Snow Cover Period Research Articles

Local and regional variability in snow conditions in northern Finland: A reindeer herding perspective.

Weather station measurements were used to force the SNOWPACK snow model and combined with reindeer herders' experiences to study the local and regional variations in snow conditions in a Finnish reindeer herding area for the 1981-2010 period. Winter conditions varied significantly between the four selected herding districts and between open and forest environments within the districts. The highest snow depths and densities, the thicknesses of ground ice, and the lengths of snow cover period were generally found in the northernmost districts. The snow depths showed the strongest regional coherence, whereas the thicknesses of ground ice were weakly correlated among the districts. The local variation in snow depths was higher than the regional variation and limits for rare or exceptional events varied notably between different districts and environments. The results highlight that forests diversify snow and foraging conditions, e.g., ground ice rarely forms simultaneously in different environments. Sufficient and diverse forest pastures are important during the critical winter season if reindeer herding is pursued on natural grazing grounds also in the future.

Impacts of the removal of vascular plants on physiological and biochemical characteristics of Syntrichia caninervis during winter season in a temperate desert

Aims Patchily distributed biological soil crusts and shrubs is one of the main vegetation cover types in Gurbantunggut desert. The existence of shrubs in desert areas serves not only as a shelter for small animals, but also a good living condition for cryptogams and some herbs. Syntrichia caninervis, a dominant moss species in Gurbantunggut desert, is patchily distributed under shrub canopy and open spaces between vascular plants. To our knowledge, the impacts of the removal of shrub canopy on physiological and biochemical characteristics of S. caninervis during the winter is still unknown. Methods We simulated grazing of animals on Ephedra distachya at various rates (shrubs left intact, 50% shrubs removed, and shrubs removed completely) by cutting different percent of above-ground shoots of E. distachya. The shoot water content, chlorophyll fluorescence, proline content, soluble sugar content, soluble protein content, malonyldialdehyde (MDA) content, peroxidase (POD) and superoxide dismutase (SOD) activity were compared. Important findings The results show that, as for proline and soluble sugar contents of tested S. caninervis, there were no significant differences among three treatments of shrub canopy. However, the MDA content, and the activities of POD, SOD, CAT were significantly higher than nature shrubs in snow cover periods. During ©植物生态学报 Chinese Journal of Plant Ecology 724 植物生态学报 Chinese Journal of Plant Ecology 2016, 40 (7): 723–734 www.plant-ecology.com snow-melting periods, soil moisture and temperature did not served as limiting factors on the growth of S. caninervis. The soluble sugar content, and the activities of POD, CAT with shrub removal were significantly higher than shrubs left intact. This may indicate that the decline of the function of maintaining constant soil temperature due to shrub canopy increased the damage of temperature on moss plants. In addition, as for physiological and biochemical characteristics, there were no significant differences between two treatments of 50% shrub canopy and shrub canopy left intact. In snow covered periods and snow melting periods, the MDA content, the activities of POD, SOD and CAT of S. caninervis under shrub canopy removed completely were significantly higher than that of 50% shrub canopy and shrub canopy left intact, except for soluble protein content. The duration of chlorophyll fluorescence activity of S. caninervis growing in habitats with shrubs removed completely was significantly shorter than that of S. caninervis growing in habitats of 50% shrub canopy and shrub canopy left intact. This result indicated that the removal of shrubs may increase the UV-B radiation and weaken the “moisture island effects” developed by the existence of shrub canopy.

Annual maximum snow depth along the altitudinal gradient and snow cover period on the subalpine zone of Mt. Fuji, in Japan

富士山亜高山帯の生態系の動態に大きな影響を及ぼしている積雪環境を明らかにするため，山体四方位の標高1600〜2500mの斜面に標高100m 毎の定点調査地（合計40 地点）を設置し，1999/2000〜2014/2015年の16冬季の年最大積雪深を簡易最大積雪深計で測定した．各斜面の積雪深（16年平均）を亜高山帯下部（標高1600〜1900m），同上部（同2000〜2400m），森林限界付近（同2500m）に分けてみると，東面：85cm，152cm，344cm，南面：44cm，102cm，259cm，北面：68cm，90cm，109cm，西面：21cm，36cm，54cmの順に小さかった．各斜面の亜高山帯下部から上部までの積雪深には高度依存性がみられたが，標高の増大に伴う積雪深の増加率と森林限界付近の高度依存性の変化は斜面で異なっていた．北面の標高2220mの雪崩跡地で，2002/2003〜2014/2015年の13冬季の積雪日を地表面温度から推定した結果，積雪日が連続した期間は135.7±21.9日（平均値±標準偏差，111〜181日）で，年によって最大約70日の違いが認められた．富士山の積雪環境は斜面の方位や高度，年によって大きく変化しており，生態系への影響を考える場合にはこれらについて十分留意することが重要である．

Are Reintroduced Wisents a Threat to Mountain Forests?

