Satellite-Driven Estimates of Water Mass Formation and Their Spatio-Temporal Evolution


We derive water mass transformation and formation rates using satellite-derived datasets of salinity, temperature and fluxes of heat and freshwater over the North Atlantic, North Pacific and Southern Ocean. The formation rates are expressed in three coordinate systems: (1) density, (2) temperature-salinity and (3) latitude-longitude. In the North Atlantic and North Pacific, peak formation occurs south of the western boundary current extensions during the winter months of the study period. In the Southern Ocean, wintertime peak formation occurs just north of the sub-Antarctic Front. The satellite-derived water mass properties and formation areas agree well with previous estimates from literature. The location of peak Mode Water formation varies slightly with time in all coordinate systems. We assess seasonal and inter-annual variability in all three basins from 2012 to 2014. We assess the impact of satellite uncertainties on final estimates of formation rates and areas with Monte-Carlo simulations. The simulations provide insights on the associated uncertainty of formation estimates. They also provide information on the geographic spread of the water mass formation area subject to the satellite errors. We find that the total uncertainty is dominated by the uncertainty in the sea surface salinity dataset. This stresses the need for frequent and increasingly accurate sea surface salinity data for reliable estimates of water mass formation rates and areas. Our study highlights the feasibility of providing satellite-based estimates of water mass formation rates and areas. The good spatio-temporal coverage of satellite data further adds to the utility of the approach.
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