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EKE and circulation variability in the Labrador Sea and the North Atlantic subpolar gyre

Andreas Funk(1) , Peter Brandt(1) , Friedrich Schott(1) , Lars Czeschel(1) , and Carsten Eden(1)

(1) IFM-GEOMAR, D├╝sternbrooker Weg 20, 24105 Kiel, Germany

Abstract

The eddy field from 1993 to 2001 in the Labrador Sea was calculated from sea level anomalies (SLA) measured by TOPEX/Poseidon and ERS-2 altimeters. Correlation between in-situ measurements in the Central Labrador Sea and eddy kinetic energy (EKE) calculated from altimeter data was improved using a quadratic correction with respect to significant wave height. The mean EKE field comprises maxima within the main boundary currents and in the Central Labrador Sea. The annual cycle is most distinctive in the Central Labrador Sea. A southward propagation of EKE from the West Greenland Current (WGC) into the Central Labrador Sea can be seen with a propagation speed of about 3 cm/s. The EKE Maximum in the Labrador Current stays well separated from the one in the Central Labrador Sea. Distinctive interannual variability is seen in the WGC and in the Central Labrador Sea. The WGC shows strong EKE maxima in early winters 1993 and 1997-1999, while in the Central Labrador Sea the strongest maxima are found in March/April 1993-1995 and 1997. The WGC shows continuously high levels of EKE during 1994-1996 and a seasonal cycle with minima in summer and maxima in winter during 1997-2000. Results from altimetry are compared with in-situ observations and results from a eddy-resolveddy-resolving model. Along-track altimeter data from TOPEX/Poseidon, Jason-1, ERS-2, Envisat, and GFO acquired over the North Atlantic subpolar gyre are compared using EOF analysis and, after adjusting their respective means, merged together providing a continuous time series from 1993 to 2005. The interannual variability of the SLA is analysed and shows a decreasing strength of the North Atlantic subpolar gyre. A similar analysis of EKE is performed. The SLA and EKE variability as obtained from altimetry is discussed with respect to different forcing mechanisms represented by large-scale indices like, e.g. the North Atlantic Oscillation.

 

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                 Last modified: 07.10.03