Controls on interior West Antarctic Ice Sheet Elevations: inferences from geologic constraints and ice sheet modeling

QUATERNARY SCIENCE REVIEWS

卷:65

Article

Ackert, Robert P., Jr.¹  Putnam, Aaron E.^2,6  Mukhopadhyay, Sujoy¹  Pollard, David³  DeConto, Robert M.⁴  Kurz, Mark D.⁵  Borns, Harold W., Jr.⁶ 

[1] Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA

[2] Lamont Doherty Earth Observ, Palisades, NY 10904 USA

[3] Penn State Univ, Earth & Environm Syst Inst, University Pk, PA 16802 USA

[4] Univ Massachusetts, Dept Geosci, Amherst, MA 01003 USA

[5] Woods Hole Oceanog Inst, Dept Marine Chem & Geochem, Woods Hole, MA 02543 USA

[6] Univ Maine, Climate Change Inst, Orono, ME 04469 USA

关键词: WAIS;    He-3;    Cl-36;    40Ar/39Ar;    Exposure dating;    Ice sheet model;    Mt. Waesche;    Ohio Range;   

DOI  :  10.1016/j.quascirev.2012.12.017

来源: Elsevier

【 摘 要 】

Knowledge of the West Antarctic Ice Sheet (WAIS) response to past sea level and climate forcing is necessary to predict its response to warmer temperatures in the future. The timing and extent of past interior WAIS elevation changes provides insight to WAIS behavior and constraints for ice sheet models. Constraints prior to the Last Glacial Maximum (LGM) however, are rare. Surface exposure ages of glacial erratics near the WAIS divide at Mt. Waesche in Marie Byrd Land, and at the Ohio Range in the Trans-antarctic Mountains, range from similar to 10 ka to >500 ka without a dependence on elevation. The probability distribution functions (PDF) of the exposure ages at both locations, are remarkably similar. During the last glaciation, maximum interior ice elevations as recorded by moraines and erratics were reached between 10 ka and 12 ka. However, most exposure ages are older than the LGM and cluster around similar to 40 ka and similar to 80 ka. The peak in the exposure age distributions at similar to 40 ka includes ages of alpine moraine boulders at Mercer Ridge in the Ohio Range. Comparison of the PDF of exposures ages from the Ohio Range and Mt. Waesche with the temperature record from the Fuji Dome ice core indicates that the youngest peak in the exposure age distributions corresponds to the abrupt warming during the Last Glacial termination. A prominent peak in the Ohio Range PDF corresponds to the penultimate termination (stage 5e). During the intervening glacial period, there is not a consistent relationship between the peaks in the PDF at each location and temperature. A combined ice sheet/ice shelf model with forcing scaled to marine delta O-18 predicts that interior WAIS elevations near the ice divide have varied similar to 300 m over the Last Glacial cycle. Peaks in the PDF correspond to model highstands over the last 200 ka. In the simulated elevation history, maximum ice elevations at Ohio Range (+100 m) and Mt. Waesche (+60 in) occur at similar to 10 ka, in agreement with observations from these sites. During collapse of the marine portion of the WAIS, ice elevations at Ohio Range and Mt. Waesche are drawn down at least 200 m below the present ice elevation. The good correspondence between the model results and observations at both the Ohio Range and Mt. Waesche supports the conclusion that interior WAIS highstands do not occur during glacial maximums. Rather, the highstands are controlled primarily by increased accumulation during temperature maximums that occur early in the interglacials. Interior down-draw events follow highstands, resulting from the arrival of a wave of thinning triggered by retreat of the WAIS grounding line coupled with decreasing accumulation rates. (c) 2013 Elsevier Ltd. All rights reserved.

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