590: 6555: 6531:Cosmic Calendar 6523:Astronomic time 6513: 6455: 6410: 6374: 6360:Original Julian 6330: 6297: 6259: 6158:Ab urbe condita 6136: 6113: 6065: 6060: 5993: 5988: 5979: 5977: 5969: 5958: 5886: 5825: 5814: 5776: 5773: 5769: 5721: 5714: 5633: 5616: 5611: 5600:Popular Science 5592: 5585: 5575: 5573: 5564: 5563: 5559: 5551: 5547: 5539: 5535: 5527: 5523: 5515: 5511: 5503: 5499: 5491: 5487: 5474: 5473: 5469: 5459: 5457: 5453: 5452: 5448: 5438: 5436: 5429:"Documentation" 5425: 5421: 5413: 5409: 5399: 5397: 5388: 5387: 5383: 5373: 5371: 5364: 5360: 5323: 5319: 5311: 5300: 5292: 5283: 5275: 5271: 5263: 5259: 5251: 5247: 5239: 5235: 5227: 5220: 5212: 5208: 5200: 5196: 5188: 5184: 5176: 5172: 5164: 5160: 5152: 5148: 5140: 5136: 5113:(B2): 6–1–6–2. 5099: 5095: 5066: 5062: 5052: 5050: 5046: 5039: 5033: 5029: 5021: 5017: 5004: 5003: 4999: 4994: 4990: 4942: 4936: 4932: 4903: 4899: 4862: 4858: 4850: 4846: 4838: 4834: 4826: 4819: 4811: 4807: 4799: 4795: 4787: 4780: 4728: 4724: 4720:, pp. 222, 225. 4716: 4709: 4701: 4697: 4676:measurements". 4675: 4670: 4666: 4629: 4625: 4618: 4601: 4594: 4586: 4582: 4572: 4570: 4566: 4543: 4537: 4533: 4525: 4518: 4508: 4506: 4501: 4500: 4496: 4441: 4437: 4429: 4425: 4417: 4410: 4400: 4398: 4391: 4387: 4377: 4375: 4374:on 10 July 2017 4366: 4365: 4361: 4353: 4349: 4341: 4334: 4326: 4322: 4314: 4303: 4293: 4291: 4284: 4280: 4272: 4268: 4248: 4242: 4238: 4230: 4226: 4194: 4188: 4181: 4173: 4152: 4144: 4140: 4132: 4128: 4120: 4116: 4108: 4104: 4089: 4085: 4036: 4032: 4022: 4020: 4016: 4009: 4001: 3997: 3989: 3985: 3973: 3967: 3963: 3956: 3942: 3938: 3930: 3923: 3915: 3911: 3903: 3899: 3891: 3887: 3877: 3875: 3866: 3865: 3861: 3824: 3820: 3779: 3775: 3767: 3760: 3752: 3748: 3740: 3736: 3688: 3684: 3676: 3670: 3659: 3651: 3647: 3639: 3635: 3615: 3611: 3603: 3592: 3554: 3550: 3542: 3531: 3521: 3519: 3508: 3501: 3491: 3489: 3479: 3475: 3467: 3463: 3453: 3451: 3450:on 28 June 2017 3436: 3432: 3424: 3420: 3410: 3408: 3407:on 28 June 2017 3393: 3389: 3379: 3377: 3367: 3363: 3358: 3354: 3339:(68): 131–136. 3325: 3321: 3314: 3300: 3296: 3281:(68): 322–330. 3267: 3263: 3255: 3251: 3243: 3239: 3231: 3227: 3219: 3215: 3207: 3200: 3192: 3188: 3173:(68): 260–270. 3159: 3155: 3145: 3143: 3134: 3133: 3129: 3121: 3114: 3106: 3099: 3091: 3080: 3072: 3065: 3057: 3053: 3046: 3032: 3028: 3018: 3016: 3012: 3005: 2999: 2995: 2988: 2968: 2964: 2956: 2952: 2945: 2931: 2927: 2919: 2912: 2904: 2895: 2887: 2880: 2870: 2868: 2862: 2858: 2854: 2837: 2821:warming climate 2781: 2769:monsoon seasons 2753: 2751:Non-polar cores 2721: 2677:McMurdo Station 2625: 2616: 2544:Queen Maud Land 2521:, described by 2519:James E. Church 2491: 2486: 2480: 2468: 2451: 2439: 2437: 2436: 2435: 2433: 2426: 2424: 2423: 2422: 2420: 2413: 2411: 2410: 2409: 2407: 2400: 2398: 2397: 2396: 2394: 2384: 2382: 2381: 2380: 2379: 2369: 2367: 2366: 2365: 2364: 2350: 2348: 2347: 2346: 2345: 2342:solar radiation 2335: 2333: 2332: 2331: 2330: 2313: 2300: 2298: 2297: 2296: 2294: 2289: 2287: 2286: 2285: 2283: 2278: 2275: 2274: 2273: 2269: 2266: 2265: 2264: 2262: 2257: 2254: 2253: 2252: 2250: 2245: 2242: 2241: 2240: 2238: 2233: 2231: 2230: 2229: 2227: 2222: 2219: 2218: 2217: 2215: 2210: 2208: 2207: 2206: 2204: 2197: 2194: 2193: 2192: 2190: 2184: 2181: 2180: 2179: 2176: 2172: 2167: 2164: 2163: 2162: 2158: 2155: 2154: 2153: 2151: 2146: 2143: 2142: 2141: 2139: 2124: 2121: 2120: 2119: 2117: 2112: 2109: 2108: 2107: 2105: 2101: 2095: 2092: 2091: 2090: 2088: 2082: 2079: 2078: 2077: 2073: 2070: 2069: 2068: 2066: 2061: 2058: 2057: 2056: 2054: 2041: 2038: 2037: 