Greenland Ice Sheet. Credit: Prof Andrew
Shepherd
Academics
from Northumbria University are part of an international research team which
has used data from satellites to track changes in the thickness of the
Greenland Ice Sheet.
Global warming is causing the Ice Sheet
to melt and flow more rapidly, raising sea levels and disturbing weather
patterns across our planet. Because of this, precise measurements of its
changing shape are of critical importance for tracking and adapting to the
effects of climate warming.
Scientists have now delivered the first
measurements of Greenland Ice Sheet thickness change using CryoSat-2 and
ICESat-2—the ESA and NASA ice satellite missions. Both satellites carry
altimeters as their primary sensor, but they make use of different technologies
to collect their measurements. CryoSat-2 carries a radar system to determine the Earth's surface height, while
ICESat-2 has a laser system for the same task.
Although radar signals can pass through
clouds, they also penetrate into the ice sheet surface and have to be adjusted for this effect.
Laser signals, on the other hand, reflect from the actual surface, but they
cannot operate when clouds are present. The missions are therefore highly
complementary, and combining their measurements has been a holy grail for polar
science.
A study by scientists at the UK Center for Polar Observation and Modeling (CPOM), based at Northumbria University, and published in Geophysical Research Letters shows that CryoSat-2 and ICESat-2 measurements of Greenland Ice Sheet elevation change agree to within 3%.
Animation showing where the Greenland Ice Sheet
is thinning using data from two satellites. Credit: Center for Polar
Observation and Modeling, Northumbria University
This confirms that the satellites
can be combined to produce a more reliable estimate of ice loss than either
could achieve alone. It also means that if one mission were to fail, the other
could be relied upon to maintain our record of polar ice change.
Between 2010 and 2023, the
Greenland Ice Sheet thinned by 1.2 meters on average. However, thinning across
the ice sheet's margin (the ablation zone) was over five times larger,
amounting to 6.4 meters on average.
The most extreme thinning occurred
at the ice sheets outlet glaciers, many of which are speeding up.
At Sermeq Kujalleq in west central
Greenland (also known as Jakobshavn Isbræ), peak thinning was 67 meters, and at
Zachariae Isstrøm in the northeast peak thinning was 75 meters. Altogether, the
ice sheet shrank by 2,347 cubic kilometers across the 13-year survey
period—enough to fill Africa's Lake Victoria.
The biggest changes occurred in
2012 and 2019 when summer temperatures were extremely hot and the ice sheet
lost more than 400 cubic kilometers of its volume each year.
Greenland's ice melting also
affects global ocean circulation and disturbs weather patterns. These changes
have far-reaching impacts on ecosystems and communities worldwide.
The availability of accurate,
up-to-date data on ice sheet changes will be critical in helping us to prepare
for and adapt to the impacts of climate change.
Lead author and CPOM researcher
Nitin Ravinder said, "We are very excited to have discovered that
CryoSat-2 and ICESat-2 are in such close agreement.
"Their complementary nature
provides a strong motivation to combine the data sets to produce improved
estimates of ice sheet volume and mass changes.
"As ice sheet mass loss is a
key contributor to global sea level rise, this is incredibly useful for the
scientific community and policymakers."
The
study made use of four years of measurements from both missions, including
those collected during the Cryo2ice campaign, a pioneering ESA-NASA partnership
initiated in 2020. By adjusting CryoSat-2's orbit to synchronize with ICESat-2,
ESA enabled the near-simultaneous collection of radar and laser data over the
same regions.
This alignment allows scientists to
measure snow depth from space, offering unprecedented accuracy in tracking sea
and land ice thickness.
Tommaso Parrinello, CryoSat Mission
Manager at ESA, expressed optimism about the campaign's impact, "CryoSat
has provided an invaluable platform for understanding our planet's ice coverage
over the past 14 years, but by aligning our data with ICESat-2, we've opened
new avenues for precision and insight.
"This collaboration represents an
exciting step forward, not just in terms of technology but in how we can better
serve scientists and policymakers who rely on our data to understand and
mitigate climate impacts."
Thorsten Markus, project scientist for
the ICESat-2 mission at NASA, said, "It is great to see that the data from
'sister missions' are providing a consistent picture of the changes going on in
Greenland.
"Understanding the similarities and
differences between radar and lidar ice sheet height measurements allows us to
fully exploit the complementary nature of those satellite missions.
"Studies like this are critical to
put a comprehensive time series of the ICESat, CryoSat-2, ICESat-2, and, in the
future, CRISTAL missions together."
ESA's CryoSat-2 continues to be
instrumental in our understanding of climate-related changes in polar ice,
working alongside NASA's ICESat-2 to provide robust, accurate data on ice sheet changes.
Together, these missions represent a
significant step forward in monitoring polar ice loss and preparing for its
global consequences.
CPOM is a partnership of six
universities and the British Antarctic Survey (BAS), based at Northumbria
University, with the aim of providing a national capability in observation and
modeling of the processes that occur in the polar regions of the Earth. CPOM
uses satellite observations to monitor change in the polar regions and
numerical models to better predict how their ice and oceans might evolve in the
future.
By providing long-term capabilities to the scientific community and leading international assessments, CPOM helps global policymakers plan for the effects of climate change and sea level rise.
Source: ESA and NASA satellites deliver first joint picture of Greenland Ice Sheet melting
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