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Title: Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier [Sub-ice shelf sediments record 20 th century retreat history of Pine Island Glacier]

The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line—which marks the boundary between grounded ice and floating ice shelf—is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreat is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming anmore » ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Furthermore our results suggest that, even when climate forcing weakened, ice-sheet retreat continued.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [1] ;  [1] ;  [8] ;  [1] ;  [9] ;  [10] ;  [1]
  1. British Antarctic Survey, Cambridge (United Kingdom)
  2. Univ. of Copenhagen, Copenhagen (Denmark)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Alaska, Fairbanks, AK (United States)
  5. Naval Postgraduate School, Monterey, CA (United States)
  6. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  7. Lamont-Doherty Earth Observatory of Columbia Univ., Palisades, NY (United States)
  8. Univ. of Leipzig, Leipzig (Germany)
  9. British Antarctic Survey, Cambridge (United Kingdom); Univ. of Geneva, Geneva (Switzerland)
  10. Univ. of Geneva, Geneva (Switzerland)
Publication Date:
Report Number(s):
LLNL-JRNL-697878
Journal ID: ISSN 0028-0836
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 541; Journal Issue: 7635; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES
OSTI Identifier:
1414362