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Global sea level rise on faster pace than expected

Dr. Mario Picazo
Meteorologist, PhD

Tuesday, June 5, 2018, 11:23 -

Editor's note: This article was originally published in February of 2018

A recent study based on 25 years of NASA and European satellite data shows how sea level rise on earth is increasing faster than originally thought. Water levels have been going up by accelerating incrementally in recent decades, rather than in the steady mode past studies had suggested.

Global warming and consequently the rapid ice melt occurring in both Greenland and Antarctica, are responsible for this acceleration. The research project that has brought light to this new finding is led by Steve Nerem, a professor of aerospace engineering science at the University of Colorado Boulder, fellow at the Institute for Research in Environmental Sciences (CIRES), and a member of NASA´s Sea Level Change team.

Professor Nerem's team suggests that with water levels rising at the accelerated rate seen, sea level rise projected for 2100 could be double compared to past projected scenarios that assumed a fairly constant rate increase.

Image courtesy of NASA. Global sea level rise since 1880 when records began.

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Sea level rise is caused by both the expansion of warming waters and the melting of continental ice sheets and glaciers. Of the 2.8 inch sea level rise measured during the past 25 years, 55% can be attributed to water expansion and the other 45% to melting ice. Satellite data used in this study also shows that more than three quarters of the acceleration since 1993 is a result of melting ice sheets in both Antarctica and Greenland.  

Watch below: Greenland ice loss 2002-2016

The rate of sea level rise in the satellite era has risen from about 0.1 inch (2.5 millimeters) per year in the 1990s to about 0.13 inches (3.4 millimeters) per year today. But even with 25 years of data, detecting sea level rise acceleration is not an easy task. Climate variability can make it more challenging -- for example during a major volcanic eruption like Pinatubo in 1991 which decreased the global mean sea level, or with other phenomena like El Niño and La Niña in the Pacific, which can also cause global sea level fluctuation.

Watch below: Greenland ice loss 2002-2016

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Nerem and his team have used different climate models to simulate the effects of major volcanic eruptions, as well as other datasets to determine the impact of El Niño and La Niña on sea level. This together with tide gauge data to assess potential errors in the altimeter estimate, has been key to come up with the underlying rate and acceleration of sea level rise over the last quarter century.

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Past data shows that sea levels had been stable for about 3,000 years until the 20th century, then they began to rise as a result of global warming caused by an increase in the burning of fossil fuels.  "Our results are almost certainly a conservative estimate," Nerem said. "The extrapolation used assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."

"If sea levels do rise another two feet by the end of the century the effects would be quite noticeable in cities like Miami or New Orleans, But I don't I don´t still view that as catastrophic" because those cities can survive at great expense added Nerem.

In 2018, NASA will launch two new satellite missions that will be critical to improving future sea level projections: the Gravity Recovery and Climate (GRACE-FO), will continue measurements of the mass of the Greenland and Antarctic ice sheets; while the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) will make highly accurate observations of the elevation of ice sheets and glaciers.

WATCH BELOW: Sea level rise accelerates over time

Sources: NASA | PNAS

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