Linear weakening of the AMOC in response to receding glacial ice sheets in CCSM3

Zhu, J, Liu ZY, Zhang X, Eisenman I, Liu W.  2014.  Linear weakening of the AMOC in response to receding glacial ice sheets in CCSM3. Geophysical Research Letters. 41:6252-6258.

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age, Atlantic Meridional Overturning Circulation, atlantic thermohaline circulation, carbon-dioxide, cycle, deglaciation, global climate-change, ice, ice sheet retreat, last, model, sea ice transport, sheet orography, simulations, stability, surface


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.