Area change of glaciers in the Canadian Rocky Mountains, 1919 to 2006

C. Tennant,R. Wheate,B. Menounos,J. J. Clague

doi:10.5194/tc-6-1541-2012

C. Tennant, R. Wheate + Show 2 more

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https://doi.org/10.5194/tc-6-1541-2012

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Abstract

Abstract. Glaciers in the Canadian Rocky Mountains constitute an important freshwater resource. To enhance our understanding of the influence climate and local topography have on glacier area, large numbers of glaciers of different sizes and attributes need to be monitored over periods of many decades. We used Interprovincial Boundary Commission Survey (IBCS) maps of the Alberta–British Columbia (BC) border (1903–1924), BC Terrain Resource Information Management (TRIM) data (1982–1987), and Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) imagery (2000–2002 and 2006) to document planimetric changes in glacier cover in the central and southern Canadian Rocky Mountains between 1919 and 2006. Over this period, glacier cover in the study area decreased by 590 ± 70 km2 (40 ± 5%), 17 of 523 glaciers disappeared and 124 glaciers fragmented into multiple ice masses. Glaciers smaller than 1.0 km2 experienced the greatest relative area loss (64 ± 8%), and relative area loss is more variable with small glaciers, suggesting that the local topographic setting controls the response of these glaciers to climate change. Small glaciers with low slopes, low mean/median elevations, south to west aspects, and high insolation experienced the largest reduction in area. Similar rates of area change characterize the periods 1919–1985 and 1985–2001; −6.3 ± 0.6 km2 yr−1 (−0.4 ± 0.1% yr−1) and −5.0 ± 0.5 km2 yr−1 (−0.5 ± 0.1% yr−1), respectively. The rate of area loss, however, increased over the period 2001–2006; −19.3 ± 2.4 km2 yr−1 (−2.0 ± 0.2% yr−1). Applying size class-specific scaling factors, we estimate a total reduction in glacier cover in the central and southern Canadian Rocky Mountains for the period 1919–2006 of 750 km2 (30%).

Highlights

Glaciers in the Canadian Rocky Mountains constitute an important freshwater resource
There is an initial increase in runoff followed by a decline as ice volume is lost; declining glacier runoff is likely occurring in the Canadian Rocky Mountains (Moore and Demuth, 2001; Moore et al, 2009; Marshall et al, 2011; Kienzle et al, 2012)
We focus on glaciers in the central and southern Canadian Rocky Mountains that were mapped during the 1903–1924 Interprovincial Boundary Commission Survey (IBCS) of the Alberta–British Columbia (BC) border

Summary

Introduction

Glaciers in the Canadian Rocky Mountains constitute an important freshwater resource. Glacier meltwater flows into four major watersheds, those of the Mackenzie, Nelson, Fraser, and Columbia river basins and drains into the Arctic, Atlantic, and Pacific oceans. The contribution of meltwater to total discharge may be low, but glacier runoff supplements summer flow and regulates stream temperature, both of which are important for aquatic ecosystems, irrigation, industry, hydro power and human consumption (Henoch, 1971; Barry, 2006; Granshaw and Fountain, 2006; Stahl and Moore, 2006; Moore et al, 2009). Jost et al (2012) and Jiskoot and Mueller (2012) estimate that the late summer contribution from glaciers west of the Continental Divide to the upper Columbia River basin is ca. There is an initial increase in runoff followed by a decline as ice volume is lost; declining glacier runoff is likely occurring in the Canadian Rocky Mountains (Moore and Demuth, 2001; Moore et al, 2009; Marshall et al, 2011; Kienzle et al, 2012)

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