Benthic storms in the north-western Mediterranean continental rise caused by deep dense water formation

PUIG, P.; PALANQUES, A.; MARTÍN, J.; RIBÓ, M.; GUILLÉN, J.

Congreso; 2nd Deep-Water Circulation Congress: The Contourite Log-book; 2014

The north-western Mediterranean Sea is a well-known region where dense water formation occurs on a yearly basis due to winter heat losses and evaporation caused by cold and dry northerly winds. Dense waters are formed offshore by open-sea convection, but also on coastal regions along the Gulf of Lions shelf, from where they overflow the shelf edge and cascade downslope until reaching their equilibrium depth. During severe winters, both convection and cascading can reach the basin (>2000m depth), increasing bottom currents and inducing sediment resuspension. To investigate in detail this process, a focused analysis of time series observations collected in the north-western Mediterranean continental rise during winter 2012 has been conducted. Several peaks of suspended sediment concentration coincident with enhanced current speeds were observed during the spreading phase of newly formed dense water. Maximum concentrations reached ~9mg/l while associated current increases ranged between 20 to 40cm.s-1. Such sediment resuspension events can be considered ?benthic storms? and play a major role in the redistribution of sediment particles along this region, presumably contributing to the development of a large field of muddy sediment waves found in the continental rise south from Cap de Creus and La Fonera submarine canyons