Variability of Rhodes and Ierapetra Gyres during Levantine Intermediate Water Experiment: Observations and model results

This work is aimed at studying the variability of Rhodes and Ierapetra Gyres during the Levantine Intermediate Water Experiment. Sea surface temperature maps, derived from Global Area Coverage advanced very high resolution radiometer (AVHRR) data in the framework of the Pathfinder Project and sea level anomalies, derived from TOPEX/ Poseidon altimeter, were used to track the evolution, both in terms of dimension and position, of the cyclonic Rhode Gyre and Ierapetra anticyclone. The analysis was performed for the period from October 1994 to the end of April 1995, i.e., from the preconditioning to the spreading phase of Levantine Intermediate Water. The description of the surface fields was complemented by a temporal evolution study of the Rhodes and Ierapetra Gyres hydrological vertical structure. European Centre for Medium-Range Weather Forecasts AVHRR-derived fluxes have been used as forcing for a numerical model to study the variability of the mixed layer in both gyres. The simulated upper layer dynamics remarkably matched remotely sensed and in situ observations. This work shows that using a combined analysis of observational data and model simulations, we were able to propose a dynamical scenario for the winter of 1995 where the Levantine basin was characterized by short intense heat loss events occurring during at the beginning of December. The intense air-sea interaction contributed to deep, instead of intermediate, mixing as confirmed by remote sensing, in situ data, and model experiments. A hypothesis on the role of the lateral contribution on the water column bouyancy content in the Rhodes Gyre was formulated.