The Okhotsk Sea plays an important role in the North Pacific Ocean circulation through its influence on the formation of the North Pacific Intermediate Water (NPIW). In addition, it has a highly variable sea ice cover, which influences not only water mass formation, but also the atmospheric circulation over the sub-polar North Pacific. The dense water formed along the Okhotsk Sea shelves is the source of this NPIW and depends critically on the details of the coastal polynyas and tidal mixing, and their relation to the stratification and mean circulation. Though recent observations have shown that brine rejection from sea ice sinks at the tidal front over the shelves, many questions remain as to the relationship among polynya openings, ice production, ocean-ice heat exchange, and shelf dynamics.
Intellectual merit: In this project, oceanographers at the University of Washington will perform a series of sensitivity experiments with a regional coupled ice-ocean model to investigate the sea ice and water mass formation and their inter-annual variability. In addition to coupling the Regional Ocean Model System, a terrain following coastal ocean model, and the Community Sea Ice Model, a sophisticated dynamic-thermodynamic sea ice model, the researcher will also employ new, high quality datasets for model forcing, initialization, and verification. The outcomes of the work will include an integration of available data with a model of the Okhotsk Sea that will also take into account the important physical oceanographic processes in the region. An analysis of the heat and fresh water budgets of the region will also be made, focusing on both the seasonal cycle and inter-annual variability. The dense water formation in the model will be quantified, and the sensitivity of the model to the influence of tides will be tested. In addition to the regional modeling, the researcher will also analyze the influence of the Okhotsk Sea on a larger scale using the Community Climate System Model (CCSM, a global climate model). The regional ocean-ice model will be used to estimate the importance of processes that are absent from the CCSM.
Broader Impacts: The results from this work will not only lead to an improved understanding of polynyas but also to the potential global importance of the Okhotsk Sea. In addition to training a graduate student, the work will also develop a partnership with the Community Climate System Model project at NCAR. The use of the CCSM sea-ice model in a regional context will help with future development of the CCSM as the new generation of super-computers allow for higher resolution climate simulations.
