Projected Changes in Seasonal Snow in the Columbia River Basin, British Columbia, Canada

Abstract:

In western North America, many communities rely on runoff from mountain snowpacks. Projections of how future climate change will affect the seasonal snowpack are thus of interest to water managers, communities, and policy makers. We investigated projected changes in seasonal snowpack under global warming for the 21st century and the Canadian portion of the Columbia River basin using a physically-based snow distribution model (SnowModel) at 500 m horizontal resolution. Forcing data for the reference (1979-1994) and future (2045-2059, 2085-2099) periods originate from a 4-member initial condition ensemble of global Community Earth System Model (CESM1) simulations based on the RCP 8.5 scenario. The ensemble has been dynamically downscaled (DD) to 10 km resolution using the Weather Research and Forecasting model (WRF). In addition, we also evaluated the performance of SnowModel using publicly available, statistically-downscaled (SD) temperature and precipitation projections. We observe a 38% and 30% decrease in WRF-simulated snow depth and SWE, respectively by the end of this century relative to the reference period. Snow depth and snow water equivalent (SWE) are most affected for elevations below 2000 m asl. The averaged SD-forced snow depth and SWE over the area represents a reduction of 28% and 15% toward the end of the century. Our results indicate that the projected loss of snowpack depends largely on elevation and season, while stronger projected thinning of the snowpack occurs for the dynamically downscaled simulations by end of century compared to the statistically downscaled simulation. Nevertheless, both SD- and DD-forced simulated snow depth and SWE show loss in most areas by the end of the century. This has significant implications for water resource availability for various sectors and communities living in these areas.