sciencemag.org SCIENCE 1120 1 DECEMBER 2017 • VOL 358 ISSUE 6367
On the high plateau of western Tibet, 17 July 2016 started out as a lovely day. “The air smelt particularly fresh after a heavy rainfall the night before,” says Dradül, the chief of Aru village, who like many Tibetans goes by one name. Then, Dradül got a chilling phone call. In a torrent of words, a villager described how
an avalanche of ice had just “swallowed the
grassland,” wiping out a rich pasture where
villagers, including some of Dradül’s relatives, were tending yaks and sheep.
Dradül rushed out to Aru Co Lake,
5100 meters above sea level, to help with the
rescue. The grassland had disappeared, en-
tombed under a 30-meter-high wall of ice.
Eyewitnesses said the glacier had barreled
in like a fast train, dumping enough ice to
fill 40,000 Olympic-size swimming pools.
The surge crushed nine people, including
Dradül’s sister and her four children, as well
as hundreds of head of livestock.
Thousands of glaciers perch near human
settlements, and in recent decades, dozens
of surges have claimed lives. One of the
worst calamities occurred in 2002, in the
Caucasus Mountains of southern Russia,
when Kolka Glacier rumbled into a valley,
killing 140 people. Anecdotes, and even
some preliminary tallies, suggest surges are
becoming more frequent. Just 2 months af-
ter the Aru disaster, Chinese scientists were
on hand when a surge from an adjacent
glacier engulfed another swath of grass-
land. No one was injured that time. But the
back-to-back surges were “simply astound-
ing,” says Yao Tandong, a glaciologist at the
Chinese Academy of Sciences’s Institute
of Tibetan Plateau Research in Beijing. “It
makes you wonder what’s going on.”
Most surges, broadly defined as a flow at
least 10 and often hundreds of times faster
than a glacier’s usual pace of advance, are
quieter affairs. Many are imperceptibly
slow, but others attain staggering speeds. In
1953, for example, Kutiah Glacier in Paki-
stan advanced 12 kilometers over 3 months.
Besides overwhelming settlements, glacier
surges can threaten distant communities.
They can block rivers, creating lakes that
can later unleash floods, and by depleting
glacier mass, they can threaten the flow
of meltwater that downstream towns and
farms may depend on.
Now, by studying glaciers from Tibet
to the Arctic islands of the Svalbard archipelago in Norway, researchers are starting
to understand why some glaciers swing
between extremes of stagnation and crushing flow, and how surges may be predicted.
Until recently, most glaciologists believed
that a glacier’s physical characteristics,
By Jane Qiu, in Aru, Tibet, and Ny-Ålesund, Svalbard archipelago
Scientists are unraveling why certain glaciers are prone to
surging abruptly—sometimes wiping out people in their path
ICE ON THE RUN