Debris Cover Affects Himalayan Glaciers’ Response to Climate Change

The Himalayan glaciers<!–[if supportFields]> XE “glaciers” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–> are an important source of drinking water, agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> and hydropower<!–[if supportFields]> XE “hydropower” <![endif]–><!–[if supportFields]><![endif]–> for central and south Asia, however, the remoteness of these glaciers makes ground-based data collection tricky. Thus, scientists are forced to use glacier retreats and advances to measure the impact of climate change on the glaciers. However, Scherler et al. (2011) claim these approaches are not entirely accurate as supraglacial debris can affect the the glacier’s response to climate change. In order to asses this further, the authors analyzed 286 glaciers in the greater Himalayan Range between 2000 and 2008. They discovered that glaciers that are heavily covered with debris and have stagnant (not moving), low-gradient terminus regions have stable fronts while the monsoon<!–[if supportFields]> XE “monsoon” <![endif]–><!–[if supportFields]><![endif]–>-driven glaciers are retreating. Their results indicate that Himalayan glaciers dynamics seem to be heavily dependent on the debris cover, and show no uniform response to climate change. —Sachi Singh

Supraglacial debris are said to influence the terminus dynamics of glaciers<!–[if supportFields]> XE “glaciers” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–> and modify their response to climate change. To further study the terminus dynamics of the glaciers in the greater Himalaya region, the authors studied the frontal changes and surface velocities of 286 glaciers between 2000 and 2008. They also mapped debris cover to test whether regional disparities in debris cover accounted for the spatial variations in glacier terminus dynamics. The authors found that the regional distribution of stagnant glaciers with stable fronts varied significantly in the greater Himalayan region: they were most common in the Hindukush, southern, and northern central Himalayas<!–[if supportFields]> XE “Himalayas” <![endif]–><!–[if supportFields]><![endif]–> and were completely absent in the Karakoram region. Since accumulation areas in Karakoram are relatively steep, stagnant glaciers are absent and cannot account for the stable or advancing glaciers in the region. The authors claim that the westerly-derived winter precipitation could explain the positive mass balance disturbance in Karakoram.

In all other places, the formation of stagnant ice relies on low-gradient slopes and is confined to the terminus region of debris-covered glaciers<!–[if supportFields]> XE “glaciers” <![endif]–><!–[if supportFields]><![endif]–><!–[if supportFields]> XE “glacier” <![endif]–><!–[if supportFields]><![endif]–> with shallow gradients. The authors claim that debris-cover—which is almost always a few centimeters thick—leads to a reduction in melt rates and slows down the glacier’s response to climate change. Debris-cover also influences anthropogenic and natural radiative heat transfer. Thus, the authors conclude that topographic factors, which usually vary with terrain, have significant effects on the glacier’s response to climate change and should be accounted for in future mas-balance calculations. 

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