Glacial changes in the Hunza Basin, western Karakoram, since the Little Ice Age

Abstract

Glaciers have remained relatively stable in the Karakoram over the past few decades, in contrast to rapid retreat in other regions of the Tibetan Plateau and its surrounding mountains. This study investigated glacial changes in the Karakoram since the Little Ice Age (LIA) to examine if this relatively stable scenario has occurred for a longer term. We mapped 432 contemporary glaciers and their corresponding 313 LIA glaciers in the Hunza Basin, western Karakoram, using Google Earth and Landsat images. We also derived geomorphometric parameters for each glacier using the Shuttle Radar Topographic Mission digital elevation model and reconstructed the equilibrium line altitudes (ELAs) for both contemporary and LIA glaciers based on the toe-to-ridge altitude method. Our results revealed 6.6% decrease in the total area, 14.5% shortening in the total length along the flowline of each LIA glacier, and approximately 98 m rising in the mean ELA since the LIA. The relative area reduction was strongly affected by geomorphometric factors and small glaciers tended to experience relatively large areal reductions. In contrast, the change in ELA was not strongly affected by glacial area but had some correlations with slope and mean elevation. Compared to other areas on the Tibetan Plateau and its surrounding mountains, glacial changes have been less extensive in the Hunza Basin since the LIA. These findings confirmed a relatively stable behavior of glaciers in this area since the LIA and a strong control of local geomorphometric characteristics on glacial change.