Monitoring the Eastern Alboran Using Combined Altimetry, in Situ and Temperature Data

As part of the EU funded OMEGA project a cruise to the Eastern Alboran (Western Mediterranean) was carried out on board RRS Discovery during December 1996 and January 1997. During the cruise, a fine scale survey, designed to be oriented along ERS ground tracks, was repeated several times. Several additional survey legs were carried out, part of which lay along additional ERS or TOPEX/POSEIDON altimeter ground tracks. Hydrographic and current profile data were collected continuously along these survey tracks using an undulating, towed CTD and an Acoustic Doppler Current Profiler referenced to a Global Positioning System. The in situ data have been merged with the along track altimeter data to give profiles of the absolute surface current at several locations across the Almeria-Oran front, which limits the easternmost gyre in the Alboran gyre system. Where a track was repeated, several estimates of the absolute current profile have been made in order to try and understand some of the possible sources of error in the estimates. After the “one-time” calculation of the absolute profiles, several years of repeated altimeter data have been used to monitor the flow across the Almeria-Oran front. At times, the front appears to move to the south, apparently when the eastern Alboran gyre collapses, as observed in previous in situ and remote sensed studies. It is also possible to see times when the front moves northward and intensifies.