Observations of open-ocean deep convection in the northwestern Mediterranean Sea: Seasonal and interannual variability of mixing and deep water masses for the 2007-2013 Period
Houpert, L. ; Durrieu de Madron, X. ; Testor, P. ; Bosse, A. ; D'Ortenzio, F. ; Bouin, Marie-Noëlle ; Dausse, D. ; Le Goff, H. ; Kunesch, S. ; Labaste, M. ; Coppola, L. ; Mortier, L. ; Raimbault, P.
We present here a unique oceanographic and meteorological data set focus on the deep convection processes. Our results are essentially based on in situ data (mooring, research vessel, glider, and profiling float) collected from a multiplatform and integrated monitoring system (MOOSE: Mediterranean Ocean Observing System on Environment), which monitored continuously the northwestern Mediterranean Sea since 2007, and in particular high-frequency potential temperature, salinity, and current measurements from the mooring LION located within the convection region. From 2009 to 2013, the mixed layer depth reaches the seabed, at a depth of 2330m, in February. Then, the violent vertical mixing of the whole water column lasts between 9 and 12 days setting up the characteristics of the newly formed deep water. Each deep convection winter formed a new warmer and saltier 'vintage' of deep water. These sudden inputs of salt and heat in the deep ocean are responsible for trends in salinity (3.3?±?0.2 × 10?3/yr) and potential temperature (3.2?±?0.5 × 10?3 C/yr) observed from 2009 to 2013 for the 600-2300 m layer. For the first time, the overlapping of the three 'phases' of deep convection can be observed, with secondary vertical mixing events (2-4 days) after the beginning of the restratification phase, and the restratification/spreading phase still active at the beginning of the following deep convection event.
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