Even current worst-case scenarios about the threat of global sea level rise may be too optimistic, according to NASA. The “basic physics” of ice and water on a warming planet strongly suggest that sea levels around the globe are rising, and will continue to rise, at a dangerously accelerated rate, space agency officials said in an Aug. 26 statement.
According to what scientists know about Earth’s ancient weather patterns, ice sheets can collapse in an alarmingly short time. The world could be now be facing such a dramatic environmental event, NASA says, while noting that more research must be done.
“We’ve seen from the paleoclimate record that sea level rise of as much as 10 feet in a century or two is possible, if ice sheets fall apart rapidly, said Tom Wagner, the cryosphere program scientist at NASA headquarters in Washington, D.C., in the space agency statement. “We’re seeing evidence that the ice sheets are waking up, but we need to understand them better before we can say we’re in a new era of rapid ice loss.”
But warning signs are there. Using new state-of-the-art satellite technology, scientists can now make accurate estimates of yearly ice losses from Greenland and West Antarctica. Since 2004, Greenland has been losing an average of 303 gigatons of ice each year. Antarctica is losing 118 gigatons annually, mostly from West Antarctica.
“People need to understand that the planet is not only changing, it’s changed,” said Wagner, as reported by The Christian Science Monitor.
The most worrying aspect of the steady ice sheet loss is the accelerated rate at which it is happening. Ice melt in Greenland has been accelerating by 31 gigatons each year and by 28 gigatons in West Antarctica. The Antarctic ice sheet is larger than the U.S. and India combined.
“Given what we know now about how the ocean expands as it warms and how ice sheets and glaciers are adding water to the seas, it’s pretty certain we are locked into at least 3 feet of sea level rise and probably more,” said Steve Nerem of the University of Colorado, Boulder, and lead of NASA new Sea Level Change Team, in the statement. “But we don’t know whether it will happen within a century or somewhat longer.”
If the nearly Alaska-sized Greenland Ice Sheet completely melted away, it would raise global sea levels by more than 20 feet, NASA says. The Arctic region, where Greenland is located, is warming twice as fast as the rest of the planet. Greenland has now reached a critical tipping point, where sheds more ice in summertime than it regains in winter.
To get more precise answers to questions of how Earth’s glacial regions will react to continuing warming temperatures and how much glacial melting will contribute to sea level rise, NASA scientists are beginning an ambitious three-year study by air and by sea, called Oceans Melting Greenland, or OMG (no, the irony of this acronym has not gone unnoticed).
“We’ve learned so much from the satellites that we’ve been surfing the wave of new understanding for the last 20 years,” said Ted Scambos, lead scientist at the University of Colorado’s National Snow and Ice Data Center, in the NASA statement. “But now, to go further, we have to try to get instruments on the ground while maintaining the ability we have with airborne and satellite missions to watch the ice sheet from a global perspective.”