Karakoram Glaciers and Climate Change

Abstract

This chapter looks at fluctuations in Karakoram glaciers, mainly in the last 200 years, their consequences and implications for future responses to climate change. Most of the evidence available concerns terminus changes. Improvements in satellite coverage and analytical techniques have increased the range and quality of information but results can raise as many problems as answers. Records are reviewed back to the mid-nineteenth century for some of the larger and more frequently visited glaciers, including Baltoro, Biafo, Batura, Chogo Lungma and Hispar. This information broadly confirms an ice cover decline since the Little Ice Age (LIA), although it does not seem to exceed 5 % of the greatest LIA extent. Large glaciers with high elevation watersheds appear less reduced than small and minor ice masses, although evidence from the latter is very limited. The timing of the greatest advances in the LIA varies by decades for different glaciers, in some cases by centuries. Between the 1920s and 1980s, most of the larger glaciers had a net retreat, but an almost chaotic situation emerges from the late LIA through the early twentieth century, and again since the mid-1990s. This is only partly accounted for by unsystematic fluctuations in surge-type glaciers. There has been no great loss of ice, and more than 40 high Karakoram glaciers have undergone advances of varying extent. At the latest time frame to 2010, few if any glaciers were at their most advanced positions of the past 150 years but also, no case was at its greatest reported retreat. Advances and retreats have been more or less out of phase even in neighbouring glaciers. Few of the large glaciers have retreated in proportion to the amount of thinning, and some have even advanced while appearing to thin. The recent picture differs from other parts of the Himalaya and common global trends. This may be due to the distinctive climatic regime or how it responds to global climate change as discussed in earlier chapters. Out-of-phase relations of terminus fluctuations may also follow from different styles of nourishment, thermal regimes and shifts causing movement instability. As yet unrecognised surge-type glaciers are another source of complexity. Confusion has also arisen in relating Quaternary glaciations to the state of present-day glaciers, notably debris covers, and ice margin and pro-glacial deposits near them. This is illustrated by former and emerging interpretations of the so-called Great Lateral Moraine, the nearly ubiquitous, relatively well-preserved and massive lateral margin deposits overlooking present ice levels. They create an impression of glacier decline that may be misleading. Originally viewed as equivalent to the ‘1850’ Little Ice Age moraines of the European Alps, the deposits turn out to be more diverse in age and origin. Post-glacial geomorphic developments along the Indus streams are at least as important as climate change and neoglaciation.