Abstract
Previous studies have shown contrasting glacier elevation and mass changes in the sub-regions of high-mountain Asia. However, the elevation changes on an individual catchment scale can be potentially influenced by supraglacial debris, ponds, lakes and ice cliffs besides regionally driven factors. Here, we present a detailed study on elevation changes of glaciers in the Lahaul-Spiti region derived from TanDEM-X and SRTM C-/X-band DEMs during 2000–2012 and 2012–2013. We observe three elevation change patterns during 2000–2012 among glaciers with different extent of supraglacial debris. The first pattern (<10% debris cover, type-1) indicates maximum thinning rates at the glacier terminus and is observed for glaciers with no or very low debris cover. In the second pattern (>10% debris cover, type-2), maximum thinning is observed up-glacier instead of glacier terminus. This is interpreted as the insulating effect of a thick debris cover. A third pattern, high elevation change rates near the terminus despite high debris cover (>10% debris cover, type-3) is most likely associated with either thinner debris thickness or enhanced melting at supraglacial ponds and lakes as well as ice cliffs. We empirically determined the SRTM C- and X-band penetration differences for debris-covered ice, clean ice/firn/snow and correct for this bias in our elevation change measurements. We show that this penetration bias, if uncorrected, underestimates the region-wide elevation change and geodetic mass balance by 20%. After correction, the region-wide elevation change (1712 km 2 ) was estimated to be −0.65 ± 0.43 m yr − 1 during 2000–2012. Due to the short observation period, elevation change measurements from TanDEM-X for selected glaciers in the period 2012–2013 are subject to large uncertainties. However, similar spatial patterns were observed during 2000–2012 and 2012–2013, but at different magnitudes. This study reveals that the thinning patterns of debris-covered glaciers cannot be generalized and spatially detailed mapping of glacier elevation change is required to better understand the impact of different surface types under changing climatic conditions.
Highlights
Hindu Kush-Pamir-Karakoram-Himalaya (HKPKH) is a widely spread mountain range in high-mountain Asia with a glacial extent of ∼60,100 km2 [1]
We present a detailed study on elevation changes of glaciers in the Lahaul-Spiti region derived from TanDEM-X and Shuttle Radar Topography Mission (SRTM) C-/X-band DEMs during 2000–2012 and 2012–2013
This study presents region-wide and glacier-specific elevation change and geodetic mass balance observations derived from SRTM C-/X-band and TanDEM-X DEMs during 2000–2012 and 2012–2013
Summary
Hindu Kush-Pamir-Karakoram-Himalaya (HKPKH) is a widely spread mountain range in high-mountain Asia with a glacial extent of ∼60,100 km2 [1]. A segment is located in the Lahaul-Spiti region of western Himalaya, India. The glaciers in the Lahaul-Spiti receive precipitation throughout the year but majorly during July–September by Indian summer monsoon (ISM) and during January–April by mid-latitude winter westerlies (MLW) [2]. The warming trend of surface air temperature (e.g., 0.46◦ per decade during 1971–2007) in western Himalaya is higher than the global average [3]. These increasing air temperatures have substantial implications on glacier mass balance as they foster ablation [4]. Glacier mass balance has been considered as the most appropriate variable in order to assess glacier status and its response to climate change
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