SEA LEVEL
RISE
Greenland and Antarctica Already Melting at
'Worst-Case-Scenario' Rates
Olivia Rosane Sep. 03, 2020 11:49AM EST
Antarctica
and Greenland's ice sheets are currently melting at a pace consistent with
worst-case-scenario predictions for sea level rise, with serious consequences
for coastal communities and the reliability of climate models.
A paper
published in Nature Climate Change Monday compared the latest satellite
observations of polar ice melt with the predictions outlined in the
Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report. It
found that the ice sheets are currently raising sea levels at a rate 45 percent
above the IPCC's central prediction and closer to its worst-case scenario. If
this continues, the two ice sheets could raise sea levels a further 17
centimeters (approximately 7 inches) more than central predictions by 2100.
"If
ice sheet losses continue to track our worst-case climate warming scenarios we
should expect an additional 17cm of sea level rise from the ice sheets
alone," study coauthor and University of Leeds researcher Anna Hogg said
in a university press release. "That's enough to double the frequency of
storm-surge flooding in many of the world's largest coastal cities."
Since the
1990s, the two ice sheets have already increased global sea levels by 1.8
centimeters (approximately 0.7 inches). But it was between 2007 and 2017 that
the ice sheets began to lose mass at a rate consistent with worst-case-scenario
projections, adding around 1.23 centimeters (approximately 0.5 inches) to the
water line during that decade, according to the study.
A
worst-case-scenario sea level rise as currently predicted would expose 44 to 66
million people to yearly coastal flooding by century's end. But one of study's
most alarming implications is that, if sea level rise is already tracking
worst-case-scenario predictions, the actual worst-case scenario could be even
more dire.
"We
need to come up with a new worst-case scenario for the ice sheets because they
are already melting at a rate in line with our current one," lead author
and Centre for Polar Observation and Modelling (CPOM) at the University of
Leeds researcher Thomas Slater told AFP. "Sea level projections are
critical in helping governments plan climate policy, mitigation and adaptation
strategies. If we underestimate future sea level rise, then these measures may
be inadequate and leave coastal communities vulnerable."
One of the
reasons climate models might underestimate the worst-case scenario, Slater told
AFP, is that they do not account for short-term weather changes such as the
heat wave that drove Greenland's record melt in the summer of 2019.
The models
that will be used for the IPCC's next report are better at predicting how the
ice sheets, oceans and atmosphere interact, Slater said.
The latest
study follows a slew of bad news for the world's ice. One study published in
August found that the Greenland ice sheet had passed the "point of no
return" and would continue to melt even if the climate crisis were halted.
Another
recent study, also driven by Leeds' CPOM, calculated that the earth had lost 28
trillion tonnes (approximately 31 trillion U.S. tons) of ice in just 23 years.
These
studies reflect a new global reality: In the last five years, melt from ice
sheets and glaciers has outpaced the expansion of warming ocean water as the
main cause of sea level rise.
"It is
not only Antarctica and Greenland that are causing the water to rise," Dr.
Ruth Mottram, a coauthor on Monday's study and a climate researcher at the
Danish Meteorological Institute, told the University of Leeds. "In recent
years, thousands of smaller glaciers have begun to melt or disappear altogether,
as we saw with the glacier Ok in Iceland, which was declared 'dead' in 2014.
This means that melting of ice has now taken over as the main contributor of
sea level rise."
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