Ice melting 4x faster than expected
For some time, scientists have worried about the rapidly rising sea level of the world’s oceans. It was believed that the main contributor to this increase was glaciers in southeast and northwest Greenland releasing large chunks of ice into the Atlantic Ocean. Now, a study published in the Proceedings of the National Academy of Sciences has found that the greatest quantity of ice lost since 2003 was from southwest Greenland, which does not have many glaciers and was not previously considered a threat to sea levels.
Michael Bevis, professor of geodynamics at The Ohio State University and lead author of the study, said, “Whatever this was, it couldn’t be explained by glaciers, because there aren’t many there. It had to be the surface mass — the ice was melting inland from the coastline.”
For 17 years, NASA and Germany have jointly operated the Gravity Recovery and Climate Experiment (GRACE), which uses twin satellites to measure ice loss in Greenland. The data from GRACE has been invaluable to glaciologists, who estimate that Greenland lost 280 gigatons of ice every year between 2002 and 2016 — that equates to 0.03 inches of sea level rise per year. Bevis and his team analyzed data from GRACE and GPS stations on the coasts of Greenland to calculate changes in the overall ice mass of the island. They found that by 2012, the rate of ice loss was four times that just nine years prior. The increase originated from Greenland’s southwest region, which had not been known to be losing ice so quickly.
Bevis believes that the accelerated melting is caused largely by global warming, resulting in inland water streaming into the ocean during the summer. “We knew we had one big problem with increasing rates of ice discharge by some large outlet glaciers,” he said. “But now we recognize a second serious problem: Increasingly, large amounts of ice mass are going to leave as meltwater, as rivers that flow into the sea.”
The paper theorizes that the North Atlantic Oscillation, a natural weather phenomenon which brings warmer air to West Greenland, in addition to the naturally clearer skies of the summer season, combines with the effects of human-caused climate change to melt an unprecedented amount of ice every year. While the North Atlantic Oscillation always has the potential to produce runoff from melted ice, its effects would not be so drastic without man-made global warming.
According to Bevis, “These oscillations have been happening forever. So why only now are they causing this massive melt? It’s because the atmosphere is, at its baseline, warmer. The transient warming driven by the North Atlantic Oscillation was riding on top of more sustained, global warming.”
While GPS systems are already in place to monitor Greenland’s ice conditions in the future, there are few resources available specifically to study the southwest region. Following his study’s findings, Bevis hopes that additional instruments will be added.
The findings also have a serious impact on the U.S. Rising sea levels put islands and coastal cities at risk of flooding and severe weather events. Bevis said, “The only thing we can do is adapt and mitigate further global warming — it’s too late for there to be no effect…the only question is: How severe does it get?”