The MEDGIB experiment, a valuable data set to test the MYOCEAN system in the Strait of Gibraltar and Alboran Sea

Abstract

The Gibraltar Strait is a hot spot area of maritime traffic being the natural door for the shortest route between Asia and Europe. 1/6 of the global marine trade is passing by the Gibraltar Strait every year. From an oceanographic point of view, the Gibraltar Strait is a challenging place for any operational system because it is the natural connection between the Mediterranean basin circulation and the Atlantic Ocean. On September 2014 an intensive drifter deployment was carried out in the Gibraltar Strait to validate the European MYOCEAN operational system on the frame of MEDESS-4MS project. The experiment consisted on deploying 35 satellite tracked drifters, mostly of CODE type equipped with temperature sensor and at sampling rate of 30 minutes, distributed along the strait and on both sides of the Gibraltar strait. Particular attention was put to perform a spatially quasi-synoptic deployment by coordinating four boats covering an area of about 340 nmˆ2 in 6 h. Up to our knowledge, the obtained set of trajectories gives for the first time a comprehensive lagrangian view of the inflow of the Atlantic waters and their recirculation over the Alboran Sea constituting a valuable data set to validate the operational systems in such challenging area. We show results intercomparing the drifters trajectories against the MY-OCEAN IBI system, the VHF surface radar fields and the regional high resolution SAMPA system. Additionally we test how surface quasigeostrophic theory (SQG) can be a very useful diagnostic tool to obtain operational velocity fields from direct processing of SST images