Using NASA space lasers, scientists have tracked how ice sheets in Greenland and the Antarctic have changed over the last 16 years, showing the drastic effects of climate change (opens in new tab).
The research relied on observations from NASA's Ice, Cloud and Land Elevation Satellite (ICESat), which launched in 2003, and its successor ICESat-2 (opens in new tab), which launched in 2018 as one of the most advanced Earth-observing laser instruments. Using that data, scientists have shown that, while ice has increased a tiny amount in East Antarctica, West Antarctica has lost an enormous amount of ice.
This study revealed that Greenland's ice sheet lost an average of 200 gigatons of ice per year while Antarctica's lost an average of 118 gigatons of ice per year. For reference, one gigaton of ice can fill 400,000 Olympic-sized swimming pools, according to a NASA statement (opens in new tab). The combined ice loss in Greenland and Antarctica has lifted sea levels by 0.55 inches (14 millimeters) between 2003 and 2019.
Related: The effects of global warming (opens in new tab)
"If you watch a glacier or ice sheet for a month, or a year, you're not going to learn much about what the climate is doing to it," Ben Smith, a glaciologist at the University of Washington and lead author of this new paper, said in the same statement. "We now have a 16-year span between ICESat and ICESat-2 and can be much more confident that the changes we're seeing in the ice have to do with the long-term changes in the climate."
To come to this conclusion, the researchers overlaid measurements gathered by ICESat between 2003 and 2009 with more recent ones that ICESat-2 took in 2019. They used data from tens of millions of different points where the two datasets met and, by comparing the two sets, they were able to see how much the elevation had changed.
The scientists in this study also developed a new model to calculate density across ice sheets, which allowed them to calculate total ice-sheet mass and therefore total mass loss.
ICESat-2, like its predecessor, is a laser altimeter. It sends 10,000 pulses of light per second down to Earth. These beams bounce right back to the satellite. The satellite is so precise that it can show how Earth's surface changes down to an inch.
This work shows exactly how climate change is affecting these ice sheets, which in turn affects sea levels. Although snowfall in certain parts of Antarctica has increased, causing the ice sheet to thicken, this gain is far outweighed by the extreme loss in ice caused by a warming ocean, according to the statement.
"The new analysis reveals the ice sheets' response to changes in climate with unprecedented detail, revealing clues as to why and how the ice sheets are reacting the way they are," Alex Gardner, a glaciologist at NASA's Jet Propulsion Laboratory in California and co-author on the paper, said in the statement.
These findings were published April 30 to the journal Science.
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