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Original Research Papers

Cessation and partial reversal of deep water freshening in the northern North Atlantic: observation-based estimates and attribution

Authors:

Artem Sarafanov ,

P.P. Shirshov Institute of Oceanology, 36, Nakhimovskiy Prospect, 117997 Moscow, RU
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Herlé Mercier,

Laboratoire de Physique des Océans, Ifremer, UMR 6523 CNRS/IFREMER/IRD/UBO, Plouzané, FR
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Anastasia Falina,

P.P. Shirshov Institute of Oceanology, 36, Nakhimovskiy Prospect, 117997 Moscow, RU
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Alexey Sokov,

P.P. Shirshov Institute of Oceanology, 36, Nakhimovskiy Prospect, 117997 Moscow, RU
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Pascale Lherminier

Laboratoire de Physique des Océans, Ifremer, UMR 6523 CNRS/IFREMER/IRD/UBO, Plouzané, FR
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Abstract

Recent decadal salinity changes in the Greenland-Scotland overflow-derived deep waters are quantified using CTD data from repeated hydrographic sections in the Irminger Sea. The Denmark Strait OverflowWater salinity record shows the absence of any net change over the 1980s–2000s; changes in the Iceland—Scotland Overflow Water (ISOW) and in the deep water column (σ0 > 27.82), enclosing both overflows, show a distinct freshening reversal in the early 2000s. The observed freshening reversal is a lagged consequence of the persistent ISOW salinification that occurred upstream, in the Iceland Basin, after 1996 in response to salinification of the northeast Atlantic waters entrained into the overflow. The entrainment salinity increase is explained by the earlier documented North Atlantic Oscillation (NAO)-induced contraction of the subpolar gyre and corresponding northwestward advance of subtropical waters that followed the NAO decline in the mid-1990s and continued through the mid-2000s. Remarkably, the ISOW freshening reversal is not associated with changes in the overflow water salinity. This suggests that changes in the NAO-dependent relative contributions of subpolar and subtropical waters to the entrainment south of the Iceland—Scotland Ridge may dominate over changes in the Nordic Seas freshwater balance with respect to their effect on the ISOW salinity.

How to Cite: Sarafanov, A., Mercier, H., Falina, A., Sokov, A. and Lherminier, P., 2010. Cessation and partial reversal of deep water freshening in the northern North Atlantic: observation-based estimates and attribution. Tellus A: Dynamic Meteorology and Oceanography, 62(1), pp.80–90. DOI: http://doi.org/10.1111/j.1600-0870.2009.00418.x
21
Citations
  Published on 01 Jan 2010
 Accepted on 12 Oct 2009            Submitted on 20 Mar 2009

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