The GAMDAM glacier inventory: a quality-controlled inventory of Asian glaciers

We present a new glacier inventory for high-mountain Asia named Glacier Area Mapping for Discharge from the Asian Mountains (GAMDAM). Glacier outlines were delineated manually using 356 Landsat ETM+ scenes in 226 path-row sets from the period 1999-2003, in conjunction with a digital elevation model (DEM) and high-resolution Google Earth (TM) imagery. Geolocations are largely consistent between the Landsat imagery and DEM due to systematic radiometric and geometric corrections made by the United States Geological Survey. We performed repeated delineation tests and peer review of glacier outlines in order to maintain the consistency and quality of the inventory. Our GAMDAM glacier inventory (GGI) includes 87 084 glaciers covering a total area of 91 263 +/- 13 689 km(2) throughout high-mountain Asia. In the Hindu Kush-Himalaya range, the total glacier area in our inventory is 93% that of the ICIMOD (International Centre for Integrated Mountain Development) inventory. Discrepancies between the two regional data sets are due mainly to the effects of glacier shading. In contrast, our inventory represents significantly less surface area (-24 %) than the recent global Randolph Glacier Inventory, version 4.0 (RGI), which includes 119 863 +/- 9201 km(2) for the entirety of high Asian mountains. Likely causes of this disparity include headwall definition, effects of exclusion of shaded glacier areas, glacier recession since the 1970s, and inclusion of seasonal snow cover in the source data of the RGI, although it is difficult to evaluate such effects quantitatively. Further rigorous peer review of GGI will both improve the quality of glacier inventory in high-mountain Asia and provide new opportunities to study Asian glaciers.