Abstract
ABSTRACTSeasonal snow-cover modulates water and energy budgets across large areas of the Northern Hemisphere. Previous research, based on satellite imagery interpreted and curated by the Rutgers University Snow Laboratory, has identified significant negative and positive trends in annual snow-covered duration and area at hemispheric and continental scales between 1971 and 2014. This study uses the same dataset to generate more detailed descriptions of spatial variations in these trends, maps intraannual variations in sign, statistical significance and strength, and quantifies associations with latitude and elevation. It also considers the limitations and uncertainties associated with a binary classification of this type, and the implications for trend magnitudes of adopting alternatives to the conventional assumption of 100% (0%) actual fractional snow-covered area in ‘snow-covered’ (‘snow-free’) spatial units at different stages of the snow-season. This prompts adoption of alternative terminology, referring to ‘snow-dominated’ area and duration. In response to questions about the dataset's veracity raised by some prior studies, it discusses climatological factors of potential relevance in explaining spatio-temporal trend patterns, and considers how biases might possibly have been introduced as a result of extraneous influences.
Highlights
The importance of seasonal snow-cover to climatological, hydrological, ecological and anthropological processes over large areas in the terrestrial mid-to-polar latitudes of the Northern Hemisphere (NH) is difficult to overstate
Over the total area experiencing median seasonal snow-dominated duration (SDD) of 4– 48 weeks, significant (p < 0.05) negative SDD trends were identified for snow-grid points (SGPs) representing 23.3% (11.0 × 106 km2), and positive trends were detected over 5.4% (2.5 × 106 km2) of the same spatial domain
Of particular note are the highly significant negative trends in south-central Eurasia, the Alborz and Zagros ranges of northwestern Iran, the eastern front ranges of the Himalaya, the Rocky Mountains of western North America, and throughout the circumpolar regions of North America, Scandinavia and Russia
Summary
The importance of seasonal snow-cover to climatological, hydrological, ecological and anthropological processes over large areas in the terrestrial mid-to-polar latitudes of the Northern Hemisphere (NH) is difficult to overstate. In ecosystems associated with climates where snow is the dominant phase of precipitation during the cooler months, many forms of biota have adapted to the challenges and opportunities introduced by these conditions (Jones, 1999) Recognition of these key influences of seasonal snow, and of the potential for shifts from historical distribution patterns as a consequence of anthropogenic climate-change, has prompted a series of investigations into interannual trends in snow-covered area (SCA) and duration (SCD) (Groisman and others, 1994; Clark and others, 1999; Frei and others, 1999; Brown, 2000; Dye, 2002; Rikiishi and others, 2004; Mote, 2006; Déry and Brown, 2007; Choi and others, 2010; Biancamaria and others, 2011; Brown and Robinson, 2011; Cohen and others, 2012; Liu and others, 2012; Vaughan and others, 2013; Hernández-Henríquez and others, 2015; Zhao and others, 2016; Yeo and others, 2017).
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