Surface temperature on glaciated terrain which controls the melting rate of snow and glacier ice is directly governed by the heat budget at the glaciated surface. An understanding of surface temperature is therefore crucial for studying the impact of climate change on glaciers which are considered sensitive indicators of climatic variability. The Karakoram Himalayan region, often termed as the ‘Water tower of Asia’ is source of many perennial rivers since large glacial masses exist in this region other than those present in the Arctic and Antarctic. Our study area viz. Shyok Basin, East Karakoram region lies in Indian territory, and interestingly Siachen Glacier, which is the longest in the Karakoram range and the second longest glacier in the non-polar regions of the world lies in this part only.
Thermal remote sensing data has the potential to provide spatial and temporal land surface temperature (LST). In this study, spatio-temporal variations of LST over Shyok Basin during 15 years (2001-2015) were analyzed using MOD11A1 LST product data of MODIS. The data was analyzed at different temporal resolutions viz. monthly, seasonal and annual basis for complete Shyok basin as well as for glaciated and non-glaciated terrain to study the prevailing temperature trends in the respective regions. The study shows that the estimated mean annual, winter and summer LST is approx. 2.2 °C, -7.8 °C and 12.1 °C respectively for entire Shyok Basin. Further, for glaciated regions, estimated annual, winter and summer mean temperature is -7.5 °C, -16.3 °C and 1.1 °C respectively. Whereas, for non-glaciated regions, the estimated annual, winter and summer LST were found to be 4.3 °C, -6.0 °C and 14.5 °C respectively. The inter-annual variability of LST over different parts of Shyok basin was studied and anomaly maps of LST were also generated. Short term trends (2001-2015) of LST over glaciated and non-glaciated regions in Shyok Basin depict warming. To ascertain the reliability of MODIS derived LST in representing the temperature trends over Shyok basin, the retrieved LST trends were also compared with field observed air-temperature data.
Since glaciers are very sensitive to temperature fluctuations, the observed warming trends in LST have also been linked to rising number of glacier lakes during 2002-2014. In addition, maximum number of lake formation was observed in the altitude range of 5000-5500 m, which could be due to the fact that since maximum ablation zones of glaciated areas lie in this altitude range, and rising LST especially during the months of July and August months manifests itself in form of enhanced glacial melt. This study has further scope to assess various glaciers’ hazards in the region like earth flow, snow & ice avalanches and variations in glaciers.
Keywords: Land surface temperature, MODIS, MOD 11A1, Karakoram Himalaya