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East Antarctica is Melting From Above and Below
18
December, 2016
East
Antarctica is remote even by Antarctic standards. Harsh winds and
ocean currents have largely cut off the region from the rest of the
world.
That’s
left its massive stores of ice largely intact, especially compared
to West Antarctica where
a massive meltdown is underway that could raise seas by 10
or more feet in
the coming centuries. But as carbon pollution warms the air andthe
ocean,
there are signs that the region’s stability is under threat. Two
new studies of different ice shelves — tongues of ice that
essentially act as bathtub plugs — have seen major melting that
could portend a less stable future for the region.
The
calving front of the Totten ice shelf.Credit: Australian Antarctic Division
But
strange things have been happening
recently.
During a 2014 flyover of the Roi Baudouin ice shelf, scientists
noticed a curious depression more than a mile wide in the undulating
ice. When they
finally investigated it
in January this year, they found walls that were about 10 feet high
and meltwater pouring into moulins — features that funnel surface
meltwater into the heart of the ice.
The
moulins were just one sign of melt happening on the surface. When
scientists drilled a hole in the ice and lowered a camera, they found
an otherworldly blue lake stretching more than half a mile across.
Research
published in Nature
Climate Change shows
that the cause of these bizarre features are the powerful winds that
blow down from Antarctica’s interior. Jan
Lenaerts,
a postdoctoral researcher at the Utrecht University in the Netherland
who led the study, said that those winds helped heat the air and
caused white ice to melt out, exposing a layer of dark ice beneath.
That darker ice in turns absorbs more sunlight, further expediting
the melt.
“Although
we only found this on one ice shelf, we find the same mechanisms on
many East Antarctic ice shelves,” Lenaerts said. “Given the
strong response of surface meltwater production and extent of
meltwater processes on the shelf to summer temperature, we can expect
that in a warmer climate, these ice shelves might be vulnerable to
instability that is driven by meltwater hydrofracturing.”
But there are also signs that warm water is undercutting at least one
of East Antarctica’s other ice shelves. The Totten ice shelf is one
of the most important ice shelves in the region. It backstops so much
ice that if it were to melt, it would result in up to 12 feet of sea
level rise.
Recent
research has shown that its geology and interactions with the ocean
mean that losing just
4.2 percent of its mass could
kickstart the process to send more inland ice to the sea. And it has
been melting faster than most other glaciers and ice shelves in East
Antarctica.
“We
knew from satellite data that the Totten has been thinning faster
than other glaciers in East Antarctica, but we didn’t know
why,” Steve
Rintoul,
the interim head of CSIRO’s Climate Science Center, said in a
statement.
That’s
why Rintoul and his colleagues set out to look more closely at the
ice in January 2015 on the Aurora Australis, an Australian research
boat. They were able to visit the calving front of the ice — where
the shelf ends in the ocean — thanks to a fortuitous path that
broke in the sea ice in January 2015. It’s the first time direct
measurements have ever been taken by boat in the region.
Their
findings from that trip, published on Friday in Science
Advances,
show that the bedrock underlying the ice shelf is a major driver in
the melt process. They found two massive ocean channels up to 6 miles
wide and a half mile deep are funneling warm water under the ice
shelf and melting it out from underneath.
Taken individually, the studies are disconcerting enough. Put together, though, they paint a picture of a region that could become a much bigger player in sea level rise if carbon pollution isn’t curtailed soon.
This Melting Glacier in Antarctica Could Raise Sea Levels By 11 Feet
18
December, 2016
The
Earth’s climate, it seems, isn’t listening to the politicians
that are insisting it’s not warming. The temperature continues to
rise incrementally, and the globe’s large glaciers—giant vaults
of stored water—continue to melt, releasing into the oceans. The
global sea level, due to thermal expansion and glacial melting,
continues to rise, building up a head of steam like a train just
beginning its descent down a steep hill.
Greenland’s
hulking glacier and the Arctic Sea ice are now marked by their rapid
melting. And the western Antarctic ice sheet has garnered a lot
of attention recently,
too. But while scientists were fretting over the western side of
Antarctica, the eastern Antarctic ice sheet has been melting too.
Australian researchers braved treacherous sea conditions to collect
data on the melting Totten Ice Shelf there, which holds up a body of
ice that would cause over 11 feet of sea level rise, if it melted.
Their findings are published in
the journal Science
Advances.
Scientists
have concluded that ice shelves and glaciers in eastern Antarctica
have been experiencing basal melt, where the bottom layer of a body
of ice starts to melt away, but they’ve never directly observed how
it’s happening and what the main drivers of melting are until now.
The
Totten Ice Shelf. Image: Esmee van Wijk (CSIRO and ACE CRC)
In
Antarctica, the ice sheets covering the continent are so large that
they extend beyond the land’s edge. Picture a pool cover that’s
only covering half of an in-ground pool. Part of it lays on the patio
nearby, and the rest of it slopes downward onto the water’s surface
where it floats. Where the glacier hits the water is a buttress of
ice called a shelf, which keeps the land bound ice from draining into
the sea. If the shelf melts then—well, you get the idea. Such is
the Totten Ice Shelf.
Recovery
of a mooring in heavy sea ice near the Totten Ice Shelf. Image: Steve
Rintoul (CSIRO and ACE CRC)
With
fair weather conducive to research, oceanographer and lead author of
the study,Stephen
Rich Rintoul,
of the Commonwealth Scientific and Industrial Research Organization
in Australia, directed a team of scientists to collect oceanographic
data from the Totten ice front in east Antarctica. Previous
expeditions were hampered by heavy sea ice conditions and ultimately
unsuccessful. What they found was startling.
The
RSV Aurora Australis at the front of the Totten Glacier. Image: Paul
Brown (Australian Maritime College)
About
2,000 feet down, the team found a great trough—about 6 miles
wide—worn into the side of the Totten shelf. Below 2,000 feet the
gaping cavity narrows into two channels, and warm water flows through
it, boring through the ice like sugar through the enamel of a tooth.
The ice shelf, they measured, is melting at its base faster than all
other ice shelves of similar size in East Antarctica. If it were to
give way, enough ice would slide into the sea to raise global levels
by over 11 feet.
Successful
recovery of an oceanographic mooring near the Totten Ice Shelf.
Image: Steve Rintoul (CSIRO and ACE CRC)
How
the melting of these great bodies of ice will play out in the future
remains to be seen, but regardless of any continuing work done to
slow the effects of climate change, it’s possible the damage
is already
done.
Giants slabs of ice that give way 10 years from now, for example,
could be the product of melting that started a decade ago. Climate
scientist Kerim Nisancioglu, of the University of Bergen, told
the New
Yorker that
“In
some cases, you have, in theory, this irreversible process. You set
it off and it just goes. It drains.” It’s a wait and see.
The SHTF climate wise and it's only going to hit the fan more. :-(
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