Will landscape responses reduce glacier sensitivity to climate change in High Mountain Asia?

Abstract. In High Mountain Asia (HMA), ongoing climate change threatens mountain water resources as glaciers melt, and the resulting changes in runoff and water availability are likely to have considerable negative impacts on ecological and human systems. Numerous assessments of the ways in which these glaciers will respond to climate warming have been published over the past decade. Many of these assessments have used climate model projections to argue that HMA glaciers will melt significantly this century. However, we show that this is only one way in which these glaciers might respond. An alternative pathway is one in which increasing valley-side instability releases large amounts of rock debris onto glacier surfaces. The development of extensive glacier surface debris cover is common in HMA, and, if thick enough, this surface debris inhibits glacier melting to the extent that glacier ice becomes preserved under the surface debris cover. In so doing, a transition to glacier-derived rock glaciers and other ice debris landforms may prolong the lifetime of HMA glacial ice in the landscape. We call this alternative pathway the Paraglacial Transition Model. In this Perspective Article, we discuss the scientific basis of this alternative view in order to better understand how HMA glaciers may respond to climate change.