Effects of salt compensation on the climate model response in simulations of large changes of the Atlantic meridional overturning circulation

Stocker, Thomas F.; Timmermann, Axel; Renold, Manuel; Timm, Oliver (2007). Effects of salt compensation on the climate model response in simulations of large changes of the Atlantic meridional overturning circulation. Journal of Climate, 20(24), pp. 5912-5928. American Meteorological Society 10.1175/2007JCLI1662.1

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Freshwater hosing experiments with a comprehensive coupled climate model and a coupled model of intermediate complexity are performed with and without global salt compensation in order to investigate the robustness of the bipolar seesaw. In both cases, a strong reduction of the Atlantic meridional overturning circulation is induced, and a warming in the South Atlantic results. When a globally uniform salt flux is applied at the surface in order to keep the global mean salinity constant, this causes additional widespread warming in the Southern Ocean. It is shown that this warming is mainly due to heat transport anomalies that are induced by the specific parameterization in ocean models to represent eddy mixing. Surface salt fluxes tend to move outcropping isopycnals equatorward. As the density perturbation originates at the surface, changes in isopycnal slopes are generated that lead to anomalies in the bolus velocity field. The associated bolus heat flux convergence creates a warming enhancing the bipolar seesaw response, particularly in the Southern Ocean. The importance of this mechanism is illustrated in coupled model simulations in which this parameterization in the ocean model component is switched on or off. Additional experiments in which the same total amount of freshwater is delivered at rates 10 times smaller show that the effect of the global salt compensation is not important in this case, but that the eddy-mixing parameterization is still responsible for a substantial temperature response in the Southern Ocean.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics
08 Faculty of Science > Physics Institute

UniBE Contributor:

Stocker, Thomas and Renold, Manuel

Subjects:

500 Science > 530 Physics

ISSN:

0894-8755

Publisher:

American Meteorological Society

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:59

Last Modified:

05 Dec 2022 14:18

Publisher DOI:

10.1175/2007JCLI1662.1

Web of Science ID:

000252000800003

BORIS DOI:

10.7892/boris.25267

URI:

https://boris.unibe.ch/id/eprint/25267 (FactScience: 57572)

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