Manifestations and mechanisms of the Karakoram glacier Anomaly

Abstract

Global-scale glacier shrinkage is one of the most prominent signs of ongoing climatic change. However, important differences in glacier response exist at the regional scale, and evidence has accumulated that one particular region stands out: the Karakoram. In the past two decades, the region has shown balanced to slightly positive glacier budgets, an increase in glacier ice-flow speeds, stable to partially advancing glacier termini, and widespread glacier surge activity. This is in stark contrast to the rest of High Mountain Asia, where glacier retreat and slowdown dominate, and glacier surging is largely absent. Termed the Karakoram Anomaly, recent observations show that the anomalous glacier behaviour partially extends to the nearby Western Kun Lun and Pamir. Several complementary explanations have now been presented for explaining the Anomaly's deeper causes, but the understanding is far from being complete. Whether the Anomaly will continue to exist in the coming decades remains unclear, but its long-term persistence seems unlikely in light of the considerable warming anticipated by current projections of future climate. The Karakoram is the mountain range spanning the borders of Pakistan, India, and China, with extremities reaching into Afghanistan and Tajikistan (Figure 1a). The region is geomorphologically very dynamic 1 , with intense interactions between tectonic, fluvial, and mass movement processes. The extremely steep and high topography, characteristic of the region, hosts some of the 1 tallest mountains on Earth, and very dynamic glaciers (Box 1). According to current inventories , the region features roughly 13,700 glaciers, covering an area of about 22,800 km 2. The total glacier ice volume is estimated to be in the order of 2,200 km 3 , or about 30% of the total for High Mountain Asia 3. Together with snowmelt, runoff from glaciers is the primary water source for the region's rivers 4 , which include tributaries of both the Tarim and the Indus (Figure 1a). This makes the Karakoram's glaciers of utmost importance in supplying water to millions of people downstream 5-7. Glacier melt has been shown 8 to be of particular importance during periods of drought stress, and hence to contribute to social stability in an otherwise conflict-prone region. Against this background, characterizing the region's glacier evolution is of great relevance. A peculiar behaviour of Karakoram glaciers was already suspected in early reports 9-12 of 19 th century explorers. It is difficult to ascertain, however, whether or not the reports were not biased by the perception of an unusually dramatic landscape. Modern observations, instead, are more conclusive, and indeed indicate that-at least for the past decades-Karakoram's glaciers

Towards understanding the pattern of glacier mass balances in High Mountain Asia using regional climatic modelling

“…Also temperatures show a spatial autocorrelation over larger areas in the WKSK (e.g. Forsythe et al, 2017), and the glacier mass balances in HMA also vary mainly over a large scale, suggesting that large-scale weather patterns are on average more important in controlling the inter-annual variability of temperature and precipitation than the differences between valleys. The use of relative changes in temperature and precipitation has thus made our results more robust against possible errors in the detailed treatment of the complex mountain meteorology.…”

“…Suggested causes of the Karakoram anomaly include an increase in winter snowfall (Cannon et al, 2015;Kapnick et al, 2014;Norris et al, 2015Norris et al, , 2018, summertime cooling (Bocchiola and Diolaiuti, 2013;Forsythe et al, 2017;Fowler and Archer, 2006;Khattak et al, 2011;Ul Hasson et al, 2017), and an increase in summertime precipitation and clouds due to irrigation in the agricultural regions adjacent to the Kunlun Shan and Pamir (de Kok et al, 2018). So far, these hypotheses have only tried to explain the Karakoram anomaly in qualitative terms, identifying possible climatic conditions that could lead to glacier growth.…”

Linking the Recent Glacier Retreat and Depleting Streamflow Patterns with Land System Changes in Kashmir Himalaya, India

“…Himalayan glaciers are in a continuous state of retreat since the 19th century in response to climatic change and anthropogenic activities [1][2][3] except in the Karakoram region where glaciers have been reported to be in a stable phase [4][5][6]. The ever increasing temperatures have resulted in the faster melting of cryosphere reserves in the region [7,8].…”

Surging Dynamics of Glaciers in the Hunza Valley under an Equilibrium Mass State since 1990

“…Measurements of these parameters could help us to better understand the glacier responses to climate change [16,17]. Predecessors in glacier surface height changes and velocities in western Karakoram have already done a lot of significant research work and achieved fruitful results [8][9][10]13,[18][19][20][21], and the relation between the two crucial parameters is fairly precise [22]. For complex patterns of glacier changes in western Karakoram, several mechanisms are proposed, while there are knowledge gaps and uncertainty [22].…”

“…Predecessors in glacier surface height changes and velocities in western Karakoram have already done a lot of significant research work and achieved fruitful results [8][9][10]13,[18][19][20][21], and the relation between the two crucial parameters is fairly precise [22]. For complex patterns of glacier changes in western Karakoram, several mechanisms are proposed, while there are knowledge gaps and uncertainty [22]. In our study, the decadal glacier mass balance in the Hunza Basin of the western Karakoram was estimated from the differential synthetic aperture radar interferometry (DInSAR) method on the Shuttle Radar Topography Mission (SRTM) DEM and TerraSAR-X/TanDEM-X (TSX/TDX) images (2014).…”