Rising seas even more dangerous than thought, says NASA

Melting ice sheets are contributing to rising sea levels more than previously thought, suggests data from NASA satellites.

NASA Earth Observatory, Jefferson Beck and Maria-José Viñas
Scientists are concerned about sea level rise from ice melt in southern Greenland (shown here) and the Antarctic.

The consequences of global sea level rise could be even scarier than the worst-case scenarios predicted by the dominant climate models, which don't fully account for the fast breakup of ice sheets and glaciers, NASA scientists said today (Aug. 26) at a press briefing.

What's more, sea level rise is already occurring. The open question, NASA scientists say, is just how quickly the seas will rise in the future.

Rising seas

The current warming of the seas and the associated expansion of their waters account for about one-third of sea level rise around the world. [Images of Melt: Earth's Vanishing Ice]

"When heat goes under the ocean, it expands just like mercury in a thermometer," Steve Nerem, lead scientist for NASA's Sea Level Change Team at the University of Colorado in Boulder, said in the press briefing.

The remaining two-thirds of sea level rise is occurring as a result of melting from ice sheets in Greenland and Antarctica and mountain glaciers, Nerem said.

Data collected by a cadre of NASA satellites — which change position in relation to one other as water and ice on the planet realign and affect gravity's tug — reveal that the ocean's mass is increasing. This increase translates to a global sea level rise of about 1.9 millimeters (0.07 inches) per year, Nerem said.

Unpredictable pace

But the speed of sea level rise is an open question.

"Ice sheets are contributing to sea level rise sooner, and more than anticipated," said Eric Rignot, a glaciologist at the University of California, Irvine, and NASA's Jet Propulsion Laboratory in Pasadena, California.

That's because people have never seen the collapse of a huge ice sheet and therefore don't have good models of the effects, Rignot said.

The Intergovernmental Panel on Climate Change, an international organization created by the United Nations that produces climate change models, has predicted that sea levels could rise as much as 21 feet (6.4 meters) in the next century if global warming continues unabated.

But even that worst-case scenario may not capture the risk, Rignot said. That's because the IPCC models only take into account temperature changes at the surface of glaciers, but not the rapid melting that occurs when glaciers calve and break up into the ocean, Rignot said.

In addition, much of glaciers' melting occurs at deep, undersea ice canyons. Warmer water is salter and therefore heavier. That means it sinks into the deeper layers of the ocean, and the contrast between this warm water and the undersea ice canyons contributes an unknown but substantial amount of sea level rise, said Josh Willis, an oceanographer at JPL in Pasadena, California.

When the massive Jakobshavn glacier in Greenland calved earlier this summer, it moved 4.6 square miles (12 square kilometers) of ice in one day, Rignot said. [See Photos of Greenland's Melting Glaciers]

If the Jakobshavn glacier had melted completely, "it contains enough ice to raise global sea level by half a meter — just this one glacier in Greenland," Rignot said. If all the land ice on the planet were to melt, it would raise sea levels about 197 feet (60 m), he added.

Some of the melting that has already occurred is likely irreversible, and could take hundreds of years to reverse, Rignot said.

American impact

While global sea levels have risen about 2.75 inches (7 centimeters) over the past 22 years, the west coast of the United States has not seen much of a rise in ocean levels. That's largely because of a long-time-scale weather pattern called the Pacific Decadal Oscillation, which is masking the global effect. That, however, could reverse in the coming years, Willis said.

"In the long run, we expect the sea levels on the west coast to catch up to global mean and even exceed the global mean," Willis said.

Florida is also particularly vulnerable to sea level rise because its porous soil allows more seawater intrusion than does the soil in other coastal areas, Willis said.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience,Facebook Google+. Original article on Live Science.

Copyright 2015 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Rising seas even more dangerous than thought, says NASA
Read this article in
QR Code to Subscription page
Start your subscription today