Regional Snow Research Articles

Differences in compaction behavior of three climate classes of snow

In a recent paper (Sturm and others, 1995), a global seasonal snow-cover classification system was developed with each class defined by snow properties like grain-size and type. Here, characteristic bulk density vs time curves are assigned to three classes using snow-course data from Alaskan and Canadian sites. Within each class, curves have similar slopes and intercepts but between classes they are different. The relationship between slope, intercept and snow rheology has been investigated using a finite-difference model in which snow layers are assumed to behave as viscous fluids. Using observed slopes, the density-dependent compactive viscosity of each class has been determined. These are consistent with published values. Results indicate that load and load history are less important to the compaction behavior than grain and bond characteristics, snow temperature and wetness. The study suggests that differences in compaction behavior arise primarily from differences in rheology, the result of climatically controlled differences in the character of the snow. This finding explains why regional snow densities have been successfully predicted from air temperature and wind speed alone, without considering snow depth.

Temporal and spatial variability of snow accumulation in central Greenland

Snow accumulation records from central Greenland are explored to improve the understanding of the accumulation signal in Greenland ice core records. Results from a “forest” of 100 bamboo poles and automated accumulation monitors in the vicinity of Summit as well as shallow cores collected in the Summit and Crete areas are presented. Based on these accumulation data, a regression has been calculated to quantify the signal‐to‐noise variance ratio of ice core accumulation signals on a variety of temporal (1 week to 2 years) and spatial (20 m to 200 km) scales. Results are consistent with data obtained from year‐round automated accumulation measurements deployed at Summit which suggest that it is impossible to obtain regional snow accumulation data with seasonal resolution using four accumulation monitors positioned over a length scale of ∼30 km. Given this understanding of the temporal and spatial dependence of noise in the ice core accumulation signal, the accumulation records from 17 shallow cores are revisited. Each core spans the time period from 1964 to 1983. By combining the accumulation records, the regional snow accumulation record has been obtained for this period. The results show that 9 of the 20 years can be identified as having an accumulation different from the 20 year mean with 99% confidence. The signal‐to‐noise variance ratio for the average accumulation signal sampled at annual intervals is 5.8±0.5. The averaged accumulation time series may be useful to climate modelers attempting to validate their models with accurate regional hydrologic data sets.

チベット、東ヨーロッパ、シベリアの積雪偏差が大気に及ぼす影響の比較実験

The atmospheric response to the regional snow mass anomalies in early spring over Tibet, Eastern Europe, and Siberia is compared by general circulation model ensemble experiments. The positive snow mass anomalies over Tibet produce the largest cooling anomalies in the atmosphere from spring to early summer. Almost no significant forcing anomalies are systematically formed by the snow mass anomalies over Eastern Europe and Siberia.The model experiments show that the cooling source over Tibet works significantly to delay the seasonal transition from spring to summer in the Northern Hemisphere. It is confirmed by the simulated weak Asian monsoon; a weak lower tropospheric monsoon jet in South Asia, a weak large-scale divergence center at the upper troposphere in Southeast Asia, negative lower-layer geopotential height anomalies in the North Pacific and the North Atlantic, and the weak Walker circulation in the equatorial Pacific are simulated.The above noticeable response of the atmosphere to the snow mass anomalies over Tibet is associated with the following characteristics of Tibet as compared with Eastern Europe and Siberia;(1) The small snow melt speed over Tibet, probably due to its high elevation, maintains the early spring additional snow mass until almost the end of the climatic snow-melt season.(2) The snow albedo is effective because of large solar incidence and relatively small cloudiness over Tibet.(3) The existence of the anomalous snow cover works to cut the upward sensible heat flux rather than the evaporation over Tibet because of its dry ground condition.(4) The dry ground over Tibet makes it possible that all the anomalous snow-melt water is not drained as runoff, but a part of it is stored in the ground.(5) As pointed out by many researchers, the Tibetan Plateau plays an important rôle in the establishment of the Asian monsoon.The above conditions (1)-(5) for the effective snow mass anomalies are found in the model Tibet, but these conditions would be satisfied by the real regions where the snow mass anomalies affect the atmosphere efficiently.The extended atmospheric responses are found in May for the East European case and in August for the Siberian case. These are accompanied by significant ground condition anomalies in northern Eurasia. Those ground condition anomalies are not directly related to the successive ground condition anomalies followed by the anomalous snow mass melt, and seem to be created after the water and heat of the initial snow mass anomalies are supplied into the atmosphere.

