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Dazzling blue lakes are forming in Antarctica — and they’ve got scientists worried
By
Chris Mooney
HANDOUT
PHOTO: Satellite image shows a group of lakes atop Langhovde Glacier,
East Antarctica. (Satellite image courtesy of DigitalGlobe,
Inc.)
17
August, 2016
In
a new
study,
scientists who study the largest ice mass on Earth — East
Antarctica — have found that it is showing a surprising feature
reminiscent of the fastest melting one: Greenland.
More
specifically, the satellite-based study found that atop the coastal
Langhovde Glacier in East Antarctica’s Dronning Maud Land, large
numbers of “supraglacial” or meltwater lakes have been forming —
nearly 8,000 of them in summer between the year 2000 and 2013.
Moreover, in some cases, just as in Greenland, these lakes appear to
have then been draining down into the floating parts of the glacier,
potentially weakening it and making it more likely to fracture and
break apart.
This
is the first time that such a drainage phenomenon has been observed
in East Antarctica, the researchers say — though it was previously
spotted on the warmer Antarctic Peninsula and was likely part of
what drove spectacular events there like the shattering
of the Larsen B ice shelf in 2002.
When
it comes to East Antarctica, however, “that’s the part of the
continent where people have for quite a long time assumed that it’s
relatively stable, there’s not a huge amount of change, it’s
very, very cold, and so, it’s only very recently that the first
supraglacial lakes, on top of the ice, were identified,” said
Stewart Jamieson, a glaciologist at Durham University in the U.K. and
one of the study’s authors.
The
study was led by Emily Langley of Durham, who worked along with
Jamieson and Chris Stokes from her university and Amber Leeson of
Lancaster University. The work was recently published
online by
Geophysical Research Letters.
The
research raises concern, for the following reason: Mounting evidence
suggests one reason that Greenland has been melting so fast lately is
precisely these kinds of lakes. In the summer as air temperatures
warm, lakes form on top of the ice sheet, and on its finger-like
glaciers that extend outwards into deep ocean fjords.
These
lakes can then suddenly disappear all at once, or flow into rivers
that drain into the ice below, lubricating the ice and helping to
increase the lurch forward of glaciers. Sometimes, researchers have
even been able to document fresh water flowing outward directly into
the sea from the base of a glacier. That injection of cold fresh
water into salty water can then create tornado-like
underwater flow patterns at
the submerged glacier front that cause further ice loss.
In
the new study, Langley and her colleagues find large numbers of lakes
forming atop Langhovde Glacier, both inland from, and outward from,
the so-called “grounding line,” which is where the marine glacier
touches the seafloor far below the ice surface. Past the grounding
line, the glacier’s ice begins to float and forms an ice shelf,
extending out across the surface of the ocean.
The
occurrence of these lakes was strongly related to surface air
temperatures — they formed when temperatures rose above zero
Celsius, or, above freezing, and formed most frequently in the summer
of 2012-2013, which saw 37 days with temperatures above the freezing
point.
“What
we find is that the appearance of these lakes, unsurprisingly, is
correlated directly with the air temperature in the region, and so
the maximum number of lakes, and the total area of the lakes, as well
as the depth of the lakes, all of these things peak when the air
temperatures peak,” said Jamieson.
The
study found in particular that atop the Langhovde ice shelf, lakes
not only formed but appeared to sometimes drain downward, as rapidly
as in five days in one case (which is considerably slower than
the fastest
drainage events in Greenland).
Drainage of some of Langhovde’s supraglacial lakes over a 12 day period between the 14th (left) and 26th (right) of January 2005. Images are compiled from ASTER data provided by the Land Processes Distributed Active Archive Center (LP DAAC) managed by the NASA Earth Science Data and Information System (ESDIS) project.
This
raises the concern that these events could possibly be weakening
the ice shelf by widening or exploiting fractures within it. But
Jamieson said the study could not prove that, in part because it is
much harder to observe the consequences of lake draining events in
Antarctica than it is in Greenland.
When
glaciers lose large parts of their ice shelves, they become less
stable and flow faster towards the ocean, contributing to an
increased rate of global sea level rise.
“The
size of the lakes … are probably not big enough to do much at
present, but if climate warming continues in the future, we can only
expect the size and number of these lakes to increase. So that’s
what we’re looking at,” Jamieson said.
He
added that the mid-sized Langhovde Glacier is not special when it
comes to East Antarctic meltwater lakes — other parts of coastal
Antarctica see them too. The reason the study focused on Langhovde is
simply that there was a lot of satellite and temperature data
available.
