Snow cover analysis using NDSI and SWI indices in Pindari-Kafni Glacier valleys, Kumaon Himalaya

The extent of snow cover in the Western Indian Himalaya determines the fluctuations in river discharge during the summer months and affects the water supply for hydroelectric generation, agriculture and related socio-economic systems which further affect the livelihood of the population in the area and downstream. Despite this importance, there is a lack of information about this region primarily due to the complexities of the processes involved in snow hydrology and the lack of snow cover and depth data in the high elevation areas. Periodical monitoring of the snow cover area (SCA) is an indispensable demand for short-term forecasts of the daily river flows and seasonal forecasts of run-off volume. Therefore, this study is an attempt to assess the annual, seasonal and monthly variations in the extent of snow cover of the Western Indian Himalaya. SCA was estimated using the MODIS/Terra Snow Cover 8-Day L3 Global 500 m (MOD10A2) data for the period 2000–2015. Monthly composite maps of SCA were prepared from 8 days composite snow cover area maps for the Kashmir, Himachal and Kumaon Himalaya. The study found a reduction in snow cover in the Indian Western Himalaya. The inter-seasonal variation in SCA was also observed in the study area. The study found an inter-regional variations in the extent of snow cover in the Western Indian Himalaya during the period of analysis. Emerging changes in the extent of snow cover would influence the availability of water in the near future.

Results from general circulation models (GCMs) have indicated that a predicted climate warming resulting from an increase in atmospheric carbon dioxide (CO2) will be amplified in the polar regions and that temperature increases in the polar regions will be several times greater than the global average. Some GCMs predict a 4°–5°C average air temperature increase in the Arctic by the middle of the next century. Evidence from the polar regions indicates that a warming in the cryosphere may already be in progress. A 2°–4°C rise in permafrost temperature, measured in northern Alaska, is believed to have occurred during the last 100 years. In addition, many small valley glaciers and ice caps have experienced retreat and appear to have contributed up to 50% to the observed rise (10–15 cm) in sea level during the last century. Other work shows that increased snowfall which can be associated with warmer temperatures has caused thickening of some Alaskan glaciers. Though a decrease in snow and sea ice cover would be a likely consequence of global warming, a sustained decrease in global snow and sea ice extent has not been found from analysis of more than 20 years of image data (1.1‐km pixel resolution) from National Oceanic and Atmospheric Administration meteorological satellites and more than 7 years of scanning multichannel microwave radiometer snow data (30‐km pixel resolution) on the Nimbus 7 satellite. Snow and sea ice are sensitive to atmospheric temperature changes because of their large surface to volume ratio. While measurements of snow and sea ice extent, snow depth, and sea ice concentration are possible using visible, near‐infrared, or microwave sensors on satellites, it is not feasible to measure the mass balance of the ice sheets with these sensors directly. Estimates by glaciologists show that the Greenland Ice Sheet is in approximate equilibrium and that the Antarctic Ice Sheet has a positive mass balance. Satellite radar altimetry (and in the future, laser altimetry) is a promising technique for measuring the surface elevation of ice sheets. Satellite‐borne laser altimetry in conjunction with imagery on ice sheet extent will permit direct measurements of changes in mass balance of the ice sheets through time. The terminus positions and ablation area boundaries of valley glaciers are indicative of glacier mass balance; these can be studied using visible and near‐infrared data from the Landsat satellite series and data from the French Systeme Probatoire d'Observation de la Terre (SPOT) satellite and synthetic aperture radar data. Lake ice freeze‐up and breakup dates are sensitive to regional air temperature and may also be good indicators of climate trends. Monitoring the onset of lake freeze‐up and breakup dates is feasible with radar and visible image data. The very important role of snow and ice in global processes is being highlighted as large‐scale, satellite‐derived geophysical data sets have become available and are beginning to be used as realistic input to GCMs.

A willow thicket dominated by Salix planifolia and S. alaxensis, is located in a 1500-ft-deep glaciated valley at the southwest end of Watts Lake, 32 mi south of Deception Bay. This "forest" forms a solid green canopy at 12 ft and contains some trees of almost 16 ft height. It grows in deep, well-drained soils (here named arctic thicket type) developed on poorly sorted sand, gravel, pebbles and cobbles, mainly of schist. A flora of 67 species of vascular plants (here listed) have been found in the area, all but two of which are arctic species. The two exceptions are wide-ranging boreal and subarctic species. For so many arctic species to be capable of growing in the shaded environment is of interest. Factors contributing to the existence of such "forests", temperatures, moisture, deep permafrost, snow cover, wind and topography affording protection, are discussed.

