In just 16 years, Antarctica and Greenland have lost enough ice to fill Lake Michigan
Antarctica and Greenland have lost thousands of gigatons of ice in the last 16 years alone. According to new data from NASA, that ice melt has contributed to more than half an inch of sea level rise around the world.
Collectively, Antarctica and Greenland lost more than 5,000 gigatons of ice over the last decade and a half — more than enough to fill Lake Michigan. One gigaton is the equivalent of one billion metric tons, which could fill 400,000 Olympic-sized swimming pools alone, NASA said in a press release.
According to a paper published Thursday in the journal Science, the two regions have collectively been responsible for .55 inches of sea level rise between 2003 and 2019 — roughly a third of total global sea level rise during that time.
The data come from NASA's Ice, Cloud and land Elevation Satellite 2 (ICESat-2). Launched in 2018, it is the "most advanced Earth-observing laser instrument NASA has ever flown in space," in combination with data from its predecessor, ICESat, which gathered data from 2003 to 2009.
"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," said Ben Smith, a glaciologist at the University of Washington and lead author of the paper. "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."
According to the data, per year, Greenland's ice sheet lost an average of 200 gigatons of ice, and Antarctica's lost an average of 118.
Using information from both missions, researchers found not only the amount of ice melted but one of the major causes. Ice shelves around Antarctica act as barriers to slow the rate of ice loss — they don't contribute to sea level rise because they are already floating — but, as those barriers melt into warming oceans, the rate of ice loss increases.
"It's like an architectural buttress that holds up a cathedral," said Helen Amanda Fricker, co-author and glaciologist at Scripps Institution of Oceanography at the University of California San Diego. "The ice shelves hold the ice sheet up. If you take away the ice shelves, or even if you thin them, you're reducing that buttressing force, so the grounded ice can flow faster."
While a significant amount of Antarctica's ice loss came from floating ice shelves, through iceberg calving and melting from warm water, the majority of Greenland's loss was due to surface melting and runoff. In Greenland, coastal glaciers have thinned dramatically, mostly due to warmer summer temperatures.
NASA's new data is consistent with previous studies on sea levels rise, but the satellites' lasers give researchers a much more detailed analysis of how polar ice is changing over time. While East Antarctica has actually seen a small uptick in its amount of ice, that improvement has been far outweighed by the huge losses in West Antarctica, where the ocean has rapidly warmed.
"The rise in a single year is in itself not concerning," Alex Gardner, co-author and glaciologist at NASA's Jet Propulsion Laboratory, told CBS News on Friday. "What is concerning is that this will continue every year for the foreseeable future, adding up to considerable sea level rise over the next 80 years. By 2100 we are expecting 2,3, or maybe 4 feet of sea level rise."
Rising sea levels are expected to affect millions of people living in coastal cities around the world.
"This matters because civilization has evolved around coastal cities where considerable infrastructure is located near present sea levels," Gardner continued. "When there is a high-tide event or passing storm they can cause considerable damage to property. These damages will be greatly amplified as sea level continues to rise and will require municipalities and counties to make hard choices about what infrastructure to invest in to try and save and what infrastructure should be abandoned."
