Snow Accumulation Patterns Research Articles

Testing a blowing snow model against distributed snow measurements at Upper Sheep Creek, Idaho, United States of America

In this paper a physically based snow transport model (SnowTran‐3D) was used to simulate snow drifting over a 30 m grid and was compared to detailed snow water equivalence (SWE) surveys on three dates within a small 0.25 km2 subwatershed, Upper Sheep Creek. Two precipitation scenarios and two vegetation scenarios were used to carry out four snow transport model runs in order to (1) evaluate the blowing snow model, (2) evaluate the sensitivity of the snow transport model to precipitation and vegetation inputs, and (3) evaluate the linearity of snow accumulation patterns and the utility of the drift factor concept in distributed snow modeling. Spatial comparison methods consisted of (1) pointwise comparisons of measured and modeled SWE, (2) visual comparisons of the spatial maps, (3) comparisons of the basin‐wide average SWE, (4) comparisons of zonal average SWE in accumulation and scour zones, and (5) comparisons of distribution functions. We found that the basin average modeled SWE was in reasonable agreement with observations and that visually the spatial pattern of snow accumulation was well represented except for a pattern shift. Pointwise comparisons between the modeled and observed SWE maps displayed significant errors. The distribution functions of SnowTran‐3D‐modeled drift factors from two precipitation scenarios on three dates were compared with the distribution function of observation‐based drift factors obtained previously by calibration to evaluate the assumption of linearity. We found only a 14% reduction in explained variance in the distribution function of drift factors for a 69% increase in precipitation, suggesting that the simplification provided by the use of drift factor distributions will result in errors that are tolerable in many cases.

Magnitude and timing of annual maximum floods: Trends and large‐scale climatic associations for the Blacksmith Fork River, Utah

The magnitude and timing of spring snowmelt floods reflects seasonal snow accumulation and spring temperature patterns. Consequently, interannual variations in regions such as the intermountain West, with snowmelt annual maximum floods, may be related to low‐frequency variations in winter/spring large‐scale climate variability. Changes in the seasonality of basin precipitation and temperature consequent to slow changes in the baseline climate state (e.g., owing to natural climate variations and/or potential global warming trends) may have significant impacts on such floods. A case study of the Blacksmith Fork River in northern Utah that explores such a hypothesis is presented here. Trends and associations in the magnitude and timing of annual maximum floods are documented, their impact on time‐varying estimates of the 100 year flood is assessed, and relationships with known large‐scale, quasi‐oscillatory patterns of climate variability are explored. Evidence for structured low‐frequency variation in flood timing and magnitude and its relation to winter/spring precipitation and temperature and to tropical (El Niño– Southern Oscillation) and extratropical (Pacific Decadal Oscillation) Pacific climate precursors is presented. Mechanisms for these ocean‐atmosphere teleconnections to basin precipitation, temperature, and flood potential are discussed.

Application of the Canadian regional climate model to the Laurentian great lakes region: Implementation of a lake model

This study reports on the implementation of an interactive mixed‐layer/thermodynamic‐ice lake model coupled with the Canadian Regional Climate Model (CRCM). For this application the CRCM, which uses a grid mesh of 45 km on a polar stereographic projection, 10 vertical levels, and a timestep of 15 min, is nested with the second generation Canadian General Circulation Model (GCM) simulated output. A numerical simulation of the climate of eastern North America, including the Laurentian Great Lakes, is then performed in order to evaluate the coupled model. The lakes are represented by a “mixed layer” model to simulate the evolution of the surface water temperature, and a thermodynamic ice model to simulate evolution of the ice cover. The mixed‐layer depth is allowed to vary spatially. Lake‐ice leads are parametrized as a function of ice thickness based on observations. Results from a 5‐year integration show that the coupled CRCM/lake model is capable of simulating the seasonal evolution of surface temperature and ice cover in the Great Lakes. When compared with lake climatology, the simulated mean surface water temperature agrees within 0.12°C on average. The seasonal evolution of the lake‐ice cover is realistic but the model tends to underestimate the monthly mean ice concentration on average. The simulated winter lake‐induced precipitation is also shown, and snow accumulation patterns on downwind shores of the lakes are found to be realistic when compared with observations.

