Antarctic woes

The news from the bottom of the planet isn’t good, despite what one report would suggest…

Major Antarctic glacier is ‘past its tipping point’:

A major Antarctic glacier has passed its tipping point, according to a new modelling study. After losing increasing amounts of ice over the past decades, it is poised to collapse in a catastrophe that could raise global sea levels by 24 centimetres.

Pine Island glacier (PIG) is one of many at the fringes of the West Antarctic ice sheet. In 2004, satellite observations showed that it had started to thin, and that ice was flowing into the Amundsen Sea 25 per cent faster than it had 30 years before.

Now, the first study to model changes in the ice sheet in three dimensions shows that PIG has probably passed a critical “tipping point” and is irreversibly on track to lose 50 per cent of its ice in as little as 100 years, significantly raising global sea levels.

The team that carried out the study admits their model can represent only a simplified version of the physics that govern changes in glaciers, but say that if anything, the model is optimistic and PIG will disappear faster than it projects.

Once again, we see how critical it is to understand ice dynamics.

But it can’t be all that bad, right?

Antarctic sea water shows ‘no sign’ of warming:

SEA water under an East Antarctic ice shelf showed no sign of higher temperatures despite fears of a thaw linked to global warming that could bring higher world ocean levels, first tests showed yesterday.

Sensors lowered through three holes drilled in the Fimbul Ice Shelf showed the sea water is still around freezing and not at higher temperatures widely blamed for the break-up of 10 shelves on the Antarctic Peninsula, the most northerly part of the frozen continent in West Antarctica.

“The water under the ice shelf is very close to the freezing point,” Ole Anders Noest of the Norwegian Polar Institute wrote after drilling through the Fimbul, which is between 250m and 400m thick.

“This situation seems to be stable, suggesting that the melting under the ice shelf does not increase,” he wrote of the first drilling cores.

The findings, a rare bit of good news after worrying signs in recent years of polar warming, adds a small bit to a puzzle about how Antarctica is responding to climate change, blamed largely on human use of fossil fuels.

Whew! Good thing they drilled those three holes and measured the temperature! If we had done something a bit more involved, like using a satellite…

The Big Thaw? NASA Satellites Detect Unexpected Ice Loss in East Antarctica (emphasis added):

Using gravity measurement data from the NASA/German Aerospace Center’s Gravity Recovery and Climate Experiment (Grace) mission, a team of scientists from the University of Texas at Austin has found that the East Antarctic ice sheet-home to about 90 percent of Earth’s solid fresh water and previously considered stable-may have begun to lose ice.

The team used Grace data to estimate Antarctica’s ice mass between 2002 and 2009. Their results, published Nov. 22 in the journal Nature Geoscience, found that the East Antarctic ice sheet is losing mass, mostly in coastal regions, at an estimated rate of 57 gigatonnes a year. A gigatonne is one billion metric tons, or more than 2.2 trillion pounds. The ice loss there may have begun as early as 2006. The study also confirmed previous results showing that West Antarctica is losing about 132 gigatonnes of ice per year.

“While we are seeing a trend of accelerating ice loss in Antarctica, we had considered East Antarctica to be inviolate,” said lead author and Senior Research Scientist Jianli Chen of the university’s Center for Space Research. “But if it is losing mass, as our data indicate, it may be an indication the state of East Antarctica has changed. Since it’s the biggest ice sheet on Earth, ice loss there can have a large impact on global sea level rise in the future.”

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., developed the twin Grace satellites. The University of Texas Center for Space Research in Austin has overall Grace mission responsibility. Grace was launched in 2002.

More information on Grace is online at http://www.csr.utexas.edu/grace/ and http://grace.jpl.nasa.gov/.

Oops. 189 billion tons of net ice loss per year, and that’s from the end of the planet that was supposed to be “stable” and “reassuring”.