Himalayan melt may be less than thought

Satellite data suggest modest net ice loss

Rising temperatures in the Himalayas may bring more moderate melting for the region’s glaciers than some previous studies have concluded. Combining six years of topographic measurements gathered by NASA’s Ice, Cloud and land Elevation Satellite with radar data collected aboard the space shuttle Endeavour in 2000, an international team mapped out glacier activity throughout the range. Glaciers are thinning faster in some regions than others, but the researchers believe the range as a whole lost nearly 13 billion metric tons of ice per year from 2003 to 2008. While on-the-ground observations indicate heavier losses, this new figure is more than twice the melting tonnage reported earlier this year by another team using data from NASA’s GRACE satellites. The study also challenges the long-accepted idea that an insulating coat of rocky debris can slow down ice loss: Dirty glaciers like Ngozumpa in Nepal shrank at about the same rate on average as their cleaner neighbors, the researchers note August 23 in Nature.

Debris-blanketed glaciers like Nepal’s Ngozumpa, once thought to be relatively immune to melting, have been found to be shrinking at about the same rate as more exposed ice fields. Kimberly Casey

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