Spatially heterogeneous wastage of Himalayan glaciers

Abstract

We describe volumetric changes in three benchmark glaciers in the Nepal Himalayas on which observations have been made since the 1970s. Compared with the global mean of glacier mass balance, the Himalayan glaciers showed rapid wastage in the 1970s-1990s, but similar wastage in the last decade. In the last decade, a glacier in an arid climate showed negative but suppressed mass balance compared with the period 1970s-1990s, whereas two glaciers in a humid climate showed accelerated wastage. A mass balance model with downscaled gridded datasets depicts the fate of the observed glaciers. We also show a spatially heterogeneous distribution of glacier wastage in the Asian highlands, even under the present-day climate warming.

Fig. 1.

Location of the three benchmark glaciers in Nepal (A), temporal changes in the area-averaged mass balances of the glaciers compared with the pentadal global mean (gray line) (6) (B), and mass balances compared with annual precipitation (C). Color shading in B and vertical bars in C denote measurement errors of mass balance. Horizontal bars in C denote variability of annual precipitation. See SI Text about the error evaluation and the downscaling.

Fig. 2.

Area–altitude distribution (color bars), calculated ELA (thick line, five-year running mean), and preferable ELA for the present-day glacier extent (straight line with gray shading) for three benchmark glaciers in Nepal (Upper). (Lower) The area-averaged mass balance (MB; thick line, five-year running mean), as calculated to yield the minimum rmse against the observation (thick colored line), and the ice core derived mass balances (thin colored lines).

Fig. 3.

Spatial distribution of the trends in ELA (A), summer mean temperature (B), and annual precipitation (C) for the period 1988–2007.