A Sensus for the Highest Sea Surface Warming Rate in the Mediterranean Sea
Reul, Nicolas; Chapron, bertrand; Piolle, Jean-Francois

Mediterranean regions have been identified as one of the two main hot-spots of climate change (Giorgi, 2006), meaning that climate is especially responsive to global change in this area. Large decrease in mean precipitation and increase in precipitation variability during dry (warm) season are expected as well as large increase in temperature (+1.4 to +5.8°C in 2100). Large uncertainties however remain on the future evolution of climate in the Mediterranean. Progress has to be made in the monitoring and modelling of the Mediterranean climate in order to quantify the on-going changes and to better predict their future evolution as guidelines for the development of adaptation measures. In that context, satellite oceanography has made tremendous progresses since the 1970s, and today satellite observations over the ocean are key components of the global climate observing systems.

In this study, we re-analysed long-time series of high-resolution SST data acquired since 1981 from AVHHRR Pathfinder, from the Advanced Along-Track Scanning Radiometer multimission data (the AATSR Reprocessing for Climate (ARC) dataset) and from the Medspiration GHRSST products over the mediterreanean sea. Annual mean cycles are determined based on the 30 year-long time series and used to inferred 10-days averaged SST anomalies at 2 to 4 km resolution. Statistical analysis reveal that the maximum SST warming rates reaching more than 0.06°C/year for the mediterannean sea (and probably over the globe) are found south of the Crete Island. In summer time the Crete island (which is characterized by three high mountain ridges, crossing the island from west to east, and reaching altitudes of more than two kilometer) tends to block the Etesian south]eastward winds, thus causing a funneling effect of the wind through the western and eastern straits. As revealed by ASAR wind speed imagery, the wind blockade at Crete yields localized low sheared wind stress in the lee of the Island. By combining SST data, ASAR high-resolution wind and currents and Land surface temperature products, we analyse if the land surface temperature warming of Crete during summer could be responsible for a modification of the low-wind pattern extent in the lee of Crete and therefore of the highest warming rate found in the European seas.