Snowline Elevation Research Articles

Methods of Calculation and Remote-Sensing Measurements for the Spatial Distribution of Glacier Annual Mass Balances

AbstractThe areal distribution of glacier annual mass balance b(z) is an important characteristic of the existence of glacierization and its evolution. At present the measured value of annual mass balance at different elevations is only available for a limited number of mountain glaciers of the globe, because of the great amount of labour required for such measurements.The analysis of long-term mass-balance measurements made at Abramova glacier, Limmerngletscher, White Glacier, Hintereisferner, and Peyto Glacier has revealed that for each year the spatial distribution of annual mass balance is well described by quadratic equations. The main variable in these equations is altitude (z). The various parameters of these formulae are estimated by the author for mean weighted height of the ablation and accumulation areas, and for the glaciers as a whole. It is found that the parameters of annual mass balance for each glacier can be calculated from formulae which include combinations of the following variables: annual balance at one of the three weighted altitudes, maximum annual snow-line elevation, annual and seasonal amounts of precipitation, and air temperatures at nearby meteorological stations.Therefore, in order to calculate the distribution of annual mass balance as a function of absolute altitude, it is sufficient to obtain a value for mass balance measured only at a single point on a glacier, and common meteorological observational data. A comparison of actual and calculated values of mass balance has shown good agreement between them.Considering the successful use of aerial remote-sensing for the measurement of snow depth in mountains by means of special stakes, it is satisfactory to accept this method for the assessment of annual mass balance at the mean weighted altitude of the ablation zone. It is possible to use aerial photo-surveys or stereophotogrammetry to resolve this problem. Then annual mass balance for the whole area of a glacier is calculated by using data from one point together with data from a nearby meteorological station.

Methods of Calculation and Remote-Sensing Measurements for the Spatial Distribution of Glacier Annual Mass Balances

Abstract The areal distribution of glacier annual mass balance b(z) is an important characteristic of the existence of glacierization and its evolution. At present the measured value of annual mass balance at different elevations is only available for a limited number of mountain glaciers of the globe, because of the great amount of labour required for such measurements. The analysis of long-term mass-balance measurements made at Abramova glacier, Limmerngletscher, White Glacier, Hintereisferner, and Peyto Glacier has revealed that for each year the spatial distribution of annual mass balance is well described by quadratic equations. The main variable in these equations is altitude (z). The various parameters of these formulae are estimated by the author for mean weighted height of the ablation and accumulation areas, and for the glaciers as a whole. It is found that the parameters of annual mass balance for each glacier can be calculated from formulae which include combinations of the following variables: annual balance at one of the three weighted altitudes, maximum annual snow-line elevation, annual and seasonal amounts of precipitation, and air temperatures at nearby meteorological stations. Therefore, in order to calculate the distribution of annual mass balance as a function of absolute altitude, it is sufficient to obtain a value for mass balance measured only at a single point on a glacier, and common meteorological observational data. A comparison of actual and calculated values of mass balance has shown good agreement between them. Considering the successful use of aerial remote-sensing for the measurement of snow depth in mountains by means of special stakes, it is satisfactory to accept this method for the assessment of annual mass balance at the mean weighted altitude of the ablation zone. It is possible to use aerial photo-surveys or stereophotogrammetry to resolve this problem. Then annual mass balance for the whole area of a glacier is calculated by using data from one point together with data from a nearby meteorological station.

The Reconstruction of Former Ice Sheets and their Mass Balance Characteristics using a Non-Linearly Viscous Flow Model

AbstractA model of a non-linearly viscous ice sheet is used to investigate the influence of net mass-balance pattern, basal boundary condition, and subglacial topography on the size and shape of ice sheets. The aim is to enable geological evidence of the extent of former ice sheets to be used as indicators of palaeoclimate. A series of curves are presented showing the relationships between ice-sheet span, net mass balance, and equilibrium-line altitude (ELA) for zero and complete isostatic compensation. These are applicable to a very wide range of basal boundary conditions. The way in which they can be used to reconstruct net mass-balance gradients for former ice sheets is demonstrated. Changes in the basal boundary condition only have a strong influence on glacier span when they occur in the terminal zone. Ice-sheet expansion and contraction is not merely accompanied by changes in snow-line elevation, but also by changes in the net mass-balance gradient. The combinations of these required to cause ice-sheet expansion and contraction are analysed. A non-linearly viscous model for ice suggests that ice-sheet volume changes may not be a simple function of their change in areal extent.