2036: 2034: 2029: 2026: 2025: 2024: 2022: 2017: 2015: 2014: 2013: 2011: 2006: 2004: 2003: 2002: 2000: 1985: 1983: 1982: 1981: 1979: 1974: 1971: 1970: 1969: 1967: 1962: 1960: 1959: 1958: 1956: 1951: 1949: 1948: 1947: 1945: 1940: 1938: 1937: 1936: 1934: 1929: 1927: 1926: 1925: 1923: 1919:Waves and wind 1892: 1889: 1888: 1887: 1883: 1880: 1879: 1878: 1876: 1855: 1849: 1846: 1845: 1844: 1840: 1837: 1836: 1835: 1832: 1827: 1824: 1823: 1822: 1818: 1815: 1814: 1813: 1811: 1797: 1794: 1793: 1792: 1788: 1785: 1784: 1783: 1780: 1774: 1771: 1770: 1769: 1766: 1717: 1715:Glaciochemistry 1710: 1706: 1692:and also cause 1663: 1661: 1660: 1659: 1658: 1652: 1650: 1649: 1648: 1647: 1631: 1628: 1627: 1626: 1624: 1619: 1616: 1615: 1614: 1612: 1607: 1604: 1603: 1602: 1600: 1595: 1592: 1591: 1590: 1588: 1583: 1580: 1579: 1578: 1576: 1571: 1568: 1567: 1566: 1564: 1563:(nitrogen) and 1559: 1556: 1555: 1554: 1552: 1547: 1544: 1543: 1542: 1540: 1535: 1532: 1531: 1530: 1528: 1522: 1519: 1518: 1517: 1515: 1510: 1507: 1506: 1505: 1503: 1478: 1475: 1474: 1473: 1471: 1463: 1460: 1459: 1458: 1456: 1447: 1444: 1443: 1442: 1440: 1437:paleoatmosphere 1421:Vostok ice core 1418: 1409: 1399: 1396: 1395: 1394: 1392: 1382: 1380: 1379: 1378: 1377: 1371: 1369: 1368: 1367: 1366: 1322: 1309: 1305: 1304: 1287: 1285: 1282: 1281: 1275: 1273: 1268: 1266: 1261: 1255: 1248: 1246: 1245: 1244: 1243: 1237: 1235: 1234: 1233: 1232: 1223: 1218: 1215: 1210: 1208: 1203: 1202:has a negative 1197: 1195: 1194: 1193: 1192: 1190: 1185: 1179: 1177: 1176: 1175: 1174: 1168: 1166: 1165: 1164: 1163: 1134: 1132: 1127: 1120: 1116: 1104: 1103: 1079: 1073: 1072: 1071: 1059: 1056: 1055: 1045: 1042: 1041: 1039: 1033: 1032: 1031: 1009: 1003: 1002: 1001: 989: 986: 985: 975: 972: 971: 969: 963: 962: 961: 959: 953: 952: 939: 935: 934: 932: 929: 928: 916: 914: 913: 912: 911: 905: 903: 902: 901: 900: 894: 892: 891: 890: 889: 883: 881: 880: 879: 878: 872: 870: 869: 868: 867: 861: 859: 858: 857: 856: 850: 848: 847: 846: 845: 839: 837: 836: 835: 834: 827: 825: 824: 823: 821: 814: 812: 811: 810: 808: 801: 799: 798: 797: 795: 792: 758: 756:Visual analysis 706: 703: 702: 701: 699: 673: 671: 670: 669: 668: 661: 659: 658: 657: 656: 650: 647: 646: 645: 643: 630: 627: 626: 625: 623: 618: 615: 614: 613: 611: 566: 561: 540: 539: 538: 537: 536: 529: 521: 520: 517: 506: 485:thermal shock. 462: 460:Core processing 417: 336:n-butyl acetate 330:solutions; and 324:ethylene glycol 280:electric drills 252: 246: 231:make some snow 221:micrometeorites 154: 148: 101:nuclear testing 93:wind-blown dust 17: 12: 11: 5: 7560: 7550: 7549: 7544: 7539: 7522: 7521: 7519: 7518: 7513: 7508: 7503: 7497: 7494: 7493: 7490: 7489: 7487: 7486: 7481: 7476: 7471: 7466: 7461: 7456: 7451: 7446: 7441: 7435: 7433: 7427: 7426: 7424: 7423: 7418: 7413: 7408: 7403: 7398: 7393: 7388: 7383: 7378: 7372: 7370: 7366: 7365: 7363: 7362: 7355: 7350: 7345: 7340: 7335: 7330: 7325: 7320: 7315: 7310: 7305: 7300: 7298:Hanging valley 7295: 7293:Glacial striae 7290: 7285: 7280: 7275: 7270: 7265: 7260: 7255: 7249: 7247: 7240: 7234: 7233: 7231: 7230: 7225: 7220: 7215: 7209: 7207: 7203: 7202: 7200: 7199: 7194: 7188: 7186: 7182: 7181: 7179: 7178: 7173: 7168: 7163: 7158: 7156:Periglaciation 7153: 7148: 7146:Outburst flood 7143: 7138: 7133: 7128: 7123: 7118: 7112: 7110: 7106: 7105: 7103: 7102: 7097: 7092: 7087: 7082: 7077: 7072: 7070:Medial moraine 7067: 7062: 7057: 7055:Glacier tongue 7052: 7047: 7042: 7037: 7032: 7027: 7022: 7017: 7012: 7007: 7001: 6999: 6995: 6994: 6992: 6991: 6989:Valley glacier 6986: 6981: 6976: 6974:Outlet glacier 6971: 6966: 6961: 