Assimilation of Cryosat 2 Arctic Sea-Ice Freeboard in an Ensemble of Coupled GEOS5

Guillaume Vernieres1, Bin Zhao2, Richard I Cullather3, Santha Akella4, Yury V Vikhliaev5, Nathan T Kurtz2 and Robin M Kovach5, (1)NASA GSFC, Greenbelt, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)University of Maryland College Park, Earth System Science Interdisciplinary Center, College Park, MD, United States, (4)Global Modeling and Assimilation Office (GMAO), NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)NASA, GSFC, Greenbelt, MD, United States
Abstract:
An ensemble of coupled GEOS5 (ocean, atmosphere and sea-ice) hindcast is used to temporally downscale monthly retrievals of Arctic sea-ice freeboard estimated from Cryosat 2. The downscaling technique uses an asynchronous ensemble Kalman filter to project the observed monthly mean sea-ice freeboard onto the 5 prognostic sea ice thickness categories of the sea-ice model. The analysis is diagnosed by comparing against independent observations of sea-ice thickness, sea-ice fraction, and sea-ice drift within the assimilation window of the study.

The sensitivity of the long range (9 months) forecast to the initialization of sea-ice thickness is also investigated by comparing 2 forecasts initialized with and without observed freeboard.

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