Canadian Snow and Sea Ice: Trends (1981–2015) and Projections (2020–2050)

Abstract

Abstract. The Canadian Sea Ice and Snow Evolution Network (CanSISE) 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, 15 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-20 year ice loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last eight years. The multimodel 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. 25 IntroductionSeasonal 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). Snow also influences freshwater storage through soil moisture recharge and surface runoff (Barnett et al., 2005). Understanding historical and projected future changes to snow and ice is essential both to assess the importance of 30 physical changes to the climate system, and to thus assess their consequent impacts and risks. A previous assessment of the The Cryosphere Discuss., https://doi.org/10. 5194/tc-2017-198 Manuscript under review for journal The Cryosphere Previous studies have shown that warming temperatures, which are amplified at higher latitudes as a natural response to increasing greenhouse gases (Serreze et al., 2009;Pithan and Mauritsen, 2014), reduce the spatial extent and mass of snow 45 and ice (for example, see Derksen et al., 2012). In reality, the linkage between warming temperatures and snow/sea ice reduction is more nuanced due to: regional and seasonal climate variability: for example, surface temperature warming across Canadian land and ocean areas is not uniform in space and time, but contains regional and seasonal variability driven by natural climatic processes such as the El Niño Southern Oscillation (ENSO) and other...

Canadian In Situ Snow Cover Trends for 1955–2017 Including an Assessment of the Impact of Automation

“…The median grid point trends in JDfirst and SSL were 1.96 and −1.98 days decade −1 , respectively, with JDfirst having the largest fraction of grid points with locally significant trends (15.5%) for all the snow cover variables investigated in the 1981-2017 period (Table 1b). These results are consistent with the multi-dataset analysis of Mudryk et al (2018) who found that the largest significant decreases in snow cover fraction over Canada from 1981 to 2015 occurred in October to December in response to stronger fall warming during that period. The mainly decreasing trend in SSL contrasts with increasing SSL trends over Eurasia reported by Ye and Ellison (2003), but their results were for an earlier period with less influence from anthropogenic warming.…”

“…Several points in the southern interior of British Columbia stand out as having contrasting trends in SCD and SDmax. Inspection of time series at these points showed evidence of a regime shift around 1980 to a period with increasing SD that has some support from annual maximum snow water equivalent (SWE) trends presented in Mudryk et al (2018). The increases in SDmax observed over the Maritimes is consistent with previously published trend results and was attributed to increasing winter snowfall by Brown and Braaten (1998).…”

“…little quality control of SD observations in the ECCC climate archive . incomplete or inaccessible metadata on the SD-observing methods at stations For these reasons, recent assessments of snow trends over Canada have focused on the complete spatial coverage offered by satellite and model-derived datasets (Derksen et al, 2019;Mudryk et al, 2018). Still, robust trends from surface networks are highly desirable as a complement to satellite and model-derived datasets, and it is recognized that surface networks provide essential observations for ingestion in state-of-the-art satellite algorithms (e.g., Pulliainen et al, 2020) and data assimilation products, such as the fifth generation atmospheric reanalysis from the European Centre for Medium-range Weather Forecasts (ERA5; Hersbach et al, 2020).…”

Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure

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“…The absence of any clear trend in precipitation suggests that variation in summer rainfall did not influence ice-wedge melt pond expansion or single-year wetness conditions corresponding to the image acquisition dates ( Figure S1b). Maximum snow water equivalent before spring melt for the period 1985-2015 shows only weak, non-significant positive trends over small areas of eastern Banks Island [58]. However, increasingly efficient snow capture within subsiding troughs [9] would raise winter ground temperature above ice wedges and provide a source of ponded water with low albedo to stimulate a positive thermokarst feedback [6,59,60].…”