Since the Last Glacial Maximum, ∼20 k.y. ago, Alpine glaciers have retreated and thinned. This transition exposed bare bedrock surfaces that could then be eroded by a combination of debuttressing or local frost cracking and weathering. Quantification of the respective contributions of these processes is necessary to understand the links between long-term climate and erosion in mountains. Here, we quantified the erosion histories of postglacial exposed bedrock in glacial valleys. Combining optically stimulated luminescence and terrestrial cosmogenic nuclide (TCN) surface exposure dating, we estimated the erosion rate of bedrock surfaces at time scales from 101 to 104 yr. Bedrock surfaces sampled from the flanks of the Mer de Glace (Mont Blanc massif, European Alps) revealed erosion rates that vary from 3.5 ± 1.2 ⋅ 10−3 mm/yr to 4.3 ± 0.6 mm/yr over ∼500 m of elevation, with a negative correlation between erosion rate and elevation. The observed spatial variation in erosion rates, and their high values, reflect morphometric (elevation and surface slope) and climatic (temperature and snow cover) controls. Furthermore, the derived erosion rates can be used to correct the timing of deglaciation based on TCN data, potentially suggesting very rapid ice thinning during the Gschnitz stadial.

Glacial environments on the Tibetan Plateau and global cooling

Catchment-wide information on glacier snow-cover depth, surface albedo and surface roughness is important input data for distributed models of glacier energy balance. In this study, we investigate the small-scale (mm to 100 m) spatial variability in these properties, with a view to better simulating this variability in such models. Data were collected on midre Lovénbreen, a 6 km2 valley glacier in northwest Svalbard. The spatial variability of all three properties was found to be self-similar over the range of scales under investigation. Snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated. Late-winter and summer properties of snow depth differed, with smaller depths in summer due to melt, and shorter correlation lengths. Similar correlation lengths for snow depth and surface albedo may suggest that snow-depth variation is an important control on the small-scale spatial variability of glacier surface albedo. For surface roughness, the data highlight a possible problem in energy-balance studies which use microtopographic surveys to calculate aerodynamic roughness, in that the scale of the measurements made affects the calculated roughness value. This suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed.

Here three glacier surface area records (years 1975, 1999 and 2005) available for Aosta Valley (western Italian Alps) have been synthesized. The 1975 data have been collected by previous authors who compiled the first Aosta Valley regional glacier database. The 1999 and 2005 surface area data were computed by the authors here combining registered colour orthophotos with differential GPS (DGPS) field measurements. The surface changes of 174 glaciers (those shared within the three records of data) were calculated to describe the recent evolution of a representative subset of Italian glaciers. Aosta Valley glaciers lost 44.3 km2 during 1975–2005, i.e. c. 27% of the initial area. Small glaciers contributed strongly to total area loss, and during 2005 147 glaciers (c. 84.5% of the studied ones) were smaller than 1 km2, covering 20.7 km2 (c. 17% of the total area), but accounted for 43% of the total loss in area (losing 19 km2 from 1975 to 2005). The area change rate accelerated recently (1999–2005: mean area loss of c. 2.8 km2/year; 1975–1999: mean area loss of c. 1.1 km2/year). We then analyse records (1975–2005) of temperature, precipitation and snow cover from three high-altitude (1332 m asl to 3488 m asl) stations within Aosta Valley, to investigate modified climate within the area. We find increasing temperature especially during late spring and summer, and substantially unchanged total precipitation, with marked reduction of snowfall, snow cover, number of snowfall events and duration of continuous snow cover, especially during spring and summer, likely driving shrinking of glacier coverage.

