The hazardous 2017-2019 surge and river damming by Shispare Glacier, Karakoram.

In 2017-2019 a surge of Shispare Glacier, a former tributary of the once larger Hasanabad Glacier (Hunza region), dammed the proglacial river of Muchuhar Glacier, which formed an ice-dammed lake and generated a small Glacial Lake Outburst Flood (GLOF). Surge movement produced the highest recorded Karakoram glacier surface flow rate using feature tracking (~18 ± 0.5 m d-1) and resulted in a glacier frontal advance of 1495 ± 47 m. The surge speed was less than reports of earlier Hasanabad advances during 1892/93 (9.3 km) and 1903 (9.7 km). Surges also occurred in 1973 and 2000-2001. Recent surges and lake evolution are examined using feature tracking in satellite images (1990-2019), DEM differencing (1973-2019), and thermal satellite data (2000-2019). The recent active phase of Shispare surge began in April 2018, showed two surface flow maxima in June 2018 and May 2019, and terminated following a GLOF on 22-23 June 2019. The surge likely had hydrological controls influenced in winter by compromised subglacial flow and low meltwater production. It terminated during summer probably because increased meltwater restored efficient channelized flow. We also identify considerable heterogeneity of movement, including spring/summer accelerations.

Large observational bias on discharge in the Indus River since 1970s.

The discharge of one of the world's largest river - Indus River was reported to be increasing that was not supported by the Karakoram (KK) glacier expansion. A major hydrometric bias was ignored, which seemed similar to the montage that the Himalayan glaciers would disappear. This study proposed a framework for quantifying the bias resulting from inaccurate data affecting hydrologic studies on the Indus. We constructed a statistical model by converting the rating curves of rivers into air temperature (T) - discharge (Q) curves from an adjacent catchment in China where flow measurement was carried out using a standard method. We found that most flow data for the Indus were much greater than the error limits of T-Q curves estimated by daily data, a greater bias occurred in recent decades when discharge increased, the higher the flow was, the larger the bias was. The estimated mean annual and maximum monthly bias was 22.5% and 210%, respectively. These biases indicated that discharge increase in the Indus probably resulted from the large errors of hydrometrics without a scientific basis. We suggested a montage bias was needed in the hydrologic science of KK's rivers that may strongly affect water resource management.

Glacier and landslide feedbacks to topographic relief in the Himalayan syntaxes.

Despite longstanding research on the age and formation of the Tibetan Plateau, the controls on the erosional decay of its margins remain controversial. Pronounced aridity and highly localized rock uplift have traditionally been viewed as limits to the dissection of the plateau by bedrock rivers. Recently, however, glacier dynamics and landsliding have been argued to retard headward fluvial erosion into the plateau interior by forming dams and protective alluvial fill. Here, we report a conspicuous clustering of hundreds of natural dams along the Indus and the Tsangpo Rivers where these cross the Himalayan syntaxes. The Indus is riddled by hundreds of dams composed of debris from catastrophic rock avalanches, forming the largest concentration of giant landslide dams known worldwide, whereas the Tsangpo seems devoid of comparable landslide dams. In contrast, glacial dams such as river-blocking moraines in the headwaters of both rivers are limited to where isolated mountain ranges intersect the regional snowline. We find that to first-order, high local topographic relief along both rivers corresponds to conspicuously different knickzones and differences in the type and potential longevity of these dams. In both syntaxes, glacier and landslide dams act as a negative feedback in response to fluvial dissection of the plateau margins. Natural damming protects bedrock from river incision and delays headward knickpoint migration, thereby helping stabilize the southwestern and southeastern margins of the Tibetan Plateau in concert with the effects of upstream aridity and localized rock uplift.