Scharffenberg, Martin, M. G., Institut for Marine Research,, Hamburg, Germany, martin.scharffenberg@zmaw.de
Stammer, Detlef, D. ., Institut for Marine Research, Center for Marine and Atmospheric Sciences , University Hamburg, Hamburg, Germany, detlef.stammer@zmaw.de

ANNUAL VARIATIONS OF GEOSTROPHIC CURRENTS AND EDDY KINETIC ENERGY INFERRED FROM TOPEX/POSEIDON-JASON-1 TANDEM MISSION DATA

Geostrophic surface velocity anomalies are used to analyze the annual variations of the large-scale geostrophic currents and of the Eddy Kinetic Energy (EKE) field of the mesoscale circulation. The underlying current field was estimated from the Jason-TOPEX/Poseidon (JTP) tandem altimetric sea surface height (SSH) data using the parallel track approach with a 10 km along-track resolution over 109 repeat cycles, equivalent to a 3 year period (09/2002 – 09/2005). The analysis of the flow-field reveal seasonal changes of all major current systems. Furthermore zonal jets emerge on the seasonal cycle in the tropical Pacific, Atlantic and Indian Ocean. There the amount of the seasonal signal at the total variance for the zonal velocity component is greater than 70 %. A comparison with the Acoustic Doppler Current Profiler (ADCP) data obtained on board the VOS Oleander along a nominal path connecting Bermuda with the U.S. main land, was performed to test the annual signal of the geostrophic flow-field against in situ data with a comparable time scale. Below 75 m, to be out of the Ekman layer, magnitude and phase of the ADCP and JTP velocities agree reasonably. One third of the 3 year mean EKE values are explained within the annual EKE signal. Major current systems stand out in magnitude of seasonal EKE variations beside strong seasonal signals in the Gulf of Tehuantepec and the whole equatorial Pacific, Atlantic and Indian Ocean.

Poster presentation

Presentation is given by student: Yes
Session #:006
Date: 03-03-2008
Time: 17:30 - 19:30