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

• Published in: Geophysical Research Letters
• Main Authors: Zhu, Jiang, Liu, Zhengyu, Zhang, Xu, Eisenman, Ian, Liu, Wei
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2014
• Subjects: Climate Action; Atlantic Meridional Overturning Circulation; ice sheet retreat; ice sheet orography; sea ice transport; Meteorology & Atmospheric Sciences; Ice Sheet; North Atlantic; Sea ice
• Online Access: https://escholarship.org/uc/item/18f047t7; https://escholarship.org/content/qt18f047t7/qt18f047t7.pdf; https://doi.org/10.1002/2014gl060891

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.