New constraints on the gas age-ice age difference along the EPICA ice cores, 0–50 kyr
-
Published:2007-08-28
Issue:3
Volume:3
Page:527-540
-
ISSN:1814-9332
-
Container-title:Climate of the Past
-
language:en
-
Short-container-title:Clim. Past
Author:
Loulergue L.,Parrenin F.,Blunier T.,Barnola J.-M.,Spahni R.,Schilt A.,Raisbeck G.,Chappellaz J.
Abstract
Abstract. Gas is trapped in polar ice sheets at ~50–120 m below the surface and is therefore younger than the surrounding ice. Firn densification models are used to evaluate this ice age-gas age difference (Δage) in the past. However, such models need to be validated by data, in particular for periods colder than present day on the East Antarctic plateau. Here we bring new constraints to test a firn densification model applied to the EPICA Dome C (EDC) site for the last 50 kyr, by linking the EDC ice core to the EPICA Dronning Maud Land (EDML) ice core, both in the ice phase (using volcanic horizons) and in the gas phase (using rapid methane variations). We also use the structured 10Be peak, occurring 41 kyr before present (BP) and due to the low geomagnetic field associated with the Laschamp event, to experimentally estimate the Δage during this event. Our results seem to reveal an overestimate of the Δage by the firn densification model during the last glacial period at EDC. Tests with different accumulation rates and temperature scenarios do not entirely resolve this discrepancy. Although the exact reasons for the Δage overestimate at the two EPICA sites remain unknown at this stage, we conclude that current densification model simulations have deficits under glacial climatic conditions. Whatever the cause of the Δage overestimate, our finding suggests that the phase relationship between CO2 and EDC temperature previously inferred for the start of the last deglaciation (lag of CO2 by 800±600 yr) seems to be overestimated.
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Global and Planetary Change
Reference68 articles.
1. Ahn, J., Wahlen, M., Deck, B. L., Brook, E. J., Mayewski, P. A., Taylor, K. C., and White, J. W. C.: A record of atmospheric CO2 during the last 40 000 years from the Siple Dome, Antarctica ice core, J. Geophys. Res., 109, 13 305, https://doi.org/10.1029/2003JD004415, 2004. 2. Andersen, K. K., Svensson, A., Johnsen, S. J., Rasmussen, S. O., Bigler, M., Röthlisberger, R., Ruth, U., Siggaard-Andersen, M.-L., Steffensen, J. P., Dahl-Jensen, D., Vinther, B. M., and Clausen, H. B.: The Greenland Ice Core Chronology 2005, 15–42 ka. Part 1: constructing the time scale, Quat. Sci. Rev., 25, 3246–3257, 2006. 3. Anklin, M., Barnola, J.-M., Schwander, J., Stauffer, B., and Raynaud, D.: Processes affecting the CO2 concentration measured in Greenland ice, Tellus Ser., B(47), 461–470, 1995. 4. Arnaud, L., Barnola, J.-M., and Duval, P.: Physical modeling of the densification of snow/firn and ice in the upper part of polar ice sheets. Physics of Ice Core Records, T. Hondoh, Sapporo, Hokkaido University Press, 285–305, 2000. 5. Barnola, J.-M., Pimienta, P., Raynaud, D., and Korotkevich, Y. S.: CO2-climate relationship as deduced from the Vostok ice core: a re-examination based on new measurements and on a re-evaluation of the air dating, Tellus, 43 B, 83–90, 1991.
Cited by
110 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献
|
|