Exploratory Research on the Causes of Salinity Errors in the CCSM Coupled Climate Models with Focus on the Subpolar North Pacific

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0451479Intellectual Merit: Tremendous advances in coupled climate models have been made in the last 10 years and they are being used both for both region and global predictions of climate. As such, there is an urgent need to evaluate their performance critically. The Community Climate System Model (CCSM version 2) developed at National Center for Atmospheric Research (NCAR) with help from the scientific community shows significant errors in sea surface salinity in the sub-polar North Pacific where the sea surface salinity (SSS) is too high. Preliminary investigation indicates that similar errors occur in the most recent version of the model. Related to the SSS errors are far too deep mixed-layers is the western sub-polar North Pacific. This project will analyze the fully coupled ocean-atmosphere model and a mixed-layer ocean coupled to an atmospheric general circulation model when it becomes available. In particular, the research will focus on what is causing the errors and what the consequences for the errors on the ocean model.The expected results include a better understanding of the role that SSS plays in the coupled climate system. How errors in the upper ocean salinity budget act to break the fresh water dominated stratification in the subpolar North Pacific will be established. The importance of evaporation, precipitation, and runoff errors, as well as errors owing to sea-ice and ocean transport and mixing processes will be addressed. Tthe heat and fresh water transport in the ocean, with focus on the North Pacific and how mode and intermediate water form in the coupled model will also be examined. This study will lead to improved understanding on how the CCSM model works and what improvements need to be made in the model.Broader Impacts: The proposed research will add a significant contribution to the evaluation and development of the Community Climate System Modeling (CCSM) effort at NCAR by members of the academic oceanographic community. The lead investigator is also a participant in a community effort to establish petascale computing needs for the geosciences. Direct involvement with the CCSM model will help in this effort. Both PI's are from an under-represented group in oceanography and the collaboration with CCSM scientists at NCAR will enable them to further develop their careers. The lead PI is also actively involved in the planning of a workshop to establish a mentoring network for women in physical oceanography.