North Atlantic climate responses to perturbations in Antarctic Intermediate Water

Graham, Jennifer A. ORCID: https://orcid.org/0000-0002-1950-5266, Stevens, David P. ORCID: https://orcid.org/0000-0002-7283-4405, Heywood, Karen J. ORCID: https://orcid.org/0000-0001-9859-0026 and Wang, Zhaomin (2011) North Atlantic climate responses to perturbations in Antarctic Intermediate Water. Climate Dynamics, 37 (1-2). pp. 297-311.

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Abstract

Recent observations suggest Antarctic Intermediate Water (AAIW) properties are changing. The impact of such variations is explored using idealised perturbation experiments with a coupled climate model, HadCM3. AAIW properties are altered between 10 and 20°S in the South Atlantic, maintaining constant potential density. The perturbed AAIW remains subsurface in the South Atlantic, but as it moves northwards, it surfaces and interacts with the atmosphere leading to density anomalies due to heat exchanges. For a cooler, fresher AAIW, there is a significant decrease in the mean North Atlantic sea surface temperature (SST), of up to 1°C, during years 51-100. In the North Atlantic Current region there are persistent cold anomalies from 2,000 m depth to the surface, and in the overlying atmosphere. Atmospheric surface pressure increases over the mid-latitude Atlantic, and precipitation decreases over northwest Africa and southwest Europe. Surface heat flux anomalies show that these impacts are caused by changes in the ocean rather than atmospheric forcing. The SST response is associated with significant changes in the Atlantic meridional overturning circulation (MOC). After 50 years there is a decrease in the MOC that persists for the remainder of the simulation, resulting from changes in the column-averaged density difference between 30°S and 60°N. Rather than showing a linear response, a warmer, saltier AAIW also leads to a decreased MOC strength for years 51-100 and resulting cooling in the North Atlantic. The non-linearity can be attributed to opposing density responses as the perturbed water masses interact with the atmosphere.

Item Type:	Article
Uncontrolled Keywords:	sdg 13 - climate action ,/dk/atira/pure/sustainabledevelopmentgoals/climate_action
Faculty \ School:	Faculty of Science > School of Environmental Sciences Faculty of Science > School of Mathematics University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Collaborative Centre for Sustainable Use of the Seas Faculty of Science > Research Groups > Fluid and Solid Mechanics
Depositing User:	Rosie Cullington
Date Deposited:	21 Jan 2011 11:37
Last Modified:	13 Apr 2023 13:32
URI:	https://ueaeprints.uea.ac.uk/id/eprint/19461
DOI:	10.1007/s00382-010-0981-1

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