Why a Growing Glacier Isn't Good News for the Climate

Greenland's Jakobshavn glacier is gaining ice due to cyclical changes in ocean temperature, but that doesn’t mean things are getting better.

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Mar 26 2019, 6:00pm

Jakobshavn glacier calving. Image: NASA/GSFC/Jefferson Beck

An iconic glacier in Greenland is growing again after two decades of shrinking. But that doesn’t mean things are looking up, experts say—just the opposite. The icy behemoth remains a looming climate threat.

The Jakobshavn glacier, also called the Ilulissat glacier, has been called Greenland’s “fastest-flowing and fastest-thinning” by NASA. Twenty years of retreat ranked Jakobshavn as one of Earth’s ticking timebombs for climate change, as its ice melt could contribute to catastrophic global sea level rise. So, a new NASA study claiming that the glacier is now gaining mass seems hopeful on the surface.

A team of researchers led by NASA’s Oceans Melting Greenland (OMG) project published their findings on Monday in Nature Geoscience. Jakobshavn, which is Greenland’s largest glacier and covers roughly 110,000 square kilometers, had been retreating 1.8 miles and thinning 130 feet per year as of 2012, NBC News reported. But two years ago, parts of it began to grow at approximately the same rate.

“The thinking was once glaciers start retreating, nothing's stopping them,” Josh Willis, OMG’s lead scientist and one of the study’s authors, told National Geographic. “We've found that that's not true.”

The growth was significant enough to be characterized as a reversal of Jakobshavn’s long standing retreat, attributed to a circulation of cooler ocean water in Disko Bay, which feeds the Ilulissat Icefjord where the glacier is located.

Natural ocean cycles (similar to El Niño) have made these waters 3.6 degrees Celsius cooler at certain depths than the norm in recent years. But as the authors stress, they will eventually warm again, and shouldn’t be seen as climate change progress. In fact, the NASA scientists’ findings suggest that changes in ocean temperature are more impactful when it comes to glacier melt (and growth) than previously thought.

“In the long run we’ll probably have to raise our predictions of sea level rise again,” Willis told NBC News.

A different study published in Nature last year also found that Greenlandic ice as a whole is perilously sensitive to warming temperatures.

It’s important to note that glacier melt throughout Greenland isn’t stopping—and the behavior of Jakobshavn shouldn’t be expected from the island’s hundreds of other glaciers.

Greenland’s ice sheet is the world’s largest contributor to sea level rise, losing 270 billion tons of ice each year, primarily due to climate change. These losses raised the global sea level 7.5 millimeters between 1992 and 2011, and were a frightening preview of Greenland’s capacity to submerge metropolitan areas such as lower Manhattan in New York City.

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