The diet of wisents (Bison bonasus) inhabiting the Carpathians, studied during a snow-cover period, consisted of 46.8% of woody species consumed in the following manners: debarking (86.3% of dry mass), gnawing (12.6%) and browsing (1.1%). The top two species consumed were the common ash (39.5%) and fir (22.9%). Of the 23 consumed tree and shrub species, 19 species were debarked and 10 were browsed. Fallen trees, cut tree branches and logs of seven woody species were gnawed. The proportion of consumed woody species was positively correlated with snow depth. When ground flora were available, the percentage of twigs and tree bark in the wisent diet decreased, and brambles provided 99.1% of the consumed ground flora dry mass. Access to timber remnants at logging sites and non-valuable species like the willow or aspen may significantly reduce debarking of economically important tree species.

Dynamics of fluoride atmospheric fallouts in the Baikal region

The variations of the density of atmospheric fallouts of fluorides depending on the source location, sampling period, and research area were subjected to the comparative analysis using the data of snow chemical survey in Bratsk and the results of observations over fluoride atmospheric fallouts in Listvyanka settlement. It is demonstrated that it is reasonable to analyze the actual values of the density of fluoride atmospheric fallouts based on the data of snow chemical survey or plane observations, for assessing the yearly dynamics of the intensity of anthropogenic sources of fluorine. The analysis should account urban (regional) background values, air temperature, and amount of precipitation for the same period of time (the period of stable snow cover or plane observations).

Changes in runoff in two neighbouring catchments in the Bohemian Forest related to climate and land cover changes

Abstract There is public concern that large-scale disturbances to forest cover caused by insects and storm winds in the Bohemian Forest could intensify high water flows and enhance the expected flooding risks predicted in current regional climate change scenarios. We analysed stream discharge in Upper Vydra and Große Ohe, neighbouring catchments in the Bohemian Forest, the largest contiguous forested area in Central Europe. Upper Vydra, in the Šumava National Park, and Große Ohe (including the Upper Große Ohe headwater catchment in the Bavarian Forest National Park) are similar in size, but differ in land use cover and the extent of disturbed Norway spruce stands. Publicly available runoff and meteorological data (1978–2011) were examined using non-parametric trend and breakpoint analysis. Together with mapped vegetation cover changes, the results were used to address the following questions: 1) are there significant changes in the hydrological cycle and, if so, do these changes relate to 2) the extent and expansion of disturbance in forests stands and/or 3) altered precipitation dynamics and thermal conditions? We found no marked overall change in annual runoff or in annual or seasonal precipitation, but a significant increase in high flows in March. This overall trend related to the marked warming in late winter and early spring (+~4 K in April, p < 0.01), irrespective of altitude and slope position. It significantly shifted the end of the snow cover period by more than three weeks to the beginning/middle of April depending on altitude, and intensified snow melt. In the Upper Große Ohe catchment, a significant decrease in catchment balance, the difference between the long term precipitation and runoff (–72 mm, 11%) was found when the loss of tree cover reached 30% of catchment area. Diminished evapotranspiration losses from severely disturbed stands increased groundwater recharge during summer and caused a significant rise in low flows in autumn. However, observed increases in late winter high flows were due to warming only. They could be further intensified by the increasing winter precipitation predicted under present climate change scenarios, and would therefore increase the risk of flooding at lower elevations.

