Science Meetings

Modeling Skin-Layer Salinity With an Extended Surface-Salinity Layer
Song, Y., Lee, T., Moon, J., Qu, T., and Yueh, S. (12-Nov-14)

Due to near-surface salinity stratification, it is problematic to compare satellite-measured surface salinity within the first few centimeters (skin-layer) of the ocean with Argo-measured top-level salinity at 5 m, or with ocean models that do not resolve the skin layer. Although an instrument can be designed to measure the surface salinity, a global scale measurement is currently not available. A regional model can be configured to have a vertical grid in centimeters, but it would be computationally prohibited on a global scale due to time step constraints. Here, we propose an extended surface- salinity layer (ESSL) within a global ocean circulation model to diagnose skin SSS without increasing the computational cost, while allowing comparable solutions with both satellite and Argo salinity at the respective depths. Cross-comparisons with Aquarius and Argo data show that the gridded Aquarius surface salinity has a much stronger seasonal variability than the gridded Argo top-level salinity at 5 m or 10 m, particularly in regions of high precipitation variability, suggesting the exist of strong near-surface vertical salinity stratification. The near-surface stratification is well reproduced by the proposed ESSL model. In comparisons with data-assimilated HYCOM results, the ESSL provides much stronger seasonal variability of SSS, similar to the Aquarius observations. The ESSL solution also provides a useful reference for the global mean SSS to constrain the global calibration constants in Aquarius SSS retrieval.