6956: 6951: 6946: 6941: 6936: 6930: 6928: 6924: 6923: 6916: 6915: 6908: 6901: 6893: 6884: 6883: 6881: 6880: 6875: 6870: 6865: 6860: 6855: 6850: 6848:New Chronology 6845: 6839: 6837: 6836:Related topics 6833: 6832: 6830: 6829: 6823: 6821: 6817: 6816: 6814: 6813: 6807: 6805: 6801: 6800: 6797: 6796: 6794: 6793: 6788: 6783: 6778: 6773: 6767: 6765: 6759: 6758: 6756: 6755: 6750: 6745: 6740: 6739: 6738: 6733: 6728: 6723: 6713: 6711:Paleomagnetism 6708: 6703: 6698: 6693: 6688: 6683: 6677: 6675: 6666: 6658: 6657: 6654: 6653: 6651: 6650: 6645: 6640: 6635: 6630: 6625: 6619: 6617: 6613: 6612: 6610: 6609: 6604: 6598: 6596: 6592: 6591: 6589: 6588: 6583: 6578: 6572: 6570: 6563: 6557: 6556: 6554: 6553: 6548: 6543: 6538: 6533: 6527: 6525: 6519: 6518: 6515: 6514: 6512: 6511: 6509:New Earth Time 6506: 6501: 6500: 6499: 6494: 6484: 6479: 6474: 6469: 6463: 6461: 6457: 6456: 6454: 6453: 6448: 6438: 6433: 6418: 6416: 6412: 6411: 6409: 6408: 6403: 6398: 6393: 6388: 6382: 6380: 6376: 6375: 6373: 6372: 6370:Revised Julian 6367: 6362: 6357: 6351: 6349: 6342: 6336: 6335: 6332: 6331: 6329: 6328: 6323: 6318: 6313: 6307: 6305: 6299: 6298: 6296: 6295: 6290: 6288:Lists of kings 6285: 6280: 6278:Canon of Kings 6275: 6269: 6267: 6261: 6260: 6258: 6257: 6256: 6255: 6250: 6245: 6240: 6230: 6220: 6215: 6210: 6205: 6203:Before present 6200: 6195: 6190: 6185: 6180: 6175: 6170: 6161: 6154: 6148: 6146: 6137: 6135: 6134: 6129: 6124: 6118: 6115: 6114: 6112: 6111: 6106: 6101: 6100: 6099: 6089: 6084: 6079: 6073: 6071: 6067: 6066: 6059: 6058: 6051: 6044: 6036: 6030: 6029: 6027:Third Pole ice 6024: 6019: 6014: 6009: 6004: 5999: 5992: 5991:External links 5989: 5987: 5986: 5962: 5956: 5943: 5907: 5890: 5884: 5871: 5845:(3): 219–243. 5830: 5807: 5787:(1): 191–203. 5771: 5767: 5761: 5726: 5707: 5687:(2): 325–330. 5672: 5637: 5631: 5617: 5615: 5612: 5610: 5609: 5583: 5557: 5553:MacKinnon 1980 5545: 5541:MacKinnon 1980 5533: 5529:MacKinnon 1980 5521: 5517:MacKinnon 1980 5509: 5505:MacKinnon 1980 5497: 5493:MacKinnon 1980 5485: 5467: 5446: 5419: 5407: 5381: 5358: 5317: 5298: 5281: 5269: 5257: 5245: 5233: 5218: 5206: 5194: 5182: 5170: 5158: 5146: 5134: 5093: 5060: 5027: 5015: 4997: 4988: 4930: 4897: 4876:(3): 707–708. 4856: 4844: 4842:, pp. 227–228. 4832: 4817: 4805: 4803:, pp. 231–232. 4793: 4778: 4722: 4707: 4695: 4684:(4): 391–396. 4673: 4664: 4623: 4616: 4592: 4580: 4531: 4516: 4494: 4435: 4423: 4408: 4385: 4359: 4347: 4332: 4320: 4318:, pp. 165–170. 4301: 4278: 4266: 4255:. 84–85: 1–4. 4236: 4224: 4205:(2): 141–155. 4179: 4150: 4138: 4126: 4114: 4102: 4083: 4040:Björck, Svante 4030: 3995: 3983: 3961: 3954: 3936: 3921: 3919:, pp. 325–327. 3909: 3907:, pp. 191–192. 3897: 3885: 3859: 3832:The Cryosphere 3818: 3797:(3): 431–435. 3773: 3758: 3746: 3734: 3682: 3668: 3645: 3643:, pp. 265–266. 3633: 3609: 3590: 3548: 3529: 3499: 3487:The New Yorker 3473: 3461: 3430: 3418: 3387: 3361: 3352: 3319: 3312: 3294: 3261: 3259:, pp. 252–254. 3249: 3247:, pp. 173–175. 3237: 3235:, pp. 109–111. 3225: 3213: 3198: 3196:, pp. 259–263. 3186: 3153: 3127: 3112: 3097: 3078: 3063: 3051: 3044: 3026: 2993: 2986: 2962: 2950: 2943: 2925: 2910: 2893: 2878: 2855: 2853: 2850: 2849: 2848: 2843: 2836: 2833: 2817: 2816: 2813: 2810: 2807: 2804: 2801: 2798: 2795: 2792: 2780: 2777: 2767:events and of 2752: 2749: 2720: 2717: 2693:Berkner Island 2666:Kohnen Station 2623: 2615: 2612: 2580:Ross Ice Shelf 2531:Alfred Wegener 2490: 2487: 2479: 2476: 2467: 2464: 2450: 2447: 2445:, 172 years). 2438: 2425: 2412: 2399: 2383: 2368: 2359:for climate. 