Most other Central Asian glaciers retreated under the same heat spell, some 9,000 years ago, but the Himalayan glaciers lengthened from one to six kilometres.
A new study by Brigham Young University (BYU) geologist Summer Rupper pieces together the chain of events surrounding the unexpected glacial growth.
"Stronger monsoons were thought to be responsible," said Rupper. "Our research indicates that the extra snowfall from monsoonal effects can only take credit for up to 30 percent of the glacial advance."
As Central Asia’s summer climate warmed as much as six degrees Celsius, shifting weather patterns brought more clouds to the Southeast Himalayas. The additional shade created a pocket of cooler temperatures.
Temperatures also dropped when higher winds spurred more evaporation in this typically humid area, the same process behind household swamp coolers.
The story of these seemingly anomalous glaciers underscores the important distinction between the terms “climate change” and “global warming".
“Even when average temperatures are clearly rising regionally or globally, what happens in any given location depends on the exact dynamics of that place,” Rupper said.
The findings come from a framework Rupper developed as an alternative to the notion that glaciers form and melt in direct proportion to temperature, said a BYU release.
Her method is based on the balance of energy between a glacier and a wide range of climate factors, including wind, humidity, precipitation, evaporation and cloudiness.
These findings are slated for publication in the September issue of the Quaternary Research.
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