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<header class="css-d92687">VOOR DE DIPSHIT WEGKIJKER
FLUKS:<br>
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<p class="text-uppercase text-low"> August 13, 2020 </p>
<h1 class="text-extra-large line-low mb-2">Warming
Greenland ice sheet passes point of no return</h1>
<p class="article-byline text-low"> by Laura
Arenschield, <a class="article-byline__link"
href="http://www.osu.edu" target="_blank">The Ohio
State University</a> </p>
<div class="css-1x1jxeu">
<div class="css-7kp13n">By</div>
<div class="css-7ol5x1"><span class="css-1q5ec3n">Laura
Arenschield</span></div>
<div class="css-8rl9b7">phys.org</div>
<div class="css-zskk6u">4 min</div>
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<figure> <img
src="https://pocket-image-cache.com//filters:no_upscale()/https%3A%2F%2Fscx1.b-cdn.net%2Fcsz%2Fnews%2F800%2F2020%2Fwarminggreen.jpg"
alt=""> </figure>
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<figcaption>Icebergs near Greenland form
from ice that has broken off--or
calved--from glaciers on the island. A
new study shows that the glaciers are
losing ice rapidly enough that, even
if global warming were to stop,
Greenland's glaciers would continue to
shrink. Credit: Michalea King</figcaption></figure>
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<p>Nearly 40 years of satellite data from
Greenland shows that glaciers on the island
have shrunk so much that even if global
warming were to stop today, the ice sheet
would continue shrinking.</p>
<section> </section>
<p>The finding, published today, Aug. 13, in
the journal <i>Nature Communications Earth
and Environment</i>, means that
Greenland's glaciers have passed a tipping
point of sorts, where the snowfall that
replenishes the <a rel="tag"
href="https://phys.org/tags/ice+sheet/">ice
sheet</a> each year cannot keep up with
the ice that is flowing into the ocean from
glaciers.</p>
<p>"We've been looking at these remote sensing
observations to study how ice discharge and
accumulation have varied," said Michalea
King, lead author of the study and a
researcher at The Ohio State University's
Byrd Polar and Climate Research Center. "And
what we've found is that the ice that's
discharging into the ocean is far surpassing
the snow that's accumulating on the surface
of the ice sheet."</p>
<p>King and other researchers analyzed monthly
satellite data from more than 200 large
glaciers draining into the ocean around
Greenland. Their observations show how much
ice breaks off into icebergs or melts from
the glaciers into the ocean. They also show
the amount of snowfall each year—the way
these glaciers get replenished.</p>
<p>The researchers found that, throughout the
1980s and 90s, snow gained through
accumulation and ice melted or calved from
glaciers were mostly in balance, keeping the
ice sheet intact. Through those decades, the
researchers found, the ice sheets generally
lost about 450 gigatons (about 450 billion
tons) of ice each year from flowing outlet
glaciers, which was replaced with snowfall.</p>
<p>"We are measuring the pulse of the ice
sheet—how much ice glaciers drain at the
edges of the ice sheet—which increases in
the summer. And what we see is that it was
relatively steady until a big increase in
ice discharging to the ocean during a short
five- to six-year period," King said.</p>
<p>The researchers' analysis found that the
baseline of that pulse—the amount of ice
being lost each year—started increasing
steadily around 2000, so that the glaciers
were losing about 500 gigatons each year.
Snowfall did not increase at the same time,
and over the last decade, the rate of ice
loss from glaciers has stayed about the
same—meaning the ice sheet has been losing
ice more rapidly than it's being
replenished.</p>
<p>"Glaciers have been sensitive to seasonal
melt for as long as we've been able to
observe it, with spikes in ice discharge in
the summer," she said. "But starting in
2000, you start superimposing that seasonal
melt on a higher baseline—so you're going to
get even more losses."</p>
<p>Before 2000, the ice sheet would have about
the same chance to gain or lose mass each
year. In the current climate, the ice sheet
will gain mass in only one out of every 100
years.</p>
<p>King said that large glaciers across
Greenland have retreated about 3 kilometers
on average since 1985—"that's a lot of
distance," she said. The glaciers have
shrunk back enough that many of them are
sitting in deeper water, meaning more ice is
in contact with water. Warm ocean water
melts glacier ice, and also makes it
difficult for the glaciers to grow back to
their previous positions.</p>
<p>That means that even if humans were somehow
miraculously able to stop climate change in
its tracks, ice lost from glaciers draining
ice to the <a rel="tag"
href="https://phys.org/tags/ocean/">ocean</a>
would likely still exceed ice gained from
snow accumulation, and the ice sheet would
continue to shrink for some time.</p>
<p>"Glacier retreat has knocked the dynamics
of the whole ice sheet into a constant state
of loss," said Ian Howat, a co-author on the
paper, professor of earth sciences and
distinguished university scholar at Ohio
State. "Even if the climate were to stay the
same or even get a little colder, the ice
sheet would still be losing mass."</p>
<p>Shrinking <a rel="tag"
href="https://phys.org/tags/glaciers/">glaciers</a>
in Greenland are a problem for the entire
planet. The ice that melts or breaks off
from Greenland's ice sheets ends up in the
Atlantic Ocean—and, eventually, all of the
world's oceans. Ice from Greenland is a
leading contributor to sea level rise—last
year, enough ice melted or broke off from
the Greenland ice sheet to cause the oceans
to rise by 2.2 millimeters in just two
months.</p>
<p>The new findings are bleak, but King said
there are silver linings.</p>
<p>"It's always a positive thing to learn more
about glacier environments, because we can
only improve our predictions for how rapidly
things will change in the future," she said.
"And that can only help us with adaptation
and mitigation strategies. The more we know,
the better we can prepare."</p>
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