Variability of the mixed layer depth and the ocean surface properties in the Cape Ghir region, Morocco for the period 2002–2014

Abstract

The mixed layer depth (MLD) is an active part of the marine environment that couples the underlying ocean to the atmosphere. The aim of this original study in Morocco is to investigate for the period 2002–2014 the relationship between the variability of the MLD with the oceanic sea surface properties and the primary productivity in the Cap Ghir region. This area is very productive along the Atlantic coast of Morocco and we examined in this study the monthly variability of the MLD and its relationship with sea surface properties using data from Copernicus—Marine environment monitoring products, coupling between MLD with SST and upwelling activity in the Cape Ghir area. During winter seasons, the MLD is deeper and observed at around 90 m. Compared to others seasons, it is varying between 10 and 25 m. The monthly mean SST show very cold temperature (around 17 °C) during winter season and a warm temperature (around 23 °C), during summer season. In fact, the colder waters in surface coincide with the deepest MLD and the warmer waters coincide with the shallowest MLD. From 2009 to 2011, the MLD was very shallower (40 m) with some observed variability between 30°30N and 31°N, due to the dynamic of Cape Ghir. Regarding to the upwelling activity, the upwelling index shows a clear seasonality (higher activity in summer and weaker in winters) and some relationship between the upwelling index and the MLD were investigated. The characteristic’s feature of the variability of the MLD mixed layer in the Cape Ghir area is based on the fast response of the upwelling activity than the other parameters like SST. When the MLD is shallower, the SST is still cooler for two months more. The oceanographic dynamic of the Cape Ghir area is very complex in nature and, following the MLD, this parameter is an adequate parameter for detecting the activity of the upwelling in this area.