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.
The pattern of glacial records since the end of the Little Ice Age (LIA) are essential for evaluating glacier fluctuations and their link to post-LIA climate change. Although recession of the Himalayan glaciers is well-documented in this period, debate continues as to the magnitude and accuracy of estimated recession rates. This study presents a reconstruction of the pattern of fluctuations at the Bara Shigri Glacier in the Himachal Himalaya during the termination of the LIA (∼1850). A multi-data integrative analysis (MDIA) technique consisting of repeat terrestrial photographs, historical archives and reports, geomorphological evidence and maps, and high to medium spatial resolution satellite images (Corona, Hexagon, Landsat and WorldView-2) was used with supplemented by extensive field validation. The results indicate that during the early part of the 19th century the terminus of Bara Shigri Glacier was at ∼3900 m asl. Following this, there was a continuous recession with a total retreat of 2898 ± 50 m, which corresponds to a frontal areal loss of 4 ± 1 km2 in the last 151 years (1863–2014). Compared to this, during the last half century (1965–2014), the glacierised area was reduced by 1.1 ± 0.02 km2 with a concomitant terminus retreat of 1100 ± 32 m. The early 19th century advance is ascribed to a combination of cooling during this period, glacier topographical characteristics and contributions from steep-fronted avalanching tributaries. The late 19th century recession can be attributed to an overall increase in the temperature with a corresponding decrease in precipitation in the north-western Himalaya. Results are at variance with earlier, larger estimates of the frontal area loss for the Bara Shigri Glacier using either Survey of India (SoI) topographic maps or coarse spatial resolution satellite images (e.g. Landsat MSS) as historical datasets, and demonstrate the utility of mixed method approaches including higher-resolution satellite imagery for accurate estimation of glacier behaviour in this region.