Recent climatic trend and thermal response of permafrost in Salluit, Northern Quebec, Canada

AbstractNot all places may in fact warm under global change scenarios. This paper presents an example of climatic cooling from northern Quebec, Canada. Ground temperature measurements along the southern shore of Hudson Strait, northern Quebec indicate a cooling trend over the last seven years (1987‐93). Long‐term air temperature records show that this area has actually experienced continuous cooling for more than 40 years. Related studies suggest that the cooling is likely to continue due to freshening of subpolar water in the North Atlantic and Labrador Sea area. A one‐dimensional geothermal model was used to simulate the effect of continued cooling on permafrost thermal regime in Salluit, northern Quebec. The results show that, if the climatic trend continues for the next 50 years, the thickness of the active layer would decrease by 30cm (from 2.3 to 2.0 m) in gneiss and by 20cm (from 1.3 to 1.1 m) in till. Permafrost temperature at 20 m depth would decrease by 0.65 °C. Under the cooling scenario, rate of permafrost creep and slope activities would be reduced. Ice‐wedge regrowth would continue, and the buried ice wedges may even become reactivated. The results also indicate that regional snow precipitation data cannot be used directly in predicting ground thermal regimes.

Recent variations and regional relationships in Northern Hemisphere snow cover

An analysis of snow-cover variability over Northern Hemisphere land masses reveals a continuation of the subnormal coverage that began in the late 1980s (relative to the 1972–present interval). While the 1994 snow year (September 1993–August 1994) exhibited a return to near-normal hemispheric extent, only three months during this period had above-normal coverage. Only 11 of the past 88 months (through October 1994) have been above the norm. Deficits have been most common in spring, over both the Eurasian and North American continents. This is a hemisphere-wide situation; positive correlations are identified between hemispheric and regional snow extents in spring, as well as in fall and winter. A number of significant associations are also recognized between regions during these three seasons; however, it is uncommon to see more than 50% of the variance in one region explained by another. These correlations are most common between adjacent regions, but some are found between regions on different continents. Only in spring are significant positive relationships between non-adjacent regions on the same continent observed.

Recent variations and regional relationships in Northern Hemisphere snow cover

An analysis of snow-cover variability over Northern Hemisphere land masses reveals a continuation of the subnormal coverage that began in the late 1980s (relative to the 1972–present interval). While the 1994 snow year (September 1993–August 1994) exhibited a return to near-normal hemispheric extent, only three months during this period had above-normal coverage. Only 11 of the past 88 months (through October 1994) have been above the norm. Deficits have been most common in spring, over both the Eurasian and North American continents. This is a hemisphere-wide situation; positive correlations are identified between hemispheric and regional snow extents in spring, as well as in fall and winter. A number of significant associations are also recognized between regions during these three seasons; however, it is uncommon to see more than 50% of the variance in one region explained by another. These correlations are most common between adjacent regions, but some are found between regions on different continents. Only in spring are significant positive relationships between non-adjacent regions on the same continent observed.

Use of NOAA-AVHRR data to monitor snow cover and spring meltoff in the wildlife habitats in Jameson Land, East Greenland

NOAA-AVHRR satellite data have been used for a multi-year analysis of the seasonal variation of snow cover on the peninsula of Jameson Land located from 70°30?N to 72°N on the eastern coast of Greenland. Monitoring programmes for muskoxen and geese populations in Jameson Land wert started in the early 1980s to assess the impact of oil exploration in the area. This study was conducted to provide snow cover data to the wildlife monitoring programmes because snow cover is an important factor which can affect the numbers and distribution of muskoxen and other wildlife in the area. Snow cover mapping is based on the geometric correction and radiometric calibration of each satellite scene before the visual bands are corrected for the terrain-effects and high solar zenith angle by using a simple radiation model. The atmospheric effect on the thermal infrared bands is corrected by using the “split-window” method. An automatic filtering routine with empirically determined thresholds is used to determine cloud-and haze-covered areas before the snow cover is computed from a linear expression using albedos of bare ground and full snow cover. By combining the satellite information with ground measurements and a digital terrain model, both the spatial distribution of snow cover and the total snow cover depletion can be obtained. The method makes it possible to analyse the variation in regional and seasonal snow cover in wildlife habitats. The variation in snow cover depletion has been analysed in five subareas in the muskox area, and the results indicate that the snow cover pattern is an important factor which influences muskox calf crop and regional distribution of the muskox population. The method has proved useful for monitoring the duration of snow cover, and its application ought to facilitate the future study of wildlife habitats in extensive alpine and arctic areas.

