Saturday, 28 March 2015

Focus on Antarctica

"From denial to despair"

It was a landmark event to hear Kim Hill interview Professor Tim Naish is the Director of the Antarctic Research Centre at Victoria University of Wellington.

One cannot but feel that this was a game of catch-up as little of the information was new (I have known about the melting of Antarctica from below for at least a year. Neither did it acknowledge the existance of the methane clathrate gun or any of the numerous positive feedbacks that are changing the climate much faster than any of the omputer models spoken about in this interview.

For all that it was a reolutionary interview that spoke the truth about what is happening in Antarctica. For this I have to compliment Kim Hill.

For those interested, Kim Hill interviewed Guy McPherson mid-year, 2014. On that occasion she wanted to hear everything but the stark truth.

Here is today's interview

Radio NZ's Kim Hill interviews Prof. Kim Naish on the ice melt in the Antarctica

Antarctica may have set its highest temperature ever recorded Tuesday

Need another indicator of climate warming in Antarctica? The trio of weather bloggers at Weather Underground report the temperature there likely hit a record-breaking 63.5F (17.5C) Tuesday.

27 March, 2015

The balmy reading was logged at Argentina’s Esperanza Base, which lies on the northern tip of the Antarctic Peninsula.

Weather Underground bloggers Jeff Masters and Bob Henson write the 63.5F reading breaks the previous mark set just the day before [March 23] at Argentina’s Marambio Base (a small islet off the Antarctic Peninsula) and a reading of 62.6F (also from Esperanza Base) from October 1976.

Tuesday’s new record is not yet official. Argentina’s Esperanza Base, the site of the record, may not be considered part of Antarctica for the purposes of weather records according to Weather 

Underground historian Christopher Burt. He explains four different ways Antarctica can be defined in a blog post.  Ultimately, for the record to be official, the World Meteorological Organization will need to validate the temperature reading and determine it is, in fact, Antarctic.

Irrespective of whether the record stands, it fits right into the pattern of rapid climate warming recently observed in the Antarctic Peninsula region. The British Antarctic Survey writes this region has warmed about 5F (2.8 C) in the last 50 years. “[This] makes this the most rapidly warming region in the Southern Hemisphere – comparable to rapidly warming regions of the Arctic,” it notes.

Not only are temperatures rising on its Peninsula, but multiple studies this past year have also documented a loss of ice along Antarctica’s coasts and within its interior, as The Post’s Sarah Kaplan writes today:

How bad is Antarctic ice loss? Let scientists count the ways. In December, researchers reported that West Antarctica, one of the world’s most unstable ice sheets, is collapsing faster than anyone had predicted and contributing to rapid sea level rise. Earlier this month, the same was found to be true of Totten Glacier in East Antarctica.

This week, glaciologists report the massive floating ice shelves that form a fringe along the continent’s coastline are also deteriorating.

This week’s possible temperature record was setup by a large, warm ridge of high pressure – or heat dome – originating from southern South America that extended over the Antarctic Peninsula. The intensity of this weather system was almost off-the-charts, judging by the purple shades on the map below, portraying the difference from normal conditions:

Record warmth reported in Antarctica as Melbourne shivers

Warming up: possible record temperatures recorded on the Antarctic Peninsula.
Warming up: possible record temperatures recorded on the Antarctic Peninsula. Photo: Newscom

the Age,
22 March, 2015

To call this week's wintry chill across southern Australia a "burst from Antarctica" would be doing a disservice to parts of the usually frigid continent.

Melbourne's meagre maximum of 15.3 degrees on Tuesday was actually more than 2 degrees cooler than Esperanza Base, an Argentine research station on the northern tip of the Antarctic Peninsula.

The Victorian capital may be famous for its temperature swings – often within a day – but the 17.5 degree reading at Esperanza was outlandish even by Melburnian standards. That maximum is likely to be the highest ever recorded on the Antarctic continent, according to the Weather Underground blog.