A Comparison of Methods Reveals that Enhanced Diffusion Helps Explain Cold-Season Soil CO2 Efflux in a Lodgepole Pine Ecosystem

Wintertime respiration contributes significantly to the annual loss of carbon from terrestrial ecosystems to the atmosphere, but the magnitude and physical transport mechanisms of this flux through snow remain unclear. Here, we quantify wintertime soil CO2 efflux in a Lodgepole pine (Pinus contorta Dougl.) forest by comparing chamber, flux gradient, and subcanopy eddy covariance measurements. CO2 efflux estimates from the flux gradient system deviated from the eddy covariance measurements during early and late winter but were only ca. 25% lower than eddy covariance measurements during the main snow accumulation period in mid-winter. During the snow-covered period, the flux gradient carbon efflux estimate (15gCm−2) was ca. three-fold less than eddy covariance measurements (49gCm−2). An analysis of the relationship between friction velocity and eddy covariance-measured CO2 efflux lends support to the notion that advection through snow is an important transport mechanism for trace gasses. A spectral Granger causality analysis indicates that the wind speed time series contributes information to the subnivean CO2 concentration time series during the melt period at time scales greater than 10hours. All three methodologies indicate that wintertime respiration is a major contributor to the annual carbon budget: the sum of eddy covariance-measured CO2 efflux during the snow-covered period was 1/3 of that during the snow-free period of 2011 (ca. 140gCm−2). Future studies should incorporate adjustments for advection when using snow flux gradient systems to avoid underestimating the often-underappreciated contribution of the cold season to ecosystem CO2 efflux.

Deriving Snow Cover Metrics for Alaska from MODIS

Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow cover products provide an opportunity for determining snow onset and melt dates across broad geographic regions; however, cloud cover and polar darkness are limiting factors at higher latitudes. This study presents snow onset and melt dates for Alaska, portions of western Canada and the Russian Far East derived from Terra MODIS snow cover daily 500 m grid data (MOD10A1) and evaluates our method for filling data gaps caused by clouds or polar darkness. Pixels classified as cloud or no data were reclassified by: spatial filtering using neighboring pixel values; temporal filtering using pixel values for days before/after cloud cover; and snow-cycle filtering based on a time series assessment of a pixel’s position within snow accumulation, cover or melt periods. During the 2012 snow year, these gap-filling methods reduced cloud pixels from 27.7% to 3.1%. A total of 12 metrics (e.g., date of first and last snow, date of persistent snow cover and periods of intermittence) for each pixel were calculated by snow year. A comparison of MODIS-derived snow onset and melt dates with in situ observations from 244 weather stations generally showed an early bias in MODIS-derived dates and an effect of increasing cloudiness exacerbating bias. Our results show that mean regional duration of seasonal snow cover is 179–311 days/year and that snow cover is often intermittent, with 41% of the area experiencing ≥2 snow-covered periods during a snow season. Other regional-scale patterns in the timing of snow onset and melt are evident in the yearly 500 m gridded products publically available at http://static.gina.alaska.edu/NPS_products/MODIS_snow/.

Wintering Population Change of the Cranes according to the Climatic Factors in Cheorwon, Korea: Effect of the Snow Cover Range and Period by Using MODIS Satellite Data.

Wintering Population Change of the Cranes according to the Climatic Factors in Cheorwon, Korea: Effect of the Snow Cover Range and Period by Using MODIS Satellite Data.

Effect of winter conditions on wild ungulates mortality in the Owl Mountains (Poland)

Abstract Relations between climatic factors during the winter season (n days with frost <0oC and −10oC; n days with snow cover: >1 cm, >10 cm and >30 cm; maximum snow cover during season [cm]) and mortality in free-living ungulates (red deer Cervus elaphus Linnaeus, 1758, roe deer Capreolus capreolus Linnaeus, 1758 and mouflon Ovis aries musimon Linnaeus, 1758) in the Owl Mountains (Lower Silesia – Poland) in years 1998–2010 were investigated. Significant effects of all analysed climatic factors on ungulates mortality were documented. Correlations (Pearson) between such weather factors as the depth of snow cover and number of days with frost and recorded mortality in total animal populations analysed ranged from r = 0.33 to r = 0.77. The least adapted to local weather conditions was mouflon introduced to this area ca. 100 years ago from more southern parts of Europe. Roe deer species seems to be environmentally plastic, and are doing quite well in severe winters. Tolerance of red deer to the snow cover is much lower at low temperatures due to the fact that this species, during the period of snow cover, has limited access to the plants covered with snow and difficult access to food base.

