Ice cover in the Hudson Bay region (HBR) goes through a complete cryogenic cycle each year. Freeze-up typically occurs in October and November, ice cover reaches its peak thickness from late March to May, and water bodies in the HBR are usually ice-free beginning in early August. In this study, the timing and magnitude of the annual peak in ice thickness were identified for each year from weekly ice observations compiled by the Canadian Ice Service. The Mann-Kendall test was used to determine the statistical significance of the temporal trends, and their magnitude was estimated using the Theil-Sen approach. The results indicate an asymmetry in temporal trends of landfast ice thickness; statistically significant thickening of the ice cover over time was detected on the western side of Hudson Bay, while a slight thinning lacking statistical significance was observed on the eastern side. This asymmetry is related to the variability of air temperature, snow depth, and the dates of ice freeze-up and break-up. Increasing maximum ice thickness at a number of stations is correlated to earlier freeze-up due to negative temperature trends in autumn. Nevertheless, changes in maximum ice thickness were reciprocal to the variability in the amount of snow covering the ground. These results are in contrast to the projections from general circulation models (GCMs), and to the reduction in sea-ice extent and thickness observed in other regions of the Arctic. This contradiction must be addressed in regional climate change impact assessments.
KEY WORDS: Hudson Bay · Lake ice · Sea ice thickness · Snow depth · Temperature trends
Resale or republication not permitted without written consent of the publisherClim Res 32: [177][178][179][180][181][182][183][184][185][186] 2006 since they are often taken in close proximity to a weather station.The study area was the Hudson Bay region (HBR), including Hudson Bay proper, James Bay in the south, Foxe Basin to the north, Hudson Strait to the east, as well as adjacent land areas (see Fig. 2). The HBR is covered by first-year ice. Sea-ice formation begins in northern Hudson Bay proper in late October and spreads southward in November and December (Prinsenberg 1986a). Second-year ice, i.e. ice that has survived the summer season, is found on rare occasions, but is limited to NE Hudson Bay proper (Etkin & Ramseier 1993). Hudson Bay proper is completely covered by ice from January to May, with the exception of occasional leads (cracks or fractures) along the coast (Maxwell 1986). In June, the coastal leads become more extensive and areas of open water first appear in southern James Bay as the 0°C isotherm moves northward, and in NW Hudson Bay proper, because of the prevailing NW winds in the region. Areas of open water also appear in early summer along the eastern coast as the spring runoff from rivers emptying into James Bay flows northward (Markham 1986, Prinsenberg 1986a. In June and July, the NW winds push the broken ice away from the northern areas, enlarging the area of open w...