Esperanza Base, on the Antarctic Peninsula.
Esperanza Base, on the Antarctic Peninsula. Photo: Wikipedia

Tuesday's high at Esperanza – which translates to "hope" in English – beat its previous record, set in 1976, by half a degree, according to the blog post's author Christopher Burt. The new maximum was also about 17 degrees above the March average for the site, he said.

Climate specialists say strong north-westerly winds may have contributed to the unusual warmth over the Antarctic Peninsula, creating a so-called Fohn wind effect. Esperanza is on the leeward side of the peninsula, and temperatures are being nudged higher as dry winds descend after losing their moisture through rain or snow on the mountains.

Reports of the record warmth in Antarctica come as a study published on Thursday in the journal Science found the region's massive floating ice shelves are shrinking as the globe warms up.

Unusual warmth over parts of Antarctica.
Unusual warmth over parts of Antarctica. Photo: University of Maine

The study, covering satellite observations of more than 1 million square kilometres from 1994-2012 found some shelves have shrunk 18 per cent in that time.

During the first half of that period, the overall decline of ice volume around Antarctica was small, with West Antarctica losses almost balanced out by gains in East Antarctica, Reuters reported. After that, western losses accelerated and gains in the east ended.

"There has been more and more ice being lost from Antarctica's floating ice shelves," Helen Fricker, a glaciologist of the Scripps Institution of Oceanography at the University of California said.

While Antarctic sea ice extent remains at or near record levels, the extra ice is less than a third of the loss of Arctic ice cover, climatologists say. The Arctic sea-ice extent is likely to report a record low this year in another sign of global warming, US agencies said this month.

While records may be melting at the Earth's polar extremes, the same was not true for Melbourne this week.

The chilliest March day on record was back in 1940, when the mercury made it to just 12 degrees, according to the Bureau of Meteorology.

And if it's any consolation, Melbourne's top on Friday of about 18 degrees is positively tropical compared with Esperanza's temperature of about 1 degree, closer to a typical March day for the region.

Antarctica's Ice Shelves Thin, Threaten Significant Sea Level Rise

As Antarctica's ice sheets thin, the massive rivers of ice behind them can surge forward into the sea.
Credit: Michael Studinger/NASA

26 March, 2015

Over the past two decades, the massive platforms of floating ice that dot the coast of Antarctica have been thinning and doing so at an increasing rate, likely at least in part because of global warming. Scientists are worried about its implications for significant sea level rise.

The ice shelves—some of which are larger than California and tens to hundreds of yards thick—are the linchpins of the Antarctic ice sheet system, holding back the millions of cubic miles of ice contained in the glaciers that flow into them, like doorstops. As the ice sheets thin, the massive rivers of ice behind them can surge forward into the sea.

Antarctica holds enough ice, if it all melted, to raise sea levels more than 200 feet. That would take hundreds to thousands of years, but the recent thinning of the ice shelves means that there has already been an increase in the rate of Antarctica’s contribution to sea level rise, and it’s accelerating.

While it was known that many ice shelves were thinning and glaciers were flowing faster to sea, this study is “another in a series of really blockbuster studies” that uses satellite data to show just how much and where Antarctica is changing, Ted Scambos, a glaciologist with the National Snow & Ice Data Center in Boulder, Colo., said. Scambos who was not involved with the study.

There’s some very large changes that have added up,” study author Helen Amanda Fricker, a glaciologist at the Scripps Institution of Oceanography in California, said.

Delicate balance

The melting of ice shelves or the breaking off of icebergs aren’t themselves signs of climate change. They’re natural processes that help keep the mass of a glacier in balance: Snow that falls in the continent’s interior adds ice to the glacier, while ice shelf melt and iceberg calving keep the glacier in balance by losing about the same amount of ice that is dded.

The problem comes when the ice shelves lose more mass than the glaciers are gaining.

The ice shelves shouldn’t be losing volume if they’re in balance,” Fricker said.
This balance is what Fricker and her graduate student Fernando Paolo were looking at when they stitched together 18 years of satellite data (from 1994 to 2012) from three overlapping European Space Agency missions that measured the volume of Antarctica’s ice shelves with radar altimetry.

