Review article: Inferring permafrost and permafrost thaw in the mountains of the Hindu Kush Himalaya region

Abstract

Abstract. The cryosphere reacts sensitively to climate change, as evidenced by the widespread retreat of mountain glaciers. Subsurface ice contained in permafrost is similarly affected by climate change, causing persistent impacts on natural and human systems. In contrast to glaciers, permafrost is not observable spatially and therefore its presence and possible changes are frequently overlooked. Correspondingly, little is known about permafrost in the mountains of the Hindu Kush Himalaya region, despite permafrost area exceeding that of glaciers in nearly all countries. Based on evidence and insight gained mostly in other permafrost areas globally, this review provides a synopsis on what is known or can be inferred about permafrost in the mountains of the HKH region. Given the extreme nature of the environment concerned, it is to be expected that the diversity of conditions and phenomena encountered in permafrost exceed what has previously been described and investigated. We further argue that climate change in concert with increasing development will bring about diverse permafrost-related impacts on vegetation, water quality, geohazards, and livelihoods. To better anticipate and mitigate these effects, a deepened understanding of high-elevation permafrost in subtropical latitudes as well as the pathways inter-connecting environmental changes and human livelihoods are needed.

Status and Change of the Cryosphere in the Extended Hindu Kush Himalaya Region

“…Existing research has largely focused on local regions, such as the TP (Fort and van Vliet-Lanoe 2007;Jakob 1992; Barsch and Jakob 1998;Owen and England 1998;Regmi 2008;Hewitt 2014), western Himalaya (Fort 2003), Bhutan (Iwata et al 2003), Pamir-Alai (Gorbunov and Titkov 1989), or systematic remote mapping of rock glaciers (Schmid et al 2015). Further, only a few observations have been made of ground ice (Rastogi and Narayan 1999;Gruber et al 2017) or ground temperature (Shiraiwa 1992;Klimeš and Doležal 2010) exist.…”

Rockslides and rock avalanches in the Central Andes of Argentina and their possible association with permafrost degradation

“…This modifies the total friction and the fracture toughness of rock bridges at the microscale. Gruber et al . also note that high‐volume events in mountain areas, triggered during cold seasons, are probable indicators of processes and changes at depth, built up over several decades or centuries and not necessarily responding to recent climate warming.…”

Rock‐glacier dams in High Asia

“…The principal components also highlight the tight correlations between many topographic and climatic inputs, which can produce overly confident classification models: the model using 13 raw inputs had the highest AUC values, and thus offers, at least nominally, the most accurate classification. These data, like some other satellite-derived products for mountain areas with few climate stations, rely heavily on topographic interpolation (Gruber et al, 2017). Principal components warrant independence, but are harder to interpret than original attributes such as elevation or feederbasin area.…”

“…Many of High Asia's topographic and climatic conditions are conducive to permafrost, and hence also rock glaciers (Gruber et al, 2017). All studied ranges lie leeward of the influence of the Indian monsoon, and receive low amounts of precipitation, partly delivered by cyclones from the west-wind drift.…”

“…Some uncertainty is also tied to the climatic parameters from the WorldClim data. These data, like some other satellite-derived products for mountain areas with few climate stations, rely heavily on topographic interpolation (Gruber et al, 2017). For example, the WorldClim data indicate a mean annual precipitation of~570 mm (with a nominal range of 455-697 mm) for 644 rock glaciers in the Tien Shan, whereas Bolch and Gorbunov (2014) estimate this at~1005 mm (with a nominal range of 553-1349 mm), at least for 74 rock glaciers in the region.…”