Recent Variations of Snow Cover and Snowfall in North America and Their Relation to Precipitation and Temperature Variations

Abstract Contemporary large-scale changes in solid and total precipitation and satellite-derived snow cover were examined over the North American continent. Annual snow cover extent over the last 19 years decreased up to 6×105 km2 relative to a 0.93°C (0.33°C) increase in North American (Northern Hemisphere) temperature. A strong correlation exists between snow cover and temperature where up to 78% of the variance in regional snow cover and snowfall is explained by the anomalies of monthly mean maximum temperature. Over the last two decades the decrease in snow cover during winter (December-March) has largely occurred through reduced frequency of snow cover in areas that typically have a high probability of snow on the ground with little change in the frequency of snow cover in other areas. Similar characteristics were observed during spring (April-May) in areas with high snow cover probability except for an expansion of the snow-free regions. Anomalies in these two seasons dominate the interannual variab...

Glacier recession in Iceland and Austria

Valley and mountain glaciers and ice caps respond to changes in regional climate on the scale of decades; thus, they can serve as indicators of regional climate change. During the last century, most valley and mountain glaciers and ice caps receded [Meier, 1984; Haeberli et al., 1989], although some advances have occurred during periods of cooling [Wood, 1988]. Glaciers in Iceland [Rist, 1975] and in the eastern Alps of Austria [Patzelt, 1980] have followed a similar pattern.Images acquired by satellite sensors can provide a regional overview for studying changes in glacier area, terminus position, glacier facies [Williams et al., 1991], and the position of the regional snow line, while insitu studies usually provide measurements at only a single point. Major changes in glaciers may be obvious from initial inspection of satellite images; however, detailed study of digital image data can reveal the presence of small changes that are useful indicators of regional trends in glacier mass balance. If observed over a long enough period of time in many different geographic settings, glacier‐terminus position changes can be related to changes in regional and even global climate.

Operational satellites and the global monitoring of snow and ice

Global climate models indicate that the effects of increasing greenhouse gas concentrations will be greatest in high latitudes. The latitudinal dependence of the projected warming is at least partially attributable to the albedo-temperature feedback involving snow and ice, which must therefore he regarded as key variables in the monitoring for global change. The areal coverage and extent of sea ice have been monitored systematically for the past 17–18 years by infrared and microwave sensors onboard polar orbiting satellites. Statistical analyses of these data have led to mixed conclusions about recent trends of hemisphere sea ice coverage, although slow variations of regional ice coverage and extent are apparent in the data. The primary needs are more detailed fields of surface albedo and ice thickness (ice type). Multichannel microwave imagery provides information on the areal coverage of multiyear sea ice, but uncertainties remain in the algorithms. Seasonal snow cover has been mapped for over 20 years by NOAA/NESDIS on the basis of imagery from a variety of satellite sensors. Weekly maps from this period have been digitized and used for the near-real-time monitoring of hemispheric and regional snow cover. The primary needs pertaining to snow cover are systematic measurements of snow depth, liquid water equivalent, and surface albedo. Accurate albedo measurements are essential for parameterization and verification of the albedo-temperature feedback in climate model experiments, while the liquid water equivalent has major hydrological implications. Multichannel passive microwave data show some promise for the routine monitoring of snow depth (volume) over unforested land areas.

Merging operational satellite and historical station snow cover data to monitor climate change

Since the middle of 1987, snow cover Northern Hemisphere lands has been less extensive than at any time since the advent of reliable satellite snow charting in 1972. In fact, 1990 should of down as being the lowest snow year on record: monthly minima have been established for February through September (based on observations through September). However, with less than a two-decade long record of satellite observations of snow cover, it is impossible to place this recent dearth of cover in proper perspective. To do so requires a longer period of record, one which can only be supplied from station data. Regional intercomparisons of visible satellite-derived snow products and networks of station observations agree well on a seasonal time scale, given a network of high-quality stations in non-mountainous terrain. Thus, where these conditions are met, lengthy time series of regional snow cover may be compiled confidently from station observations, permitting documentation of natural fluctuations and trends of cover that may occurred over the past century. For instance, decadal fluctuations in snow cover have been identified over the United States Great Plains this century, and a trend towards increasing duration of cover from the 1930's to 1970's has been observed in the central Plains. Such information enhances the utility of satellite-derived snow cover observations identifying and monitoring future climate change.

