Over the last decade ocean data assimilation has reached a maturity to match that of atmospheric data assimilation and much progress has been made towards routine generation of global products. This progress was accelerated by the Global Ocean Data Assimilation Experiment (GODAE) which realized that the support for a sustained ocean observing system relied on the prompt and dependable availability of ocean information products.

From a climate perspective, ocean data assimilation is critical for generating initial conditions for seasonal to decadal prediction and for a synthesis (re-analysis) of the historical ocean measurements for climate research. Several global ocean analyses are available today, ranging in sophistication. Although there is the potential for ocean re-analyses to play a similar role in model development and climate research as atmospheric re-analyses, ocean analyses suffer even more from changes in the observing system. As for the atmosphere, ocean re-analyses need scrutiny in regards to many such issues.

One of the primary roles of assimilation in the ocean is to compensate for errors in surface forcing. Thus, information in ocean observations in an assimilation context should also hold information on atmosphere-ocean exchanges. As it seeks to understand, quantify and attribute climate variability and trends, the climate community is increasingly interested in integrated analyses – that is, analyses that are consistent between atmosphere, ocean, land surface, and sea-ice, as well as between our physical and biogeochemical environments.

The presentation will summarize current capabilities and future directions for ocean data assimilation and analyses for climate applications. Some of the challenges to be faced in coupling ocean analyses to those of other Earth system components will be noted as well as some of the progress already made.