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The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability

The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability
The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability
Evidence from paleo-proxy records suggests that the Atlantic Meridional Overturning Circulation (AMOC) can be in both an AMOC on state, the AMOC as we observe it today, and an AMOC off state, where the AMOC becomes extremely weak or even collapses. The freshwater transport due to the AMOC () at 34°S in the Atlantic has often been used as an indicator for bi-stability, with a positive suggesting a monostable AMOC and a negative suggesting a bi-stable AMOC. Often studies have shown that the sign of the divergence of the might be a good indicator of AMOC bi-stability. In this study we investigate how model bias affects the sign of across all latitudes in the Atlantic basin, through a detailed analysis of the Coupled Model Inter-Comparison Project 5 (CMIP5) model ensemble. , in the CMIP5 models is generally too positive in the southern Atlantic due to a salinity bias, while in the subtropical North Atlantic the values of are influenced by a combination of velocity and salinity biases. We compare these results to observations, reanalysis products and Hadley Centre Global Environmental Model version 3 global configuration version 2, a current generation coupled model which exhibits a stable AMOC off state, and discuss the differences that can lead to the possibility of a bi-stable AMOC as opposed to a monostable AMOC.
0280-6495
Mecking, J.V.
9b090069-5061-4340-b736-9690894ce203
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Jackson, L.C.
d1c72916-2a89-47b8-89c8-137b63f404a6
Andrews, M.B.
fcc7d406-57cc-4778-99a1-f419da805dcc
Mecking, J.V.
9b090069-5061-4340-b736-9690894ce203
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Jackson, L.C.
d1c72916-2a89-47b8-89c8-137b63f404a6
Andrews, M.B.
fcc7d406-57cc-4778-99a1-f419da805dcc

Mecking, J.V., Drijfhout, S.S., Jackson, L.C. and Andrews, M.B. (2017) The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability. Tellus A, 69 (1), [1299910]. (doi:10.1080/16000870.2017.1299910).

Record type: Article

Abstract

Evidence from paleo-proxy records suggests that the Atlantic Meridional Overturning Circulation (AMOC) can be in both an AMOC on state, the AMOC as we observe it today, and an AMOC off state, where the AMOC becomes extremely weak or even collapses. The freshwater transport due to the AMOC () at 34°S in the Atlantic has often been used as an indicator for bi-stability, with a positive suggesting a monostable AMOC and a negative suggesting a bi-stable AMOC. Often studies have shown that the sign of the divergence of the might be a good indicator of AMOC bi-stability. In this study we investigate how model bias affects the sign of across all latitudes in the Atlantic basin, through a detailed analysis of the Coupled Model Inter-Comparison Project 5 (CMIP5) model ensemble. , in the CMIP5 models is generally too positive in the southern Atlantic due to a salinity bias, while in the subtropical North Atlantic the values of are influenced by a combination of velocity and salinity biases. We compare these results to observations, reanalysis products and Hadley Centre Global Environmental Model version 3 global configuration version 2, a current generation coupled model which exhibits a stable AMOC off state, and discuss the differences that can lead to the possibility of a bi-stable AMOC as opposed to a monostable AMOC.

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Accepted/In Press date: 16 February 2017
e-pub ahead of print date: 20 March 2017
Published date: 2017

Identifiers

Local EPrints ID: 413502
URI: http://eprints.soton.ac.uk/id/eprint/413502
ISSN: 0280-6495
PURE UUID: 40015724-2b80-407c-a6ea-d569aac813e2

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Date deposited: 25 Aug 2017 16:31
Last modified: 06 Oct 2020 16:44

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Contributors

Author: J.V. Mecking
Author: S.S. Drijfhout
Author: L.C. Jackson
Author: M.B. Andrews

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