Glacier changes in the Garhwal Himalaya, India, from 1968 to 2006 based on remote sensing

Glacier outlines are mapped for the upper Bhagirathi and Saraswati/Alaknanda basins of the Garhwal Himalaya using Corona and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite images acquired in 1968 and 2006, respectively. A subset of glaciers was also mapped using Landsat TM images acquired in 1990. Glacier area decreased from 599.9±15.6 km² (1968) to 572.5±18.0 km² (2006), a loss of 4.6±2.8%. Glaciers in the Saraswati/Alaknanda basin and upper Bhagirathi basin lost 18.4±9.0 km² (5.7±2.7%) and 9.0±7.7 km² (3.3±2.8%), respectively, from 1968 to 2006. Garhwal Himalayan glacier retreat rates are lower than previously reported. More recently (1990-2006), recession rates have increased. The number of glaciers in the study region increased from 82 in 1968 to 88 in 2006 due to fragmentation of glaciers. Smaller glaciers (<1 km² ) lost 19.4±2.5% (0.51±0.07%a^-1 ) of their ice, significantly more than for larger glaciers (>50 km2 ) which lost 2.8±2.7% (0.074±0.071%a^-1). From 1968 to 2006, the debris-covered glacier area increased by 17.8±3.1%(0.46±0.08%a^-1) in the Saraswati/Alaknanda basin and 11.8±3.0%(0.31±0.08%a ^-1)in the upper Bhagirathi basin. Climate records from Mukhim (∼1900ma.s.l.) and Bhojbasa (∼3780ma.s.l.) meteorological stations were used to analyze climate conditions and trends, but the data are too limited to make firm conclusions regarding glacier-climate interactions.