The Chernobyl Reference Horizon (?) in the Greenland Ice Sheet

Published reports of the presence of radioactive debris from the Chernobyl reactor accident in snow on the Greenland ice sheet raised the strong prospect that such debris might constitute a valuable time stratigraphic marker all over the ice sheet. Large volume snow samples to test this possibility were collected from 7 snowpits as part of a wide ranging regional snow chemistry survey conducted during 1987 and 1988. Snow “labeled” with Chernobyl derived radioactivity was detected in all of the pits. However, the total amount of radioactive debris found at the different locations varied over a 20 fold range. The variability in total fallout showed no clear large scale spatial pattern that could be related to the presumed progress of the radioactive plume over Greenland, suggesting that small scale differences in precipitation pattern and reworking of the snow by wind were predominantly responsible for the patchy preservation of the Chernobyl “layer” on the Greenland ice sheet.

Late glacial and late Holocene moraines in the Cerros Cuchpanga, central Peru

Small ice fields on the western cordillera northeast of Lima were expanded to three times their present size in the recent past, and the regional snow line was probably about 100 m lower than it is today. Outwash from the expanded glaciers formed deltas of silt in valley-bottom lakes. When the ice lobes retreated, the reduced outwash was trapped behind recessional moraines, and the clear meltwater infiltrated into the limestone bedrock and emerged at the heads of the deltas in spring pools. The delta surfaces then became covered with peat, and radiocarbon dates for the base of the peat (1100 ± 70 and 430 ± 70 yr B.P. for two different deltas) indicate that the maximum ice advance was older than those dates and, thus, older than the Little Ice Age of many north-temperate regions. Much older moraines date from expansion of the same local summit glaciers to even lower levels in the main valleys, which had previously been inundated by the cordilleran ice field. The cordilleran deglaciation and this expansion of local glaciers probably occurred between 12,000 and 10,000 yr ago, on the basis of slightly contradictory radiocarbon dates.

Snow and ice balance in britain at the present time, and during the last glacial maximum and late glacial periods

AbstractSimple parameterizations are used to estimate monthly mean ablation of snow and ice, and also the distribution of monthly mean precipitation in Britain. Together these enable estimates to be made of snow storage at various levels and the gradients of days with snow cover with elevation. Small semi‐permanent snow patches below the regional snow line are included in the discussion. The theoretical estimates fit the actual observations very closely. A similar approach is then used to estimate snow balances for the British Devensian ice sheets. Probable snow accumulation/elevation relationships are produced for 24,000 yr BP. Estimates suggest that the British ice sheet was just in balance at the lime of its maximum advance around 18,000 yr BP. The growth and decay of British ice sheets are considered and two stable states are suggested for ice‐age climates, one without an ice‐sheei and the other with a massive ice‐sheet.

An empirical representation of snow-control cost as a function of snow-disaster index, population and regional snow conditions

The severity of snow disaster in Japan depends on the conditions of natural environment and human activities. This paper at first describes the past research of present authors : Nakatao (1968, 1976) proposed a snow-disaster index T based on the climatic and snow removal conditions; Nakatao and Mizukoshi (1978) gave an empirical expression for prefectural snow-control cost M=γNT, where N is the population which reflects (an index of) social and economic conditions. The constant γ for each prefecture had a mean error of ±47%; further, Nakatao and Mizukoshi (1979) introduced the distance x from the sea-coast to the weather station in the most populous city (usually the capital of the prefecture) into an improved empirical expression where the mean error of γ was 33%. The rest of the paper describes an analysis of the relation between the population distribution in each prefecture and the snow-control cost; a new empirical formula for M is introduced for sparsely populated prefectures. Combining two formulas for densely-populated and sparsely-populated prefectures, the snow-control cost M is given, and the constant γ is within an error of 22% except for Yamaguchi Prefecture.

Avalanche zoning in alaska, U.S.A.

