Could old, cold water rising in Antarctic seas solve climate change mystery?

Ancient, chilly waters upwelling from the deep in the Antarctic seas could explain why winter sea ice off Antarctica isn't shrinking in response to global warming.

|
Courtesy of K. Armour/UW
Observed warming over the past 50 years (in degrees Celsius per decade) shows rapid warming in the Arctic, while the Southern Ocean around Antarctica has warmed little, if at all.

A persistent chill in the ocean off Antarctica that defies the global warming blamed for melting Arctic ice at the other end of the planet is caused by cold waters welling up from the depths after hundreds of years, scientists said on Monday.

The Southern Ocean off Antarctica may be among the last places on Earth to feel the impact of man-made climate change, with a lag of centuries to affect waters emerging from up to 5,000 meters (16,000 ft) deep, the U.S. study said.

Many people who doubt mainstream scientific findings that human use of fossil fuels is warming the planet often point to the paradox of expanding winter sea ice off Antarctica in recent decades and a rapid shrinking of ice in the Arctic.

"Our findings are a step toward resolving the mystery," lead author Kyle Armour of the University of Washington, Seattle, told Reuters of the study in the journal Nature Geoscience.

He noted the upwelling of cold water helped to explain the persistence of sea ice but not its expansion, a trend other studies have linked to shifts in winds off the vast frozen continent.

Monday's report found that warm waters in the Gulf Stream cool as they flow north into the North Atlantic, then sink and loop south towards Antarctica as part of an aquatic conveyor belt that takes centuries to complete.

Eventually, gale force winds in the Southern Ocean around Antarctica blow surface waters northwards and draw the chill, ancient waters from the depths.

That upwelling helps explain why the surface of the Southern Ocean have warmed by just 0.02 degree Celsius (0.036 Fahrenheit) per decade since 1950, a fraction of the global average of 0.08 degree (0.144F), the study said.

It was unclear if the cold waters could delay a melt of ice locked up on land in Antarctica, the biggest worry about the continent that could sharply raise global sea levels.

Colin Summerhayes of the Scott Polar Research Institute, who was not involved in the study, said even the slight warming in waters to about 1 degree Celsius (33.8°F) had been bad news for ice shelves around the fringes of Antarctica.

"Even water that cool is still warm enough to melt the ice at the base of the ice shelves," he wrote in a comment.

(Reporting By Alister Doyle; Editing by Tom Heneghan)

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

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 Could old, cold water rising in Antarctic seas solve climate change mystery?
Read this article in
https://www.csmonitor.com/Science/2016/0530/Could-old-cold-water-rising-in-Antarctic-seas-solve-climate-change-mystery
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe