A Coupled Atmosphere-Sea Ice Model Study of the Role of Sea Ice in Climatic Predictability

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  • 1 Institute of Atmospheric Physics, University of Arizona, Tucson 85721
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Abstract

The potential role of early autumn sea ice extent as a Predictor of late autumn climatic anomalies is investigated with a coupled atmosphere-sea ice model. Two ensembles of four simulations, one with an initially large ice extent and one with a small extent, are made and a 30-day mean, late autumn climatic state is calculated for each ensemble. The mean states are compared in order to determine how the initial difference in ice cover evolves, whether statistically significant differences exist between ensemble-mean climatic states, and what mechanisms are responsible for the differences. The late autumn ice covers of the two ensembles differ principally in the thickness of ice rather than ice extent. Statistically significant regional differences in the 750 mb streamfunction and potential temperature exist but appear to be of limited value for forecasting midlatitude climatic anomalies. There is a stronger surface cooling of the atmosphere in the ensemble with thicker ice which is compensated by a larger convergence of the eddy flux of sensible beat. A feedback mechanism, which is elective over the mean but not over land, relates the differences in the 750 mb streamfunction and heating fields.

Abstract

The potential role of early autumn sea ice extent as a Predictor of late autumn climatic anomalies is investigated with a coupled atmosphere-sea ice model. Two ensembles of four simulations, one with an initially large ice extent and one with a small extent, are made and a 30-day mean, late autumn climatic state is calculated for each ensemble. The mean states are compared in order to determine how the initial difference in ice cover evolves, whether statistically significant differences exist between ensemble-mean climatic states, and what mechanisms are responsible for the differences. The late autumn ice covers of the two ensembles differ principally in the thickness of ice rather than ice extent. Statistically significant regional differences in the 750 mb streamfunction and potential temperature exist but appear to be of limited value for forecasting midlatitude climatic anomalies. There is a stronger surface cooling of the atmosphere in the ensemble with thicker ice which is compensated by a larger convergence of the eddy flux of sensible beat. A feedback mechanism, which is elective over the mean but not over land, relates the differences in the 750 mb streamfunction and heating fields.

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