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Barbante C, Fischer H, Masson-Delmotte V, Waelbroeck C, Wolff EW, . (2010). Climate of the last million years: new insights from EPICA and other records
. Quat Sci Rev, 29(1-2), 1–7.
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Capron E, Landais A, Lemieux-Dudon B, Schilt A, Masson-Delmotte V, Buiron D, Chappellaz J, Dahl-Jensen D, Johnsen S, Leuenberger M, Loulergue L, Oerter H, . (2010). Synchronising EDML and NorthGRIP ice cores using δ18O of atmospheric oxygen (δ18Oatm) and CH4 measurements over MIS5 (80-123 kyr)
. Quat Sci Rev, 29(1-2), 222–234.
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Masson-Delmotte V, Stenni B, Pol K, Braconnot P, Cattani O, Falourd S, Kageyama M, Jouzel J, Landais A, Minster B, Barnola J M, Chappellaz J, Krinner G, Johnsen S, Rothlisberger R, Hansen J, Mikolajewicz U, Otto-Bliesner B, . (2010). EPICA Dome C record of glacial and interglacial intensities
. Quat Sci Rev, 29(1-2), 113–128.
Abstract: Climate models show strong links between Antarctic and global temperature both in future and in glacial climate simulations. Past Antarctic temperatures can be estimated from measurements of water stable isotopes along the EPICA Dome C ice core over the past 800 000 years. Here we focus on the reliability of the relative intensities of glacial and interglacial periods derived from the stable isotope profile. The consistency between stable isotope-derived temperature and other environmental and climatic proxies measured along the EDC ice core is analysed at the orbital scale and compared with estimates of global ice volume. MIS 2,12 and 16 appear as the strongest glacial maxima, while MIS 5.5 and 11 appear as the warmest interglacial maxima. The links between EDC temperature, global temperature, local and global radiative forcings are analysed. We show: (i) a strong but changing link between EDC temperature and greenhouse gas global radiative forcing in the first and second part of the record; (ii) a large residual signature of obliquity in EDC temperature with a 5 ky lag; (iii) the exceptional character of temperature variations within interglacial periods. Focusing on MIS 5.5, the warmest interglacial of EDC record, we show that orbitally forced coupled climate models only Simulate a precession-induced shift of the Antarctic seasonal cycle of temperature. While they do capture annually persistent Greenland warmth, models fail to capture the warming indicated by Antarctic ice core delta D. We suggest that the model-data mismatch may result from the lack of feedbacks between ice sheets and climate including both local Antarctic effects due to changes in ice sheet topography and global effects due to meltwater-thermohaline circulation interplays. An MIS 5.5 sensitivity study conducted with interactive Greenland melt indeed induces a slight Antarctic warming. We suggest that interglacial EDC optima are caused by transient heat transport redistribution comparable with glacial north-south seesaw abrupt climatic changes. (C) 2009 Elsevier Ltd. All rights reserved.
Keywords: glaciology, meteorology climatology,
Programme: 458
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Dreyfus Gabrielle B, Jouzel Jean, Bender Michael L, Landais Amalle, Masson-Delmotte Valrie, Leuenberger Markus, . (2010). Firn processes and δ15N: potential for a gas-phase climate proxy
. Quat Sci Rev, 29(1-2), 28–42.
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. (2010). What caused Earth's temperature variations during the last 800,000 years? Data-based evidence on radiative forcing and constraints on climate sensitivity
. Quat Sci Rev, 29(1-2), 129–145.
Abstract: The temperature on Earth varied largely in the Pleistocene from cold glacials to interglacials of different warmths. To contribute to an understanding of the underlying causes of these changes we compile various environmental records (and model-based interpretations of some of them) in order to calculate the direct effect of various processes on Earth's radiative budget and, thus, on global annual mean surface temperature over the last 800,000 years. The importance of orbital variations, of the greenhouse gases CO 2 , CH 4 and N 2 O, of the albedo of land ice sheets, annual mean snow cover, sea ice area and vegetation, and of the radiative perturbation of mineral dust in the atmosphere are investigated. Altogether we can explain with these processes a global cooling of 3.90.8K in the equilibrium temperature for the Last Glacial Maximum (LGM) directly from the radiative budget using only the Planck feedback that parameterises the direct effect on the radiative balance, but neglecting other feedbacks such as water vapour, cloud cover, and lapse rate. The unaccounted feedbacks and related uncertainties would, if taken at present day feedback strengths, decrease the global temperature at the LGM by 8.01.6K. Increased Antarctic temperatures during the Marine Isotope Stages 5.5, 7.5, 9.3 and 11.3 are in our conceptual approach difficult to explain. If compared with other studies, such as PMIP2, this gives supporting evidence that the feedbacks themselves are not constant, but depend in their strength on the mean climate state. The best estimate and uncertainty for our reconstructed radiative forcing and LGM cooling support a present day equilibrium climate sensitivity (excluding the ice sheet and vegetation components) between 1.4 and 5.2K, with a most likely value near 2.4K, somewhat smaller than other methods but consistent with the consensus range of 24.5K derived from other lines of evidence. Climate sensitivities above 6K are difficult to reconcile with Last Glacial Maximum reconstructions.
