News24

Antarctic ice melting from below

2012-04-25 22:30

Washington - Antarctica's massive ice shelves are shrinking because they are being eaten away from below by warm water, a new study finds. That suggests that future sea levels could rise faster than many scientists have been predicting.

The western chunk of Antarctica is losing 7m of its floating ice sheet each year. Until now, scientists were not exactly sure how it was happening and whether or how man-made global warming might be a factor.

The answer, according to a study published on Wednesday in the journal Nature, is that climate change plays an indirect role - but one that has larger repercussions than if Antarctic ice merely were melting from warmer air.

Hamish Pritchard, a glaciologist at the British Antarctic Survey, said research using an ice-gazing Nasa satellite showed that warmer air alone could not explain what was happening to Antarctica. A more detailed examination found a chain of events that explained the shrinking ice shelves.

Twenty ice shelves showed signs that they were melting from warm water below. Changes in wind currents pushed that relatively warmer water closer to and beneath the floating ice shelves. The wind change probably is caused by a combination of factors, including natural weather variation, the ozone hole and man-made greenhouse gases, Pritchard said in a phone interview.

As the floating ice shelves melt and thin, that in turn triggers snow and ice on land glaciers to slide down to the floating shelves and eventually into the sea, causing sea level rise, Pritchard said. Thicker floating ice shelves usually keep much of the land snow and ice from shedding to sea, but that is not happening now.

That whole process causes larger and faster sea level rise than simply warmer air melting snow on land-locked glaciers, Pritchard said.

"It means the ice sheets are highly sensitive to relatively subtle changes in climate through the effects of the wind," he said.

What's happening in Antarctica "may have already triggered a period of unstable glacier retreat," the study concludes. If the entire Western Antarctic Ice Sheet were to melt, which would take many decades if not centuries, scientists have estimated it would lift global sea levels by about 3m.

Nasa chief scientist Waleed Abdalati, an expert in Earth's ice systems who was not involved in the research, said Pritchard's study "makes an important advance" and provides crucial information about how Antarctica will contribute to global sea level rise.

Another outside expert, Ted Scambos of the National Snow and Ice Data Centre, said the paper will change the way scientists think about melt in Antarctica. Seeing more warm water encircling the continent, he worries that with "a further push from the wind" newer areas could start shrinking.

Comments
  • amanda.victor2 - 2012-04-26 00:54

    I wonder why the Arctic Ice is at near record levels? I see they don't mention this. Must be the global warming farce. I'm so sick of all these predictions that don't come true. When are they going to stop trying to con the public? Money, money, money. When they can control the sun then they can come speak to me.

      zaatheist - 2012-04-26 05:59

      Where did you get your doctorate in climatology? You sound like a real expert who can prove all these stupid scientists wrong. Oh, I see from your Facebook that you are a raving fundie right wing nutter who thinks the Norwegian mass murderer did nothing wrong. That explains everything.

      themarkthrasher - 2012-04-26 09:22

      Read The Skeptical Environmentalist by Bjørn Lomborg. Scientific rigor applied to the Doomsayer Environmentalists.

      mariuskowie - 2012-04-26 09:38

      WOW!!! I have been following the news reports regarding climate change for some time now. What strikes me the most is the level of aggression in the responses against any one who opposes climate change and more specifically man-made global warming. The level of personal attack is just horrifying. Demands about the person's source of qualifications in climatology abound. The next attack is the "peer reviewed" attack. The fact is that a lot of this climate related news are NOT peer reviewed. It is the opinion of some scientist and in many cases the motivation is not science at all. The current climate change is not understood at all. Scientists create models and simulations based on the tiny bit of information gathered. They use this models to attempt to predict the future behavior of the climate. There are a lot of money to be made in the climatology echelons. Not every supposed to be scientist involved with climate studies is as Lilly white and honorable as pretended. That is my opinion. I am entitled to my opinion and am entitled to air it on this public forum. That does not entitle the cyber bullies to launch a scathing attack because my opinion differs from theirs. This is not e closed forum accessible to Doctorates and PHD's only. This is a forum for public discussion and public viewpoints, irrespective if the viewpoint is correct or not.

      Stirrer - 2012-04-26 10:03

      @Rebel: Well said, deserves 1000 thumbs-ups! Please ignore zaatheist and MemeMan, they lost all credibility long ago.

      zaatheist - 2012-04-26 11:27

      @Rebel. "The fact is that a lot of this climate related news are NOT peer reviewed." But of course a lot of it is.

      Ernst - 2012-04-27 15:50

      @Rebel_without_a_cause: Yes, you are entitled to your own opinion. If a person perpetuates the same climate myths that have been proved to be not true, then it warrants to be attacked. "The current climate change is not understood at all. Scientists create models and simulations based on the tiny bit of information gathered. They use this models to attempt to predict the future behavior of the climate." While there are uncertainties with climate models, they successfully reproduce the past and have made predictions that have been subsequently confirmed by observations. Predicting what the climate is going to do over long time intervals is much easier than over short time intervals. An analogy is the oil price. The oil price is volatile over short intervals. However, what is the oil price going to do over the next 50 years? Its going to go up. "The current climate change is not understood at all." That humans are causing global warming is the position of the Academies of Science from 19 countries plus many scientific organizations that study climate science. More specifically, around 95% of active climate researchers actively publishing climate papers endorse the consensus position.

      Ernst - 2012-04-27 16:07

      @ "Read The Skeptical Environmentalist by Bjørn Lomborg. Scientific rigor applied to the Doomsayer Environmentalists." Bjorn Lomborg has never published a scientific paper in his life. He is hardly a credible source of information and is an attention seeking fraud.

  • DuToitCoetzee - 2012-04-26 11:00

    Well, there you have it! I told you guys to stop peeing in the sea.;)

  • Trevor - 2012-04-26 11:33

    Alll you dim witted skeptics , thinking about the bottom dollar < logical science proves climate change is man made ! think of your children and what legacy you leave for them ! it makes me sick just thinking of it !

      Stirrer - 2012-04-26 12:04

      "logical science proves climate change is man made" - say what?!! Nothing has been proven, it's all speculation, and the result of computer modelling based on suspect data. There were eras in the past where the planet was much warmer than now, was that also man made? Or was it a natural cycle? Who can prove it's not a natural cycle now? That said, I agree that we should not screw up our planet with any kind of pollution, or any kind of dimwit action like fracking. It's just plain stupid.

      Ernst - 2012-04-27 15:30

      @stirrer: "There were eras in the past where the planet was much warmer than now, was that also man made? Or was it a natural cycle? Who can prove it's not a natural cycle now?" Natural climate change in the past proves that climate is sensitive to an energy imbalance. If the planet accumulates heat, global temperatures will go up. Currently, CO2 is imposing an energy imbalance due to the enhanced greenhouse effect. Past climate change actually provides evidence for our climate's sensitivity to CO2. Climate reacts to whatever forces it to change at the time; humans are now the dominant forcing.

  • Ray - 2012-04-27 15:18

    @Rebel-I agree,well said.I do have a PhD in science,but it doesn't mean that my opinion is the only one worth listening to.Keep it up.

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