Mackenzie Basin Snow Cover: Variability and Trends from Conventional Data, Satellite Remote Sensing, and Canadian Regional Climate Model Simulations

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Abstract

Variability and trends in Mackenzie River Basin (MRB) snow cover were investigated using in situ snow depth observations, NOAA snow extent charts, and satellite retrievals coupled with Canadian regional climate model (CRCM) simulations. Most stations with long conventional snow depth records showed significant decreases in spring snow cover duration and earlier snow disappearance, but no significant trends for snow cover onset in the autumn. These results are consistent with air temperature trends over the region. Within the MRB, the NOAA dataset show an east-west gradient with earlier snow melt concentrated in the mountains west of the Mackenzie River, and little change or slight increases in spring snow cover in the northeast. Southern MRB showed cyclical behavior in snow cover, linked to the Pacific-North American and Pacific Decadal Oscillation modes of atmospheric variability.

Spaceborne passive microwave datasets revealed a zone across the northern fringe of the boreal forest with high winter season snow water equivalent (SWE) of >100 mm; and the presence of this zone was confirmed by ground snow surveys. A series of CRCM simulations were conducted to identify feedbacks between the atmosphere and land surface for a domain focused on the northern boreal forest. The patterns of accumulated SWE correspond closely with the mean monthly patterns of 850 hPa frontogenesis forcing, suggesting that lower tropospheric frontal activity was responsible for the snowfall events that led to the deposition of the northern boreal SWE band.