Glacial Melt and Potential Impacts on Water Resources in the Canadian Rocky Mountains

P Castellazzi,A Rivera,D Burgess,L Longuevergne,J Huang,M N Demuth

doi:10.1029/2018wr024295

Abstract

AbstractAs a result of global climate change, glacial melt occurs worldwide. Major impacts are expected on the dynamics of aquifers and rivers in and downstream of mountain ranges. This study aims at quantifying the melt water input fluxes into the watersheds draining the Canadian Rocky Mountains and improving our knowledge about the fate of meltwater within the hydrological cycle. To this end, we use (1) time‐variable gravity data from GRACE satellites that are decomposed into water storage compartments; (2) an ensemble of glacier information: in situ observations, geodetic measurements, and a mass balance model; and (3) in situ surface water and groundwater level observations. The glacier mass balance model estimates a total ice mass change of ~43 Gt for the period 2002–2015, corresponding to an average of −3,056 (±2,275) MCM/yr (million cubic meters per year). 78% of the meltwater total flows west of the continental divide (to the Pacific Ocean), while 22% flows east of the continental divide (to the Arctic Ocean and Hudson Bay). However, the GRACE‐derived total water storage increases, suggesting that groundwater storage compensates for the glacial melt with an increase of 3,976 (±2,819) MCM/yr. A plausible explanation is that meltwater is not immediately flowing down in rivers but rather stored locally in aquifers. This hypothesis is supported by in situ river base flow observations, showing base flow increase in basins draining the ice melt, mostly west of the continental divide. Direct in situ evidences such as well water level time series are not sufficiently available to fully support this hypothesis.

Highlights

Glaciers across the entire study area have thinned at an average of 0.86 m/yr WTE, whereas the glacier cover west and east of the continental divide have thinned by 0.96 m/yr WTE and 0.67 m/yr WTE respectively (Figure 4a)
We present a state‐of‐the‐art and comprehensive decomposition of Gravity Recovery And Climate Experiment (GRACE) data, with particular attention given to concentrated mass recovery applicable to hydrological features such as glaciers and large lakes
We present (1) an empirical model for describing the glacial melt at high resolution and quantifying surplus of water inputs to each major drainage basin of the Canadian Rocky Mountains (CRM); (2) a spatially constrained GRACE data decomposition with particular attention given to concentrated mass recovery applicable to significant hydrological features such as glaciers and large lakes; (3) a complete surface water storage and glacial isostatic adjustment analysis for the region; (4) an analysis of the mass balance for every water storage compartment for 2002–2015; and (5) an in situ data analysis attempting to confirm the groundwater storage increase, as deduced through the geodetic‐based mass balance

Summary

Introduction

It has been observed and reported that glaciers are melting and losing mass throughout the World, for example, in the Himalayas (Bolch et al, 2012; Farinotti et al, 2015), the Alps (Bauder et al, 2007; Haeberli et al, 2007; Rabatel et al, 2018), the Andes (Kozhikkodan Veettil & de Souza, 2017), and the Rocky Mountains (Clarke et al, 2015; Demuth et al, 2008). Since the end of the Little Ice Age (~1850), glaciers and ice caps have been losing mass steadily with rates of mass loss over the past two decades being historically unprecedented (Zemp et al, 2015). Updated measurements of glacier change to 2014 indicate that contributions to global sea level rise from ice sheets have increased to 1.26 mm/yr sea level equivalent, whereas contributions from mountain glaciers have remained constant. Regardless, mountain glaciers and ice caps will continue to be significant contributors to global sea level rise (IPCC, 2014, 2019) as they are expected to lose 43% to 74% of their mass between 2010 and 2100 (Huss & Hock, 2018), thereby imposing additional strain on water availability for human and natural systems functioning. Rates of mass loss from glaciers in western Canada have increased fourfold since the mid‐2000s (Menounos et al, 2018), with projections indicating that up to 90% of current glacier mass in the Canadian Rockies and Interior Ranges will be gone by the end of the century (Clarke et al, 2015)

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