In
Greenland, when meltwater from the ice sheet’s surface flows out
from beneath glaciers and enters the sea, it often takes with
it sediment from the glacier bedrock, washing it out as
well. This leads to the appearance of what are called “meltwater
plumes” in the ocean near glaciers, areas of water with
significantly different coloration due to high levels of sediment
concentration.
So
far, such plumes have not been observed around East Antarctica,
Jamieson said.
Still,
the lakes, and especially the apparent drainage events, raise a
distinct worry about the future of Antarctica, which contains vastly
more ice than Greenland and which, thus far, has not been losing
nearly as much. “The parallels between these mechanisms, and those
observed on Greenland/the Antarctic Peninsula, suggest that lakes may
similarly affect rates and patterns of ice melt, ice flow and ice
shelf disintegration in East Antarctica,” the study concludes.
Richard
Alley, a glaciologist at Penn State who was not involved in the
study, noted in an email comment that seeing some Antarctic surface
melt is not too surprising. “Across many sensors and studies, there
is summertime melting on the surface of Antarctica around the edges,
and sometimes in some places extending farther inland than you might
think,” he said.
However,
Alley continued, we should be very concerned about such melting
increasing. Alley referred to a study from
earlier this year, by Rob DeConto of the University of Massachusetts,
Amherst, and David Pollard of Penn State, which found that surface
melt is one factor that could greatly speed total Antarctic ice loss,
by increasing the tendency for “hydrofracture” to occur, in which
meltwater helps to break apart ice shelves.
“The
lesson of DeConto and Pollard was that, based on current
understanding, avoiding a major expansion of surface melting in
Antarctica is taking out insurance against a very large and rapid
sea-level rise,” Alley said. “This new work is part of the body
of science needed to help us learn just how much warming may be too
much if we wish to avoid large and rapid sea-level rise.”
For
now, scientists plan to use the instruments available — mainly, at
the moment, satellites — to further study the Antarctic lakes.
“It’s
not hitting the glacier really hard at the moment, this process, but
of course, as things warm up, we’d expect it to start doing more
damage, like we see in Greenland,” said Jamieson.
The Looming Extinction of Humankind, Explained
For
most people, driving with a seat belt tightly strapped around their
bodies is a smart habit. Not only is racing down the highway without
it illegal—“click it or ticket,” as the slogan goes—but seat
belts also “reduce serious crash-related injuries and deaths by
about half.” Yet as we've previously estimated, your chances of
dying in a car crash are at least 9.5 times lower than dying in a
human extinction event.
If
this sounds incredible—and admittedly, it does—it’s because the
human mind is susceptible to cognitive biases that distort our
understanding of reality. Consider the fact that you’re more likely
to be killed by a meteorite than a lightning bolt, and your chances
of being struck by lightning are about four times greater than dying
in a terrorist attack. In other words, you should be more worried
about meteorites than the Islamic State or al-Qaeda (at least for
now).
A
changing climate means less rain and lower water supplies in regions
where many people live and much of the planet’s food is produced:
the mid-latitudes of the Northern and Southern hemispheres, including
the U.S. Southwest, southern Europe and parts of the Middle East,
southern Africa, Australia and Chile. As WRI-Aqueduct’s future
scenarios for water supply show, diminished water supplies will be
apparent in these areas by 2020 — less than four years away — and
are expected to grow worse by 2030 and 2040.
Now
a new
study in the journal Nature provides
some of the first evidence that this widely-predicted phenomenon —
the movement of clouds and rainfall from the mid-latitudes towards
the North and South poles — is already taking place. Just like the
retreat of glaciers and polar sea ice, now clouds and rain are
retreating poleward.
Arctic Sea Ice Minimum Volumes 1979-2015
This
is an animated visualization of the startling decline of Arctic Sea
Ice, showing the minimum volume reached every September since 1979,
set on a map of New York with a 10km grid to give an idea of scale.
It is clear that the trend of Arctic sea ice decline indicates that
it'll be ice-free for an increasingly large part of the year, with
consequences for the climate.
The
rate of ice loss in the Arctic is staggering. Since 1979, the volume
of Summer Arctic sea ice has declined by more than 80% and
accelerating faster than scientists believed it would, or even could
melt.
Based
on the rate of change of volume over the last 30 years, I expect the
first ice-free summer day in the Arctic Ocean (defined as having less
than 1 million km² of sea ice) to happen between 2016 and 2022, and
thereafter occur more regularly with the trend of ice-free duration
extending into August and October.
Here
is some hopeful researc on methane – hopeful, that is, if you see
things isolation, rather than take a system approach
Rethinking
Methane In the Arctic
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