CGRG Bibliography of Canadian Geomorphology
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Author : Bonsal, B.R.; and Prowse, T.D.
Date : 2001.
Title : Trends and variability in the 0°C isotherm and relationships to lake and river ice cover characteristics over Northern Canada.
Publication : Annual Scientific Meeting of the Canadian Geophysical Union. May 14-17, 2001, University of Ottawa, Ottawa.
Issue :
Page(s) :
Abstract
During the last half century, there has been considerable spatial variability in mean annual temperature trends over northern Canada including significant warming over the north-west and cooling over the north-east. The trends are most pronounced during winter and spring with summer and autumn showing smaller warming trends over most of the region. Over the last 150 years, the duration of lake and river ice cover over most of the Northern Hemisphere has significantly decreased due to both earlier break-up dates and later freeze-up dates. In addition, the interannual variability in these dates has increased since 1950. It has also been shown that ice cover duration is directly related to surface air temperature and in particular, break (freeze) up dates with the 0°C isotherm during spring (autumn). This study examines recent trends and variability in the spring and autumn 0°C isotherm over northern Canada. Using recently updated, homogenized daily mean temperature data, spatial and temporal characteristics of these isotherms are analyzed for the period 1946-98 (and longer where data are available). The investigation also determines key regions over the Canadian north where significant and/or abrupt changes in these dates have occurred and compares them with spatial and temporal changes in lake and river ice duration. Projected changes in temperature from recent GCM experiments will also be applied to infer what changes in lake ice duration are likely in a warmer world. Preliminary results suggest that over north-western regions of the country, the date of the 0°C isotherm has become significantly earlier, particularly, since the mid 1970s. However, little change is evident in the 0°C isotherm during autumn. For both spring and autumn, considerable interannual variability in these dates is apparent. Results from this analysis will provide a better understanding of both past and potential future trends and variability in ice cover duration over various regions of northern Canada.
Bibliography of Canadian Geomorphology