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Studying the response of the Antarctic ice sheets during periods when climate conditions were similar to the present can provide important insights into current observed changes and help identify natural drivers of ice sheet retreat. In this context, the marine isotope substage 11c (MIS11c) interglacial offers a suitable scenario, given that during its later portion orbital parameters were close to our current interglacial. Ice core data indicate that warmer-than-present temperatures lasted for longer than during other interglacials. However, the response of the Antarctic ice sheets and their contribution to sea level rise remain unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three glaciological and one sedimentary proxy records of ice volume. Our results indicate that the East and West Antarctic ice sheets contributed 4.0–8.2 m to the MIS11c sea level rise. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea level reconstructions, the range is reduced to 6.7–8.2 m independently of the choices of external sea level forcing and millennial-scale climate variability. Within this latter range, the main source of uncertainty arises from the sensitivity of the East Antarctic Ice Sheet to a choice of initial ice sheet configuration. We found that the warmer regional climate signal captured by Antarctic ice cores during peak MIS11c is crucial to reproduce the contribution expected from Antarctica during the recorded global sea level highstand. This climate signal translates to a modest threshold of 0.4 ∘ C oceanic warming at intermediate depths, which leads to a collapse of the West Antarctic Ice Sheet if sustained for at least 4000 years. [ABSTRACT FROM AUTHOR]

After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2-56.9 ka) and 2 (23.2-16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka). [ABSTRACT FROM AUTHOR]

Studying the behaviour of the Antarctic Ice Sheet during periods with a climate that wassimilar or warmer than today can yield analogues for understanding its present-day changesand future trajectory. Among these, Marine Isotope Stage 11 (MIS 11) is one of thebest candidates given its limited insolation variability, which is very close to ourcurrent interglacial. However, Antarctic ice core data indicates that CO2 levels weremerely close to pre industrial, but that warmer-than-present temperatures (about 2 K)lasted for much longer than other Quaternary interglacials. Sea level was 6 to 13 mhigher than present, implying a potential substantial contribution from Antarctica. While substantial work has been conducted regarding the behaviour of the Greenland IceSheet during MIS 11, the Antarctic Ice Sheet history and dynamics during this period remainpoorly constrained, both in terms of its configuration and its potential contribution to sealevel. Thus, in this study we present an ensemble of continental scale transient simulations ofthe Antarctic Ice Sheet between 420 ka and 394 ka using the ice sheet model SICOPOLISforced by climate simulations from CCSM3. We evaluate the possible range of icesheet geometries, the Antarctic contribution to sea level rise and the associatedrange of uncertainties during the longest interglacial of the Quaternary period. Ourresults aim to provide insights into the style of the Antarctic deglaciation towards thepeak warming of MIS 11 and help set the bounds on the minimum volumes andextents of the western and eastern ice sheet counterparts as possible future analogues. [ABSTRACT FROM AUTHOR]