Snow and blue-ice distribution patterns on the coastal Antarctic Ice Sheet

Surface patterns of alternating snow and blue-ice bands are found in the Jutulgryta area of Dronning Maud Land, Antarctica. The snow-accumulation regions exist in the lee of blue-ice topographic ridges aligned perpendicular to winter winds. The snow bands are c. 500–2000 m wide and up to several kilometres long. In Jutulgryta, these features cover c. 5000 km2. These alternating snow and blue-ice bands are simulated using a snow transport and redistribution model, SnowTran-3D, that is driven with a winter cycle of observed daily screen-height air temperature, humidity, and wind speed and direction. The snow-transport model is coupled to a wind model that simulates wind flow over the relatively complex topography. Model results indicate that winter winds interact with the ice topographic features to produce alternating surface patterns of snow accumulation and erosion. In addition, model sensitivity simulations suggest that subtle topographic variations, on the order of 5m elevation change over a horizontal distance of 1 to 1.5 km, can lead to snow-accumulation variations that differ by a factor of six. This result is expected to have important consequences regarding the choice of sites for ice-coring efforts in Antarctica and elsewhere.

Seedling occurrence in alpine treeline conifers: A case study from the central Rocky Mountains, USA

Abstract Information concerning the occurrence of very young (1- to 10-year-old) tree seedlings in the alpine treeline ecotone is rare. Seedling occurrence of the dominant conifers Picea engelmannii and Abies lasiocarpa was measured in the treeline ecotone of the Medicine Bow Mountains, Wyoming (central Rocky Mountains, USA), an area composed of elongated tree islands separated by open meadows (ribbon forest) that grade into the closed forest. No seedlings were found on the windward sides of tree islands, while a mean of 0.6 seedlings.m–2 occurred on the leeward (downward) sides. These values compared to the 4.2 seedlings.m–2 in the closed forest. In addition, a strong correspondence was found between snowpack depth and seedling abundance, with depths that were either too shallow ( 1.5 m) associated with fewer or no seedlings. A. lasiocarpa seedlings made up much less of the overall seedling population in the ribbon forest (6 %) than in the closed forest (22 %). Seedling establishment in this portion of the alpine treeline ecotone appears to be occurring at a low rate that differs between the two dominant species and may be strongly influenced by wind-driven snow accumulation patterns.

Cryoplanation terrace orientation in alaska

Exploratory analysis of the orientation of 303 cryoplanation terraces in interior and western Alaska lends tentative support to the hypothesis that these landforms develop through localized erosion related to spatial patterns of snow accumulation and ablation. Cryoplanation terraces exhibit orientation patterns similar to those of cirques in several regions of Alaska. In climatically continental east‐central Alaska, cryoplanation terraces are developed preferentially on north‐facing slopes and the frequency distribution of terrace orientation is similar to but less concentrated than that of glacial cirques. In south‐central Alaska, both cirques and terraces have bimodal frequency distributions corresponding to generalized wind patterns that predominated during Pleistocene glaciations. In western Alaska, terraces and cirques have relatively diffuse patterns without preferred orientation. No clear relation is apparent between the orientation of cryoplanation terraces and their size or elevation, although this may be an artifact of the current inability to differentiate terraces by age. Data from the Eagle Summit/Mastodon Dome area in interior Alaska indicate a possible relation between snowline elevation and the concentration of terrace orientation.