The Reconstruction of Former Ice Sheets and their Mass Balance Characteristics using a Non-Linearly Viscous Flow Model

AbstractA model of a non-linearly viscous ice sheet is used to investigate the influence of net mass-balance pattern, basal boundary condition, and subglacial topography on the size and shape of ice sheets. The aim is to enable geological evidence of the extent of former ice sheets to be used as indicators of palaeoclimate. A series of curves are presented showing the relationships between ice-sheet span, net mass balance, and equilibrium-line altitude (ELA) for zero and complete isostatic compensation. These are applicable to a very wide range of basal boundary conditions. The way in which they can be used to reconstruct net mass-balance gradients for former ice sheets is demonstrated. Changes in the basal boundary condition only have a strong influence on glacier span when they occur in the terminal zone. Ice-sheet expansion and contraction is not merely accompanied by changes in snow-line elevation, but also by changes in the net mass-balance gradient. The combinations of these required to cause ice-sheet expansion and contraction are analysed. A non-linearly viscous model for ice suggests that ice-sheet volume changes may not be a simple function of their change in areal extent.

A Model Study of the Role of High-Latitude Topography in the Climatic Response to Orbital Insolation Anomalies

Abstract The response of a combined global zonal-averaged energy balance model and a continental ice-sheet model to insulation anomalies produced by orbital perturbations is examined. Although the role of ice sheet dynamics is included in the model, this paper focuses mostly on the response of the atmosphere–hydrosphere to the perturbations. The model, developed from that of Suarez and Held (1979), explicitly incorporates surface topography, surface energy balances, snow and sea-ice budgets and variable static stability. The ice-sheet model is based on a power-law rheology. It is found that the presence of a high-latitude plateau significantly increases the sensitivity of the climate to the insolation perturbation. The sensitivity is maximized when the elevation of the summer snowline is near the elevation of the plateau, as appears to be the case with Baffin Island today. There appears to be a rapid response of the seasonal cycle to an insolation anomaly through albedo–temperature feedback, and with the ...

A Comparison between the Modern and Composite Pleistocene Snow-lines, Absaroka and Beartooth Mountains, Montana-wyoming, U.S.A.

Abstract The modern and composite Pleistocene snow-lines of the Absaroka and Beartooth Mountains, Montana-Wyoming, were established from a population of 135 north-facing cirques and cirque glaciers distributed across Boulder River, Stillwater River, Rosebud, and Rock Creeks. The 3110 m elevation of the modern snow-line was established by connecting the accumulation-area ratios of 35 existing cirque glaciers. The composite Pleistocene snow-line was established by joining the mean floor elevations of the lowest abandoned cirques. Comparison of the modern and composite Pleistocene snow-lines indicates that the composite Pleistocene snow-line was depressed, at minimum, 305 m during the Pleistocene. The 305 m depression suggests that the mean Pleistocene temperatures were, at a minimum, 1.9 deg lower than the present mean annual temperatures found in the study area. Both the modern and Pleistocene snow-lines slope towards lower elevations in the Boulder and Stillwater drainages than in the Rosebud–Rock Creek drainages. Modern precipitation rates also show greater precipitation in the Boulder–Stillwater drainages than the Rosebud–Rock Creek drainages. The parallelism of the modern and composite Pleistocene snow-lines, and present precipitation rates suggest that temperature rather than precipitation is the controlling factor causing the depression of the snow-lines. The distribution of cirque elevations indicates that snow-lines fluctuated a minimum of four times during the Pleistocene.

A Comparison between the Modern and Composite Pleistocene Snow-lines, Absaroka and Beartooth Mountains, Montana-wyoming, U.S.A.