Variations in functional diversity in snowbed plant communities determining snowbed continuity

Snowbed habitats are home to plant species that have adapted to particular environmental conditions (i.e. long-lasting snow cover and short growing seasons). The presence of most of these species is dependent on a long period of snow cover and so their conservation may well depend in the future on their ability to adapt to the effects of climate change. The aim of this study was to assess the persistence of snowbed communities using functional trait and functional diversity indices. We used data for plant species abundances from 32 snowbeds in Andorra (Pyrenees) classified according to certain environmental variables (elevation, exposure, soil type and temperature) and snow cover duration. Nine functional traits were used to evaluate the functional diversity, which was characterised as consisting of functional richness, functional evenness, functional dispersion, functional divergence and the community-weighted mean trait values. In two snowbeds, plant traits were also recorded and variation analysed along a snowmelt gradient. We found that snowbed specialist species had functional traits that were well adapted to the particular abiotic conditions of snowbed habitats but that there was a predominance of the functional traits of grass species in species originating in neighbouring communities. We found less functional richness, fewer strategies and lower competitive ability in the adapted species as the severity of the abiotic conditions increased. Snowbed specialist species appear to be less sensitive to the length of the growing season than species from neighbouring communities. Our results suggest that non-specialist species will tend to appear more frequently in those snowbed habitats affected by the reduction in snow cover duration.

A wild boar dominated ungulate assemblage from an early Holocene natural pit fall trap: Cave shaft sediments in northwest England associated with the 9.3 ka BP cold event

A highly unusual pit fall ungulate assemblage dominated by wild boar ( Sus scrofa) was recovered during the recent exploration of a cave shaft in the upland karstic landscape of northwest England. Both the opening of the cave shaft to the surface and its infilling by clastic sediments are attributable to accelerated landscape erosion associated with the 9.3 ka BP climatic deterioration. Evidence that wild boar had died in winter or spring suggests that their deaths relate to the prolonged periods of annual snow cover experienced by the uplands of northwest England during the 9.3 ka BP event. The dominance of wild boar in the pit fall assemblage is explained by the snow pack concealing the open shaft and turning it into a baited trap for wild boar whenever it contained carrion. Wild boar bones splintered and chewed by wild boar demonstrate carrion cannibalism. Human presence is attested by slight butchery to an aurochs ( Bos primigenius). How Mesolithic people adapted to climate change associated with the 9.3 ka BP event is a subject well worth pursuing.

Effects of climate change and agricultural adaptation on nutrient loading from Finnish catchments to the Baltic Sea

Climate change is expected to increase annual and especially winter runoff, shorten the snow cover period and therefore increase both nutrient leaching from agricultural areas and natural background leaching in the Baltic Sea catchment. We estimated the effects of climate change and possible future scenarios of agricultural changes on the phosphorus and nitrogen loading to the Baltic Sea from Finnish catchments. In the agricultural scenarios we assumed that the prices of agricultural products are among the primary drivers in the adaptation to climate change, as they affect the level of fertilization and the production intensity and volume and, hence, the modeled changes in gross nutrient loading from agricultural land. Optimal adaptation may increase production while supporting appropriate use of fertilization, resulting in low nutrient balance in the fields. However, a less optimal adaptation may result in higher nutrient balance and increased leaching. The changes in nutrient loading to the Baltic Sea were predicted by taking into account the agricultural scenarios in a nutrient loading model for Finnish catchments (VEMALA), which simulates runoff, nutrient processes, leaching and transport on land, in rivers and in lakes. We thus integrated the effects of climate change in the agricultural sector, nutrient loading in fields, natural background loading, hydrology and nutrient transport and retention processes.

Variations of winter surface net shortwave radiation caused by land-use change in northern Hokkaido, Japan

To evaluate changes in surface albedo and net shortwave radiation caused by land-use changes, we developed a simple model using the MicroMet/SnowModel. Simulated results were compared with plot-scale observations and verified with reasonable agreement, following which we simulated surface albedo and net shortwave radiation over a large domain (0.5° × 0.5°, 100-m resolution). We found that the histogram of spatial distribution of net shortwave radiation could assume a Gaussian distribution in the case of uniform land use, despite complex topography. However, complex land use within the domain caused two histogram peaks with large standard deviation, meaning that a Gaussian distribution could not be assumed. For such complex land use, the spatial distribution of net shortwave radiation was determined by surface albedo, which was found to be strongly related to land use. For natural forest cover within the domain, the spatial distribution of net shortwave radiation was found to be related to slope azimuth angle, but surface albedo had only minor effect. For regenerated forest, net shortwave radiation was influenced by surface albedo rather than slope azimuth angle. Simulated results for bare ground within the domain were related to surface albedo and altitude, because higher altitudes had longer periods of snow cover and much greater snow accumulation. Overall, land-use changes were more important than orographic effects in the evaluation of net shortwave radiation.

