An Update on the Ice Climatology of the Hudson Bay System

The objective of this paper is to examine the thermodynamic and dynamic forcing of sea ice within the Hudson Bay System, including Hudson Bay, Hudson Strait, and Foxe Basin. Changes in fall and spring sea ice extents (SIEs) are examined in relation to seasonal surface air temperatures (SATs) and winds, as are changes in freeze-up dates and breakup dates. The proportional leverage of the fall (lag1) and spring SATs and winds on ice is statistically examined per basin. Results show SATs have increased significantly since the mid-1990s and that increases in the fall are higher than the spring period. Fall SATs are highly related to fall SIEs (R-2 = 0.79-0.82). For every 1 degrees C increase in SAT, SIB decreases by 14% (% of basin area) within the Hudson Bay System; a 1 degrees C increase delays freeze-up by 0.7 to 0.9 weeks on average. Spring SIEs and breakup dates are shown to be highly correlated with fall (lag1) and spring SATs, and with U and V component winds. Proportionately, spring and fall SATs combined play a dominant role (70-80%) in SIB, and the remaining leverage is attributed to dynamic forcing (winds). The relative leverage of fall (lag1) SATs and surface winds are shown to be significant and vary by basin. The open water season has on average increased by 3.1 (+/- 0.6) weeks in Hudson Bay, 4.9 (+/- 0.8) weeks in Hudson Strait, and 3.5 (+/- 0.9) weeks in Foxe Basin.