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WIREs Clim Change
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Paleoclimates: what do we learn from deep ice cores?

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Abstract Since the early 1960s, the ice core community has produced a wealth of scientific results from a still relatively limited number of deep drilling sites in Greenland and Antarctica with the longest record extending back to the last interglacial in Greenland and covering eight glacial–interglacial cycles in Antarctica. Although measurements performed on the first ice cores, Camp Century and Byrd, largely focused on the isotopic composition of the ice as an indicator of climate change, the number of studied parameters has steadily increased encompassing numerous measurements performed on the entrapped air bubbles, on various impurities as well as on the ice itself. The climatic information provided by these various paleodata time is extremely rich. The relationships between forcing factors and climate, about the importance of carbon cycle feedbacks, about the occurrence of abrupt climate variability, and about the interplay between polar climate, ice sheet dynamics, and sea‐level variations are examples that are highly relevant to future climate change. Copyright © 2010 John Wiley & Sons, Ltd. This article is categorized under: Paleoclimates and Current Trends > Paleoclimate

Greenland and Antarctic deep drilling sites synthetized for the International Partnership in Ice Core Sciences (from http://www.pages‐igbp.org/ipics/). Filled circles indicate ice cores already drilled. Open black circles indicate ongoing projects. Red circles and stars indicate future projects. Shaded areas highlight poorly covered areas.

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Comparison between Greenland (NGRIP, gray) and Antarctic (Dome C, light blue; EDML, purple; Byrd, pink) temperature variations indicated by water stable isotopes over the time interval from 10 to 60 ky BP. Ice cores are synchronized using global variations in methane concentrations (lower panel).19 Further synchronization is now available back to the last interglacial111 (Reprinted with permission from Ref. 19. Copyright 2006 Nature.)

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NorthGRIP record of past Greenland temperature change (rainbow color). The temperature reconstruction takes into account borehole and gas thermal fractionation estimates (upper panel, red bars) to scale water stable isotope records.39 For comparison, changes in past and future 75°N summer insolation103 and in past global sea level117 are displayed. Note that we have adjusted the sea‐level reconstruction, derived from marine benthic data, to highlight the 4–6 m higher sea level during the last interglacial clearly depicted by coral and other geological records.100,118.

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Long‐term climate variations depicted by the EPICA Dome C ice core over the past 800,000 years, with atmospheric methane concentration (green, ppbv, from Ref 95), carbon dioxide concentration (red, ppmv, from Refs 15,101,102, Antarctic temperature as indicated by ice core δD (black, ‰, from Ref 4) and compared to global sea level estimated from deep sea sediment cores (blue, ‰, from Ref 96). Variations in the Earth's orbital parameters (precession parameter, obliquity and excentricity)103 are also displayed.

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Polarized light photograph of a thin section of Antarctic ice (M. Delmotte) showing ice crystals, visible impurities, and air bubbles (dark). Local climate parameters are estimated using measurements of ice core water stable isotope composition (left). The Antarctic map displays the sites where such data are available. The lower panel displays the present day Antarctic linear relationship between local surface temperature and ice core δD (the ‘isotopic thermometer’). Geochemical analyses conducted on ice cores provide a wealth of regional to global climate and environmental information, including a characterization of climate forcings (volcanism and solar activity).

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Schematic view of successive deep drilling operations conducted at Vostok station, Antarctica. (Reprinted with permission from Ref. 22. Copyright 2007 International Glaciological Society.)

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