CGRG Bibliography of Canadian Geomorphology
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Author : Colgan, W.; and Sharp, M.
Date : 2006.
Title : Combined oceanic and atmospheric influences on net accumulation on the Devon Island Ice Cap, Nunavut, Canada.
Publication : 3rd Annual ArcticNet Scientific Meeting. December 12-15, 2006. Victoria, British Columbia.
Issue : Abstracts Volume
Page(s) : 39-40.
Abstract
The influence of changes in moisture source areas on net snow accumulation on the Devon Island Ice Cap, Nunavut, was examined for the 1979-2003 period. Variations in moisture source areas were assumed to arise from combined variations in both atmospheric transport and open water fraction. Daily site-specific 120hr air mass back-trajectories were calculated using NCEP Reanalysis data and the METEX model. Moisture source probabilities were calculated by coupling these back-trajectories to the open water fraction of each cell in a standard 1° latitude cylindrical grid. Open water fraction was derived from a satellite passive microwave sea ice dataset (Walsh and Chapman, 2006). Moisture source probability provides a measure of the relative probability of air masses arriving at the Devon Island Ice Cap having passed within 500m of open water at the ocean surface in a given grid cell and season. High-resolution anion stratigraphies and firn density profiles allowed calculation of annual net accumulation records for five ice cores. The mean of these records was used as a proxy for the net accumulation history on the ice cap, and correlated with both late-spring/early-summer (MAMJ) and latesummer/ early-fall (JASO) cell moisture source probabilities. Stronger relationships were found to exist in the JASO season, with a small cluster of positive correlations (p<0.05) in the North Open Water Polynya (NOW) and a larger region of negative correlations (p<0.05) throughout the Queen Elizabeth Islands (QEI) and western Baffin Bay (BB). Although significant correlations are seen in the NOW area, neither NOW air mass frequency nor open water fraction are significantly correlated (p>0.05) to the net accumulation record, suggesting that moisture source probability provides information about accumulation variability that is not contained in either record independently. The reduction in moisture source probabilities throughout the QEI during high net accumulation years is due to both a decrease in air masses transiting the QEI en route to the ice cap and a decrease in QEI open water fraction. Variability in moisture source probabilities appears to be influenced by the Arctic Oscillation (AO), which is known to affect both sea ice extent and concentration and atmospheric transport in the Arctic. When comparing the three years of highest and lowest JASO AO index values, decreased (p<0.05) JASO moisture source probabilities were found in BB during higher JASO AO index years. This is largely due to a decrease (p<0.05) in air mass frequency. There was no significant difference (p>0.05) in open water fraction between JASO AO phases. No significant differences (p>0.05) are seen between the three years of highest and lowest MAMJ AO index values. As moisture source probabilities were found to reach a maximum in BB during JASO, previous conclusions of JASO as the main accumulation season on the Devon Island Ice Cap and BB as the key moisture source region are supported (Koerner, 2002). In addition however, these findings suggest increasing suppression of Devon Island Ice Cap net accumulation with increased frequency of passage of air masses over the relatively arid QEI. Moisture source probabilities only provide a first approximation of the likely location of moisture sources, as important parameters that influence evaporative moisture uptake, such as air mass temperature and relative humidity, are not considered.
Bibliography of Canadian Geomorphology