Temperature variability in the Bay of Biscay during the past 40 years, from an in situ analysis and a 3D global simulation

Type Article
Date 2009-04
Language English
Author(s) Michel Sylvain1, Treguier Anne-Marie2, Vandermeirsch Frederic1
Affiliation(s) 1 : IFREMER, Dynam Environnement Cotier Phys Hydrodynam & Sedi, F-29280 Plouzane, France.
2 : IFREMER, CNRS, Lab Phys Oceans, IRD,UBO, F-29280 Plouzane, France.
Source Continental Shelf Research (0278-4343) (Elsevier), 2009-04 , Vol. 29 , N. 8 , P. 1070-1087
DOI 10.1016/j.csr.2008.11.019
WOS© Times Cited 30
Keyword(s) Ocean circulation model, Air sea flux, Heat budget, Climatic change, Interannual temperature variability, Bay of Biscay
Abstract A global in situ analysis and a global ocean simulation are used jointly to study interannual to decadal variability of temperature in the Bay of Biscay, from 1965 to 2003. A strong cooling is obtained at all depths until the mid-1970's, followed by a sustained warming over similar to 30 years. Strong interannual fluctuations are superimposed on this slow evolution. The fluctuations are intensified at the surface and are weakest at similar to 500 m. A good agreement is found between the observed and simulated temperatures, in terms of mean values, interannual variability and time correlations. Only the decadal trend is significantly underestimated in the simulation. A comparison to satellite sea surface temperature (SST) data over the last 20 years is also presented. The first mode of interannual variability exhibits a quasi-uniform structure and is related to the inverse winter North Atlantic Oscillation (NAO) index. Regarding the vertical structure, most cool and warm anomalies are generated at the surface, with the strongest ones penetrating down to 700 m and lasting up to 5 years. The complete heat budget from 1965 to 2004 is presented, including the contributions of vertical transport, freshwater flux and surface elevation. Interannual anomalies are mainly generated by the surface heat flux, while oceanic transports may become more important at longer time scales. (C) 2009 Elsevier Ltd. All rights reserved.
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