[Rantman] Keep an eye on the Pine Island Glacier.

[Richard Pauli]

We want to remember this name:  Pine Island Glacier

Because even though this Antarctic glacier is melting fast, it's being 
carefully watched as a source of catastrophic sea level rise.   And it 
could happen soon or very soon - months to years.

Right now seas rise about 3mm per year - about a match head.   Not 
much.   (depending on your display, this may be the thickness of the 
letter 'o' in this line.)

All of this could add up to 9 inches if Pine Island glaciers and 
tributaries let loose.   And it is speeding up.

Keep in mind this glacier is floating on an ocean affected by tides.   
And for almost 250 km up river the ice is not grounded.  So as sea level 
rises, so does the floating ice.  Add to this the rising and falling 
tides - this is the kind of mechanism that gets progressively unstable.

The Pine Island Glacier is over 1000 feet thick in areas.  When the 
floating section breaks free, then the uphill section - even thicker ice 
- will rapidly flow to the sea.  It probably will not happen all at 
once, but it could happen soon.   Oceanographers say that whenever a big 
splash happens - it might take a month or so for the sea level increase 
to propagate around the planet.

So stay tuned and pay attention.

RP
June-2011


  Ocean Currents Speed Melting of Antarctic Ice: A Major Glacier Is
  Undermined from Below

enlarge <http://www.sciencedaily.com/images/2011/06/110626145308-large.jpg>
<http://www.sciencedaily.com/images/2011/06/110626145308-large.jpg>
/Scientists aboard the Nathaniel B. Palmer visited the Amundsen Sea 
region in 2009 to study oceanic changes. (Credit: Frank Nitsche, 
Lamont-Doherty Earth Observatory)/

ScienceDaily (June 26, 2011)--- Stronger ocean currents beneath West 
Antarctica's Pine Island Glacier Ice Shelf are eroding the ice from 
below, speeding the melting of the glacier as a whole, according to a 
new study in/Nature Geoscience/. A growing cavity beneath the ice shelf 
has allowed more warm water to melt the ice, the researchers say -- a 
process that feeds back into the ongoing rise in global sea levels. The 
glacier is currently sliding into the sea at a clip of four kilometers 
(2.5 miles) a year, while its ice shelf is melting at about 80 cubic 
kilometers a year -- 50 percent faster than it was in the early 1990s -- 
the paper estimates.

"More warm water from the deep ocean is entering the cavity beneath the 
ice shelf, and it is warmest where the ice is thickest," said study's 
lead author, Stan Jacobs, an oceanographer at Columbia University's 
Lamont-Doherty Earth Observatory.

In 2009, Jacobs and an international team of scientists sailed to the 
Amundsen Sea aboard the icebreaking ship Nathaniel B. Palmer to study 
the region's thinning ice shelves -- floating tongues of ice where 
landbound glaciers meet the sea. One goal was to study oceanic changes 
near the Pine Island Glacier Ice Shelf, which they had visited in an 
earlier expedition, in 1994. The researchers found that in 15 years, 
melting beneath the ice shelf had risen by about 50 percent. Although 
regional ocean temperatures had also warmed slightly, by 0.2 degrees C 
or so, that was not enough to account for the jump.

The local geology offered one explanation. On the same cruise, a group 
led by Adrian Jenkins, a researcher at British Antarctic Survey and 
study co-author, sent a robot submarine beneath the ice shelf, revealing 
an underwater ridge. The researchers surmised that the ridge had once 
slowed the glacier like a giant retaining wall. When the receding 
glacier detached from the ridge, sometime before the 1970s, the warm 
deep water gained access to deeper parts of the glacier. Over time, the 
inner cavity grew, more warm deep water flowed in, more melt water 
flowed out, and the ice thinned. With less friction between the ice 
shelf and seafloor, the landbound glacier behind it accelerated its 
slide into the sea. Other glaciers in the Amundsen region have also 
thinned or widened, including Thwaites Glacier and the much larger Getz 
Ice Shelf.

One day, near the southern edge of Pine Island Glacier Ice Shelf, the 
researchers directly observed the strength of the melting process as 
they watched frigid, seawater appear to boil on the surface like a 
kettle on the stove. To Jacobs, it suggested that deep water, buoyed by 
added fresh glacial melt, was rising to the surface in a process called 
upwelling. Jacobs had never witnessed upwelling first hand, but 
colleagues had described something similar in the fjords of Greenland, 
where summer runoff and melting glacier fronts can also drive buoyant 
plumes to the sea surface.

In recent decades, researchers have found evidence that Antarctica is 
getting windier, and this may also help explain the changes in ocean 
circulation. Stronger circumpolar winds would tend to push sea ice and 
surface water north, says Jacobs. That in turn, would allow more warm 
water from the deep ocean to upwell onto the Amundsen Sea's continental 
shelf and into its ice shelf cavities.

Pine Island Glacier, among other ice streams in Antarctica, is being 
closely watched for its potential to redraw coastlines worldwide. Global 
sea levels are currently rising at about 3 millimeters (.12 inches) a 
year. By one estimate, the total collapse of Pine Island Glacier and its 
tributaries could raise sea level by 24 centimeters (9 inches).

The paper adds important and timely insights about oceanic changes in 
the region, says Eric Rignot, a professor at University of California at 
Irvine and a senior research scientist at NASA's Jet Propulsion 
Laboratory. "The main reason the glaciers are thinning in this region, 
we think, is the presence of warm waters," he said. "Warm waters did not 
get there because the ocean warmed up, but because of subtle changes in 
ocean circulation. Ocean circulation is key. This study reinforces this 
concept."

The study received funding from the US National Science Foundation and 
the UK National Environment Research Council.

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------------------------------------------------------------------------

*Story Source:*

    The above story is reprinted (with editorial adaptations by
    Science/Daily/staff) from materials provided by*The Earth Institute
    at Columbia University* <http://www.earth.columbia.edu/>,
    viaEurekAlert! <http://www.eurekalert.org/>, a service of AAAS.

------------------------------------------------------------------------

*Journal Reference*:

   1. Stanley S. Jacobs, Adrian Jenkins, Claudia F. Giulivi, Pierre
      Dutrieux.*Stronger ocean circulation and increased melting under
      Pine Island Glacier ice shelf*./Nature Geoscience/, 2011;
      DOI:10.1038/ngeo1188 <http://dx.doi.org/10.1038/ngeo1188>


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