2349: 2334: 2312: 2309: 2306: 2305: 2299: 2288: 2276: 2267: 2255: 2243: 2232: 2220: 2209: 2202: 2195: 2182: 2165: 2156: 2144: 2136: 2122: 2110: 2093: 2080: 2071: 2059: 2050: 2049: 2039: 2027: 2016: 2005: 1997: 1994: 1990: 1989: 1984: 1972: 1961: 1950: 1939: 1928: 1920: 1917: 1913: 1912: 1909: 1906: 1890: 1881: 1847: 1838: 1825: 1816: 1795: 1786: 1772: 1716: 1713: 1708: 1704: 1662: 1651: 1629: 1617: 1605: 1593: 1581: 1569: 1557: 1545: 1533: 1520: 1508: 1500:orbital cycles 1476: 1461: 1445: 1416: 1408: 1405: 1397: 1381: 1370: 1329: 1325: 1321: 1317: 1312: 1308: 1303: 1300: 1297: 1293: 1290: 1272: 1265: 1247: 1236: 1222: 1214: 1207: 1196: 1189: 1178: 1167: 1145: 1140: 1137: 1130: 1123: 1115: 1112: 1107: 1102: 1099: 1091: 1088: 1085: 1082: 1076: 1067: 1062: 1058: 1053: 1048: 1044: 1036: 1027: 1024: 1021: 1018: 1015: 1012: 1006: 997: 992: 988: 983: 978: 974: 966: 956: 951: 947: 942: 938: 915: 904: 893: 882: 871: 860: 849: 838: 826: 813: 800: 791: 788: 757: 754: 743:palaeoclimatic 704: 692:Laschamp event 672: 660: 648: 628: 616: 565: 562: 560: 557: 530: 523: 522: 518: 511: 510: 509: 508: 507: 505: 502: 461: 458: 416: 413: 296:drilling fluid 245: 242: 147: 144: 120:Vostok Station 70:carbon dioxide 15: 9: 6: 4: 3: 2: 7559: 7548: 7545: 7543: 7540: 7538: 7535: 7534: 7532: 7517: 7514: 7512: 7509: 7507: 7504: 7502: 7499: 7498: 7495: 7485: 7482: 7480: 7477: 7475: 7472: 7470: 7467: 7465: 7462: 7460: 7457: 7455: 7452: 7450: 7447: 7445: 7442: 7440: 7437: 7436: 7434: 7432: 7431:Glaciofluvial 7428: 7422: 7421:Veiki moraine 7419: 7417: 7414: 7412: 7409: 7407: 7404: 7402: 7401:Rogen moraine 7399: 7397: 7396:Pulju moraine 7394: 7392: 7389: 7387: 7384: 7382: 7381:Erratic block 7379: 7377: 7374: 7373: 7371: 7367: 7361: 7360: 7356: 7354: 7351: 7349: 7346: 7344: 7343:Tunnel valley 7341: 7339: 7338:Trough valley 7336: 7334: 7331: 7329: 7326: 7324: 7321: 7319: 7316: 7314: 7311: 7309: 7306: 7304: 7301: 7299: 7296: 7294: 7291: 7289: 7286: 7284: 7281: 7279: 7276: 7274: 7271: 7269: 7268:Crag and tail 7266: 7264: 7261: 7259: 7256: 7254: 7251: 7250: 7248: 7244: 7241: 7239: 7235: 7229: 7226: 7224: 7221: 7219: 7216: 7214: 7211: 7210: 7208: 7204: 7198: 7195: 7193: 7190: 7189: 7187: 7183: 7177: 7174: 7172: 7169: 7167: 7164: 7162: 7159: 7157: 7154: 7152: 7151:Overdeepening 7149: 7147: 7144: 7142: 7139: 7137: 7134: 7132: 7129: 7127: 7126:Basal sliding 7124: 7122: 7119: 7117: 7114: 7113: 7111: 7107: 7101: 7098: 7096: 7093: 7091: 7088: 7086: 7083: 7081: 7078: 7076: 7073: 7071: 7068: 7066: 7063: 7061: 7058: 7056: 7053: 7051: 7048: 7046: 7043: 7041: 7038: 7036: 7033: 7031: 7028: 7026: 7023: 7021: 7018: 7016: 7013: 7011: 7008: 7006: 7005:Ablation zone 7003: 7002: 7000: 6996: 6990: 6987: 6985: 6982: 6980: 6977: 6975: 6972: 6970: 6967: 6965: 6962: 6960: 6957: 6955: 6952: 6950: 6947: 6945: 6942: 6940: 6937: 6935: 6932: 6931: 6929: 6925: 6921: 6914: 6909: 6907: 6902: 6900: 6895: 6894: 6891: 6879: 6876: 6874: 6871: 6869: 6866: 6864: 6861: 6859: 6856: 6854: 6851: 6849: 6846: 6844: 6841: 6840: 6838: 6834: 6828: 6825: 6824: 6822: 6818: 6812: 6809: 6808: 6806: 6802: 6792: 6789: 6787: 6784: 6782: 6779: 6777: 6774: 6772: 6769: 6768: 6766: 6764: 6760: 6754: 6751: 6749: 6746: 6744: 6741: 6737: 6734: 6732: 6729: 6727: 6724: 6722: 6719: 6718: 6717: 6714: 6712: 6709: 6707: 6704: 6702: 6699: 6697: 6694: 6692: 6689: 6687: 6684: 6682: 6679: 6678: 6676: 6674: 6670: 6667: 6665: 6662:Chronological 6659: 6649: 6646: 6644: 6641: 6639: 6636: 6634: 6631: 6629: 6628:Geochronology 6626: 6624: 6621: 6620: 6618: 6614: 6608: 6605: 6603: 6600: 6599: 6597: 6593: 6587: 6584: 6582: 6579: 6577: 6574: 6573: 6571: 6567: 6564: 6562: 6561:Geologic