气候变化领域集成服务门户(CCPortal): Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

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DOI	10.5194/tc-9-1633-2015
	Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core
	Tison J.-L.; De Angelis M.; Littot G.; Wolff E.; Fischer H.; Hansson M.; Bigler M.; Udisti R.; Wegner A.; Jouzel J.; Stenni B.; Johnsen S.; Masson-Delmotte V.; Landais A.; Lipenkov V.; Loulergue L.; Barnola J.-M.; Petit J.-R.; Delmonte B.; Dreyfus G.; Dahl-Jensen D.; Durand G.; Bereiter B.; Schilt A.; Spahni R.; Pol K.; Lorrain R.; Souchez R.; Samyn D.
发表日期	2015
ISSN	19940416
卷号	9 期号:4
英文摘要	An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ18Oice, δ18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice-bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica. © Author(s) 2015.
学科领域	carbon dioxide; crystallization; dome; ice core; ice sheet; ice thickness; ice-ocean interaction; oxygen isotope; paleoclimate; remote sensing; satellite data; subglacial environment; substrate; topography; Antarctica; Central America
语种	英语
scopus关键词	carbon dioxide; crystallization; dome; ice core; ice sheet; ice thickness; ice-ocean interaction; oxygen isotope; paleoclimate; remote sensing; satellite data; subglacial environment; substrate; topography; Antarctica; Central America
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119835
作者单位	Laboratoire de Glaciologie, Université Libre de Bruxelles, CP 160/03, 50, av. F.D. Roosevelt, Bruxelles, 1050, Belgium; Laboratoire de Glaciologie et Géophysique de l'Environnement, 54, Rue Molière Domaine Universitaire, Saint-Martin d'Hères, 38402, France; British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET, United Kingdom; Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, Bern, 3012, Switzerland; Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, 106 91, Sweden; University of Florence, Chemistry Dept., via della Lastruccia, 3, Sesto Fiorentino, Florence 50019, Italy; Alfred Wegener Institute, Bremerhaven, Germany; Laboratoire des Sciences du Climat et de l'Environnement/Institut Pierre Simon Laplace, CEA-CNRS-UVSQ, CEA Saclay, Gif-sur-Yvette, 91191, France; Dipartimento di Scienze Ambientali, Informatica e Statistica, Università Ca Foscari, Venezia, Italy;...
推荐引用方式 GB/T 7714	Tison J.-L.,De Angelis M.,Littot G.,et al. Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core[J],2015,9(4).
APA	Tison J.-L..,De Angelis M..,Littot G..,Wolff E..,Fischer H..,...&Samyn D..(2015).Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core.Cryosphere,9(4).
MLA	Tison J.-L.,et al."Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core".Cryosphere 9.4(2015).