Ocean-atmosphere coupling in the Mediterranean Sea from TOPEX/POSEIDON, ERS1 and AVHRR data

Abstract

The objective of this work is to evaluate the patterns of the oceanatmosphere coupling in the Mediterranean sea using the statistical analysis of the time series of three satellite measured variables: wind stress curl computed from the surface wind velocities measured by the European Remote Sensing SatelliteERS1, sea levelanomalies from the merged ERS1-TOPEX/POSEIDON altimetric data and the sea surface temperature from the NOAA/NASA Pathfinder AVHRR Oceans Project. This study examines the ocean-atmosphere coupling patterns in time and space through a canonical correlation analysis of the fields. The wide and exhaustive coverage of the oceanic and atmospheric fields from satellites (such as TOPEX/POSEIDON and ERS1) allow a potential detailed inspection of the coupling. In this study we assess the role of wind stress and/or sea surface temperature space/time variations as forcing mechanisms of the sea level variability for the total 440 day duration (from October 1992 to December 1993) of the three satellite data sets in the different Mediterranean sub-basins. The linear barotropic vorticity equation is computed in order to estimate if the Mediterranean sea level response to wind forcing is barotropic. Results indicate that except for the Strait of Sicily and the Adriatic sea the barotropic response is not dominant. From the canonical correlation analysis, a correlation of 0.57 for the first mode between the sea level anomaly and the wind stress curl indicates a significant local coupling between them, especially in areas of the Eastern Mediterranean. Two uncoupled annual cycles are found in the sea surface temperature data.