Abstract
Abstract. The Canadian Sea Ice and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state of the art observational data to advance dynamical prediction, projections, and understanding of seasonal snow cover and sea ice in Canada and the circumpolar Arctic. Here, we present an assessment from the CanSISE Network on trends in the historical record of snow cover (fraction, water equivalent) and sea ice (area, concentration, type, and thickness) across Canada. We also assess projected changes in snow cover and sea ice likely to occur by mid-century, as simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) suite of Earth system models. The historical datasets show that the fraction of Canadian land and marine areas covered by snow and ice is decreasing over time, with seasonal and regional variability in the trends consistent with regional differences in surface temperature trends. In particular, summer sea ice cover has decreased significantly across nearly all Canadian marine regions, and the rate of multi-year ice loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last 8 years. The multi-model consensus over the 2020–2050 period shows reductions in fall and spring snow cover fraction and sea ice concentration of 5–10 % per decade (or 15–30 % in total), with similar reductions in winter sea ice concentration in both Hudson Bay and eastern Canadian waters. Peak pre-melt terrestrial snow water equivalent reductions of up to 10 % per decade (30 % in total) are projected across southern Canada.
Highlights
Seasonal terrestrial snow and sea ice influence short-term weather and longer-term climate by altering the surface energy budget, modifying both the surface reflectivity and thermal conductivity (Serreze et al, 2007; Flanner et al, 2011; Gouttevin et al, 2012)
3.1 Observed trends in terrestrial snow and sea ice Seasonally averaged trends in terrestrial snow cover fraction (SCF) and sea ice concentration (SIC) over the 1981–2015 time period are shown in Fig. 1
Throughout the paper, we present seasonal trends for permutated months in order to more closely match the mid-season peaks of SCF (January), SWE (February–March), and SIC and sea ice thickness (March)
Summary
Seasonal terrestrial snow and sea ice influence short-term weather and longer-term climate by altering the surface energy budget, modifying both the surface reflectivity and thermal conductivity (Serreze et al, 2007; Flanner et al, 2011; Gouttevin et al, 2012). Understanding historical and projected changes to snow and ice is essential to assess both the importance of physical changes to the climate system and their consequent impacts and risks. A previous assessment of the Canadian cryosphere (snow, sea ice, freshwater ice, land ice, frozen ground) was compiled as part of the International Polar Year (IPY) in 2007–2008 and is described in Derksen et al (2012). The current study updates the IPY analysis pertaining to terrestrial snow and sea ice by adding nearly a decade of data and including climate model projections of changes over the 30 to 40 years. This study is focused on Canadian territory, which is nearly completely covered by snow and sea ice for parts of each year with nearcontinuous coverage over high-latitude and high-elevation regions. With respect to snow cover, real-time information on the amount of snow on the ground (i.e. depth and water equivalent) is used in operational decision making for water resource planning (Turcotte et al, 2007), snow clearing, evaluation of avalanche risk (Conlan and Jamieson, 2017), Published by Copernicus Publications on behalf of the European Geosciences Union
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