Southern Ocean deep convection in global climate models: A driver for variability of subpolar gyres and Drake Passage transport on decadal timescales

Behrens, Erik, Rickard, Graham, Morgenstern, Olaf, Martin, Torge, Osprey, Annette and Joshi, Manoj (2016) Southern Ocean deep convection in global climate models: A driver for variability of subpolar gyres and Drake Passage transport on decadal timescales Journal of Geophysical Research: Oceans, 121 (6). pp. 3905-3925. DOI 10.1002/2015JC011286.

[img]
Preview
Text
jgrc21749.pdf - Published Version

Download (7Mb) | Preview
[img] Text (Supporting Information S1)
jgrc21749-sup-0001-2015JC011286-s01.docx - Supplemental Material

Download (186Kb)
[img] Other (Figure S1)
jgrc21749-sup-0002-2015JC011286-s01.eps - Supplemental Material

Download (461Kb)
[img] Other (Figure S2)
jgrc21749-sup-0003-2015JC011286-s02.eps - Supplemental Material

Download (1695Kb)
[img] Other (Figure S3)
jgrc21749-sup-0004-2015JC011286-s03.eps - Supplemental Material

Download (1314Kb)

Supplementary data:

Abstract

We investigate the individual and joint decadal variability of Southern Ocean state quantities, such as the strength of the Ross and Weddell Gyres, Drake Passage transport, and sea ice area, using the National Institute of Water and Atmospheric Research UK Chemistry and Aerosols (NIWA-UKCA) model and CMIP5 models. Variability in these quantities is stimulated by strong deep reaching convective events in the Southern Ocean, which produce an Antarctic Bottom Water-like water mass and affect the large-scale meridional density structure in the Southern Ocean. An increase in the (near) surface stratification, due to freshwater forcing, can be a precondition for subsequent strong convection activity. The combination of enhanced-gyre driven sea ice and freshwater export, as well as ongoing subsurface heat accumulation, lead to a time lag between changes in oceanic freshwater and heat content. This causes an ongoing weakening of the stratification until sudden strong mixing events emerge and the heat is released to the atmosphere. We find that strong convection reduces sea ice cover, weakens the subpolar gyres, increases the meridional density gradient and subsequently results in a positive Drake Passage transport anomaly. Results of available CMIP5 models confirm that variability in sea ice, Drake Passage transport, and the Weddell Gyre strength is enhanced if models show strong open ocean convective events. Consistent relationships between convection, sea ice, Drake Passage transport, and Ross Gyre strength variability are evident in most models, whether or not they host open ocean convection.

Document Type: Article
Keywords: Southern Ocean; decadal variability; CMIP5; model bias;open ocean convection; freshwater
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
DOI etc.: 10.1002/2015JC011286
ISSN: 2169-9275
Date Deposited: 27 Oct 2016 11:18
Last Modified: 10 Apr 2017 09:37
URI: http://eprints.uni-kiel.de/id/eprint/34455

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...