A Longer–Term Perspective of the Karakoram–Pamir Anomaly: Length, Area and Mass Changes since the 1970s

Abstract:

Many glaciers in the Karakoram and Pamir show irregular behaviour with frequent advances and surges. Geodetic estimates of mass changes revealed a possible slight mass gain since the year ~2000. However, longer-term information about length and area changes is scarce and almost no mass budget analysis are available before 2000. We have thus extended both the regional coverage and duration of the time series. As a first step, a glacier inventory for the entire mountain range for the year ~2000 was generated using semi-automated glacier mapping techniques applied to Landsat data. Declassified Hexagon KH-9 data from the 1970s, the SRTM3-DEM and recent stereo data from ~2010 such as Pléiades, SPOT-5, ALOS PRISM, Cartosat and ASTER data allowed geodetic mass balance investigations of selected regions like Muztag Ata (East Pamir), Central Trans Alai Range (North Pamir) and Shimshal Valley (Central Karakoram). The investigations were extended for length and area changes using additional satellite data such as Corona KH-4 and Landsat MSS from the 1970s and Landsat TM/ETM+/OLI covering the period since ~2000.

Our analysis revealed that in the Karakoram 191 out of 251 investigated glaciers were stationary, 33 receding and 27 advancing since the end of the 1970s until ~2000. Overall, we identified a small, but insignificant area decrease for this period. Glaciers in Eastern Pamir behaved similarly: at Muztag Ata they slightly shrank on average since the mid-1970s. In contrast, we found a continuous and significant glacier retreat in the Northern Pamir over the same period. Similar to the Karakoram, glaciers in the Pamir showed a high temporal and spatial variability of their changes with frequent surge activities. Preliminary results on glacier mass budgets revealed slightly negative values from ~1975 until ~2000 and slightly positive values thereafter in all investigated regions.