NASA/UCI Find Evidence of Sea Level ‘Fingerprints’

New research will aid in sea level projections

Researchers from NASA’s Jet Propulsion Laboratory in Pasadena,
California, and the University of California, Irvine, have
reported the first detection of sea level “fingerprints” in
ocean observations: detectable patterns of sea level
variability around the world resulting from changes in water
storage on Earth’s continents and in the mass of ice sheets.
The results will give scientists confidence they can use these
data to determine how much the sea level will rise at any point
on the global ocean as a result of glacier ice melt.

As ice sheets and glaciers undergo climate-related melting,
they alter Earth’s gravity field, resulting in sea level
changes that aren’t uniform around the globe. For example, when
a glacier loses ice mass, its gravitational attraction is
reduced. Ocean waters nearby move away, causing sea level to
rise faster far away from the glacier. The resulting pattern of
sea level change is known as a sea level fingerprint. Certain
regions, particularly in Earth’s middle and low latitudes, are
hit harder, and Greenland and Antarctica contribute differently
to the process. For instance, sea level rise in California and
Florida generated by the melting of the Antarctic ice sheet is
up to 52 percent greater than its average effect on the rest of
the world.

To calculate sea level fingerprints associated with the loss of
ice from glaciers and ice sheets and from changes in land water
storage, the team used gravity data collected by the twin
satellites of the U.S./German Gravity Recovery and Climate
Experiment (GRACE) between April 2002 and October 2014. During
that time, the loss of mass from land ice and from changes in
land water storage increased global average sea level by about
0.07 inch (1.8 millimeters) per year, with 43 percent of the
increased water mass coming from Greenland, 16 percent from
Antarctica and 30 percent from mountain glaciers. The
scientists then verified their calculations of sea level
fingerprints using readings of ocean-bottom pressure from
stations in the tropics.

“Scientists have a solid understanding of the physics of sea
level fingerprints, but we’ve never had a direct detection of
the phenomenon until now,” said co-author Isabella Velicogna,
UCI professor of Earth system science and JPL research
scientist.

“It was very exciting to observe the sea level fingerprints in
the tropics, far from the glaciers and ice sheets,” said lead
author Chia-Wei Hsu, a graduate student researcher at UCI.

The findings are published today in the journal Geophysical
Research Letters. The research project was supported by UCI and
NASA’s Earth Science Division.

GRACE is a joint NASA mission with the German Aerospace Center
(DLR) and the German Research Center for Geosciences (GFZ), in
partnership with the University of Texas at Austin. For more
information on NASA’s GRACE mission, visit:

https://grace.jpl.nasa.gov/

News Media Contact

Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
Alan.buis@jpl.nasa.gov

Brian Bell
UC Irvine
949-824-8249
bpbell@uci.edu

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