The Changes in Russian Winter Snow Accumulation during 1936–83 and Its Spatial Patterns

Abstract Winter snow depth observations from 119 Russian stations during the years 1936–83 are selected. These irregularly spaced station data are then interpolated into 220 regular grids of 2° lat × 5.24° long that cover a region of 50°–70°N, 30°–140°E. The spatial variation patterns of the annual Russian winter snow accumulation during the period of 1936–83 are identified by using principal components analyses. Statistically significant trends in major snow depth variation patterns are detected. A method is constructed to estimate the spatial distributions of the total amount of snow depth change based on the significant trends of component scores during the period of 1936–83. The study found that snow depth has increased over most of northern Russia and decreased over most of southern Russia during the study period. Exceptions are found in northern European Russia, where a slight decrease in snow depth has occurred and in southern west Siberia where the snow depth has increased. The total amount of sno...

The development of a rule-based spatial model of wind transport and deposition of snow

This paper describes the early stages in the development and testing of a spatio-temporal rule-based model of snow transport by wind over complex terrain. The model uses a cell-based approach and takes into account a range of meteorological, snow-pack and topographic variables. Simple rules are used to determine movement of material from cell-to-cell within the model.A geographic information system is utilized in modelling wind vectors and the influence of topography upon those vectors, and creating the resulting pattern of snow accumulation at a resolution of 50 m. These patterns of accumulation have been compared with empirical work in the field and, although field data were limited, a good qualitative correlation has been found; for example, modelled accumulations correlate with known areas of accumulation such as gullies and hollows.

The development of a rule-based spatial model of wind transport and deposition of snow

This paper describes the early stages in the development and testing of a spatio-temporal rule-based model of snow transport by wind over complex terrain. The model uses a cell-based approach and takes into account a range of meteorological, snow-pack and topographic variables. Simple rules are used to determine movement of material from cell-to-cell within the model.A geographic information system is utilized in modelling wind vectors and the influence of topography upon those vectors, and creating the resulting pattern of snow accumulation at a resolution of 50 m. These patterns of accumulation have been compared with empirical work in the field and, although field data were limited, a good qualitative correlation has been found; for example, modelled accumulations correlate with known areas of accumulation such as gullies and hollows.

Monthly snowmelt modelling for large-scale climate change studies using the degree day approach

The degree day or temperature index snowmelt modelling approach has been adapted to provide a simple conceptual, semi-distributed snowmelt-runoff model suitable for large-scale climate impact investigations. The model is forced by pseudo-daily data derived from standard monthly meteorological data. Generic rather than site-specific parameters are used where possible to allow spatial and temporal transferability. Spatial distribution is achieved by elevation and broad vegetation cover. Snow accumulation and melt are determined from air temperature. Catchment runoff is simulated with a one-dimensional water balance sub-model consisting of two soil layers. Available water capacity, percolation and drainage rates are defined by soil texture. The model was tested in three catchments: Valuoja in Estonia and Gimdalsbyn and Kultsjön in Sweden. The catchment areas ranged from approximately 4–2200 km 2, simulation lengths were 10, 21 and 26 years. The snow season timing matched that observed in all three catchments. Comparisons of measured and estimated snow water equivalence in Kultsjön demonstrated that the model can adequately predict snow cover below the tree line. Simulated monthly runoff at Valuoja gave good agreement with observations ( r = 0.87) and a paired t-test showed no significant differences. The seasonal discharge pattern at Kultsjön also fitted well ( r = 0.85) although the hydrograph generated was too low, probably due to precipitation undercatch. The discharge pattern at Gimdalsbyn was less well modelled ( r = 0.55), but the annual runoff totals were similar suggesting a lagged runoff response. Sensitivity analysis showed that the model is insensitive to the generic parameters but is sensitive to local soil texture. The model is able to capture, from standard meteorological data, patterns of snow accumulation, melt and runoff with a reasonable degree of accuracy without the need to optimise parameters. These features make the model a potentially useful tool for evaluating the impacts of climate change on regional and continental water balances.

