Ocean State Estimation for Climate Research

Spurred by the development of satellite and in situ observing systems, global ocean state estimation has flourished in the past decade. Today, a suite of global ocean state estimates has been generated and is being applied to studies over a wide range of subjects in physical oceanography and climate research as well as other disciplines. This paper highlights some examples Of using ocean state estimations for ocean and climate research. Many assimilation groups from different countries participated in a Climate Variability and Predictability program/Global Ocean Data Assimilation Experiment global ocean reanalysis evaluation effort in which intercomparisons were performed for a suite of diagnostic quantities and indices, including evaluations against observations. Examples of the intercomparisons are presented to highlight the consistencies and uncertainties of the estimation products and to examine the ability of these products to detect climate signals. Future challenges for state estimation for climate applications are also discussed.