Browsing by Author "Domack, E"
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- ItemA community-based geological reconstruction of Antarctic ice sheet deglaciation since the last glacial maximum(Elsevier, 2014-09-15) Bentley, MJ; O'Cofaigh, C; Anderson, JB; Conway, H; Davies, B; Graham, AGC; Hillenbrand, CD; Hodgson, DA; Jamieson, SSR; Larter, RD; Mackintosh, AN; Smith, JA; Verleyen, E; Ackert, RP; Bart, PJ; Berg, S; Brunstein, D; Canals, M; Colhoun, EA; Crosta, X; Dickens, WA; Domack, E; Dowdeswell, JA; Dunbar, R; Ehrmann, W; Evans, J; Favier, V; Fink, D; Fogwill, CJ; Glasser, NF; Gohl, K; Golledge, NR; Goodwin, I; Gore, DB; Greenwood, SL; Hall, BL; Hall, K; Hedding, DW; Hein, AS; Hocking, EP; Jakobsson, M; Johnson, JS; Jomelli, V; Jones, RS; Klages, JP; Kristoffersen, Y; Kuhn, G; Leventer, A; Licht, K; Lilly, K; Lindow, J; Livingstone, SJ; Massé, G; McGlone, MS; McKay, RM; Melles, M; Miura, H; Mulvaney, R; Nel, W; Nitsche, FO; O'Brien, PE; Post, AL; Roberts, SJ; Saunders, KM; Selkirk, PM; Simms, AR; Spiegel, C; Stolldorf, TD; Sugden, DE; van der Putten, N; van Ommen, TD; Verfaillie, D; Vyverman, W; Wagner, B; White, DA; Witus, AE; Zwartz, DA 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. © 2014 The Authors. CC BY license
- ItemEast Antarctic ice sheet retreat as a response to meltwater pulse 1A(Scientific Committee on Antarctic Research, 2008-07) Mackintosh, A; Domack, E; Leventer, A; White, DA; Fink, D; Gore, DB; Dunbar, RWe develop an empirical model of East Antarctic Ice Sheet (EAIS) retreat during the last termination in Mac.Robertson Land. Exposure dating, marine cores and swath bathymetry indicate retreat from the continental shelf and ice sheet drawdown in coastal mountains began ~13 ka. Calving re-entrant bays formed during initial retreat and persisted for 100's years in Iceberg Alley and 10's years at Neilson Basin. Exposure dates in Framnes Mountains within the same drainage basin as Iceberg Alley indicate ~350 m of ice thinning was complete by ~7 ka. EAIS retreat at many sites on the Antarctic perimeter (including these three) immediately post-dated Meltwater Pulse 1A (MWP1A). Rather than being a source of MWP1A, our data support a hypothesis that rapid eustatic sea level rise during this time unhinged the ice-sheet margin from its stability point at the shelf edge. Thereafter, the rate of EAIS retreat depended on trough geometry, akin to the present-day response of fiord glaciers, until retreat ceased when sea level stabilised. Our findings reinforce a concern that marine-based portions of Antarctic Ice Sheets are vulnerable to collapse if sea level rise approaches the rates (~4m/century) achieved during MWP1A, as a consequence of melting ice in Greenland and elsewhere.
- ItemLast major retreat of Antarctic ice sheets forced by sea level rise and ocean warming(University of Auckland, 2009-07-01) Mackintosh, AN; Domack, E; Golledge, NR; Dunbar, R; Leventer, A; White, D; Fink, D; Gore, DB; Lavoie, CThe retreat of Antarctic ice sheets during the transition from the last glacial period to the Holocene provides the most recent example of ice sheet response to major climate forcing and thus allows rates of ice sheet decay and coupling to sea level rise to be quantified. We observe through a combination of land- and marine-based geochronology and ice sheet modelling, a highly-resolved temporal record of deglaciation of the East Antarctic Ice Sheet across the Mac.Robertson Land shelf. Our reconstruction demonstrates that deglaciation of deep-shelf troughs and lowering of the ice sheet surface occurred in two phases, from 14 - 12 and 12 - 7 ka before present (BP). Our consideration of possible mechanisms for the observed retreat of the marine ice margin of Mac.Robertson Land favours rapid rates of eustatic sea level rise associated with Meltwater Pulse 1a (MWP-1a) at ~14 ka BP and warming of the marginal oceans and atmosphere to nearmodern levels ~2 ka later. In support of this interpretation is the comparison of our land-marine sequence to other well-constrained marine deglacial events from both West and East Antarctica, including the Ross and Weddell Sea embayments. Our results show that periods of rapid sea level rise can initiate instability in Antarctica’s ice masses, including the margins of East Antarctica, and indicate that a combination of sea level rise and oceanic warming is a powerful driver of ice retreat.
- ItemRetreat of the East Antarctic ice sheet during the last glacial termination(Nature Publishing Group, 2011-03) Mackintosh, AN; Golledge, NR; Domack, E; Dunbar, R; Leventer, A; White, D; Pollard, D; DeConto, R; Fink, D; Zwartz, D; Gore, DB; Lavoie, CThe retreat of the East Antarctic ice sheet at the end of the last glacial period has been attributed to both sea-level rise and warming of the ocean at the margin of the ice sheet, but it has been challenging to test these hypotheses. Given the lack of constraints on the timing of retreat, it has been difficult to evaluate whether the East Antarctic ice sheet contributed to meltwater pulse 1a, an abrupt sea-level rise of approximately 20 m that occurred about 14,700 years ago. Here we use terrestrial exposure ages and marine sedimentological analyses to show that ice retreat in Mac. Robertson Land, East Antarctica, initiated about 14,000 years ago, became widespread about 12,000 years ago, and was completed by about 7,000 years ago. We use two models of different complexities to assess the forcing of the retreat. Our simulations suggest that, although the initial stage of retreat may have been forced by sea-level rise, the majority of the ice loss resulted from ocean warming at the onset of the Holocene epoch. In light of our age model we conclude that the East Antarctic ice sheet is unlikely to have been the source of meltwater pulse 1a, and, on the basis of our simulations, suggest that Antarctic ice sheets made an insignificant contribution to eustatic sea-level rise at this time. © 2011, Nature Publishing Group.