Inversely estimating the vertical profile of the soil CO2 production rate in a deciduous broadleaf forest using a particle filtering method.

Carbon dioxide (CO2) efflux from the soil surface, which is a major source of CO2 from terrestrial ecosystems, represents the total CO2 production at all soil depths. Although many studies have estimated the vertical profile of the CO2 production rate, one of the difficulties in estimating the vertical profile is measuring diffusion coefficients of CO2 at all soil depths in a nondestructive manner. In this study, we estimated the temporal variation in the vertical profile of the CO2 production rate using a data assimilation method, the particle filtering method, in which the diffusion coefficients of CO2 were simultaneously estimated. The CO2 concentrations at several soil depths and CO2 efflux from the soil surface (only during the snow-free period) were measured at two points in a broadleaf forest in Japan, and the data were assimilated into a simple model including a diffusion equation. We found that there were large variations in the pattern of the vertical profile of the CO2 production rate between experiment sites: the peak CO2 production rate was at soil depths around 10 cm during the snow-free period at one site, but the peak was at the soil surface at the other site. Using this method to estimate the CO2 production rate during snow-cover periods allowed us to estimate CO2 efflux during that period as well. We estimated that the CO2 efflux during the snow-cover period (about half the year) accounted for around 13% of the annual CO2 efflux at this site. Although the method proposed in this study does not ensure the validity of the estimated diffusion coefficients and CO2 production rates, the method enables us to more closely approach the “actual” values by decreasing the variance of the posterior distribution of the values.

Carbon storage versus albedo change: radiative forcing of forest expansion in temperate mountainous regions of Switzerland

Abstract. In this study, we assess the climate mitigation potential from afforestation in a mountainous snow-rich region (Switzerland) with strongly varying environmental conditions. Using radiative forcing calculations, we quantify both the carbon sequestration potential and the effect of albedo change at high resolution. We calculate the albedo radiative forcing based on remotely sensed data sets of albedo, global radiation and snow cover. Carbon sequestration is estimated from changes in carbon stocks based on national inventories. We first estimate the spatial pattern of radiative forcing (RF) across Switzerland assuming homogeneous transitions from open land to forest. This highlights where forest expansion still exhibits climatic benefits when including the radiative forcing of albedo change. Second, given that forest expansion is currently the dominant land-use change process in the Swiss Alps, we calculate the radiative forcing that occurred between 1985 and 1997. Our results show that the net RF of forest expansion ranges from −24 W m−2 at low elevations of the northern Prealps to 2 W m−2 at high elevations of the Central Alps. The albedo RF increases with increasing altitude, which offsets the CO2 RF at high elevations with long snow-covered periods, high global radiation and low carbon sequestration. Albedo RF is particularly relevant during transitions from open land to open forest but not in later stages of forest development. Between 1985 and 1997, when overall forest expansion in Switzerland was approximately 4%, the albedo RF offset the CO2 RF by an average of 40%. We conclude that the albedo RF should be considered at an appropriately high resolution when estimating the climatic effect of forestation in temperate mountainous regions.

Nitrous oxide emissions from perennial grass–legume intercrop for bioenergy use

Bioenergy cropping, like all agricultural practices, may lead to the release of greenhouse gases. This study was aimed at determining biomass and energy yields of reed canary grass (RCG) (Phalaris arundinacea), galega (Galega orientalis) and a mixture of these, and to relate these to fluxes of nitrous oxide (N2O), a potent greenhouse gas, emitted from the soils. Plots including a bare fallow as control were established in 2008. Gases emitted from the soil surface were collected in closed chambers from May 2011 to May 2013, except during periods of snow cover, and analysed by gas chromatography. Seasonal and annual cumulative emissions of N2O and CO2 equivalents per unit energy yield were calculated. Soil moisture content, nitrate (NO3 −)-N and ammonium (NH4 +)-N were also determined. Both species composition and crop yields affected energy yields and N2O emission from the soil. The annual cumulative emissions from mixture were marginally lower than those from fertilized RCG soils. Fertilized RCG produced twice as much biomass and correspondingly higher nitrogen and energy yields, so its low emission of N2O per Mg of dry matter was not significantly different from that of the mixtures. Cropping an RCG–galega mixture for biofuel may replace N fertilizer input since it resulted in lowering N2O fluxes, but requires management to maintain grass as the major component in order to minimize N2O emissions. In a time of climate change, low-input bioenergy crops may be a suitable strategy for land left uncropped after ploughing for one season or longer.

