Seasonal variability of the ocean mixed layer depth depending on the cape Ghir filament and the upwelling in the Moroccan Atlantic coast

Abstract The determination of the monthly variations of the ocean mixed layer depth (MLD), in relationship with upwelling and filament is important in a climate change perspective. This paper presents a monthly change of the mixed layer properties, temperature, salinity, oxygen and fluorescence, to provide a better understanding of the relationship between upwelling, filament and the monthly variability of the MLD in the cape Ghir region latitude 31°N in Moroccan Atlantic coast. Firstly, we compared the MLD using the threshold method and the gradient method of temperature and density from CTD profiles in-situ data. Secondly, we observed the activity of upwelling variability in the region by satellite data. In the other hand, we used monthly mean seawater velocity from Mercator model to identify the filament structure. The general pattern of the in-situ MLD varies between 20m in summer and 150m in winter as the MLD variability derived from Mercator model. The deepest MLD occur in December and February, it coincides with a weak activity of upwelling. During April, June and August, the mixed layer is shallow, accompanied with a high activity of upwelling filament. In October, the mixed layer was deeper following a persistent activity of upwelling.