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Antarctica is leaking from the inside out

When climate scientists look at Antarctica, they
see a ticking time bomb. If the ice sheet melts, it will
raise sea levels by tens of feet, flooding coastal cities
around the globe.

For now, the southern continent is relatively stable, but
it’s starting to look more like Greenland, where rising
temperatures are melting the island from the inside out.

For decades, Greenland primarily melted around the edges.
Giant blocks of ice would break free from the
coast
and vanish into the ocean. Recently,
however, Greenland has started melting from the middle. Pools
of water are forming atop the ice sheet in the warmer months
and then draining out to sea.

Scientists have now discovered the same thing is happening in
Antarctica. Two new studies published in the journal
Nature catalogue the melting and explain what it
could mean for sea-level
rise
.

In the first
study
, researchers examined decades of photos from
satellites and military aircraft. They documented hundreds of
meltwater channels around the perimeter of the continent.
They traced some streams deep into Antarctica’s frozen
interior and discovered ponds of meltwater more than 4,000
feet above sea level, where no one expected to find liquid
H2O. 

In some places, the terrain had contributed to the melting.
Blue ice and dark mountains absorb more sunlight than the
white snow. These features gathered the extra heat needed to
thaw Antarctic ice.

“Even though people kind of knew there were melt ponds
around, they really didn’t know that water could move long
distances across the surface,” said Jonathan Kingslake, a
glaciologist at Columbia University and lead author of the
study. He said that streams “take water away from the surface
of the ice sheet and actually export it all the way into the
ocean… And we didn’t really realize this happened at all.”

Meltwater channels tend to grow in warmer months and refreeze
in the winter. But scientists worry that rising temperatures
spur continual melting, accelerating sea-level rise. 

Ice shelves along the edge of the continent are holding back
massive, terrestrial glaciers. As the shelves break up, they
allow glaciers to slip into the ocean. Meltwater may, in some
instances, lubricate the underside of the glacier, hastening
its passage to the sea. Meltwater can also burrow into the
ice shelf, cleaving apart large chunks of ice. This is what’s
happening to the
Larsen C Ice Shelf
, which is expected to break off the
continent soon.

Kingslake said the drainage systems appear “quite stable at
the moment. But the predictions for the future — for this
century — are that melt rates will double in response to
global climate change.” He said that “what we really need to
know is how is that going to impact the stability of the ice
sheet and our predictions of sea-level rise.”

The second
study
, which Kingslake co-authored, attempts to answer
that question.

“When we turn the temperature up — of the atmosphere — we’re
going to make more melt, and it’s going to get caught in
ponds, and it’s going to act like a jackhammer and ruin the
ice shelf,” said Robin Bell, a geophysicist at Columbia
University, lead author of the second study and co-author of
the first.

But, Bell said there are signs of hope. She noted that
meltwater channels have kept West Antarctica’s Nansen Ice
Shelf intact. That’s because water is draining to the ocean
rather than amassing on the surface, where it would warm up
the ice and trigger further melting.

“Plumbing on our planet matters, and plumbing on the top of
the ice sheet matters,” said Bell. The water on the Nansen
Ice Shelf isn’t gathering into pools or “falling into these
crevices that then pop open. Instead, it’s exiting stage
right down this very subtle river valley.” The runoff has a
negligible effect on sea levels.

Antarctica is
contributing
to sea-level rise in other ways, shedding
chunks of ice around the edges. Between 2002 and 2016,
Antarctica shed
100 gigatons
of ice per year — nearly
enough water
to fill Lake
Ontario
. Antarctica — like Greenland — is less stable
than previously thought. Recent research suggests climate
change could raise sea levels by
six feet
by the end of this century, and by tens or even
hundreds of feet in the centuries to come. New research on
meltwater complicates scientists’ projections.

“We’re working hard to figure out if this stuff is relevant
to sea-level predictions,” said Douglas MacAyeal, a
glaciologist at the University of Chicago who was not
involved in the studies. He noted that, until recently,
“nobody’s been that interested in melting,” because it was
thought to be extremely rare in Antarctica.

Scientists will need to better understand the inner workings
of the Antarctic ice sheet to forecast sea levels in the
decades to come. What happens on the southern continent
rarely stays there. Melting glaciers threaten to deliver
floods to New Orleans, Miami, New York and beyond.

“This might delay how fast the other parts of Antarctica go,”
said Bell, “but it doesn’t mean that Antarctica isn’t
susceptible to changing temperatures.”

Jeremy Deaton, Josh Chamot and Owen Agnew contributed to
this report. Nexus
Media
is a syndicated newswire covering climate, energy,
policy, art and culture.

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