The Response of Alpine Glaciers in Western Canada to Early 21st Century Climate Change

Abstract:

Since 1998, the rate of global warming has slowed but the degree to which this slowdown has affected alpine glaciers in North America remains uncertain. Here we describe glacier fluctuations in the continental mountain ranges of British Columbia, Alberta, Yukon and the Northwest Territories for the period 1985-2013. Our manual digitization of over 3,000 glaciers mapped from 12 Landsat scenes builds upon a glacier inventory for the period 1985-2005 that utilized aerial photography and satellite imagery (Landsat) for the mountain ranges of British Columbia and Alberta. Landsat imagery allowed us to extend the spatial distribution of this inventory to include most alpine glaciers that straddle the Yukon and Northwest Territory border (Nahanni region) for the years 1985 and 2004. We also digitized glaciers from pan-sharpened Landsat 8 imagery for the year 2013. Glacier recession rates differ among regions between the early [1985-2005] and recent [2005-2013] periods. Recession rates during the recent period, for example, slowed by 43% and 15% for the Nahanni and Columbia Basin regions respectively. When compared to the early period, recent recession rates accelerated by 17% and 121% for glaciers in the Southern and Northern Rocky Mountains. Some of this regional variability is attributed to climate anomalies in the study area based on our analysis of instrumental (CRU 3.21) and reanalysis (ERA Interim) data, but the doubling of the recessional rate for the Northern Rocky Mountains is anomalous. Non-climatic factors that could explain this anomalous rapid retreat of Northern Rocky Mountain glaciers includes low minimum elevation of these glaciers, debris cover and shadowed terrain in the Landsat imagery.