Abstract
Abstract. Particle fluxes (including major components and grain size), and oceanographic parameters (near-bottom water temperature, current speed and suspended sediment concentration) were measured along the Cap de Creus submarine canyon in the Gulf of Lions (GoL; NW Mediterranean Sea) during two consecutive winter-spring periods (2009–2010 and 2010–2011). The comparison of data obtained with the measurements of meteorological and hydrological parameters (wind speed, turbulent heat flux, river discharge) have shown the important role of atmospheric forcings in transporting particulate matter through the submarine canyon and towards the deep sea. Indeed, atmospheric forcing during 2009–2010 and 2010–2011 winter months showed differences in both intensity and persistence that led to distinct oceanographic responses. Persistent dry northern winds caused strong heat losses (14.2 × 103 W m−2) in winter 2009–2010 that triggered a pronounced sea surface cooling compared to winter 2010–2011 (1.6 × 103 W m−2 lower). As a consequence, a large volume of dense shelf water formed in winter 2009–2010, which cascaded at high speed (up to ∼1 m s−1) down Cap de Creus Canyon as measured by a current-meter in the head of the canyon. The lower heat losses recorded in winter 2010–2011, together with an increased river discharge, resulted in lowered density waters over the shelf, thus preventing the formation and downslope transport of dense shelf water. High total mass fluxes (up to 84.9 g m−2 d−1) recorded in winter-spring 2009–2010 indicate that dense shelf water cascading resuspended and transported sediments at least down to the middle canyon. Sediment fluxes were lower (28.9 g m−2 d−1) under the quieter conditions of winter 2010–2011. The dominance of the lithogenic fraction in mass fluxes during the two winter-spring periods points to a resuspension origin for most of the particles transported down canyon. The variability in organic matter and opal contents relates to seasonally controlled inputs associated with the plankton spring bloom during March and April of both years.
Highlights
Atmospheric forcing during 2009–2010 and2010–2011 winter months showed differences in both inten- Atmospheric–ocean interactions play a key role in the modsity and persistence that led to distinct oceanographic re- ification of oceanographic processes
The lower heat losses ate or even or freezing deep in the wsuartfTearchse. eFlaoyCrererxoyafmoshpsalpell,ohcwoeoarlreienags, evaporation of the contirecorded in winter 2010–2011, together with an increased nental shelf trigger the formation of dense water that eventuriver discharge, resulted in lowered density waters over the ally spills over the shelf edge onto the continental slope
Strong wind events were concentrated in the first half of the winter, so the cumulative turbulent heat loss for the whole winter, was 1.6 × 103 W m−2 lower than the previous winter
Summary
Atmospheric forcing during 2009–2010 and2010–2011 winter months showed differences in both inten- Atmospheric–ocean interactions play a key role in the modsity and persistence that led to distinct oceanographic re- ification of oceanographic processes. EFlaoyCrererxoyafmoshpsalpell,ohcwoeoarlreienags, evaporation of the contirecorded in winter 2010–2011, together with an increased nental shelf trigger the formation of dense water that eventuriver discharge, resulted in lowered density waters over the ally spills over the shelf edge onto the continental slope (see shelf, preventing the formation and downslope transport Ivanov et al, 2004, for a review). This causes the transmisof dense shelf water. High total mass fluxes (up to 84.9 g m−2 d−1) recorded sion of the atmospheric signal from shallow to deep waters within a short time range
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