Atmospheric Forcing of Hudson Bay Sea Ice in Spring

In this study we examine thermodynamic and dynamic forcing of sea ice during spring from 1980-2005. Thermodynamic contributions to seasonal ice loss in Hudson Bay are investigated using correlations between trends in sea ice extent and surface air temperatures (SATs), while dynamic contributions are investigated using correlations between SAT anomalies and climate indices. Correspondence between changes in ice and atmospheric circulation patterns in Hudson Bay is also examined in the context of relative vorticity to ascertain regional contributions to ice and atmospheric variability, and resulting feedback mechanisms.

Results of the study show that using both fall and spring SATs significantly improve the prediction interannual spring sea ice extents. Including the relative vorticity of ice with SATs, up to 80% of the variance in spring time SIEs can be explained. Teleconnection data is presented showing that interannual SATs are highly correlated to the East Pacific/North Pacific (EP/NP) index, this index together with the PDO are predictive of SATs during the break-up period (R=0.57, p=0.0017). Analysis shows that sea ice relative vorticity exhibits significant variability from 1980 to 2006, with an increase in frequency and duration of cyclonic activity during summer following 1998. In addition, statistically significant correlations between ice relative vorticity and SIC anomalies demonstrate connections between circulation and ice accumulation and/or depletion during spring.