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Global sea level fingerprints reveal climate change effects

Sea level fingerprints (patterns of variation in sea level rise) calculated from GRACE satellite observations, 2002-2014. The blue contour (1.8 millimeters per year) shows the average sea level rise if all the water added to the ocean were spread uniformly around Earth. Credits: NASA/UCI

Climate change and its effects have grabbed eyeballs of many researchers for past many years. However, with frequent natural calamities, global warming, seasonal change, etc., this trend has gained more momentum. In one such study conducted by NASA’s Jet Propulsion Laboratory in Pasadena, California and the University of California, Irvine, has reported the first detection of sea level fingerprints in ocean observations.

The study reveals that various patterns of sea level can be detected around the world resulting from changes in water storage on Earth’s continents and in the mass of ice sheets. This is a massive revelation as the data gives scientists the power to determine how much the sea level will increase at any point in the global ocean as a result of glacier ice melt.

What is sea level fingerprints?

The global warming is playing havoc on the ice sheets and glaciers. As they are melting away, they are also altering 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, says the study. 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% greater than its average effect on the rest of the world.

Sea level rise fingerprints calculated from observations of mass changes in Greenland, Antarctica, continental glaciers and ice caps, and land water storage made by the GRACE satellites, January 2003 to April 2014. Credits: NASA/UCI

How to calculate sea level fingerprints?

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 US/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% of the increased water mass coming from Greenland, 16% from Antarctica and 30% 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 in the journal Geophysical Research Letters. The research project was supported by UCI and NASA’s Earth Science Division.

Also Read: Climate change impact on sea-ice cover in Arctic & Antarctic

NASA explains why Greenland glaciers are melting so fast