Transfer of particulate matter from the Northwestern Mediterranean continental margin: Variability and controlling factors
Abstract
Long-term observations of monthly downward particle fluxes and hourly currents and temperature
were initiated in 1993 in two canyons of the continental margin of the Gulf of Lion. The goals of this
survey were to estimate its contribution to the CO 2 global budget and to understand the role of
forcing factors in the control of present-day particle exchange across this margin. A previous
statistical analysis of the long-term time series suggested that variability in the transfer of particulate
matter to the deep ocean could be the result of the effect of the meandering of the Northern Current
and by dense water formation in winter rather than variations in the sources of matter. Numerical
simulations have been carried out to consider these hypotheses. A model is used to examine the
impact of local atmospheric forcing (wind stress, heat fluxes, precipitation–evaporation budget) on
the variability of the oceanic circulation and of mass fluxes within the canyons from December to
April, for five consecutive years between 1996 and 2001. Results show an east-west gradient of mass
export on the shelf and a positive correlation between anomalies of dense water formation rates and
interannual variability of particle fluxes. However, in the eastern part of the Gulf, the simulated mass
export from the shelf is not significant, even during a winter of strong convection, when the measured
particle fluxes are at maxima. Moreover, although the model suggests that the dense water formation
could be the major hydrodynamic forcing factor, this process is not sufficient to completely explain
the space and time variations of observed particle fluxes, especially at depth.
Origin : Files produced by the author(s)
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