Reanalyses for dense shelf water cascading in the Cap de Creus Canyon and the atmospheric winter conditions

Abstract

In the Gulf of Lion (GoL), during cold winters, the local northerly winds cool the continental shelf water, increasing its density until it loses enough buoyancy to sink mainly through the submarine canyon of Cap de Creus. This process is known as shelf water cascading. To assess the interannual variability of the intensity of these events in the past decades, we use the reanalysis dataset Med MFC from the Mediterranean Sea, which has proved to correlate well with in-situ observations of cascading. This also provides a 3D view of the water properties and how they evolve in time. Then, we calculate the sea surface heat and buoyancy fluxes that modify the density of the shelf water using the atmospheric ERA5 and hydrological GloFAS reanalyses. The river freshwater input, the heat loss and the precipitation have been proved to influence the density of shelf water and the intensity of cascading. These fluxes are correlated with the modes of climate variability of the Atlantic Ridge (AR) and Scandinavian Blocking (SCAN): positive phases of AR together with negative phases of SCAN in winter create a larger buoyancy loss on the shelf water in the GoL, and vice versa.