AbstractThe modern and composite Pleistocene snow-lines of the Absaroka and Beartooth Mountains, Montana-Wyoming, were established from a population of 135 north-facing cirques and cirque glaciers distributed across Boulder River, Stillwater River, Rosebud, and Rock Creeks. The 3110 m elevation of the modern snow-line was established by connecting the accumulation-area ratios of 35 existing cirque glaciers. The composite Pleistocene snow-line was established by joining the mean floor elevations of the lowest abandoned cirques.Comparison of the modern and composite Pleistocene snow-lines indicates that the composite Pleistocene snow-line was depressed, at minimum, 305 m during the Pleistocene. The 305 m depression suggests that the mean Pleistocene temperatures were, at a minimum, 1.9 deg lower than the present mean annual temperatures found in the study area.Both the modern and Pleistocene snow-lines slope towards lower elevations in the Boulder and Stillwater drainages than in the Rosebud–Rock Creek drainages. Modern precipitation rates also show greater precipitation in the Boulder–Stillwater drainages than the Rosebud–Rock Creek drainages. The parallelism of the modern and composite Pleistocene snow-lines, and present precipitation rates suggest that temperature rather than precipitation is the controlling factor causing the depression of the snow-lines.The distribution of cirque elevations indicates that snow-lines fluctuated a minimum of four times during the Pleistocene.

The Variation of Corrie Elevation and Equilibrium Line Altitude with Aspect in Eastern Baffin Island, N. W. T., Canada

It has been common practice to estimate ice-age climates by calculating the difference in temperature, at an assumed lapse rate, between the elevation of the present snowline and that represented by the lowest corries (cirques) in a region. Such a procedure not only ignores many other factors which may affect corrie glacierization, but is actually incorrect, because the change in snowline for a given temperature change does not depend only on lapse rate. This study suggests that the variation of equilibrium line altitude (ELA) with aspect provides a climatic signature supplementary to that of lowest ELA. A method of computing heat and water balances on glaciers from climatic data is described and tested against observations on Baffin Island glaciers. This model is used to estimate ELA as a function of aspect in the Okoa Bay area of Baffin Island, using 1963 to 1972 climatic data, and then for two contrasting climates which have been suggested for early and late stages in the last glaciation. The results are compared with distributions of corrie glaciers and ice-free corries in the area.

Snow Cover and Glacier Change Study in Nepalese Himalaya Using Remote Sensing and Geographic Information System

Snow cover and glaciers in the Himalaya play a major role in the generation of stream flow in south Asia. Various studies have suggested that the glaciers in the Himalaya are in general condition of retreat. The snowline is also found to be retreating. While there are relatively more studies on glaciers fluctuation in the Himalaya, studies on snow cover is relatively sparse. In this study, snow cover and glacier fluctuation in the Nepalese Himalaya were studied using remote sensing techniques and geographic information system. The study was carried out in two spatial scales: catchments scale and national scale. In catchments scale two catchments: Langtang and Khumbu were studied. Intermittent medium resolution satellite imageries (Landsat) were used to study the fluctuation in snow cover and glacier area in the two catchments. In the national scale study coarse resolution (MODIS) imageries were used to derive seasonal variations in snow cover. An indication of decreasing trend in snow cover is shown by this study, although this result needs verification with more data. The snowline elevation is in general higher in Khumbu compared to Langtang. In both catchments, snowline elevation are higher in east, south-east, south and south-west aspects. The areas of snow cover in those aspects are also greater. The study provides the first multi-year temporal variation in snow cover extent in Nepal. According to the analysis of MODIS data, the snow cover extent over the country is highest during late winter and spring, while it is lowest during summer monsoon season. The snow cover area shows dynamic nature and the variability during late winter and spring is quite large. The snow covered territory of Nepal was divided into four subsections: east, central, west and far-west, and snow line elevations for these subsections were derived from MODIS data. Generally, the snowline elevation is lower in the west than in the east, although the central region shows relatively lower snowline elevation, not following the general zonal trend. Key Words: Snow cover; glacier fluctuation; satellite imageries; trend; snowline DOI: http://dx.doi.org/10.3126/jhm.v6i1.5481 Journal of Hydrology and Meteorology, Vol. 6, No. 1 26-36