time 6558: 6552: 6549: 6547: 6546:Metonic cycle 6544: 6542: 6541:Galactic year 6539: 6537: 6534: 6532: 6529: 6528: 6526: 6524: 6520: 6510: 6507: 6505: 6502: 6498: 6495: 6493: 6490: 6489: 6488: 6485: 6483: 6482:ISO week date 6480: 6478: 6475: 6473: 6470: 6468: 6465: 6464: 6462: 6458: 6452: 6449: 6446: 6442: 6439: 6437: 6434: 6431: 6427: 6423: 6420: 6419: 6417: 6413: 6407: 6404: 6402: 6399: 6397: 6394: 6392: 6389: 6387: 6384: 6383: 6381: 6377: 6371: 6368: 6366: 6363: 6361: 6358: 6356: 6353: 6352: 6350: 6346: 6343: 6341: 6337: 6327: 6324: 6322: 6319: 6317: 6314: 6312: 6309: 6308: 6306: 6304: 6300: 6294: 6291: 6289: 6286: 6284: 6281: 6279: 6276: 6274: 6271: 6270: 6268: 6266: 6262: 6254: 6251: 6249: 6246: 6244: 6241: 6239: 6236: 6235: 6234: 6231: 6228: 6224: 6221: 6219: 6216: 6214: 6211: 6209: 6206: 6204: 6201: 6199: 6196: 6194: 6191: 6189: 6188:Byzantine era 6186: 6184: 6181: 6179: 6176: 6174: 6171: 6169: 6165: 6162: 6160: 6159: 6155: 6153: 6150: 6149: 6147: 6145: 6144:Calendar eras 6141: 6138: 6133: 6130: 6128: 6125: 6123: 6120: 6119: 6116: 6110: 6107: 6105: 6102: 6098: 6095: 6094: 6093: 6090: 6088: 6085: 6083: 6080: 6078: 6075: 6074: 6072: 6068: 6064: 6057: 6052: 6050: 6045: 6043: 6038: 6037: 6034: 6028: 6025: 6023: 6020: 6018: 6015: 6013: 6010: 6008: 6005: 6003: 6000: 5998: 5995: 5994: 5975: 5968: 5963: 5959: 5953: 5949: 5944: 5939: 5934: 5930: 5926: 5923:(68): 15–26. 5922: 5918: 5914: 5908: 5904: 5900: 5896: 5891: 5887: 5881: 5877: 5872: 5868: 5864: 5860: 5856: 5852: 5848: 5844: 5840: 5836: 5831: 5824: 5820: 5813: 5808: 5803: 5798: 5794: 5790: 5786: 5782: 5775: 5762: 5757: 5752: 5748: 5744: 5740: 5736: 5732: 5727: 5720: 5713: 5708: 5703: 5698: 5694: 5690: 5686: 5682: 5678: 5673: 5668: 5663: 5659: 5655: 5651: 5647: 5643: 5638: 5634: 5628: 5624: 5619: 5618: 5605: 5601: 5597: 5590: 5588: 5571: 5567: 5561: 5554: 5549: 5542: 5537: 5530: 5525: 5518: 5513: 5506: 5501: 5494: 5489: 5481: 5477: 5471: 5456: 5450: 5434: 5430: 5423: 5416: 5411: 5395: 5391: 5385: 5369: 5362: 5353: 5348: 5344: 5340: 5336: 5332: 5328: 5321: 5314: 5309: 5307: 5305: 5303: 5295: 5290: 5288: 5286: 5278: 5273: 5266: 5261: 5254: 5249: 5242: 5237: 5230: 5225: 5223: 5215: 5210: 5203: 5198: 5191: 5186: 5179: 5174: 5167: 5162: 5155: 5150: 5143: 5138: 5129: 5124: 5120: 5116: 5112: 5108: 5104: 5097: 5088: 5083: 5079: 5075: 5071: 5064: 5045: 5038: 5031: 5024: 5019: 5011: 5007: 5006:"Future Work" 5001: 4992: 4984: 4980: 4976: 4972: 4968: 4964: 4960: 4956: 4952: 4948: 4941: 4934: 4925: 4920: 4916: 4912: 4908: 4901: 4892: 4887: 4883: 4879: 4875: 4871: 4867: 4860: 4853: 4848: 4841: 4836: 4829: 4824: 4822: 4814: 4809: 4802: 4797: 4790: 4785: 4783: 4774: 4770: 4766: 4762: 4758: 4754: 4750: 4746: 4742: 4738: 4734: 4726: 4719: 4714: 4712: 4704: 4699: 4691: 4687: 4683: 4679: 4668: 4659: 4654: 4650: 4646: 4642: 4638: 4634: 4627: 4619: 4613: 4609: 4605: 4599: 4597: 4589: 4584: 4565: 4561: 4557: 4553: 4549: 4542: 4535: 4528: 4523: 4521: 4504: 4498: 4490: 4486: 4481: 4476: 4471: 4466: 4462: 4458: 4454: 4450: 4446: 4439: 4432: 4427: 4420: 4415: 4413: 4396: 4389: 4373: 4369: 4363: 4356: 4351: 4344: 4339: 4337: 4329: 4324: 4317: 4312: 4310: 4308: 4306: 4289: 4282: 4275: 4270: 4262: 4258: 4254: 4247: 4240: 4233: 4228: 4220: 4216: 4212: 4208: 4204: 4200: 4193: 4186: 4184: 4176: 4171: 4169: 4167: 4165: 4163: 4161: 4159: 4157: 4155: 4147: 4142: 4135: 4130: 4123: 4118: 4111: 4106: 4098: 4094: 4087: 4079: 4075: 4070: 4065: 4061: 4057: 4053: 4049: 4045: 4041: 4034: 4015: 4008: 4007: 3999: 3992: 3987: 3979: 3972: 3965: 3957: 3955:9780444536426 3951: 3947: 3940: 3933: 