Climate change has become a cause of concern as well as the challenge of this century. Himalayan mountain ranges with high snow fields and numerous valley glaciers may bear the brunt of such changes already being reported including Intergovernmental Panel on Climate Change (IPCC). Gangotri is one of the most prominent snow-fed catchments of Indian Himalayan Region (IHR) due to origin of river Ganga situated within it. Spatio-temporal changes in snow covered area of this basin were examined for melting seasons of the years 2006 to 2010 and a latest reference year of 2012 as a special test case. Standard snow data products (MOD10A2) of Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra sensor with spatial resolution of 500 m were used. For all the years of reference, snow covered area percentage was derived for respective months representing usual ablation or melting periods. Snow depletion curves (SDCs) were generated for such periods of the respective years. CARTOSAT digital elevation model (DEM) was used for topographic information of terrain. Relationship of SDCs with the land surface temperatures (LST) of the basin was worked upon using MODIS-Terra LST (MOD11A2) product (version 5) with 1 km resolution at 8-day interval for the day time temperature for respective months of above reference years. Thereafter, interpolation and simulation of snow covered areas was carried out on the basis of LST data. The study thus produced snow cover maps for the years of reference as well as their relationship with LST for climate change inferences.

The recent evolution of a representative subset of Alpine glaciers (i.e. 43 glaciers located in the Ortles-Cevedale group, Stelvio National Park, Italy) is described by analysing surface area changes. The database covers half a century of Alpine glacier history (from 1954 to 2007), thus allowing to describe glacier changes on a relatively long time window. Further, the subset of Alpine glaciers chosen for the analysis are among the best known and studied of Italy, also comprising the widest Italian valley glacier. The analysis provided area surface changes as −19.43 km2 ± 1.2 %, approximately −40 %, from 1954 to 2007. Small glaciers contributed strongly to total area loss. The area change rate accelerated lately, with a surface reduction of approximately 8.7 % between 2003 and 2007, i.e. a mean area loss of approximately 0.693 km2/year. The mean yearly loss over the previous periods (1954–1981, 1981–2003 and 1990–2003) were 0.242, 0.436 and 0.476 km2/year, respectively. From a geodynamical perspective, the Ortles-Cevedale group is now experiencing transition from a glacial system to a paraglacial one. The areas where most recently the main shaping and driving factors were glaciers are now subject to the action of melting water, slope evolution and periglacial processes. We also investigated seasonal values of key climatic variables (1951–2007), namely, temperature, precipitation and snow cover in the area, to evaluate their potential effects upon glacier dynamics. We performed linear regression and Mann–Kendall tests to highlight significant non-stationarity and onset of trends of our target climate variables. We investigated the correlation between local weather variables, North Atlantic Oscillation anomalies and global thermal anomaly to highlight the link of local weather patterns against global weather. We further carried out correlation analysis of weather variables (with different lags) against glacier terminus fluctuations during 1951–2006 for the two most studied glaciers of the Ortles-Cevedale group to highlight the response of glaciers to climate variability. We found increased temperature and decreased precipitation and snow cover likely to have driven accelerated glacier’s shrinkage during the last three decades.

Contemporary changes of the channel pattern and braided gravel-bed floodplain under rapid small valley glacier recession (Scott River catchment, Spitsbergen)

The subject of this paper is the glaciation of the mountain massifs Mongun-Taiga, Tavan-Boghd-Ola, Turgeni-Nuru, and Harhira-Nuru. The glaciation is represented mostly by small forms that sometimes form a single complex of dome-shaped peaks. According to the authors, the modern glaciated area of the mountain massifs is 21.2 km 2 (Tavan-Boghd-Ola), 20.3 km 2 (Mongun-Taiga), 42 km 2 (Turgeni-Nuru), and 33.1 km 2 (Harhira-Nuru). The area of the glaciers has been shrinking since the mid 1960’s. In 1995–2008, the rate of reduction of the glaciers’ area has grown considerably: valley glaciers were rapidly degrading and splitting; accumulation of morainic material in the lower parts of the glaciers accelerated. Small glaciers transformed into snowfields and rock glaciers. There has been also a degradation of the highest parts of the glaciers and the collapse of the glacial complexes with a single zone of accumulation into isolated from each other glaciers. Reduced snow cover area has led to a rise in the firn line and the disintegration of a common accumulation area of the glacial complex. In the of the Mongun-Taiga massif, in 1995–2008, the firn line rose by 200–300 m. The reduction of the glaciers significantly lagged behind the change in the position of the accumulation area boundary. In the past two years, there has been a significant recovery of the glaciers that could eventually lead to their slower degradation or stabilization of the glaciers in the study area.

