amount of ice draining collectively from those half-dozen glaciers
increased by 77 percent from 1973 to 2013, scientists report this
month in Geophysical Research Letters, a journal of the American
Geophysical Union. Pine Island Glacier, the most active of the
studied glaciers, has accelerated by 75 percent in 40 years,
according to the paper. Thwaites Glacier, the widest glacier, started
to accelerate in 2006, following a decade of stability.
study is the first to look at the ice coming off the six most active
West Antarctic glaciers over such an extended time period, said
Jeremie Mouginot, a glaciologist at University of California-Irvine
(UC-Irvine) who co-authored the paper. Almost 10 percent of the
world's sea-level rise per year comes from just these six glaciers,
we found was a sustained increase in ice discharge—which has a
significant impact on sea level rise," he said.
researchers studied the Pine Island, Thwaites, Haynes, Smith, Pope
and Kohler glaciers, all of which discharge ice into a vast bay known
as the Amundsen Sea Embayment in West Antarctica.
amount of ice released by these six glaciers each year is comparable
to the amount of ice draining from the entire Greenland Ice Sheet
annually, Mouginot said. If melted completely, the glaciers'
disappearance would raise sea levels another 1.2 meters (four feet),
according to co-author and UC-Irvine Professor Eric Rignot.
study shows major increase in West Antarctic glacial loss
decades of increasing speeds and ice loss are "a strong
indication of a major, long-term leakage of ice into the ocean from
that sector of Antarctica," noted Rignot.
region is considered the potential leak point for Antarctica because
of the low seabed. The only thing holding it in is the ice shelf,"
said Robert Thomas, a glaciologist at the NASA Wallops Flight
Facility, in Wallops Island, Va., who was not involved in the study.
Ice shelves are platforms of permanent floating ice that form where
glaciers meet the sea. In West Antarctica, ice shelves prevent the
glaciers investigated in the study from slipping more rapidly into
and his colleagues used satellite data to look at sequential images
of the glaciers from 1973 to 2013. The scientists then calculated how
fast the ice was moving by tracking surface features, such as cracks
in the ice, to determine the distance the glaciers traveled from
month to month and year to year.
the study considered the six glaciers collectively, it also revealed
unprecedented change on the individual glacier level. Thwaites
Glacier, the largest of the six with a width of 120 kilometers (75
miles), experienced a decade of near-stability until 2006, when its
speed picked up by 0.8 kilometers (half a mile) per year – a 33
percent increase in speed, according to the study. This is the first
time that such changes on Thwaites Glacier have been observed, said
all the glaciers in the study, Pine Island Glacier accelerated the
most since 1973, increasing by 1.7 kilometers (one mile), per year.
That's a 75 percent increase in speed from approximately 2.5
kilometers (1.5 miles) per year in 1973 to 4 kilometers (2.5 miles)
per year in 2013.
Pine Island and Thwaites glaciers contribute the most to overall ice
discharge—about three-fourths of the total amount documented in the
study. However, scientists also documented even higher rates of
increased discharge in some of the smaller glaciers. Smith and Pope
Glaciers nearly tripled the amount of ice they drained into the ocean
research team also found that the Pine Island Glacier is accelerating
along its entire drainage system—up to 230 kilometers (155 miles)
inland from where it meets the ocean.
paper is important in showing that a glacier can actually 'feel' what
is happening far downstream of itself," said Thomas. "It
means that if you disturb the ice sheet near the coast, the glaciers
will feel the push and rapidly respond hundreds of kilometers
finding suggests that glacier acceleration models may need to be
reevaluated, Thomas added. Most current models only take into account
isolated speed changes resulting from a local disturbance, rather
than representing how these changes affect the glacier as a whole.