Post-20th century near-steady state of Batura Glacier: observational evidence of Karakoram Anomaly

Abstract

Stable or marginal mass loss dominating in Karakoram has been reported widely through satellite and ground investigations. this work aimed to verify the variation in glacier mass by collecting groundbased data. By tracking profiles from the first survey by China-Pakistan Batura Glacier Investigation Group in 1974-1975, we revisited Batura Glacier and conducted an updated comparable measurement of the glacier surface elevation and ice thickness of this large valley glacier of Karakoram, in August 2017. Results of ground penetrating radar (GPR) measurement were used to improve the accuracy of an ice thickness distribution model (GlabTop2). The model calculation agreed reasonably with the measurement when the optimal basal shear stress (100 kPa for clean ice to 140 kPa for heavy debris cover) and shape factor (0.9) were used. We then used a glacier bed topographies map to calculate the ice flux. By subtracting the glacier surface topographies from the remote-sensing measurements, we observed a marginal thinning in Batura during 2000-2016, with a rate of variation in glacier surface elevation of −0.12 ± 0.27 m a −1. it indicated that the mass gain in the accumulation area nearly compensated the mass loss in the ablation area. In addition, both ground and satellite remote measurement reveal a steady rate of decrease in surface of the Batura tongue, implying an absence of significant variation during the past 40 years. Moreover, the mass conservation equation was applied to the Batura tongue, in combination with surface elevation variation and ice flux evolution. The tongueaveraged mass balance diminished by more than half from the 1970s to the 2010s. In summary, we inferred a near-steady state of Batura Glacier post 2000 based on the above-mentioned evidence of "Karakoram Anomaly". Glaciers are important water resources and exceptionally sensitive indicators of climate change. Glacier melt water plays an important role in the Indus basin 1 owing to its extensive upstream and glaciated area. Millions of humans rely on the meltwater from the Upper Indus Basin (UIB). The glacial response to climate change in this region has important ramifications for future water availability from UIB. UIB is composed of the Hindukush, Karakoram, and Himalayan mountains (HKH). It has the highest concentration of glaciers outside the polar regions 2. The glaciers cover 12,705 km 2. Of this, over 70% is in the Karakoram region 3. However, there is high variability in the glacier ice volume estimates of the Karakoram region, ranging from 1683 to 2827 km 3 by different approaches 4. Measured ice thickness data can be applied to validate and increase the accuracy of volume estimation at the regional scale 5,6. Measurements of the ice thickness in High Mountain Asia are few compared with those of the glacier amount. In addition, glaciers here have displayed an unusual behavior during the past decades: an absence of significant area variations 7 , rather, frequent advances and surge activities 8,9. Stable or marginal mass loss dominate in Kara...

Risks of Glaciers Lakes Outburst Flood along China Pakistan Economic Corridor

“…The surging activities of the glaciers in the Hunza Basin have also been interpreted by earlier studies [14,32,33] from a stable or slightly increasing trend of snow cover for the Hunza River basin [1,25]. It has been reported recurrent surges for several glaciers of the Hunza Basin [6].…”

Health and sustainability of glaciers in High Mountain Asia

“…The continuity equation has previously been used to determine the SMB on individual glaciers 22,23,[37][38][39][40] but never at a large scale, which requires an automated approach. We first apply our approach to 35 sites to compare to available measurements of surface mass balance 41 (Supplementary Table 1), and another 25 glaciers for which remote sensing-derived estimates of SMB are available 38 .…”

Upward Expansion of Supra-Glacial Debris Cover in the Hunza Valley, Karakoram, During 1990 ∼ 2019

“…For example, the supraglacial debris cover in the Greater Caucasus increased from 48.3 ± 3.1 km 2 in 1986 to 79.0 ± 4.9 km 2 in 2014, based on Landsat and images from the years 1986, 2000, and 2014 (Tielidze et al, 2020). Furthermore, the glaciers in Pamir, Karakoram, and West Kunlun have moved forward or backward, either in equilibrium or showing an increase in mass ("Karakoram anomaly") in recent years (Salerno et al, 2017;Farinotti et al, 2020;Gao et al, 2020), and it is of great interest to know whether this debris cover increase phenomenon exists for glaciers in anomaly areas, such as the Hunza Valley. Although some studies have mapped the spatial distribution of supra-glacial debris cover in this area (Khan et al, 2015(Khan et al, , 2020Mölg et al, 2018;Gao et al, 2020), they were limited to the extraction of spatial distribution information and lack any analysis on the temporal dynamic changes of supra-glacial debris.…”