What they found was that the massive ice shelves were losing, on the whole, about 30 to 50 cubic miles of ice per year over that span. And in that period, the rate of ice loss accelerated by an average of 7 cubic miles per year.

So there’s a loss, but that loss is increasing,” said Fernando Paolo, the lead author of the study that was detailed in the March 27 issue of the journal Science.

The study, all three scientists said, shows how crucial information on this kind of long timescale is for seeing the big picture of Antarctic melt; with a study that only lasts for a few years, “some of the ice shelves are not really responding in the way that they would over the long term,” Fricker said.

A big loss’

The story varies for specific glaciers and the different regions of Antarctica, with much more ice loss in West Antarctica than East Antarctica and for particular glaciers in the west.

West Antarctica has been a major focus of south polar climate research, in part because of the clear signs of melt there as well as some spectacular ice shelf collapses in recent decades.

Changes to the thickness and volume of Antarctica's ice shelves between 1994 and 2012. Click image to enlarge. Credit: Paolo, et al./Science  

As a whole, that half of the continent has seen a 70 percent increase in its average rate of loss from ice shelves, the satellite data showed. The Amundsen and Bellingshausen sea areas had particularly high rates of loss; while the two regions account for less than 20 percent of West Antarctica’s ice shelf area, they contributed more than 85 percent of the volume lost there over the study period.

One particular glacier in the Amundsen embayment lost 18 percent of its thickness over the 18 years of the study.

For an ice shelf that, like all the others, has been in place for hundreds of thousands of years, “that’s a big loss,” Paolo said.

East Antarctica, meanwhile, has until recently been thought to be more stable, as its glaciers rest on land that is above sea level and the waters surrounding it are thought to be cooler. Recent research has showed that there is still much to learn about the susceptibility of the glaciers in East Antarctica, which holds much more ice than the west. Totten Glacier was recently shown to have channels in the seabed beneath it that would make it much more vulnerable to an influx of warm water than previously thought, though such warm water hasn’t yet been detected there.

The satellite data in the new study showed that for the first part of the study period, East Antarctic glaciers gained mass overall, then that trend flat lined in the second half of the time period. At the level of individual glaciers, some have still been gaining mass, while others, like Totten, have thinned.

The leveling off of the East Antarctic ice shelf rates suggests that more attention needs to be paid to the eastern half of the continent because “if you turn your back on the ice shelves that are not changing” then you might miss something if suddenly start to, Fricker said.

Boots on the ice’

Having this kind of long-term record on Antarctic ice shelf thinning is key to understanding what processes are behind the thinning and how they might continue into the future.

In West Antarctica, it is thought that most of the thinning is caused by warm waters that are eating away at the ice shelves from below, a consequence of changes in prevailing winds that is potentially linked to global warming.

Paolo and Fricker said the data show the characteristic signature of this kind of melt, which happens at what is called the grounding line, or the point where the glacier last touches land and the ice shelf begins. Other recent studies examining glaciers have also bolstered this idea, and have even suggested that some glaciers in West Antarctica have reached a point where their retreat and melt is now irreversible.

The picture is murkier in the east, in part because so much less work has been done there. This study shows, though, that East Antarctic ice shelves “are actually subject to large changes as well,” Paolo said.

The biggest rates of ice loss seen in the Amundsen embayment imply that some of those ice shelves, if they continue at the same rates, could be gone within a century. Of course, “what’s going to happen 100 years from now, we cannot know,” Paolo said, which is why it’s so important to understand exactly “what are the causes, the mechanisms, behind the changes we see.”

For that, you need what Scambos calls “boots on the ice”—missions that put researchers and equipment onto the ice shelves to get more detailed information about the forces pushing them around.

That’s not an easy sell, because “the Antarctic environment is perhaps one of the most difficult environments to work,” Paolo said. But there are hopes that new satellite missions, along with remotely operated submarines and other technology can help build our knowledge of the forces at play in the southernmost continent.

As this study makes clear, Scambos said, we need continuous monitoring of this environment because “we’re faced with a planet that is changing in ways we don’t want.

For the bigger picture listen to Paul Beckwith

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