Basinwide response of the Atlantic Meridional Overturning Circulation to interannual wind forcing
An eddy-resolving Ocean general circulation model For the Earth Simulator (OFES) and a simple wind-driven two-layer model are used to investigate the role of momentum fluxes in driving the Atlantic Meridional Overturning Circulation (AMOC) variability throughout the Atlantic basin from 1950 to 2010. Diagnostic analysis using the OFES results suggests that interior baroclinic Rossby waves and coastal topographic waves play essential roles in modulating the AMOC interannual variability. The proposed mechanisms are verified in the context of a simple two-layer model with realistic topography and only forced by surface wind. The topographic waves communicate high-latitude anomalies into lower latitudes and account for about 50% of the AMOC interannual variability in the subtropics. In addition, the large scale Rossby waves excited by wind forcing together with topographic waves set up coherent AMOC interannual variability patterns across the tropics and subtropics. The comparisons between the simple model and OFES results suggest that a large fraction of the AMOC interannual variability in the Atlantic basin can be explained by wind-driven dynamics.
KeywordsAtlantic Meridional Overturning Circulation Low-frequency change Wind forcing Rossby wave
This study greatly benefits from my advisor Dr. William Johns. Without his encouragement, guidance, insightful inputs and support, this work would not be possible. Also, comments from Dr. Benjamin Kirtman, Dr. Igor Kamenkovich, and Dr. Christopher Meinen help to improve the manuscript. The OFES simulation was conducted on the Earth Simulator under the support of JAMSTEC. Support for this work provided by the U.S. National Science Foundation (NSF) under Grant 0728108 is gratefully acknowledged.
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