3928: 3926: 3918: 3913: 3906: 3901: 3894: 3889: 3873: 3869: 3863: 3854: 3849: 3845: 3841: 3837: 3833: 3829: 3822: 3813: 3808: 3804: 3800: 3796: 3792: 3788: 3786: 3777: 3770: 3765: 3763: 3755: 3750: 3743: 3738: 3729: 3724: 3719: 3714: 3710: 3706: 3702: 3698: 3694: 3686: 3675: 3671: 3665: 3658: 3657: 3649: 3642: 3637: 3628: 3624: 3620: 3613: 3606: 3601: 3599: 3597: 3595: 3584: 3579: 3575: 3571: 3567: 3563: 3562:Eos Trans AGU 3559: 3552: 3545: 3540: 3538: 3536: 3534: 3518:on 4 May 2017 3517: 3513: 3506: 3504: 3488: 3484: 3477: 3470: 3465: 3449: 3445: 3441: 3434: 3427: 3422: 3406: 3402: 3398: 3391: 3376: 3372: 3365: 3356: 3347: 3342: 3338: 3334: 3330: 3323: 3315: 3309: 3305: 3298: 3289: 3284: 3280: 3276: 3272: 3265: 3258: 3253: 3246: 3241: 3234: 3229: 3222: 3217: 3210: 3205: 3203: 3195: 3190: 3181: 3176: 3172: 3168: 3164: 3157: 3141: 3137: 3131: 3124: 3119: 3117: 3109: 3104: 3102: 3094: 3089: 3087: 3085: 3083: 3075: 3070: 3068: 3060: 3055: 3047: 3041: 3037: 3030: 3011: 3004: 2997: 2989: 2983: 2979: 2975: 2974: 2966: 2959: 2954: 2946: 2940: 2936: 2929: 2922: 2917: 2915: 2907: 2902: 2900: 2898: 2890: 2885: 2883: 2867: 2860: 2856: 2847: 2844: 2842: 2839: 2838: 2832: 2830: 2826: 2822: 2814: 2811: 2808: 2805: 2802: 2799: 2796: 2793: 2789: 2788: 2787: 2785: 2776: 2774: 2770: 2766: 2762: 2758: 2748: 2746: 2742: 2738: 2734: 2730: 2726: 2716: 2713: 2708: 2706: 2702: 2698: 2694: 2690: 2686: 2682: 2678: 2674: 2669: 2667: 2663: 2655: 2651: 2648: 2644: 2643:Novaya Zemlya 2640: 2636: 2632: 2620: 2611: 2609: 2608:Devon Ice Cap 2605: 2601: 2597: 2593: 2588: 2585: 2581: 2577: 2573: 2568: 2564: 2559: 2557: 2553: 2549: 2545: 2541: 2537: 2532: 2527: 2524: 2523:Pavel Talalay 2520: 2516: 2512: 2508: 2504: 2503:Louis Agassiz 2495: 2485: 2475: 2473: 2463: 2461: 2457: 2446: 2443: 2430: 2417: 2404: 2392: 2377: 2362: 2358: 2343: 2328: 2321: 2317: 2311:Radionuclides 2203: 2187: 2137: 2135: 2131: 2052: 2051: 2048: 1998: 1995: 1992: 1991: 1921: 1918: 1915: 1914: 1910: 1907: 1904: 1903: 1897: 1873: 1871: 1867: 1863: 1858: 1852: 1809: 1805: 1800: 1777: 1764: 1760: 1756: 1752: 1747: 1745: 1740: 1735: 1730: 1726: 1722: 1712: 1701: 1699: 1695: 1691: 1687: 1683: 1679: 1675: 1671: 1668:ratio and of 1645: 1644:fractionation 1640: 1636: 1501: 1497: 1493: 1489: 1485: 1468: 1454: 1438: 1429: 1422: 1413: 1404: 1390: 1364: 1360: 1356: 1352: 1347: 1345: 1340: 1327: 1319: 1310: 1306: 1301: 1298: 1295: 1288: 1279: 1259: 1230: 1225: 1161: 1156: 1143: 1138: 1135: 1128: 1121: 1113: 1110: 1100: 1097: 1060: 1057: 1046: 1043: 990: 987: 976: 973: 949: 940: 936: 926: 924: 831: 818: 805: 787: 783: 779: 775: 771: 762: 753: 751: 750:Richard Alley 746: 744: 740: 736: 731: 729: 725: 724:Uranium decay 721: 717: 713: 697: 693: 687: 685: 681: 666: 641: 637: 609: 605: 601: 599: 594: 589: 587: 583: 579: 575: 574:radionuclides 571: 559:Ice core data 556: 552: 550: 545: 534: 527: 515: 501: 499: 494: 492: 486: 483: 477: 471: 466: 457: 455: 451: 448:owned by the 447: 443: 439: 435: 431: 427: 423: 412: 408: 406: 402: 397: 393: 392:to the core. 391: 390:thermal shock 387: 381: 378: 368: 364: 362: 357: 352: 347: 345: 341: 337: 333: 329: 325: 321: 320:fluorocarbons 317: 313: 308: 304: 299: 297: 293: 288: 285: 281: 277: 273: 269: 265: 256: 251: 241: 238: 234: 228: 226: 222: 218: 214: 210: 206: 201: 199: 194: 192: 188: 184: 180: 176: 167: 163: 158: 153: 143: 141: 137: 133: 129: 125: 121: 117: 113: 109: 104: 102: 98: 94: 90: 86: 81: 79: 78:climate model 75: 71: 67: 63: 59: 54: 52: 48: 44: 40: 36: 32: 23: 19: 7369:Depositional 7359:Zungenbecken 7357: 7288:Glacial lake 7283:Glacial horn 