AbstractOver 30% of Alaska’s 586 400 squares miles (1 518900 km2) is subject to snow-avalanche activity. For a state-wide avalanche hazard evaluation, Alaska has been divided into six major snow— avalanche regions on the basis of topography, climatological data, dominant snow—pack conditions, and typical avalanche activity. They are: Arctic Slope, Brooks Range, Western, Interior, South—central, and South—east.Mountainous terrain was studied at scales of 1 : 250 000 and 1 : 1 584000; final compilation was at a scale of 1 : 2 500 000. Regional snow—pack and climatic conditions were cross—correlated with relief zonation of each avalanche region to produce a map of Alaska's provisional snow—avalanche potential.Most of the mountainous areas in the South—central and South—east regions, because of their northern latitude, closeness to large masses of water, and large orographic and cylonic weather processes, are susceptible to major avalanche activity. For areas near population centers, the potential avalanche terrain has been identified from data on known and suspected avalanche activity through air photographs, terrain analysis, and documented snow—avalanche occurrences compiled at scales of 1 : 250 000 and 1 : 63 360.The state—wide regional data compilation and study are initial steps toward avalanche zoning in Alaska. Local land—use planning and detailed investigations are needed to establish effective natural—hazard zoning in municipal areas as related to snow avalanche activity.

Avalanche zoning in alaska, U.S.A.

AbstractOver 30% of Alaska’s 586 400 squares miles (1 518900 km2) is subject to snow-avalanche activity. For a state-wide avalanche hazard evaluation, Alaska has been divided into six major snow— avalanche regions on the basis of topography, climatological data, dominant snow—pack conditions, and typical avalanche activity. They are: Arctic Slope, Brooks Range, Western, Interior, South—central, and South—east.Mountainous terrain was studied at scales of 1 : 250 000 and 1 : 1 584000; final compilation was at a scale of 1 : 2 500 000. Regional snow—pack and climatic conditions were cross—correlated with relief zonation of each avalanche region to produce a map of Alaska's provisional snow—avalanche potential.Most of the mountainous areas in the South—central and South—east regions, because of their northern latitude, closeness to large masses of water, and large orographic and cylonic weather processes, are susceptible to major avalanche activity. For areas near population centers, the potential avalanche terrain has been identified from data on known and suspected avalanche activity through air photographs, terrain analysis, and documented snow—avalanche occurrences compiled at scales of 1 : 250 000 and 1 : 63 360.The state—wide regional data compilation and study are initial steps toward avalanche zoning in Alaska. Local land—use planning and detailed investigations are needed to establish effective natural—hazard zoning in municipal areas as related to snow avalanche activity.

Sulfur and crustal reference elements in nonurban aerosols from Squaw Mountain, Colorado

In order to assess the effect of anthropogenic emissions of sulfur compounds to the atmosphere, sulfur and the crustal reference elements potassium, calcium, titanium, and iron were determined by proton induced x-ray emission in nonurban aerosols from a remote western US mountaintop before and after snowfall. Sulfur, mainly a submicron aerosol consitiuent, exhibited poor correlation with the crustal group. Crustal element concentrations were markedly suppressed by regional snow cover as well as by falling snow, but suflur concentrations, usually 300 to 400 ng/cu m, were suppressed only when precipitation was occurring. The data suggest that Denver, lying 40 km to the east of the sampling site and at 1600 m elevation, may not have influenced the aerosol levels on Squaw Mountain. Therefore, the aerosol sulfur concentrations may represent regional background levels. Tables, graphs, and 39 references are included.

Areal differentiation of snow cover in east central Ontario

Vegetationally based patterns of snow depth, density, and water equivalent are identified by using snow course, grid, and unaligned random sample measurements. The limitations of extrapolations from point measurements to general characteristics of regional snow cover are discussed for an area in which midwinter melt is a feature of snow cover evolution. The snow cover of the vegetation zones was most distinct in terms of water equivalent and least distinct in terms of density. Measurements of depth proved to have a high predictive value for water equivalents. The validity of generalizations from point measurements, even in terms of quite coarse measures of snow cover characteristics, is limited in areas such as this to a short period following the time of measurement.

Mass Movement Processes in Metalline Creek, Southwest Yukon Territory

In Metalline Creek, a small valley in the Kluane Range of the southwest Yukon Territory, the glacial deposits and the talus material have been affected by mass movement processes promoted by the occurrence of glacier ice and ice formed from avalanche snow. In addition, minor periglacial mass movement processes occur in the valley. Variations in the type of process are attributed to altitudinal changes, to aspect, and to change in the height of the regional snow line during the Neoglacial period.