Snowpack-atmosphere gas exchanges of carbon dioxide, ozone, and nitrogen oxides at a hardwood forest site in northern Michigan

Abstract Snowpack-atmosphere gas exchanges of CO2, O3, and NOx (NO + NO2) were investigated at the University of Michigan Biological Station (UMBS), a mid-latitude, low elevation hardwood forest site, during the 2007–2008 winter season. An automated trace gas sampling system was used to determine trace gas concentrations in the snowpack at multiple depths continuously throughout the snow-covered period from two adjacent plots. One natural plot and one with the soil covered by a Tedlar sheet were setup for investigating whether the primary source of measured trace gases was biogenic (i.e., from the soil) or non-biogenic (i.e., from the snowpack). The results were compared with the “White on Green” study conducted at the Niwot Ridge (NWT) Long Term Ecological Research site in Colorado. The average winter CO2 flux ± s.e. from the soil at UMBS was 0.54 ± 0.037 µmol m-2 s-1 using the gradient diffusion method and 0.71 ± 0.012 µmol m-2 s-1 using the eddy covariance method, and in a similar range as found for NWT. Observed snowpack-O3 exchange was also similar to NWT. However, nitrogen oxides (NOx) fluxes from snow at UMBS were 10 times smaller than those at NWT, and fluxes were bi-directional with the direction of the flux dependent on NOx concentrations in ambient air. The compensation point for the change in the direction of NOx flux was estimated to be 0.92 nmol mol-1. NOx in snow also showed diurnal dependency on incident radiation. These NOx dynamics in the snow at UMBS were notably different compared to NWT, and primarily determined by snow-atmosphere interactions rather than by soil NOx emissions.

“Winters Embittered with Hardships”: Severe Cold, Wabanaki Power, and English Adjustments, 1690–1710

In the 1690s and the first decade of the 1700s, two of the coldest decades of the Little Ice Age, severe winter weather in the American Northeast prompted adjustments first by Wabanakis and later by English colonists. Wabanaki people had generations of experience journeying through and drawing subsistence from their “winter lands.” With well-adapted seasonal practices and technologies, such as moose hunting on snowshoes, they knew how to cope with persistent cold and take advantage of periods of stable snow cover. In the Second Anglo-Wabanaki War (1688–99), Wabanakis launched winter raids against sites in northern New England, revealing a crucial seasonal vulnerability of English settlements. Frigid weather and Wabanaki attacks contributed to a sense of panic among New Englanders in the 1690s. During these years, however, English observers, soldiers, and captives also learned winter skills and strategies from their Wabanaki adversaries, which they used in the Third Anglo-Wabanaki War (1703–13). In 1703–4, colonial leaders began sending out hundreds of English “snowshoe men” to patrol Wabanaki hunting grounds, shifting the power dynamics in the winter woods. By appropriating an indigenous technology, English colonists adapted to a changing climate, provided greater security for their settlements, and dissipated fears of long winters.

Effect of climate change on the snow disappearance date in mountainous areas of central Japan

We investigated climate change in the annual snow cover period in mountainous areas of central Japan by downscaling simulations of four climate change projections based on a Coupled Model Intercomparison Project phase 3 (CMIP3) Special Report on Emission Scenarios (SRES) A1B emission scenario using a regional climate model. Our numerical simulation reproduced well the observed snow depths and areas of snow cover. The projected snow disappearance date in all areas occurred earlier in the future climate due to global warming and were substantially earlier in areas of both light and heavy snowpacks in the present climate. The time shift was smaller at areas where the present-day maximum snow depth is around 100 cm and the snow disappearance date is in mid-April. These projected changes in the duration of snow cover were associated with decreasing snowfall and accelerated snowmelt due to increasing surface air temperatures. The effect was interpreted using an idealized model of temporal variation in surface air temperature. Earlier snowmelt causes local enhancement of surface air temperature increases that will have considerable impact on mountain ecosystems.