7197:Mass balance 7191: 7185:Measurements 7121:Accumulation 7045:Glacier head 7040:Glacier cave 6984:Rock glacier 6791:Stratigraphy 6736:Uranium–lead 6706:Lichenometry 6695: 6504:Winter count 6487:Mesoamerican 6415:Astronomical 6233:Mesoamerican 6218:Sothic cycle 6193:Seleucid era 6178:Bosporan era 6166: / 6156: 6104:Paleontology 5980:14 September 5978:. Retrieved 5947: 5920: 5916: 5894: 5875: 5842: 5838: 5823:the original 5819:CRREL Report 5818: 5784: 5780: 5738: 5734: 5719:the original 5684: 5680: 5649: 5645: 5622: 5599: 5574:. Retrieved 5570:the original 5560: 5548: 5536: 5524: 5512: 5500: 5488: 5479: 5470: 5458:. Retrieved 5449: 5437:. Retrieved 5433:the original 5422: 5417:, pp. 27–28. 5415:Langway 2008 5410: 5398:. Retrieved 5393: 5384: 5372:. Retrieved 5361: 5334: 5330: 5320: 5272: 5260: 5255:, pp. 50–58. 5248: 5236: 5214:Langway 2008 5209: 5204:, pp. 17–20. 5202:Langway 2008 5197: 5192:, pp. 14–15. 5190:Langway 2008 5185: 5178:Langway 2008 5173: 5166:Langway 2008 5161: 5154:Langway 2008 5149: 5142:Talalay 2016 5137: 5110: 5106: 5096: 5077: 5073: 5063: 5053:14 September 5051:. Retrieved 5030: 5018: 5010:the original 5000: 4991: 4950: 4946: 4933: 4914: 4910: 4900: 4873: 4869: 4859: 4847: 4835: 4808: 4796: 4740: 4736: 4725: 4705:, pp. 51–55. 4698: 4681: 4677: 4667: 4640: 4636: 4626: 4607: 4583: 4571:. Retrieved 4564:the original 4551: 4547: 4534: 4507:. Retrieved 4497: 4452: 4448: 4438: 4426: 4399:. Retrieved 4388: 4376:. Retrieved 4372:the original 4362: 4350: 4330:, pp. 65–70. 4323: 4292:. Retrieved 4281: 4269: 4252: 4239: 4227: 4202: 4198: 4141: 4136:, pp. 50–51. 4129: 4117: 4112:, pp. 44–48. 4105: 4097:the original 4086: 4051: 4047: 4033: 4021:. Retrieved 4014:the original 4005: 3998: 3986: 3977: 3964: 3945: 3939: 3912: 3900: 3888: 3876:. Retrieved 3871: 3862: 3835: 3831: 3821: 3794: 3790: 3784: 3776: 3749: 3737: 3700: 3696: 3685: 3674:the original 3655: 3648: 3641:Talalay 2016 3636: 3626: 3622: 3612: 3607:, pp. 20–21. 3565: 3561: 3551: 3546:, pp. 16–19. 3520:. Retrieved 3516:the original 3490:. Retrieved 3486: 3476: 3464: 3452:. Retrieved 3448:the original 3443: 3433: 3428:, pp. 17–19. 3421: 3409:. Retrieved 3405:the original 3400: 3390: 3378:. Retrieved 3374: 3364: 3355: 3336: 3332: 3322: 3303: 3297: 3278: 3274: 3264: 3257:Talalay 2016 3252: 3245:Talalay 2016 3240: 3233:Talalay 2016 3228: 3221:Talalay 2016 3216: 3209:Talalay 2016 3194:Talalay 2016 3189: 3170: 3166: 3156: 3144:. Retrieved 3140:the original 3130: 3123:Talalay 2016 3108:Talalay 2016 3093:Talalay 2016 3076:, pp. 34–35. 3074:Talalay 2016 3061:, pp. 43–46. 3054: 3035: 3029: 3017:. Retrieved 3010:the original 2996: 2972: 2965: 2960:, pp. 35–36. 2953: 2934: 2928: 2921:Talalay 2016 2908:, pp. 48–50. 2891:, pp. 71–73. 2869:. Retrieved 2859: 2846:Ice drilling 2818: 2782: 2779:Future plans 2754: 2722: 2709: 2670: 2660: 2629: 2589: 2572:Byrd Station 2560: 2542:(NBSAE), in 2528: 2500: 2469: 2452: 2325: 2130:hydrocarbons 1874: 1862:carbon black 1806:over time. 1748: 1718: 1702: 1698:stratosphere 1637: 1492:low-latitude 1469: 1434: 1389:carbon cycle 1363:interglacial 1351:Camp Century 1348: 1341: 1280: 1226: 1157: 927: 793: 784: 780: 776: 772: 768: 747: 732: 688: 680:particulates 606: 602: 590: 567: 553: 541: 495: 487: 478: 475: 418: 409: 398: 394: 382: 377:leaf-springs 373: 361:drill string 348: 334:, including 300: 289: 276:brace handle 261: 250:Ice drilling 229: 213:beryllium-10 205:forest fires 202: 195: 171: 162:Taku Glacier 112:Byrd Station 105: 82: 55: 30: 28: 18: 7474:Outwash fan 7469:Kettle hole 7353:Valley step 7333:Trough lake 7313:Ribbon lake 7273:Finger lake 7015:Bergschrund 6731:Radiocarbon 6406:Dual dating 6265:Regnal year 6243:Short Count 6183:Bostran era 6164:Anno Domini 6097:Big History 6077:Archaeology 5543:, p. 26-29. 