Snow water equivalent (SWE) is important for understanding the hydrological significance of glaciers. In this study, the spatial and temporal variability in SWE and its impact over the Vestre Broggerbreen and Feiringbreen glaciers around Ny-Ålesund in Svalbard (high Arctic) were investigated in the early snow season for the period 2012–2017. The physical properties like depth and density were measured directly in the field and spatial characteristics curvature, slope and aspect were extracted from the digital elevation model. The Vestre Broggerbreen (4.1 km2) is a NE flowing glacier, situated around 3 km SW to Ny-Ålesund village while the Feiringbreen (7.5 km2) is a SW flowing glacier, situated around 14 km NE across the Kongsfjorden. The SWE for the studied period (2012–2017) varied from 141 to 1188 mm. The significant (R2 = 0.97) correlation indicated a possible control of snow depth over SWE compared to altitude (R2 = 0.65) and other spatial characteristics. The glaciers have experienced negative balance and lost a significant amount of ice (~4 m.w.e.) since 2012. The observations suggest that the increased liquid precipitation and temperature in the early snow season have reduced SWE over both these valley glaciers. The reduced SWE has also contributed to decreases in the mass balance of these glaciers.

Spatiotemporal changes of glacier and seasonal snow fluctuations over the Namcha Barwa–Gyala Peri massif using object-based classification from Landsat time series

The large, highly glacierized Copper River basin is an important water resource for the south‐central region of Alaska. Thus, information is needed on the reaction of its hydrologic timing and streamflow volumes to historical changes in climate, in order to assess the possible impact of future changes. However, the basin is remote, and therefore, it has proved difficult to collect field data in a frequent temporal and spatial manner. An extension of the distributed‐parameter, physical‐process code Precipitation Runoff Modeling System, PRMSglacier, has been specifically developed to simulate daily hydrology without requiring extensive input data. In this study, PRMSglacier was used to characterize the hydrology of the Copper River basin from 1959 to 2015. The basin was split into subbasins for specific regional climatic calibrations and finer resolution characterization. The model was calibrated and performed well against data of glacier mass balance, glacier area change, snow cover, gaged streamflow, evapotranspiration, and solar radiation. Ice melt contributed 26% of the total basin streamflow, with differences temporally from climate oscillations. Furthermore, differences were seen geographically in subbasins depending on the state of the glaciers in each subbasin. Decreasing trends in ice melt volume were mostly seen on smaller steeper glaciers responding to a critical level of glacier recession, while increasing trends in ice melt volume were mostly seen on larger valley glaciers responding to increasing temperature. The areas with substantially decreasing ice melt had decreasing streamflow, possibly indicating health concerns for the ecosystems therein.

Central Asia is facing a water shortage due to the negative impacts of climate change. Water resources in this region originate mainly in the mountains of Pamir and Tian-Shan due to snow-and glacier melt. Thus, it is important to understand variations in the cryosphere (snow and glaciers) in this region to foster climate change adaptation measures.This study focuses on the analysis of spatio-temporal changes of snow and glaciers in the Amu Darya, Syr Darya and Zerafshan river basins in Central Asia. Due to limited availability of observational network in the region, we used, besides available station data, also remote sensing-based snow cover area data for the period of 2000-2023. As for the glacier change analysis, we used a degree-day modelling approach to assess changes of glacier thickness in the period of 2000-2023. Eight glaciers were chosen for modelling purposes that are all located in the selected eight river basins for this study. Spatio-temporal analysis of snow cover area change show significantly decreasing number of snow cover days above a certain elevation in Upper Amu Darya and Upper Syr Darya river basins. In both river basins, there are regions with up to 40 days less snow coverage between 2000 and 2023. In the Upper Syr Darya river basins this change is observed in the Akshiirak Massif area, whereas in the Amu Darya River Basin, this change is observed in the Murghab area in the far western part of the river basin. Below a certain elevation zone, there are also areas with increased number of snow cover days of up to 10 days. The attribution of this change into meteorological parameters leads to various hypothesis. The modelling results of glacier thickness change was validated against glacier area evolution that was derived using the Landsat images.  In most of the river basins, a maximum of 60-70 meters of ice thickness loss was estimated with an increase of ice thickness of some glaciers in the accumulation area of about 10-15 meters. However, in two of the valley glaciers (Vanch and Zerafshan River Basins), higher amount of glacier thickness loss was estimated in the last 23 years.The study suggests quantified cryosphere changes in the last 23 years for Central Asian region and emphasizes the need for climate change adaptation as the water resources originating in the mountains of the region (water towers) are important for socio-economic stability.