A new survey finds that the region has contributed almost an inch to rising seas since 1971.
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| A melting iceberg floats along a fjord leading away from the edge of the Greenland ice sheet near Nuuk, Greenland, in 2011. (Brennan Linsley/AP) |
A new scientific survey
has found that the glaciers of the Arctic are the world’s biggest
contributors to rising seas, shedding ice at an accelerating rate that
now adds well over a millimeter to the level of the ocean every year.
That
is considerably more ice melt than Antarctica is contributing, even
though the Antarctic contains far more ice. Still, driven by glacier
clusters in Alaska, Canada and Russia and the vast ice sheet of
Greenland, the fast-warming Arctic is outstripping the entire ice
continent to the south — for now.
However, the
biggest problem is that both ice regions appear to be accelerating their
losses simultaneously — suggesting that we could be in for an even
faster rate of sea-level rise in future decades. Seas are rising by
about three millimeters each year, according to NASA. That’s mainly
driven by the Arctic contribution, the Antarctic and a third major
factor — that ocean water naturally expands as it warms.
For
Arctic ice loss, “the rate has tripled since 1986,” said Jason Box,
first author of the new study and a scientist at the Geological Survey
of Denmark and Greenland. “So it clearly shows an acceleration of the
sea-level contribution.”
“Antarctica will
probably take over at some point in the future, but during the past 47
years of this study, it’s not controversial that the Arctic is the
largest contribution of land ice to sea-level rise,” he said.
Scientists
in the United States, Chile, Canada, Norway and the Netherlands
contributed to the work, published in Environmental Research Letters.
The Arctic is also losing floating sea ice at a rapid pace,
but that loss does not contribute substantially to rising seas (though
it has many other consequences). Sea ice losses closely match what is
happening on land, which makes sense because both phenomena are being
driven by the fast warming of the atmosphere in the Arctic, which has
heated up at a rate much faster than seen in lower latitudes. Warming
seas are also driving some of the ice loss.
Here’s the new study’s tally of where all the Arctic ice loss has come from since 1971:
The research was performed by merging a highly
reliable gravity-based measurement of Arctic mass loss from NASA’s
Gravity Recovery and Climate Experiment (GRACE) satellites with older
direct ice measurements, taken from the field, going back to 1971.
The
total Arctic loss at present is 447 billion tons of ice per year —
which Box calculated is about 14,000 tons of water per second. That’s
for the period between 2005 and 2015. Between 1986 and 2005, the loss is
calculated at around 5,000 tons per second — therefore, the rate has
almost tripled.
Separate research has recently found that the Antarctic’s loss rate has also tripled in just a decade, reaching 219 billion tons per year from 2012 to 2017.
Assuming
these numbers are correct and summing them together, the world’s polar
regions are losing about 666 billion tons of ice to the ocean each year —
amounting to a little bit less than two millimeters of sea-level rise
annually.
Treating the Arctic as a whole can
miss something, though, notes Christopher Larsen, a glacier expert at
the University of Alaska at Fairbanks.
Namely,
the Arctic acceleration documented in the study is really being driven
by Greenland, which contains more than 20 feet of potential sea-level
rise, dwarfing all other Arctic ice sources.
“With
respect to the present rate of ice mass loss, and the increasing rates
thereof, it is Greenland that has the most significant rate of increased
mass loss in the present day,” Larsen said in an email.
“This
is especially noteworthy as ultimately Greenland has the most ice to
lose in the Northern Hemisphere,” he said. “As rapid as ice loss is now
or may become anywhere in the north, the regional totals of ice mass
within Alaska or the Arctic Canada are smaller than what Greenland
holds.”
To give a sense of the scale of the
Arctic losses, Box imagined what it would mean if they were distributed
among Earth’s human population.
“If you take
the 7.7 billion people on Earth and divide the present-day numbers, from
2005 to 2015, each person on Earth would have the equivalent of 160
liters per day, every day, every year,” Box said.
Links
- The Arctic Ocean has lost 95 percent of its oldest ice — a startling sign of what’s to come
- Antarctic ice loss has tripled in a decade. If that continues, we are in serious trouble.
- Global sea-level contribution from Arctic land ice: 1971–2017
- A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat
- Unprecedented U.S.-British project launches to study the world’s most dangerous glacier
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