Implementation of Estuary-Shelf Freshwater Exchange Parameterizations in the Community Earth System Model

Monday, May 12, 2014 - 07:00
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Riverine freshwater inputs are critical to ocean stratification and influence ocean circulation patterns, water mass formation and global water budgets. The standard configuration of Community Earth System Model (CESM) cannot fully resolve the coastal and estuary dynamics due to high computational costs, which lead to a poor representation of the physical processes in the estuaries and continental shelves. We have developed two computationally efficient parameterizations for coastal freshwater exchanges based on energy, salt, heat, and volume balances, and incorporated them as new modules in the CESM for practical global climate applications. The first is the empirical parameterization based on the improved augmented precipitation method. We consider the impacts of local vertical mixing process within estuaries and coastal river plumes in setting the effective depth of freshwater exchange. A reduction of 5% of the surface salinity biases can be found in the coastal areas. Details of the sensitivity of the simulations are examined for three representative regions with strong runoff in mid-latitudes, tropics and Arctic. The second is a better representation of the riverine volume and stratification fluxes using an estuary-box model. The estuary-box model is formulated in terms of the potential energy balance reflecting the competition of stratifying and mixing processes in each estuary system. The framework for integrating the estuary-box modeling system with CESM also will be evaluated and discussed for Columbia River and Amazon river estuary systems.