On the stability of the Atlantic meridional overturning circulation during the last deglaciation
Using a generalized stability indicator L, we explore the stability of the Atlantic meridional overturning circulation (AMOC) during the last deglaciation based on a paleoclimate simulation. From the last glacial maximum, as forced by various external climate forcings, notably the meltwater forcing,...
Published in: | Climate Dynamics |
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Main Authors: | , , , |
Other Authors: | , , , , , , , |
Format: | Journal/Newspaper |
Language: | English |
Published: |
climate dynamics
2015
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Subjects: | |
Online Access: | https://hdl.handle.net/20.500.11897/206108 https://doi.org/10.1007/s00382-014-2153-1 |
Summary: | Using a generalized stability indicator L, we explore the stability of the Atlantic meridional overturning circulation (AMOC) during the last deglaciation based on a paleoclimate simulation. From the last glacial maximum, as forced by various external climate forcings, notably the meltwater forcing, the AMOC experiences a collapse and a subsequent rapid recovery in the early stage of deglaciation. This change of the AMOC induces an anomalous freshwater divergence and later convergence across the Atlantic and therefore leads to a positive L, suggesting a negative basin-scale salinity advection feedback and, in turn, a mono-stable deglacial AMOC. Further analyses show that most anomalous freshwater is induced by the AMOC via the southern boundary of the Atlantic at 34 degrees S where the freshwater transport (M-ovS) is about equally controlled by the upper branch of the AMOC and the upper ocean salinity along 34 degrees S. From 19 to 17 ka, as a result of multiple climate feedbacks associated with the AMOC change, the upper ocean at 34 degrees S is largely salinified, which helps to induce a switch in M-ovS, from import to export. Our study has important implications to the deglacial simulations by climate models. A decomposition of L shows that the AMOC stability is mostly determined by two terms, the salinity stratification at 34 degrees S and the change of stratification with the AMOC. Both terms appear positive in model. However, the former is likely to be distorted towards positive, as associated with a common bias existing over the South Atlantic in climate models. Therefore, the AMOC is potentially biased towards mono-stability in most paleoclimate simulations. Meteorology & Atmospheric Sciences SCI(E) 2 ARTICLE wliu5wisc@gmail.com 5-6 1257-1275 44 |
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