Variability and Uncertainties in Water Masses Formation Estimation from Space

Roberto Sabia, Telespazio-Vega for European Space Agency, Frascati, Italy, Marlene Klockmann, Max Planck Institute for Meteorology, Hamburg, Germany, Craig Donlon, European Space Agency, ESTEC, Villanueva De La Can, Spain and Diego Fernandez-Prieto, European Space Research Institute (ESRIN) - European Space Agency (ESA), Frascati, Italy
Abstract:
Satellite-based measurements of sea surface salinity (SSS) and sea surface temperature (SST) have recently been used to generate routinely remotely-sensed surface T-S diagrams. Even more recently, these T-S diagrams have been exploited as a diagnostic tool to derive water masses formation rates and their related geographical extent. As such, SSS data now available through SMOS and Aquarius satellite missions allow to study the effect of temporally-varying global SSS fields on water mass formation.

The SST and SSS (and therefore density) at the ocean surface are largely determined by fluxes of heat and freshwater. A surface density flux can be primarily parameterized as a function of the latter two and describes the change of the seawater density at the surface. The formation of water masses as a function of SST and SSS is derived from the surface density flux by integrating the latter over a specific area and time period in bins of SST and SSS and then taking the derivative of the total density flux with respect to density.

Yearly, seasonal and monthly water mass formation rates for different SST and SSS ranges are evaluated, and the formation peaks are remapped geographically to analyze the extent and the temporal evolution of the formation area. Known water masses can then be identified and traced.

Ongoing work aims at extending this study mainly along two avenues by: 1) expanding systematically the spatial and temporal domain of the study to various ocean basins and to the entire lifetime of available SMOS/Aquarius SSS observations, also characterizing any water mass formation seasonal to inter-annual variability; 2) performing a thorough error propagation by using Monte Carlo trials to assess how errors in satellite SSS and SST translate into uncertainties in water masses formation rates and geographical areas extent.

Back to: Satellite-Data-Based Studies of Heat and Freshwater Budgets and the Air-Sea Interface: From Diurnal to Decadal Timescales I