East–west asymmetry in long-term trends of landfast ice thickness in the Hudson Bay region, Canada

Abstract

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...

Observations: Cryosphere

“…• Gagnon and Gough (2006) analyzed sea-ice variability in Hudson Bay, Canada (cf. using data from 13 stations located along the shoreline of Hudson Bay (seven) and in surrounding nearby lakes (six).…”

Climate Change in the Hudson Bay Complex: Opportunities and Vulnerabilities for the Port of Churchill's Marine Operations

“…Between 1958 and 2003, most stations showed a trend towards an earlier occurrence of maximum ice thickness and this trend was significant at three stations (Gagnon and Gough, 2006). Data from the seven locations indicate a significant trend towards thicker ice in western Hudson Bay and a non-significant trend towards thinner ice in the eastern Bay.…”

“…Sea ice thickness is also linked to the trends in freeze-up and breakup dates, because these dates determine the length of time that sea ice can grow as well as the length of time that snow can accumulate on the ice (Gagnon and Gough, 2006). The trends in freeze-up and breakup dates are mostly driven by changes in atmospheric temperatures and wind strength .…”

“…The thickness trend in western Hudson Bay was accompanied by a trend towards lower snow depth but trends in snow depth did not correlate with all results. Autumn air temperatures were also linked to the sea ice thickness trends (Gagnon and Gough, 2006). It must be noted that the analysis of Gagnon and Gough (2006) was limited to landfast ice along the coast and there are very few observations of ice thickness in the mobile pack ice of Hudson Bay.…”

“…Gagnon and Gough (2006) analyzed this dataset and found that maximum ice thickness averaged 175 cm in Hudson Bay and increased from south to north, due to the temperature gradient across Hudson Bay, and west to east, due to the transport of ice to the eastern side of Hudson Bay under the prevailing westerly winds (Gagnon and Gough, 2006). Maximum ice thickness was typically reached in Climate Change in the Hudson Bay Complex March in the southern part of the Hudson Bay Complex and later at higher latitudes, occurring in May in the northernmost areas (Gagnon and Gough, 2006).…”