Ice Melt Linked to Accelerated Regional Freshwater Depletion
Continuous monitoring of glaciers and ice caps has provided unprecedented insights to global ice loss that could have serious socioeconomic impacts on some regions.
Seven of the regions that dominate global ice mass losses are
melting at an accelerated rate, a new study shows, and the quickened melt rate
is depleting freshwater resources that millions of people depend on.
The impact of melting ice in Greenland and Antarctica on
the world's oceans is well documented. But the largest contributors to sea
level rise in the 20th century were melting ice caps and glaciers located in
seven other regions: Alaska, the Canadian Arctic Archipelago, the Southern
Andes, High Mountain Asia, the Russian Arctic, Iceland and the Norwegian
archipelago Svalbard. The five Arctic regions accounted for the greatest share
of ice loss.
And this ice melt is accelerating, potentially affecting
not just coastlines but agriculture and drinking water supplies in communities
around the world, according to the study by scientists at NASA's Jet Propulsion
Laboratory; the University of California, Irvine; and the National Center for
Atmospheric Research in Boulder, Colorado. The study was led by Enrico Ciraci,
a UCI graduate student researcher in Earth system science.
"In the Andes Mountains in South America and in High Mountain
Asia, glacier melt is a major source of drinking water and irrigation for
several hundred million people," said study coauthor Isabella Velicogna, a
senior scientist at JPL and professor of Earth system science at UCI. "Stress
on this resource could have far-reaching effects on economic activity and
political stability."
The researchers based their work on data from the recently
decommissioned U.S.-German Gravity Recovery and Climate Experiment (GRACE) pair
of satellites that operated from 2002 to 2017, and their successor pair, GRACE Follow On
(launched in 2018). The researchers calculated that, on average, these seven
regions lost more than 280 billion tons of ice per year.
This interactive visualization of GRACE and GRACE-FO data shows changes in Earth's gravity from 2010 to 2020. These changes can help researchers track the redistribution of water from ice caps and glaciers to the oceans. Blue regions show an increase in water mass; red indicates water mass loss. View the full interactive at Eyes on the Earth Credit: JPL/Eyes
This ice loss contributed a
total of 13 millimeters (0.5 inches) in global sea level rise between 2002 and
2019, and the rate has increased from 0.7 millimeters (0.028 inches) per year
in 2002 to 0.9 millimeters (0.035 inches) per year in 2019.
As with GRACE, the GRACE-FO satellites continuously measure
very slight changes in Earth's gravitational pull as they orbit the Earth. Over
time, shifts in the distribution of water are the largest source of gravity
changes on the planet, so scientists can use the measurements of gravity change
to track variations in the mass of water as it cycles from the ice caps and
glaciers to the oceans.
GRACE was a joint mission of NASA and the German Aerospace
Center, in partnership with the University of Texas at Austin. GRACE-FO is a partnership
between NASA and the German Research Centre for Geosciences. When it launched
in May 2018, 11 months had passed since GRACE made its last measurements.
Velicogna and her coauthors closed the resulting data gap between
the end of GRACE and the initiation of GRACE-FO by using a state-of-the-art
modeling tool called Modern-Era Retrospective Analysis for Research and
Applications, Version 2 (MERRA-2) from NASA's Global Modeling and Assimilation
Office. MERRA-2 utilizes a host of independent observational datasets to boost
the precision of its estimates. For this study, the researchers noted how well
the MERRA-2 results lined up with the GRACE and GRACE-FO data, giving them a
high degree of confidence of what these satellites would have observed if one
or both were operating in the period of the data gap.
Having a record based on the long-term, precision
measurements of hundreds of thousands of the world's glaciers for over 18 years,
Velicogna said, significantly enhances our understanding of their evolution.
"This
paper demonstrates that GRACE-FO, in addition to GRACE, is providing precise,
reliable, worldwide observations of the fate of mountain glaciers, which are
not only important for understanding sea level change, but also for managing
our freshwater resources," she said.
The study, titled "Continuity of the Mass Loss of the
World's Glaciers and Ice Caps From the GRACE and GRACE Follow-On
Missions," was published April 30 in Geophysical Research Letters.
JPL managed the GRACE mission and manages the GRACE-FO
mission for NASA's Earth Science Division in the Science Mission Directorate at
NASA Headquarters in Washington. The California Institute of Technology (Caltech)
in Pasadena, California, manages JPL for NASA.
More information on GRACE and GRACE-FO can be found here:
https://www.nasa.gov/mission_pages/Grace/index.html
https://gracefo.jpl.nasa.gov/mission/overview/
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