ESTIMATING PATTERNS OF PERMAFROST OCCURRENCE IN THE HINDU-KUSH HIMALAYA REGION

Climate changes affect glacial and periglacial mountain landscapes. We can observe and measure the loss of surface ice (glaciers) and infer a similarly widespread loss of subsurface ice in permafrost. Investigating the role of permafrost thaw in mountain geomorphic dynamics, however, is difficult as we cannot obtain spatial observations of permafrost occurrence of characteristics. In the Hindu-Kush Himalaya region, our knowledge of permafrost occurrence is so sparse that often, it is difficult to even decide where a detailed investigation may be warranted. The Global Permafrost Zonation Index provides estimates of permafrost extent, i.e. the areal proportion of permafrost. The suitability of its parameterizations and driving data in Asian high mountains, however, is unknown.

We performed a first-order evaluation of this data based on the mapping of rock glaciers. These are used, because they are visual indicators of permafrost, and because they can be delineated based on high-resolution remote sensing imagery freely available on Google Earth. For the mapping 4,000 square samples (approx. 30 km²) were randomly distributed over the project region. Every sample was investigated and rock glaciers were mapped by two independent researchers following precise mapping instructions. Samples with insufficient image quality were recorded but not mapped.

It is shown that mapping of rock glaciers in Google Earth can be used as first-order evidence for permafrost in mountain areas without ground truth. The minimum elevation of rock glaciers varies between 3,500 and 5,500 m a.s.l. within the region. The Global Permafrost Zonation Index appears to be a reasonable first-order prediction of permafrost in the HKH and based on this, summary statistics and maps are presented.