On the stability of the Atlantic meridional overturning circulation during the last deglaciation

TitleOn the stability of the Atlantic meridional overturning circulation during the last deglaciation
Publication TypeJournal Article
Year of Publication2015
AuthorsLiu W, Liu Z, Cheng J, Hu H
JournalClimate Dynamics
Volume44
Pagination1257-1275
Date Published2015/03
ISBN Number0930-7575
Accession NumberWOS:000350364500006
Abstract

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.

DOI10.1007/s00382-014-2153-1
Short TitleClim. Dyn.
Student Publication: 
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