Photographer: Jonathan Nackstrand / AFP via Getty Images
Photographer: Jonathan Nackstrand / AFP via Getty Images
Greenland broke its 2012 record for ice loss last year by 15%, a surprising sign that a major contribution to global sea level rise could be faster.
On its own, ice loss from the largest island in the world is responsible for more than 20% of sea level rise since 2005, according to new data released Thursday. This includes ice breaking off from the land and drifting and ice melting directly into the water. It is also about the same contribution as all other glaciers in the world combined.
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Another study on sea level rise Wednesday confirmed that conclusion. It also finds that another 40% of the rise since the oceans since 1993 can be attributed to rising temperatures, causing water to expand.
Taken together, the results are more important than just the community of scientists studying ice. Once that becomes water, it will embark on a journey that will lead it to New York Harbor, Miami Beach, Tokyo, Shanghai, London, and the other vulnerable coastal cities of the world as higher tide and greater flood risk.
The changes in Greenland’s ice formation “are surprisingly surprising,” said Thomas Frederikse, a NASA scientist, about the new data on ice loss. The Greenlandic study, of which he is known but was not a part, shows that “in 2019 alone Greenland caused as much sea level rise as was caused by all the processes combined in an average year in the 20th century,” he said.
Ingo Sasgen of the Alfred Wegener Institute and the lead author of the Greenland paper said he was surprised that the 2012 record was darkened in just seven years. The rates of melt were actually similar, he said, but 2019 saw less snowfall to compensate for the lost ice.
“I’m starting to get used to higher and higher rates of mass loss, which makes sense as the warming in the Arctic continues,” he said. “But apparently this is not a good thing, because this will ultimately mean that sea level rise is caused by the Greenland ice sheet.”
The data on last year’s ice loss was published Thursday by an international team in the journal Communication Earth and environment. The study bridges a gap between two NASA missions that include satellites that control the flow of water around the planet.
The Gravity Recovery and Climate Experiment launched in 2002 on a mission to map variations in the Earth’s gravity. It lasted until June 2017, well past its expected lifespan, and collected years of data on shrinking ice sheets and declining groundwater resources by picking up on minute gravity changes. A follow-up mission, GRACE-FO (for “Follow On”), launched in mid-2018, but left scientists there for almost a year without meaningful data.
Sasgen and his colleagues analyzed what happened in the 11 dark months between the loss of GRACE and the launch of GRACE-FO. They concluded that during the period saw an unusual decline in the rate of ice loss. From 2003 to 2016, Greenland emits approximately 255 billion metric tons (gigatons) of ice per year. Regional realities in 2017 and 2018 caused that loss percentage to fall by more than half, to about 100 GT a year, before returning to 532 GT in 2019.
Frederik from NASA led another study, published Wednesday in Nature, that presumably the amount of sea level rise scientists have observed with its sources going back to the year 1900. The work will allow scientists to have more confidence in their sea level rise estimates for the years and decades ahead, he said. The last time the Intergovernmental Panel on Climate Change published a major scientific assessment in 2013, the rate of sea level rise was a meddlesome question.
“This is one of the puzzle pieces that is still missing,” he said. “We can say with more confidence that we understand why sea levels have changed in the past.”
The next IPCC report is expected next year.
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