Linear Weakening of the AMOC in response to Receding Glacial Ice Sheets in CCSM3


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Xu.Zhang [ at ] awi.de

Abstract

The transient response of the Atlantic Meridional Overturning Circulation (AMOC) to a deglacial ice-sheet retreat is studied using the Community Climate System Model version 3 (CCSM3), with a focus on orographic effects rather than meltwater discharge. It is found that the AMOC weakens significantly (41%) in response to the deglacial ice-sheet retreat. The AMOC weakening follows the decrease of the Northern Hemisphere ice-sheet volume linearly, with no evidence of abrupt thresholds. A wind-driven mechanism is proposed to explain the weakening of the AMOC: lowering the Northern Hemisphere ice sheets induces a northward shift of the westerlies, which causes a rapid eastward sea-ice transport and expanded sea-ice cover over the subpolar North Atlantic; this expanded sea ice insulates the ocean from heat loss and leads to suppressed deep convection and a weakened AMOC. A sea ice-ocean positive feedback could be further established between the AMOC decrease and sea-ice expansion.



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Eprint ID
36169
DOI 10.1002/2014GL060891

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Zhu, J. , Liu, Z. , Zhang, X. , Eisenman, I. and Liu, W. (2014): Linear Weakening of the AMOC in response to Receding Glacial Ice Sheets in CCSM3 , Geophysical Research Letters, 41 (17), pp. 6252-6258 . doi: 10.1002/2014GL060891


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