5313:Jouzel 2013 5294:Jouzel 2013 5267:, pp. 3–26. 5229:Jouzel 2013 5180:, pp. 9–11. 5144:, pp. 9–11. 5080:(63): 183. 4917:: 307–312. 4527:Jouzel 2013 4431:Jouzel 2013 4419:Jouzel 2013 4343:Jouzel 2013 4232:Jouzel 2013 4175:Jouzel 2013 4054:(1): 3–17. 4023:5 September 3791:Radiocarbon 3754:Jouzel 2013 3742:Jouzel 2013 3728:2158/969431 3568:(49): 549. 2712:Allan Hills 2681:Taylor Dome 2602:drilled by 2598:; cores at 2550:(JIRP), in 2489:Early years 2134:halocarbons 1415:Graph of CO 1403:over time. 735:Pleistocene 544:brittle ice 504:Brittle ice 482:WAIS Divide 468:Sawing the 217:cosmic rays 215:created by 179:Summit Camp 97:Radioactive 35:core sample 7547:Glaciology 7531:Categories 7501:Glaciology 7484:Urstromtal 7464:Kame delta 7416:Till plain 7213:Jökulhlaup 7171:Starvation 7050:Ice divide 6964:Ice stream 6326:Vietnamese 6238:Long Count 6173:Anno Mundi 6168:Common Era 6070:Key topics 6063:Chronology 5337:(1): 3–4. 5315:, p. 2529. 5296:, p. 2528. 5243:, pp. 3–5. 5231:, p. 2527. 5156:, pp. 5–6. 5023:Alley 2000 4703:Alley 2000 4529:, p. 2534. 4433:, p. 2531. 4357:, p. 1097. 4355:Alley 2010 4345:, p. 2532. 4328:Alley 2000 4234:, p. 2533. 4177:, p. 2530. 4146:Alley 2000 4134:Alley 2000 4122:Alley 2000 4110:Alley 2000 3771:, p. 1098. 3769:Alley 2010 3756:, p. 2535. 3629:(49): 302. 3471:, pp. 8–9. 3397:"Partners" 3059:Alley 2000 2958:Alley 2000 2906:Alley 2000 2889:Alley 2000 2852:References 2705:Talos Dome 2685:Siple Dome 2567:glaciology 2482:See also: 1922:Sea salt: 1804:combustion 1729:electrodes 1694:ozone loss 1496:insolation 386:antifreeze 359:which the 305:to reduce 248:See also: 237:hoar frost 150:See also: 64:, and the 49:with hand 7542:Water ice 7246:Erosional 7238:Landforms 7109:Processes 7090:Randkluft 7085:Penitente 7030:Dirt cone 6959:Ice shelf 6954:Ice sheet 6949:Ice field 6863:Year zero 6843:Chronicle 6786:Seriation 6721:Lead–lead 6595:Standards 6576:Deep time 6536:Ephemeris 6422:Lunisolar 6386:Gregorian 6379:Gregorian 6340:Calendars 6303:Era names 6273:Anka year 6152:Human Era 6082:Astronomy 5903:0149-1776 5460:21 August 5400:30 August 4983:206558530 4854:, p. 228. 4830:, p. 225. 4815:, p. 222. 4791:, p. 221. 4590:, p. 191. 3993:, p. 315. 3934:, p. 192. 3895:, p. 325. 3211:, p. 101. 2923:, p. 263. 2829:ice cores 2757:Himalayas 2733:NorthGRIP 2707:in 2007. 2645:, and at 2578:, on the 1639:Diffusion 1307:δ 1302:× 1289:δ 1229:Deuterium 1111:× 1098:− 937:δ 636:carbonate 491:polythene 303:viscosity 233:sublimate 209:volcanoes 191:clathrate 89:Greenland 74:heat flow 72:. Since 39:ice sheet 7506:Category 7444:Diluvium 7439:Alpentor 7348:U-valley 7192:Ice core 7161:Plucking 7116:Ablation 7100:Terminus 7025:Crevasse 7020:Blue ice 6920:Glaciers 6858:Timeline 6696:Ice core 6569:Concepts 6316:Japanese 6248:Tzolk'in 6213:Egyptian 5974:Archived 5867:55357216 5604:Archived 5555:, p. 30. 5531:, p. 39. 5519:, p. 36. 5507:, p. 42. 5495:, p. 41. 5439:17 March 5279:, p. 11. 5216:, p. 23. 5044:Archived 5025:, p. 73. 4975:27244483 4765:26153860 4678:Tellus B 4606:(2010). 4489:26976561 4276:, p. 25. 4148:, p. 56. 4124:, p. 49. 4078:40380068 3872:Phys.org 3223:, p. 79. 3125:, p. 77. 3095:, p. 59. 2973:Glaciers 2835:See also 2759:and the 2741:EastGRIP 2600:Law Dome 2329:produce 1870:ammonium 1488:monsoons 1484:wetlands 1470:Because 925:(SMOW): 739:Holocene 737:and the 642:). 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