Constrains On Regional Freshwater Fluxes From A Dynamically Consistent Bidecadal Ocean State Estimate

Jean-Michel Campin1, Gaël Forget2, Patrick Heimbach1,3, Christopher N Hill1, Rui M Ponte4 and Carl I Wunsch5, (1)Massachusetts Institute of Technology, Cambridge, MA, United States, (2)Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States, (3)University of Texas at Austin, Oden Institute for Computational Engineering and Sciences, Austin, TX, United States, (4)Atmospheric and Environmental Research Lexington, Lexington, MA, United States, (5)Harvard University, Cambridge, MA, United States
Abstract:
A dynamically consistent global state estimate for the period 1992-2011 has been produced by the "Estimating the Circulation and Climate of the Ocean" consortium (referred to as ECCO version 4), which combines a wide range of satellite and in-situ (notably float and ship-based) observations, with a coupled ocean-sea ice general circulation model forced by an atmospheric re-analysis. The adjoint technique was used to reduce the model-data misfit in a least-square sense by adjusting a large number of control variables, including initial conditions, atmospheric forcing and some model internal parameters, but preserving a consistent model solution over the full period.

Here we investigate the role of freshwater flux in the context of multi-year salinity variations and transports. The freshwater flux adjustment of the constrained solutions is analyzed in terms of its spatial structures and impact on the solution. Because available freshwater flux estimates suffer from large uncertainties, the product inferred here through formal inversion based on ocean observations is discussed in terms of potential improvements and as a scale dependent problem.

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