WASHINGTON (AP) -
The huge West Antarctic ice sheet is starting a glacially slow collapse in
an unstoppable way, two new studies show. Alarmed scientists say that means
even more sea level rise than they figured.
outcomes won’t be seen soon. Scientists are talking hundreds of years, but
over that time the melt that has started could eventually add 4 to 12 feet
to current sea levels.
A NASA study
looking at 40 years of ground, airplane and satellite data of what
researchers call “the weak underbelly of West Antarctica” shows the melt is
happening faster than scientists had predicted, crossing a critical
threshold that has begun a domino-like process.
“It does seem to be
happening quickly,” said University of Washington glaciologist Ian Joughin,
lead author of one study. “We really are witnessing the beginning stages.”
It’s likely because
of man-made global warming and the ozone hole which have changed the
Antarctic winds and warmed the water that eats away at the feet of the ice,
researchers said at a NASA news conference Monday.
“The system is in
sort of a chain reaction that is unstoppable,” said NASA glaciologist Eric
Rignot, chief author of the NASA study in the journal Geophysical Research
Letters. “Every process in this reaction is feeding the next one.”
from fossil fuels to slow climate change will probably not halt the melting
but it could slow the speed of the problem, Rignot said.
Rignot, who also is
a scientist at the University of California Irvine, and other scientists
said the “grounding line” which could be considered a dam that stops glacier
retreat has essentially been breached. The only thing that could stop the
retreat in this low-altitude region is a mountain or hill and there is none.
Another way to think of it is like wine flowing from a horizontal uncorked
bottle, he said.
Rignot looked at
six glaciers in the region with special concentration on the Thwaites
glacier, about the size of New Mexico and Arizona combined.
Thwaites is so
connected to the other glaciers that it helps trigger loss elsewhere, said
Joughin, whose study was released Monday by the journal Science.
uses computer simulations and concludes “the early-stage collapse has
begun.” Rignot, who used data that showed a speed up of melt since the
1990s, said the word “collapse” may imply too fast a loss, it would be more
the start of a slow-motion collapse and “we can’t stop it.”
experts in Antarctica praised the work and said they too were worried.
“It’s bad news.
It’s a game changer,” said Ted Scambos, lead scientist at the National Snow
and Ice Data Center, who wasn’t part of either study. “We thought we had a
while to wait and see. We’ve started down a process that we always said was
the biggest worry and biggest risk from West Antarctica.”
The Rignot study
sees eventually 4 feet of sea level rise from the melt. But it could trigger
neighboring ice sheet loss that could mean a total of 10 to 12 feet of sea
level rise, the study in Science said, and Rignot agreed.
The recent reports
from the Intergovernmental Panel on Climate Change don’t include melt from
West Antarctic or Greenland in their projections and this would mean far
more sea level rise, said Sridhar Anandakrishnan, professor of geosciences
at Pennsylvania State University.
That means sea
level rise by the year 2100 is likely to be about three feet, he said.
Even while the West
Antarctic ice sheet is melting, the much larger East Antarctic ice sheet
seems stable because it is cooler, Scambos said.
studies show Antarctica is a complicated continent in how it reacts. For
example, just last month Antarctic sea ice levels - not the ice on the
continent - reached a record in how far they extended. That has little or no
relation to the larger more crucial ice sheet, Scambos and other scientists