Date: May 16, 2019
Source: University of Leeds
Summary: In only 25 years,
ocean melting has caused ice thinning to spread across West Antarctica so
rapidly that a quarter of its glacier ice is now affected, according to a new
study.
By combining 25 years of
European Space Agency satellite altimeter measurements and a model of the
regional climate, the UK Centre for Polar Observation and Modelling (CPOM) have
tracked changes in snow and ice cover across the continent.
A team of researchers, led by
Professor Andy Shepherd from the University of Leeds, found that Antarctica's
ice sheet has thinned by up to 122 metres in places, with the most rapid
changes occurring in West Antarctica where ocean melting has triggered glacier
imbalance.
This means that the affected
glaciers are unstable as they are losing more mass through melting and iceberg
calving than they are gaining through snowfall.
The team found that the
pattern of glacier thinning has not been static. Since 1992, the thinning has
spread across 24% of West Antarctica and over the majority of its largest ice
streams -- the Pine Island and Thwaites Glaciers -- which are now losing ice
five times faster than they were at the start of the survey.
The study, published today
in Geophysical Research Letters, used over 800 million measurements of the
Antarctic ice sheet height recorded by the ERS-1, ERS-2, Envisat, and CryoSat-2
satellite altimeter missions between 1992 and 2017 and simulations of snowfall
over the same period produced by the RACMO regional climate model.
Together, these measurements
allow changes in the ice sheet height to be separated into those due to weather
patterns, such as less snowfall, and those due to longer term changes in
climate, such as increasing ocean temperatures that eat away ice.
Lead author and CPOM Director
Professor Andy Shepherd explained: "In parts of Antarctica the ice sheet
has thinned by extraordinary amounts, and so we set out to show how much was
due to changes in climate and how much was due to weather."
To do this, the team compared
the measured surface height change to the simulated changes in snowfall, and
where the discrepancy was greater they attributed its origin to glacier
imbalance.
They found that fluctuations
in snowfall tend to drive small changes in height over large areas for a few
years at a time, but the most pronounced changes in ice thickness are signals
of glacier imbalance that have persisted for decades.
Professor Shepherd added:
"Knowing how much snow has fallen has really helped us to detect the
underlying change in glacier ice within the satellite record. We can see
clearly now that a wave of
thinning has spread rapidly
across some of Antarctica's most vulnerable glaciers, and their losses are
driving up sea levels around the planet.
"Altogether, ice losses
from East and West Antarctica have contributed 4.6 mm to global sea level rise
since 1992."
Dr Marcus Engdahl of the
European Space Agency, a co-author of the study, added: "This is an
important demonstration of how satellite missions can help us to understand how
our planet is changing. The polar regions are hostile environments and are
extremely difficult to access from the ground. Because of this, the view from
space is an essential tool for tracking the effects of climate change."
Story Source:
Materials provided by University of Leeds. Note:
Content may be edited for style and length.
Journal Reference:
Andrew Shepherd, Lin Gilbert,
Alan S. Muir, Hannes Konrad, Malcolm McMillan, Thomas Slater, Kate H. Briggs,
Aud V. Sundal, Anna E. Hogg, Marcus Engdahl. Trends in Antarctic Ice Sheet
Elevation and Mass. Geophysical Research Letters, May 16, 2019; DOI: 10.1029/2019GL082182
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