Influence of Local Topography, Soils, and Vegetation on Microclimate and Hydrology at a High Arctic Site, Ellesmere Island, Canada

Influence of topography, soils, and vegetation on the microclimate and hydrology of four slopes and a plateau site located within a 1-km2 area in the continuous permafrost zone of Arctic Canada was studied. The field season covered two summers with contrasting climatic conditions. During the warm, dry summer (1990), the between-slope differences in radiation, and air and ground temperatures were exaggerated, while during the cloudy summer (1989), diffuse rather than direct solar radiation prevailed and the differential heating between slopes was reduced. Ground thaw increased in the warm summer, but maximum thaw depth at any site was also affected strongly by vegetation and soil characteristics, the latter being controlled by local geology and geomorphic processes. Precipitation on slopes can be influenced by wind and snow accumulation is modified by the local topography such as slope concavities. Snow ablation was largely accomplished through radiation melt so that the albedo changes were important. Meltwater runoff was maintained only downslope of deep snowbanks, and only the lower slopes experienced continuous saturation or groundwater flow. The spatial pattern of snow accumulation, frost table configuration, and surface or groundwater flows tend to recur annually, indicating the long-term influence of topography, soils, and vegetation on hydrologic processes at the local scale. Such studies linking the spatial and temporal variability of environmental attributes on energy and water flow improve our understanding of landscape ecology in northern environments and are useful when point observations are scaled up to match the dimensions of regional climate models.

Seasonal snowpack influence on the hydrology of a sub-arctic catchment in Scotland

Snow cover, depth and water equivalent have been measured in each snow season between 1989/90 and 1993/94 in the Alit a' Mharcaidh catchment in the western Cairngorms. Spatial and temporal patterns of snow accumulation vary: the peak measured water equivalent held in the catchment snowpack ranged from around 50 mm in mild winters to 200 mm in more severe ones. Snow accumulation was concentrated on north and east facing slopes in the parts of the catchment above 700 m. Point measurements of water equivalent in the areas of greatest accumulation exceeded 2000 mm as a result high densities produced by prolonged melt metamorphosis. Patterns of accumulation and melt strongly influenced the hydrology and hydrochemistry of the stream which has a distinct alpine like regime. Low base flows of high pH (>6.5) characterise cold periods of snow accumulation. Melt events are variable; slight increases in temperatures commonly melt all snow lying at low altitudes. More substantial melts involving the extensive snowpack at higher altitudes occur in the early spring as temperatures increase more significantly. Melt events strongly influence the hydrochemistry of the stream; preferential elution of Cl and SO4 were distinct characteristics of each melt season. Moreover, the most acidic (pH < 5.5) streamflows, and the highest levels of inorganic aluminium, were usually observed during snowmelt.

The influence of superimposed-ice formation on the sensitivity of glacier mass balance to climate change

The formation of superimposed ice at the surface of high-Arctic glaciers is an important control on glacier mass balance, but one which is usually modelled in only a schematic fashion. A method is developed to predict the relationship between the thickness of superimposed ice formed and the mean annual air temperature (which approximates the ice temperature at 14 m depth). This relationship is used to investigate the dependence of the proportion of snowpack water equivalent which forms superimposed ice on changes in mean annual temperature and patterns of snow accumulation. Increased temperatures are likely to reduce the extent of the zone of superimposed-ice accumulation and the thickness of superimposed ice formed. This will have a negative effect on glacier mass balance. This is true even if warming occurs only in the winter months, since near-surface ice temperatures will respond to such warming. For John Evans Glacier, Ellesmere Island, Nunavut, Canada (79°40’ N, 74°00’ W), a 1°C rise in mean annual air temperature due solely to winter warming is predicted to reduce the specific mass balance of the glacier by 0.008 m a–1 as a result of decreased superimposed-ice formation. Although such a response is small in comparison to the changes which might result from summer warming, it is nonetheless significant given the very low specific mass balance of many high-Arctic glaciers.

