Labrador Sea convection and subpolar North Atlantic Deep Water export in the SODA assimilation model.

Schott, Friedrich, Stramma, Lothar , Giese, B. S. and Zantopp, Rainer J. (2009) Labrador Sea convection and subpolar North Atlantic Deep Water export in the SODA assimilation model. Deep Sea Research Part I: Oceanographic Research Papers, 56 (6). pp. 926-938. DOI 10.1016/j.dsr.2009.01.001.

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Abstract

Labrador Sea convection was most intense and reached the greatest depths in the early 1990s, followed by weaker, shallower, and more variable convection after 1995. The Simple Ocean Data Assimilation (SODA) version 2.0.2/2.0.4 assimilation model is used to explore convective activity in the North Atlantic Ocean for the period from 1992 to 2007. Hydrographic conditions, which are relatively well observed during this period, are used to compare modeled and observed winter mixed-layer depths and water mass anomalies in relation to Deep Western Boundary Current transports and meridional overturning circulation (MOC) changes at the exit of the subpolar basin. The assimilation differs markedly from local observations in the March mixed-layer depth, which represents deep convection and water mass transformation. However, mean MOC rates at the exit of the subpolar gyre, forced by stratification in the mid-latitudes, are similar to estimates based on observations and show no significant decrease during the 1992–2007 period. SODA reproduces the deep Labrador Sea Water formation in the western North Atlantic without any clear indication of significant formation in the Irminger Sea while the lighter upper Labrador Sea Water density range is reached in the Irminger Sea in the 1990s, in agreement with existing assumptions of deep convection in the Irminger Sea and also supported by computed lag correlations with the Labrador Sea. Deep Water transformation mainly takes place in the eastern North Atlantic. The introduction of CFC-11 into the SODA model as a tracer reproduces the mean and multiyear variations of observed distributions.

Document Type: Article
Keywords: Labradorsee, SODA-Modell, assimilation, subpolarer Nordatlantik; Assimilation; SODA model; Meridional overturning; Convection; Mixed-layer depth
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.dsr.2009.01.001
ISSN: 0967-0637
Projects: SFB460
Date Deposited: 15 May 2009 12:14
Last Modified: 01 Nov 2016 13:10
URI: http://oceanrep.geomar.de/id/eprint/3244

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