Emerging threats: Cryosphere-related hazards in the Trans-Himalaya of Ladakh

Cryosphere-related hazards are a growing but largely neglected threat for rural settlements, agrarian land use and local livelihoods in the cold-arid Trans-Himalayan region of Ladakh. Despite the growing number of studies on cryosphere-related hazards across High Mountain Asia and other glacierized mountain regions, the occurrence, frequency and magnitude of glacial lake outburst floods (GLOFs) are almost entirely overlooked for the region of Ladakh. Due to the small size and high elevational location of glaciers above 5200 m a.s.l. also the glacial lakes are of small size and some of them are almost permanently ice-covered. In the recent past several GLOF events occurred which destroyed infrastructure and agricultural area. It becomes obvious that even these small glacial lakes might be a permanent threat for local livelihoods and socioeconomic development. This is even more problematic as the number and size of lakes has significantly increased over the past decades. Many of these lakes are dammed by ice-cored moraines which tend to become instable due to climate warming. A comprehensive inventory of glacial lakes for the entire Trans-Himalayan region of Ladakh was carried out. This includes several almost permanently ice-covered high altitude lakes, which have to be detected by visual image interpretation. Changes in the extent and number of glacial lakes have been quantified for the years 1969, 1993, 2000/02 and 2018 in order to assess the potential threat of future GLOFs in the region. A total of 192 glacial lakes cover an area of 5.93 ± 0.70 km² with an estimated water volume of about 61.11 ± 8.5 million m³, including 127 proglacial (PG) and 56 lakes located on recent moraines (RM) were mapped in 2018. The change detection analyses also indicated the disappearance of 22 glacial lakes (decrease by more than 90%) between 1969 and 2018. The lake development of selected former reported GLOF events were analysed in detail to reconstruct lake level changes which possibly indicate earlier GLOF events. Based on high temporal resolution remote sensing data, a sophisticated monitoring concept needs to be realized to indicate the development of short-lived lakes on glaciers or on debris landforms with buried ice or fast glacial lake growth.