100 YEARS OF GLACIER RETREAT IN CENTRAL ASIA

Glaciers are sensitive indicators/integrators of climate. Most have been retreating since the Little Ice Age (LIA: ~A.D. 1300-1850). Rates of retreat vary, and some glaciers are advancing. The NASA/USGS-sponsored GLIMS project (Global Land Ice Measurements from Space) is tracking glacier changes globally using stereo multispectral satellite images acquired since 2000. Together with older Landsat and Corona images, we can assess retreat for up to 40 yr; historical data locally permit estimates for 100 yr or more of glacier retreat, and moraines can offer a longer view. Central Asia is a key area to monitor because it is heavily glaciated, represents a continental climatic extreme, has local extreme glacier hazards, and provides a crucial glacial meltwater resource for over 500 million people in a vast arid/semiarid region. The Central Asian climate is dominated by low-pressure systems directed by the jet stream, the monsoons in the south, and strong thermal high-pressure systems in Siberia, all orographically modulated. Glacier health is controlled by the composite and sometimes asynchronous changes in these factors. Therefore, we are measuring glacier vigor, including surface flow fields and margin/terminus retreat (and local advance), for a sample of glaciers from the Himalaya to the Verkhoyansk (Siberia), and from the western Tien Shan (Kyrgyzstan) to the Khangai Nuruu (Mongolia). Glaciers across most of region are in general rapid retreat or stagnating, especially on the south side Himalaya. However, retreat appears to be less in the Verkhoyansk, and some glaciers in the lee of the Karakoram are fairly stable or advancing.