The Truth Behind The Totten Glacier

By Paul Homewood

 

http://www.abc.net.au/news/2015-01-26/sea-water-melting-totten-glacier-in-antarctica-from-below/6047076

 

The Totten Glacier in East Antarctica is the latest scare story for melting glaciers and rising sea levels. This report from ABC seems typical:

 

Warm ocean water is melting one of the world’s biggest glaciers from below, potentially leading to a rise in sea levels, Australian scientists have discovered.

Australian icebreaker Aurora Australis recently returned to Hobart from Antarctica, with a team of 23 scientists who had used new technology to collect the first water samples near the Totten Glacier.

Steve Rintoul from the Australian Climate and Environment Cooperative Research Centre said the results indicated the glacier was being melted by the sea water beneath it.

"The measurements we collected provide the first evidence that warm water reaches the glacier and may be driving that melt of the glacier from below," he said. 

According to Australian Antarctic Division estimates, the Totten Glacier holds enough water to raise sea level by six metres and scientists said it had been thinning over the past 15 years.

"We used to think the glaciers in east Antarctica were unlikely to be affected by the ocean because they were a long way away from the warm ocean waters," he said.

"The fact that it’s changing is something new, we used to think that the glaciers in east Antarctic were very stable and unlikely to change."

But he said it was too soon to tell if the glacier was melting as a result of a changing global climate.

"What our observations can’t tell us is how things have changed over time, because this is the first time anyone has made measurements in this area," he said.

"The measurements we’ve collected here are crucial for setting a benchmark that can be used to assess future change." 

 

This one is, of course, just one more in a run of scare stories about melting Antarctic glaciers. Although the scientists are reluctant to link this with global warming, many in the media will not let that fact stop from doing so.

There appear to be a few obvious, initial thoughts:

 

1) Just because warm water is reaching the glacier, this does not mean that it is warm because of global warming. It simply means that the water has found its way from warmer sources.

Indeed, it is a physical fact that, because of the massive heat content of the oceans, any effect so far from GHG would be undetectable , and would certainly not make the slightest difference to the melting of these glaciers.

2) It is acknowledged that the Totten has been receding for the past 15 years. But has it been receding for much longer? Our knowledge of Antarctica is so ridiculously short that we think anything that happens now has never happened before, and is our fault.

3) Evidence from satellites is said to show that mass changes in East Antarctica have been, in recent years, effectively zero. If the Totten is losing ice, this loss is being made up for elsewhere.

4) The scientists do point out that the Totten is not going to disappear overnight, and it could take centuries for any significant changes (for which read millenia!). By that time we will have had another Little Ice Age or two.

     

 

However, I came across a NASA paper on the Totten in 2013, which casts a totally different light on matters.

 

http://www.nasa.gov/jpl/news/reducing-salt-bad-for-glacial-health-20131205.html#.VQ7xkuHLL5y

 

A new NASA-led study has discovered an intriguing link between sea ice conditions and the melting rate of Totten Glacier, the glacier in East Antarctica that discharges the most ice into the ocean. The discovery, involving cold, extra salty water – brine – that forms within openings in sea ice, adds to our understanding of how ice sheets interact with the ocean, and may improve our ability to forecast and prepare for future sea level rise.

“I was curious why Totten was changing so fast when the glacier just next to it wasn’t changing much,” said Ala Khazender of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., lead author of the new study, published online Dec. 5 in the journal Nature Communications. Combining satellite observations with ocean numerical modeling, Khazender and his colleagues developed a hypothesis that reductions in the volume of brine would increase Totten’s thinning and melting. Additional research supported that hypothesis.

Ice loss seen in Antarctica is generally attributed to the well-documented rise in temperature of the surrounding ocean, but scientists are still puzzling out the mechanisms behind the regional variations that they are observing. The new study highlights the key role of processes occurring on small geographic scales in determining how global climate change can affect the stability of ice sheets.

Satellite observations from NASA’s ICESat-1, which measures how much ice surfaces are rising or falling over time, revealed that Totten Glacier was thinning rapidly. It currently discharges enough ice into the surrounding ocean to fill Lake Erie in just over a week. The nearby Moscow University Glacier and its floating ice shelf were showing little change.  Why the difference? “We were convinced that the answer must be in the ocean,” Khazender said.

The ocean around Antarctica is warmer than both the continent’s icy surface and the polar air. Ice shelves (the floating front edges of glaciers that extend tens to hundreds of miles offshore) melt more because of contact with ocean water below them than they do because of sunlight. Melting at the undersides of ice shelves is part of Antarctica’s natural water cycle, but when glaciers start melting unusually quickly, it’s a sign that something is off balance.

Khazender and his team of colleagues from JPL; UCLA; the University of California, Irvine; and Utrecht University in the Netherlands combined ICESat remote sensing observations from 2003 to 2008 with ocean numerical computer models to seek insights into the interaction between the ice shelves and their ocean basin.

That ocean basin, as elsewhere around Antarctica, contains polynyas (poe-LEEN-yahs), large, annually recurring openings in the winter sea ice cover. Polynya sizes and numbers vary markedly from winter to winter, although there is no overall trend in this region. The computer simulations revealed that these year-to-year variations in the polynyas greatly affected the glacier’s melting rate.

In polynyas, large quantities of sea ice form, only to be swept away by the winds that formed the openings in the first place. When seawater freezes it expels its salts, producing a layer of very dense, briny water at the freezing temperature. The cold and dense brine formed in polynyas sinks to the seafloor, where it can flow into the cavities under the ice shelves, just as warmer ocean water could.

The researchers hypothesized that when the cold brine pooled under Totten Ice Shelf, it mixed with the water there, lowering its temperature and slowing the glacier’s winter melt rate. If so, a reduction in cold brine would mean the glacier’s winter melt rate would increase.

The team then examined a data set of passive microwave measurements from the Defense Meteorological Satellite Program. These showed that in the latter part of the study period, the extent of polynyas (and therefore the production of cold brine) decreased significantly. ICESat observations showed that at the same time, the thinning of Totten Glacier increased, as the team’s hypothesis predicted it would.

If there are more winters with reduced polynya extents, Khazender points out, the cavity under Totten can fill with warmer ocean water rather than cold brine. “If that happens, the glacier’s flow could be significantly destabilized, causing it to discharge even more ice into the ocean,” he said.

”With the widespread changes seen in Antarctic sea ice conditions over the last few years, this process could be affecting other glaciers around Antarctica and the volume of ice they discharge into the ocean,” he added.

  

Put simply, the thinning of the Totten glacier increases when polynyas in the area are decreasing. As we know Antarctic sea ice is generally increasing, so therefore polynyas will also tend to be increasing as well.

 

There is a simple image which shows this well:

 

 

 

The researchers specifically find that the nearby Moscow University Glacier shows little change, which rather suggests that any changes at Totten are just a local effect, and certainly nothing to do with global warming. Indeed, expanding Antarctic sea ice would tend to suggest that, in overall terms, glaciers will melt more slowly.

 

It appears as if yet one more alarmist scare story has just bitten the dust.