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

Citation:
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.

Date Published:

2014/09

Keywords:

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

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.

Notes:

n/a

Website

DOI:

10.1002/2014gl060891