Greenland's
melting ice raised global sea level by 2.2mm in two months
Analysis of
satellite data reveals astounding loss of 600bn tons of ice last summer as
Arctic experienced hottest year on record
Oliver
Milman
@olliemilman
Thu 19 Mar
2020 08.00 GMTLast modified on Thu 19 Mar 2020 13.43 GMT
Last year’s
summer was so warm that it helped trigger the loss of 600bn tons of ice from
Greenland – enough to raise global sea levels by 2.2mm in just two months, new
research has found.
The
analysis of satellite data has revealed the astounding loss of ice in just a
few months of abnormally high temperatures around the northern pole. Last year
was the hottest on record for the Arctic, with the annual minimum extent of sea
ice in the region its second-lowest on record.
Unlike the
retreat of sea ice, the loss of land-based glaciers directly causes the seas to
rise, imperiling coastal cities and towns around the world. Scientists have
calculated that Greenland’s enormous ice sheet lost an average of 268bn tons of
ice between 2002 and 2019 – less than half of what was shed last summer. By
contrast, Los Angeles county, which has more than 10 million residents, consumes
1bn tons of water a year.
“We knew
this past summer had been particularly warm in Greenland, melting every corner
of the ice sheet, but the numbers are enormous,” said Isabella Velicogna, a
professor of Earth system science at University of California Irvine and lead
author of the new study, which drew upon measurements taken by Nasa’s Gravity
Recovery and Climate Experiment (Grace) satellite mission and its upgraded
successor, Grace Follow-On.
Glaciers
are melting away around the world due to global heating caused by the
human-induced climate crisis. Ice is reflective of sunlight so as it retreats
the dark surfaces underneath absorb yet more heat, causing a further
acceleration in melting.
Ice is
being lost from Greenland seven times faster than it was in the 1990s,
scientists revealed last year, pushing up previous estimates of global sea
level rise and putting 400 million people at risk of flooding every year by the
end of the century.
More recent
research has found that Antarctica, the largest ice sheet on Earth, is also
losing mass at a galloping rate, although the latest University of California
and Nasa works reveals a nuanced picture.
“In Antarctica, the mass loss in the west
proceeds unabated, which is very bad news for sea level rise,” Velicogna said.
“But we also observe a mass gain in the Atlantic sector of east Antarctica
caused by an increase in snowfall, which helps mitigate the enormous increase
in mass loss that we’ve seen in the last two decades in other parts of the
continent.”
The
research has further illustrated the existential dangers posed by runaway
global heating, even as the world’s attention is gripped by the coronavirus
crisis. Crucial climate talks are set to be held later this year in Glasgow,
although the wave of cancellations triggered by the virus has threatened to
undermine this diplomatic effort.
“The
technical brilliance involved in weighing the ice sheets using satellites in
space is just amazing,” said Richard Alley, a glaciologist at Penn State
University who was not involved in the study.
“It is easy
for us to be distracted by fluctuations, so the highly reliable long data sets
from Grace and other sensors are important in clarifying what is really going
on, showing us both the big signal and the wiggles that help us understand the
processes that contribute to the big signal.”
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