Longbasaba Glacier recession and contribution to its proglacial lake volume between 1988 and 2018

Abstract

During the last few decades, the lake-terminating glaciers in the Himalaya have receded faster than the land-terminating glaciers as proglacial lakes have exacerbated the mass loss of their host glaciers. Monitoring the impacts of glacier recession and dynamics on lake extent and water volume provides an approach to assess the mass interplay between glaciers and proglacial lakes. We describe the recession of Longbasaba Glacier and estimate the mass wastage and its contribution to the water volume of its proglacial lake. The results show that the glacier area has decreased by 3% during 1988–2018, with a more variable recession prior to 2008 than in the last decade. Longbasaba Lake has expanded by 164% in area and 237% in water volume, primarily as a result of meltwater inflow produced from surface lowering of the glacier. Over the periods 1988–2000 and 2000–18, the mass loss contributed by glacier thinning has decreased from 81 to 61% of the total mass loss, accompanied by a nearly doubled contribution from terminus retreat. With the current rate of retreat, Longbasaba glacier is expected to terminate in its proglacial lake for another four decades. The hazard risk of this lake is expected to continue to increase in the near future because of the projected continued glacier mass loss and related lake expansion.

Keywords

• Glacier hazards
• glacier mass balance
• glacier monitoring
• ice velocity