SOCIB Visitors: Pierre-Marie Poulain (OGS) visited SOCIB to work on the SMDT improvement
Pierre-Marie Poulain, Senior Scientist at "Istituto Nazionale di Oceanografia e di Geofisica Sperimentale" (OGS), visited SOCIB during the first week of July. The mainl objective of his visit was to work on the improvement of the SMDT (Synthetic Mean Dynamic Topography) in collaboration between A. Pascual -IMEDEA (CSIC-UIB)-, M.-H. Río (CLS) and in the frame of SOCIB Implementation Plan. This collaboration started in 2011 and the goal is to produce a new SMDT before the end of 2012 and to test it, in particular, in the vicinity of the Balearic Sea (Western Mediterranean) where other observations (e.g., from SOCIB gliders) can be used to validate the circulation patterns obtained from altimeter data and the new SMDT. Taking advantage of his visit, Pierre-Marie gave a seminar about surface circulation of the Mediterranean Sea at IMEDEA (CSIC-UIB) on July 4.
Abstract: Drifter observations and satellite-derived sea surface height data are used to study quantitatively the surface geostrophic circulation of the entire Mediterranean Sea for the period spanning 1992-2010. After removal of the wind-driven components from the drifter velocities and low-pass filtering in bins of 1° x 1° x 1 week, maps of surface geostrophic circulation (mean flow and kinetic energy levels) are produced using the drifter and/or satellite data. The mean currents and kinetic energy levels derived from the drifter data appear stronger/higher with respect to those obtained from satellite altimeter data. The maps of mean circulation estimated from the drifter data and from a combination of drifter and altimeter data are however qualitatively similar. In the Western Basin, they show the main pathways of the surface waters flowing eastward from the Strait of Gibraltar to the Sicily Channel, and the current transporting waters back westward along the Italian, French and Spanish coasts. Intermittent and long-lived sub-basin scale eddies and gyres abound in the Tyrrhenian and Algerian seas. In the Eastern basin, the surface waters are transported eastward by several currents but recirculate in numerous eddies and gyres before reaching the northward coastal current off Israel, Lebanon and Syria and veering westward off Turkey. In the Ionian Sea, the mean geostrophic velocity maps were also produced separately for the two extended seasons and for multi-year periods. Significant variations are confirmed, with seasonal reversals of the currents in the south, and changes of the circulation from anticyclonic (prior to 1 July 2007) to cyclonic, and back to anticyclonic after 31 December 2005.