|Title||Glacial melt and potential impacts on water resources in the Canadian Rocky Mountains|
|Author||Castellazzi, P; Burgess, D; Rivera, A; Huang, J; Longuevergne, L; Demuth, M|
|Source||Water Resources Research vol. 55, issue 12, 2019., https://doi.org/10.1029/2018WR024295 (Open Access)|
|Alt Series||Natural Resources Canada, Contribution Series 20180276|
|Media||paper; on-line; digital|
|Province||British Columbia; Alberta|
|Area||Canadian Rocky Mountains|
|Lat/Long WENS||-122.0000 -115.0000 54.0000 49.0000|
|Subjects||environmental geology; Nature and Environment; Science and Technology; hydrogeology; aquifers; geodetic networks; watersheds; glaciers; sea level changes; Water resources; climate change; mass
|Illustrations||location maps; gravity profiles; distribution diagrams; figures; tables; graphs|
National Aquifer Evaluation & Accounting|
|Released||2019 11 06|
|Abstract||As 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.|
The budget-based glacier mass loss
estimates the ice loss at 44 Gt for the period 2002-2015, corresponding to an average of 3.1 Gt/yr. The total error is calculated through comparison with in-situ data, geodetic ice thickness change measurements, and independent model results.
Uncertainty is estimated at +/- 2.3 Gt/yr, i.e., the model-derived ice mass loss estimation falls in the range [-0.8 -5.4] Gt/yr. In contrast, the GRACE TWS trend signal, after removal of all contributors other than glacier ice and groundwater, falls
within the range [-0.4 +2] Gt/yr. These results suggest that increased groundwater storage partially compensates for the decreased glacier mass, at a rate of [+0.4 +7.2] Gt/yr. To explore this hypothesis, observations from other authors, groundwater
storage change estimates from a global groundwater model, and river base-flow analysis are used and co-interpreted. While a groundwater storage model suggests that glaciers would be the main contribution to a potential storage increase, in-situ river
flow analysis suggests a spatially heterogeneous base-flow response depending on the watershed and its groundwater residence time. This article raises questions on discordant observations from multi-source datasets and explores explanatory scenarios.
This inter-disciplinary approach triggers further investigation regarding the fate of glacier melt water, and encourage further work using data from the GRACE-FO mission.
|Summary||(Plain Language Summary, not published)|
Although global warming and glaciers melt are well studied, little is known about the related changes into downstream water flow systems. This study aims
to quantify the glacier melt in the Canadian Rocky Mountains and Southern Interior Ranges to improve our understanding of its impacts over downstream flow systems. We present observations of glaciers, geodetic measurements of glacier melt, a glaciers
mass balance model, river base-flow analysis, and time-variable gravity data from GRACE satellites and its related decomposition data, e.g., global surface hydrology and post-glacial rebound models. Glacier mass loss estimates account for ice loss at
44 Giga-tons (Gt) for the period 2002-2015, corresponding to an average of 3.1 Gt/yr, while the GRACE Total Water Storage trend signal falls within the range [-0.4 +2] Gt/yr. We interpreted this discrepancy as related to water transfers between
glaciers and groundwater storage, suggesting that increased groundwater storage partially compensates for the decreased glacier mass, at a rate of [+0.4 +7.2] Gt/yr.