The focus reflects the growing urgency of the topic. Recent scientific reports have documented apparently accelerating ice loss from Greenland, and potential destabilization of parts of the West Antarctic ice sheet.
The agency says that we’ve seen 3 inches of global sea level increase since the year 1992 — with large regional variation — and a further rise of three feet has likely been “locked in” by warming that has already occurred. Other scientists have recently suggested that we may be about to unleash considerably more than that.
“The data shows that sea level is rising faster than it was 50 years ago, and it’s very likely to get worse in the future,” Steve Nerem, who leads NASA’s new Sea Level Change Team, said in a press call Wednesday.
The agency Wednesday released a new data visualization showing ice mass loss from Greenland since the year 2004 totaling 2,500 gigatons. (A gigaton is a billion metric tons.) Indeed, NASA says Greenland has lost an average of 303 gigatons yearly for the past decade. Since it takes 360 gigatons to raise sea level by a millimeter, that would suggest Greenland has done this about eight times over just in the last 10 years or so.
On the press call Eric Rignot, a glaciologist at the University of California, Irvine and NASA’s Jet Propulsion Laboratory, drew particular attention to the dynamic behavior of the Jakobshavn glacier in Greenland, which recently lost a gigantic chunk of ice roughly 12 square kilometers in surface area.
“The glacier keeps retreating rapidly into a deep canyon and this summer has seen another series of spectacular calving events,” Rignot said.
The glacier, alone, could raise sea level by half a meter if it were to melt entirely, Rignot said. The entire Greenland ice sheet contains about 6 meters worth of sea level rise, or 20 feet.
To determine what’s happening here, a new NASA program called Oceans Melting Greenland — yes, OMG — will be examining the coastal interface between sea and glacier and also mapping the complex topography beneath the ice, which has major implications for how fast it can slide into the seas.
In some ways an even bigger concern is about Antarctica, which is only losing an average of 118 gigatons a year right now, according to NASA — but where there is, overall, a great deal more total ice to lose. And there is recent evidence that the West Antarctica ice sheet may be undergoing what scientists call a marine instability, as warm water reaches the base of its glaciers from below.
Another new agency visualization released Wednesday illustrates the variation in sea level rise around the world — the sea level has fallen slightly along the U.S. west coast, an occurrence that the agency attributes to a cycle known as the Pacific Decadal Oscillation. But NASA warns that that could be short-lived, and that sea level rise could be faster here as a result in coming years. The PDO has recently shifted into a warm phase.
Strikingly, the video also shows that a change to the Gulf Stream system — a massive ocean current — has apparently led to sea level rise along the U.S. east coast, but a sea level fall further out in the Atlantic. “This massive current has shifted slightly in the last 23 years,” says NASA researcher Josh Willis in the video.
The overall thrust of the new presentation is that while NASA isn’t saying — yet — that sea level will be worse than expected this century, it’s certainly rushing to study the possibility, using all the tools at its disposal.
“Observations suggest that we should be very cautious to conclude too soon that conservative scenarios are reasonable,” said Rignot. “They may not be.”
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