Programme: 458
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Landais A, Dreyfus G, Capron E, Masson-Delmotte V, Sanchez-Goi MF, Desprat S, Hoffmann G, Jouzel J, Leuenberger M, Johnsen S, . (2010). What drives the millennial and orbital variations of δ18Oatm?
. Quat Sci Rev, 29(1-2), 235–246.
Abstract: The isotopic composition of atmospheric oxygen (δ18Oatm) is a complex marker that integrates changes in global sea-level, water cycle, and biosphere productivity. A strong signature of orbital precession has been identified leading to the use of low-resolution measurements of δ18Oatm to date ice core records. However, the drivers of these δ18Oatm variations are still poorly known. Here, we combine records of millennial and orbital scale variations on the NorthGRIP, Vostok, and EPICA Dome C (EDC) ice cores to explore the origin of δ18Oatm variations. We show that, superimposed on the dominant precession signal, millennial δ18Oatm variations record systematic decreases during warm phases of the Dansgaard-Oeschger events and systematic increases during the cold phases.
Programme: 458
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Lourantou A, Chappellaz J, Barnola J-M, Masson-Delmotte V, Raynaud D, . (2010). Changes in atmospheric CO2 and its carbon isotopic ratio during the penultimate deglaciation
. Quat Sci Rev, 29(17-18), 1983–1992.
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Stenni B, Masson-Delmotte V, Selmo E, Oerter H, Meyer H, Rthlisberger R, Jouzel J, Cattani O, Falourd S, Fischer H, Hoffmann G, Iacumin P, Johnsen SJ, Minster B, Udisti R, . (2010). The deuterium excess records of EPICA Dome C and Dronning Maud Land ice cores (East Antarctica)
. Quat Sci Rev, 29(1-2), 146–159.
Abstract: New high-resolution deuterium excess (d) data from the two EPICA ice cores drilled in Dronning Maud Land (EDML) and Dome C (EDC) are presented here. The main moisture sources for precipitation at EDC and EDML are located in the Indian Ocean and Atlantic Ocean, respectively. The more southward moisture origin for EDML is reflected in a lower present-day d value, compared to EDC. The EDML and EDC isotopic records (δ18O and d) show the main climate features common to the East Antarctic plateau and similar millennial scale climate variability during the last glacial period. However, quite large δ18O and d differences are observed during MIS5.5 and the glacial inception with a long-term behaviour. A possibility for this long-term difference could be related to uncertainties in past accumulation rate which are used in the glaciological models. Regional climate anomalies between the two sites during MIS5.5 could also be consistent with the observed EDML-EDC δ18O and d gradient anomalies. Simulations performed with the General Circulation Model ECHAM4 for different time slices provide a temporal temperature/isotope slope for the EDML region in fair agreement to the modern spatial slope. Tsite and Tsource records are extracted from both ice cores, using a modelling approach, after corrections for past δ18O seawater and elevation changes. A limited impact of d on Antarctic temperature reconstruction at both EDML and EDC has been found with a higher impact only at glacial inception. The AIM (Antarctic Isotope Maximum) events in both ice cores are visible also after the source correction, suggesting that these are real climate features of the glacial period. The different shape of the AIM events between EDC and EDML, as well as some climate features in the early Holocene, points to a slightly different climate evolution at regional scale. A comparison of our temperature reconstruction profiles with the aerosol fluxes show a strong coupling of the nssCa fluxes with Antarctic temperatures during glacial period and a tighter coupling of δ18O and Tsite with ssNa flux at EDML compared to EDC during the glacial period and MIS5.5.
Programme: 458
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. (2014). A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum
. Quat Sci Rev, 100, 1–9.
Abstract: A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.
Keywords: Antarctic Ice Sheet, Glacial geology, Modelling, Quaternary,
Programme: 1048
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. (2014). Terrestrial and submarine evidence for the extent and timing of the Last Glacial Maximum and the onset of deglaciation on the maritime-Antarctic and sub-Antarctic islands
. Quat Sci Rev, 100, 137–158.
Keywords: Antarctic ice sheet, Sub-Antarctica, Maritime Antarctica glaciation, Deglaciation, Quaternary, Climate,
Programme: 1048
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