Timing and significance of Late-glacial and Holocene cirque glaciation in the Sierra Nevada, California

Mapping and radiocarbon dates of cirque moraines in the Sierra Nevada demonstrate that the last significant pre-Little Ice Age glacier advance in the range, the Recess Peak, resulted from snowline lowering roughly twice that of the Matthes (Little Ice Age) advance, and that the Recess Peak advance is late Pleistocene in age. We mapped Recess Peak and Matthes deposits in 64 cirques along a profile of the main Sierran crest that spans the north-south limits of ‘Neoglacial’ deposits in the range. Equilibrium-line altitudes for the reconstructed Recess Peak glaciers vary greatly but coherently with those of the Matthes advance. The variability of both sets of deposits reflects strong topographic influences on snow accumulation and ablation patterns in their deep cirques. Tephrochronology and radiocarbon dates from lake-sediment cores provide limits on the timing of the two advances. Previous work documenting the absence of a young, regionally extensive tephra on Matthes moraines in the central Sierra demonstrates that they formed after ∼700 14C years BP (∼650 cal. years BP). The age of the Recess Peak advance has been less certain; we therefore collected and dated sediment cores from lakes dammed behind terminal moraines correlating to the Recess Peak advance in four widely separated drainages along the Sierran crest (north to south): South Fork American River, Lee Vining Creek, Middle Fork San Joaquin River, and Bishop Creek. Twenty-three high-precision AMS radiocarbon dates on gyttja, peat, and macrofossils from the cores are internally consistent and demonstrate that the Recess Peak advance, previously thought to be of late Holocene age (∼2500 years BP), ended before 11,190±70 14C years BP (∼13,100±85 cal. years BP). Recess Peak is therefore late Pleistocene in age and probably predates the North Atlantic Younger Dryas climatic reversal. The absence of any glacial deposits on the bedrock between the Recess Peak and Matthes deposits indicates that: (1) any advance related to the Younger Dryas event in central California was smaller than the Matthes advance; (2) the Matthes advance was the most extensive, and possibly the only, Neoglacial event in the range; and (3) climate in the Sierra between ∼13,000 cal. years BP and 650 cal. years BP was apparently too warm and/or dry to support glaciers larger than those of the Little Ice Age. Other mapping indicates that the Recess Peak is the first significant glacier advance after retreat of Tioga (local late-Wisconsin maximum) glaciers. These results suggest a regionally variable climate in western North America during the Younger Dryas event, because glaciers appear to have expanded in the Canadian Rockies at that time. The new Recess Peak age limits, combined with other dated lake cores, indicate that the Sierra was essentially deglaciated by 14,000–15,000 cal. years BP (∼12,000–13,000 14C years BP), substantially earlier than previously estimated. This finding indicates that current production rates of some in situ cosmogenic nuclides, calibrated on an assumed deglaciation of the range at 11,000 cal. years BP (∼10,000 14C years BP), may be systematically too high by as much as 20%.

Influence of snow patterns and snow avalanches on the alpine treeline ecotone

Abstract. Snow avalanches, snow accumulation, and snow ablation patterns were mapped and analyzed to assess their impact on the three‐dimensional position, composition (closed canopy forest, open canopy forest, meadow, krummholz, and non‐vegetated surfaces), and spatial structure of the Alpine Treeline Ecotone (ATE) in a portion of Glacier National Park, Montana, USA. Multitemporal Landsat Multispectral Scanner data were processed to derive snow accumulation and ablation patterns throughout a snow season. Landsat Thematic Mapper data were processed and combined with aerial photo interpretations for discerning and characterizing snow avalanche paths. Transition matrices were used to assess the change in the state of snow cover conditions, whereas multiple regression analyses were used to examine the position and character of snow avalanche paths. The analyses were framed and implemented within a geographic information system (GIS) approach. Results indicate a snowmelt pattern progressing from zonal to azonal; influence of local site and situation factors in snow accumulation and ablation patterns; and the importance of topography, geologic structure, and lithology in defining the starting elevation and source area of snow avalanche paths. Finally, a conceptual process is presented where sites affected by stresses and disturbances are analyzed at a local spatial scale for analysis through a deterministic model, whereas regional stresses and disturbances are assessed through remote sensing and GIS approaches for analysis through empirical models.

