CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Bonsal, B.R.; and Prowse, T.D.
Date : 2001.
Title : Trends and variability in spring and autumn 0 deg C isotherm dates over Canada.
Publication : AGU 2001 Fall Meeting, Moscone Centre, San Franciso, California, December 10-14, 2001.
Issue :
Page(s) :
Abstract
Changes to critical temperature thresholds such as the seasonal march of the 0 deg C isotherm can have significant impacts on a variety of environmental and economic activities including the break/freeze-up dates of lakes and rivers, the timing of spring freshet, the skiing industry, and bird migrations. This study examines trends and variability in spring and autumn 0 deg C isotherm dates over Canada during the 20th century. Results reveal considerable variability across the country. Significant trends toward earlier springs are observed over most of western Canada including a dramatic shift to earlier dates during the last 20-30 years. Central regions, including most of the Northwest Territories and the high Arctic, are associated with smaller, generally insignificant earlier spring trends. Conversely, extreme eastern areas experience trends toward later springs. During autumn, isotherm dates show little change over the majority of the country. An exception is over the southeast where trends toward later dates are observed. Investigation into the potential causes of observed trends and variability in isotherm dates reveals significant relationships with large scale oscillations over the Pacific and Atlantic. In particular, the North Pacific index (North Atlantic Oscillation) significantly relates to isotherm dates over western (eastern) regions of Canada during both spring and autumn. Relationships weaken toward interior areas including much of the Northwest Territories and the high Arctic. Although significant, a relatively small amount of overall variance in isotherm dates is explained by the oscillations indicating the influence of other factors. Results from this investigation improve the understanding of past trends and variability in critical temperature thresholds such as 0 deg C isotherm dates. They also provide insight into potential future climatologic impacts given the possibility of climate change.
Bibliography of Canadian Geomorphology