What is it about?
Information on the structure of the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM) and its behavior during strong freshwater discharge in the Northern Hemisphere (NH) associated with Heinrich Stadials are subject to deep uncertainty. In this study, we use an intermediate complexity Earth System model to examine the influence of the mean AMOC strength and wind forcing on the AMOC behavior during the LGM and Heinrich Stadial 1.
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Why is it important?
Our results show that it is the strength of the NH winds, and not the mean AMOC strength, that determines the stability of the AMOC during periods of freshwater discharge. Stronger NH winds maintains a stable AMOC (one that recovers when freshwater discharge terminates), increases the upper ocean stratification, cools the ocean, and decreases Arctic ice coverage. Stronger stratification increases the AMOC sensitivity to the meridional density gradient, which is mostly driven by salinity effects in the LGM. Simulations that show a bistable AMOC, in which it remains shutdown after collapse, present a weak meridional overturning freshwater transport, but not necessarily negative, which may impact the use of this index as a stability indicator.
Perspectives
There are several uncertainties about the stability of the AMOC, relative to its structure and forcings. In this paper we addressed some of these uncertainties and evaluated the most important. Future studies should address the interactions with carbon cycle and other parameters that may contribute to the AMOC behavior. This has implications for future scenarios and analysis of AMOC indicators.
Dr. Marlos Goes
Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration
Read the Original
This page is a summary of: The stability of the AMOC during Heinrich events is not dependent on the AMOC strength in an Intermediate Complexity Earth System model ensemble, Paleoceanography and Paleoclimatology, August 2019, American Geophysical Union (AGU),
DOI: 10.1029/2019pa003580.
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