Fine Resolution Altimetry Data for a Regional Application in the Bay of Biscay

Eddy properties in the Bay of Biscay are studied from 15 years of reprocessed along-track altimeter data using a wavelet-based analysis. Associated spatial scales vary from similar to 60 km in the inner bay to 130 km offshore, with amplitudes also increasing offshore. These characteristics are not correctly represented in standard gridded products, which are too smooth. Compared to observed along-track data, geostrophic currents and eddy kinetic energy estimated from standard gridded maps are too weak by a factor of 33% and 50%, respectively. A new mapping approach is proposed to better resolve the local mesoscale variability. It uses the larger wavelengths of the standard gridded maps as a first guess and adds an increment based on the short scale signals of the along-track data. First results show coherent fine scale signals, consistent with the information provided by MODIS imagery.