On the assimilation of ice velocity and concentration data into large-scale sea ice models

[摘要] Data assimilation into sea ice models designed for climate studies hasstarted about 15 years ago. In most of the studies conducted so far, it isassumed that the improvement brought by the assimilation is straightforward.However, some studies suggest this might not be true. In order to elucidatethis question and to find an appropriate way to further assimilate sea iceconcentration and velocity observations into a global sea ice-ocean model, weanalyze here results from a number of twin experiments (i.e. experiments inwhich the assimilated data are model outputs) carried out with a simplifiedmodel of the Arctic sea ice pack. Our objective is to determine to whatdegree the assimilation of ice velocity and/or concentration data improvesthe global performance of the model and, more specifically, reduces the errorin the computed ice thickness. A simple optimal interpolation scheme is used,and outputs from a control run and from perturbed experiments without andwith data assimilation are thoroughly compared. Our results indicate that,under certain conditions depending on the assimilation weights and the typeof model error, the assimilation of ice velocity data enhances the modelperformance. The assimilation of ice concentration data can also help inimproving the model behavior, but it has to be handled with care because ofthe strong connection between ice concentration and ice thickness. This studyis first step towards real data assimilation into NEMO-LIM, a global seaice-ocean model.

[学科分类] 海洋学与技术