Declining Snow Cover Research Articles

Climate change impacts on snow water availability in the Euphrates-Tigris basin

Abstract. This study investigates the effects of projected climate change on snow water availability in the Euphrates-Tigris basin using the Variable Infiltration Capacity (VIC) macro scale hydrologic model and a set of regional climate-change outputs from 13 global circulation models (GCMs) forced with two greenhouse gas emission scenarios for two time periods in the 21st century (2050 and 2090). The hydrologic model produces a reasonable simulation of seasonal and spatial variation in snow cover and associated snow water equivalent (SWE) in the mountainous areas of the basin, although its performance is poorer at marginal snow cover sites. While there is great variation across GCM outputs influencing snow water availability, the majority of models and scenarios suggest a significant decline (between 10 and 60 percent) in available snow water, particularly under the high-impact A2 climate change scenario and later in the 21st century. The changes in SWE are more stable when multi-model ensemble GCM outputs are used to minimize inter-model variability, suggesting a consistent and significant decrease in snow-covered areas and associated water availability in the headwaters of the Euphrates-Tigris basin. Detailed analysis of future climatic conditions point to the combined effects of reduced precipitation and increased temperatures as primary drivers of reduced snowpack. Results also indicate a more rapid decline in snow cover in the lower elevation zones than the higher areas in a changing climate but these findings also contain a larger uncertainty. The simulated changes in snow water availability have important implications for the future of water resources and associated hydropower generation and land-use management and planning in a region already ripe for interstate water conflict. While the changes in the frequency and intensity of snow-bearing circulation systems or the interannual variability related to climate were not considered, the simulated changes in snow water availability presented here are likely to be indicative of climate change impacts on the water resources of the Euphrates-Tigris basin.

Changes in fine-scale movement and foraging patterns of common wombats along a snow-depth gradient

Context. Feeding strategies of large herbivores in snow-covered environments can be influenced by snow depth and snow quality. Common wombats, Vombatus ursinus, are large marsupial herbivores that occur in subalpine areas of Australia where they must dig through the snow to reach low vegetation. Deeper snow at higher elevations is considered to limit foraging and constrain their range, although there have been no quantitative studies investigating the influence of snow on their foraging behaviour. Aims. The present study examined how snow influenced the foraging behaviour of common wombats along a snow-depth gradient. Methods. During the 2008 winter season, snow tracks of 17 wombats were located within the subalpine zone, in a study area ranging from 1520 to 1850 m asl, and followed to record attributes of the snow cover and environment in relation to wombat activity. Key results. Wombats selected sites to feed where the snow was shallower, and deeper snow at feeding sites caused changes in foraging behaviour. Foraging occurred along fairly direct routes between burrows; however, as snow depth increased, wombats deviated more from their path to seek out suitable foraging sites. Most foraging occurred in shallow snow in open areas or where the snow had melted around the bases of trees, shrubs or boulders. About half (52%) of the feeding sites necessitated the wombats digging through the snow to reach low vegetation, predominantly the grasses of Poa spp. Digging craters for feeding occurred in snow depths up to 100 cm, although depths less than 35 cm were preferred. Some shrub species, such as dusty daisy bush, Olearia phlogopappa, that protruded from the snow, were also eaten where the snow was deeper. Dietary analysis confirmed that monocots made up the majority of the diet (93.3%), although some individuals consumed up to 26% dicots. Conclusions. The present study demonstrated that wombats can adjust to a snow-covered environment by altering both their foraging patterns and diet as snow depth increases. However, they will be limited where snow depths are consistently greater than 100 cm. Implications. Under future climate-change scenarios of declining snow cover, wombats may be able to forage and inhabit higher altitudes than where they currently occur, and this has implications for the grazing-sensitive alpine ecosystem. Predicting shifts in the range of other herbivores to higher altitudes will require knowledge of their species-specific foraging thresholds in snow, such as presented in this study.

Nonlinear responses of wolverine populations to declining winter snowpack

AbstractUnderstanding the population‐level impacts of climate change is critical for effectively managing ecosystems. Predators are important components of many systems because they provide top−down control of community structure. Ecological theory suggests that these species could be particularly susceptible to climate change because they generally occur at low densities and have resource‐limited populations. Yet, our understanding of climate‐change impacts on predators is hindered by the difficulty in assessing complex, nonlinear dynamics over the large spatial scales necessary to depict a species’ general response to abiotic forcing. Here we use fur‐return data to characterize population dynamics of a snow‐adapted carnivore, the wolverine, across most of its North American range. Using novel modeling techniques, we simultaneously measured the impact of winter snowpack on wolverine dynamics across critical thresholds in snowpack depth and two domains of population growth. Winter snowpack declined from 1970 to 2004 in nearly the entire region studied, concordant with increases in Northern Hemisphere temperature anomalies. Fur returns have declined in many areas; our models show that snowpack has strong, nonlinear effects on wolverine population dynamics. Importantly, wolverine harvests dropped the fastest in areas where snowpack declined most rapidly and also where snowpack had the greatest effect on population dynamics. Moreover, declining snow cover appears to drive trends in wolverine population synchrony, with important implications for overall persistence. These results illustrate the vulnerability and complex responses of predator populations to climate change. We also suggest that declining snowpack may be an important and hitherto little‐analyzed mechanism through which climate change alters high‐latitude ecosystems.

Springtime warming and reduced snow cover from carbonaceous particles

Abstract. Boreal spring climate is uniquely susceptible to solar warming mechanisms because it has expansive snow cover and receives relatively strong insolation. Carbonaceous particles can influence snow coverage by warming the atmosphere, reducing surface-incident solar energy (dimming), and reducing snow reflectance after deposition (darkening). We apply a range of models and observations to explore impacts of these processes on springtime climate, drawing several conclusions: 1) Nearly all atmospheric particles (those with visible-band single-scatter albedo less than 0.999), including all mixtures of black carbon (BC) and organic matter (OM), increase net solar heating of the atmosphere-snow column. 2) Darkening caused by small concentrations of particles within snow exceeds the loss of absorbed energy from concurrent dimming, thus increasing solar heating of snowpack as well (positive net surface forcing). Over global snow, we estimate 6-fold greater surface forcing from darkening than dimming, caused by BC+OM. 3) Equilibrium climate experiments suggest that fossil fuel and biofuel emissions of BC+OM induce 95% as much springtime snow cover loss over Eurasia as anthropogenic carbon dioxide, a consequence of strong snow-albedo feedback and large BC+OM emissions from Asia. 4) Of 22 climate models contributing to the IPCC Fourth Assessment Report, 21 underpredict the rapid warming (0.64°C decade−1) observed over springtime Eurasia since 1979. Darkening from natural and anthropogenic sources of BC and mineral dust exerts 3-fold greater forcing on springtime snow over Eurasia (3.9 W m−2) than North America (1.2 W m−2). Inclusion of this forcing significantly improves simulated continental warming trends, but does not reconcile the low bias in rate of Eurasian spring snow cover decline exhibited by all models, likely because BC deposition trends are negative or near-neutral over much of Eurasia. Improved Eurasian warming may therefore relate more to darkening-induced reduction in mean snow cover.