Sensitivity of Hudson Bay Sea ice and ocean climate to atmospheric temperature forcing

A regional sea-ice-ocean model was used to investigate the response of sea ice and oceanic heat storage in the Hudson Bay system to a climate-warming scenario. Projections of air temperature (for the years 2041-2070; effective CO2 concentration of 707-950 ppmv) obtained from the Canadian Regional Climate Model (CRCM 4.2.3), driven by the third-generation coupled global climate model (CGCM 3) for lateral atmospheric and land and ocean surface boundaries, were used to drive a single sensitivity experiment with the delta-change approach. The projected change in air temperature varies from 0.8A degrees C (summer) to 10A degrees C (winter), with a mean warming of 3.9A degrees C. The hydrologic forcing in the warmer climate scenario was identical to the one used for the present climate simulation. Under this warmer climate scenario, the sea-ice season is reduced by 7-9 weeks. The highest change in summer sea-surface temperature, up to 5A degrees C, is found in southeastern Hudson Bay, along the Nunavik coast and in James Bay. In central Hudson Bay, sea-surface temperature increases by over 3A degrees C. Analysis of the heat content stored in the water column revealed an accumulation of additional heat, exceeding 3 MJ m(-3), trapped along the eastern shore of James and Hudson bays during winter. Despite the stratification due to meltwater and river runoff during summer, the shallow coastal regions demonstrate a higher capacity of heat storage. The maximum volume of dense water produced at the end of winter was halved under the climate-warming perturbation. The maximum volume of sea ice is reduced by 31% (592 kmA(3)) while the difference in the maximum cover is only 2.6% (32,350 km(2)). Overall, the depletion of sea-ice thickness in Hudson Bay follows a southeast-northwest gradient. Sea-ice thickness in Hudson Strait and Ungava Bay is 50% thinner than in present climate conditions during wintertime. The model indicates that the greatest changes in both sea-ice climate and heat content would occur in southeastern Hudson Bay, James Bay, and Hudson Strait.