Pattern of annual snow accumulation along a west Greenland flow line: no significant change observed during recent decades

Pattern of annual snow accumulation along a west Greenland flow line: no significant change observed during recent decades

Pattern of annual snow accumulation along a west Greenland flow line: no significant change observed during recent decades

At 10 positions on a traverse along a West Greenland flow line, shallow drillings and pit studies were performed in summer 1990. Continuous in situ hydrogen peroxide analyses on these samples allowed the seasonal firn stratigraphy to be established and thus to collect seasonally adjusted subsamples from the core in the field. The mean annual accumulation rate decreases from about 440 mm water equivalent at the western sites T9 and T13 to about 250 mm at the central positions T41 and Crete. Most of the prominent inter-annual changes of the surface mass balance appear to be well preserved over the area investigated. A comparison of the accumulation rates of the last decades with earlier measurements along the same Greenland flow line shows no significant change in accumulation rates during the last forty years. Further, there is no significant evidence for a pronounced increase in the Greenland surface mass balance as suggested by satellite altimetry. DOI: 10.1034/j.1600-0889.1994.t01-3-00005.x

A two-dimensional computational model of turbulent atmospheric surface flows with drifting snow

A physically based computational model of drifting snow in two-dimensional terrain is developed. The model considers the case where wind speeds are low enough to neglect the transport of particles from the saltation layer into the turbulent flow field. The model has two distinct parts, one describing the turbulent airflow, and a second describing the mass-transport process and resulting snow-accumulation patterns produced by saltation transport. The turbulent-flow model consists of a general solution of the time-averaged, two-dimensional Navier-Stokes equations, where the k-∊ turbulence model is used to close the system of equations. The turbulent-flow model is coupled to a saltation model to compute the time evolution of the surface wind fields and snowdrift formation in the vicinity of a solid fence. Modeled wind fields and snow-accumulation profiles are similar to published field and experimental data.

A two-dimensional computational model of turbulent atmospheric surface flows with drifting snow

A physically based computational model of drifting snow in two-dimensional terrain is developed. The model considers the case where wind speeds are low enough to neglect the transport of particles from the saltation layer into the turbulent flow field. The model has two distinct parts, one describing the turbulent airflow, and a second describing the mass-transport process and resulting snow-accumulation patterns produced by saltation transport. The turbulent-flow model consists of a general solution of the time-averaged, two-dimensional Navier-Stokes equations, where the k-∊ turbulence model is used to close the system of equations. The turbulent-flow model is coupled to a saltation model to compute the time evolution of the surface wind fields and snowdrift formation in the vicinity of a solid fence. Modeled wind fields and snow-accumulation profiles are similar to published field and experimental data.

Hydrologic sensitivities of the Sacramento‐San Joaquin River Basin, California, to global warming

The hydrologic sensitivities of four medium‐sized mountainous catchments in the Sacramento and San Joaquin River basins to long‐term global warming were analyzed. The hydrologic response of these catchments, all of which are dominated by spring snowmelt runoff, were simulated by the coupling of the snowmelt and the soil moisture accounting models of the U.S. National Weather Service River Forecast System. In all four catchments the global warming pattern, which was indexed to CO2 doubling scenarios simulated by three (global) general circulation models, produced a major seasonal shift in the snow accumulation pattern. Under the alternative climate scenarios more winter precipitation fell as rain instead of snow, and winter runoff increased while spring snowmelt runoff decreased. In addition, large increases in the annual flood maxima were simulated, primarily due to an increase in rain‐on‐snow events, with the time of occurrence of many large floods shifting from spring to winter.