Ocean currents speed melting of Antarctic ice

Jun 26, 2011
Upwelling seawater along parts of Pine Island Glacier Ice Shelf has carved out caves in the ice and drawn wildlife like this whale. Credit: Maria Stenzel, all rights reserved.

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 , 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 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.

Scientists aboard the Nathaniel B. Palmer visited the Amundsen Sea region in 2009 to study oceanic changes. Credit: Frank Nitsche, Lamont-Doherty Earth Observatory.

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 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 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."

Explore further: NASA balloons begin flying in Antarctica for 2014 campaign

More information: "Stronger ocean circulation and increased melting under Pine Island Glacier ice shelf" Nature Geoscience (2011)

Related Stories

Pine Island Glacier sensitive to climatic variability

Jan 02, 2014

A new study published in Science this month suggests the thinning of Pine Island Glacier in West Antarctica is much more susceptible to climatic and ocean variability than at first thought. Observations by a team of scient ...

Antarctic research details ice melt below massive glacier

Sep 12, 2013

An expedition of international scientists to the far reaches of Antarctica's remote Pine Island Glacier has yielded exact measurements of an undersea process glaciologists have long called the "biggest source ...

Recommended for you

Scientists make strides in tsunami warning since 2004

Dec 19, 2014

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

Dec 19, 2014

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 24

Adjust slider to filter visible comments by rank

Display comments: newest first

Vendicar_Decarian
1 / 5 (46) Jun 26, 2011
current sea ice extent now 1.4 million square kilometers below historic averages.

Sea ice volume at record lows for this date.

hush1
1.7 / 5 (10) Jun 26, 2011
.1) The history of atmospheric circulation is unknown.
.2) The onset of ACC is without consensus.
NotParker
1.9 / 5 (14) Jun 26, 2011
Antarctic Sea Ice is above normal.

http://arctic.atm...ctic.png

It isn't "global" warming if antarctica isn't warming.
MediocreSmoke
3.3 / 5 (11) Jun 26, 2011
Antarctic Sea Ice is above normal.

http://arctic.atm...ctic.png

It isn't "global" warming if antarctica isn't warming.


You're retarded, learn how to do an average and what that word means. Look up the word normal while you're at it.
Vendicar_Decarian
0.9 / 5 (44) Jun 26, 2011
Hmmmmm.... Up .049 million kilometers in the Antarctic, and down 1.4 million square kilometers in the Arctic.

Once again... No Parker shows it's intellectual bankruptcy.

I have noted that American Conservatives are generally incapable of adding, subtracting, multiplying and dividing.
NotParker
1.9 / 5 (14) Jun 26, 2011
Insults ... insults ... insults.

And yet, "global" isn't global at all.

Antarctica is cooling.
Vendicar_Decarian
0.8 / 5 (45) Jun 26, 2011
"Antarctica is cooling." - NoParkerTard

Well, no.. It isn't doing that either, but you have demonstrated that you have no interest in reality and would much rather live a life of ignorant make believe.

Were you ever part of the reality based community as a child?
Gilbert
3.7 / 5 (9) Jun 26, 2011
It it rather alarming at the rate that these aticles come out, each identifying another proof of unusual global temperatures, there must be thousands of different proofs now. I haven't seen one single credible peer reviewed report that supports the opposite being true, and yet these bozos here are still arguing against it, scientists lose again :(

but how do we overcome this problem?
Cin5456
4 / 5 (8) Jun 27, 2011

but how do we overcome this problem?

Keep reporting the true statistics, keep the science on track. Keep track of what the real scientists are doing. We can't do much else without a consensus, and the political-media pundits will prevent that for many years to come. But there is no way the overwhelming evidence can be ignored forever. Someday it will all come back to bite them in the butt, and then the politico-corporate shills and right wing do-nothing naysayers will eat their words and die along with the rest of the population that is effected by disease, insect-induced famine, pollution, tornadoes, floods, desertification, supercell storms and rising sea level. I imagine when Manhattan Island is knee deep in seawater someone will realize there is a global warming problem.
Vendicar_Decarian
0.2 / 5 (39) Jun 27, 2011
"but how do we overcome this problem?" - Gilbert

A national razor.
Argon
1 / 5 (11) Jun 27, 2011
What do global warming and evolution have in common? They were both conceived in the minds of filthy dreamers! FILTHY DREAMERS!
astro_optics
1.9 / 5 (13) Jun 27, 2011
The sad thing is that I would not trust anything that comes from these "researchers" do their inclination to political influence...
lengould100
4.2 / 5 (5) Jun 27, 2011
It simple logic. As very small additional melting occurs under the ice shelf, as stated in the article, the density of the resulting mixed seawater freshwater is lower than normal seawater, therefore it will rise any way possible, flowing out from under the ice and surfacing nearby, thus pumping additional warm seawater from an opposite direction in under the ice shelf to replace it. Result, increasingly rapid ice melting from the bottom surface of the shelf.

Very difficult to measure, though, as it doesn't show up anywhere convenient for measureing.
stanfrax
1 / 5 (4) Jun 27, 2011
weather patterns continue to break records across the globe http://www.wunder...num=1831 our leaders still continue to play there greed for growth game - this film shows the pathetic root cause of our problem - how we have been nurtured in a system and it gives a solution using technology as a tool http://www.youtub...re=share
NotParker
1.8 / 5 (10) Jun 27, 2011
According to the RSS satellite data, since January 2001, Antarctica is cooling at a rate of -1.27 °C / century.

The continental USA is cooling at a rate of -4.84 °C / century.

http://motls.blog...nds.html
Vendicar_Decarian
0.7 / 5 (40) Jun 27, 2011
You do realize don't you that Lobos Motl is mentally ill.

Why do you think he was recently "resigned" from his position as assistant professor at Harvard University.

Lubos was, in reality, fired last week or so from Harvard Physics
Department (outwardly he "resigned" - but no one willingly resigns from
Harvard in mid-year obviously) for precisely this kind of unprofessional
public activity. Too much blogging and calling people bad names and too
little research. Not wise for a young man without tenure.

http://mathforum....tstart=0

NotParker
1.4 / 5 (9) Jun 27, 2011
Wow. Thanks for the reference. The people who hate Lubos are clearly the most mentally ill people I've every read about.

"In my case he never bought any of my books about UFOs,
paranormal"

Now wonder you think any who dislikes books on paranormal activity should be fired.

Vendicar the PARNORMAL WORSHIPPING LUNATIC HATES PHYSICISTS who don't believe in global warming.

But, aside from your insanity, which part of his math do you disagree with?

Or is it just that your fellow AGW/paranormal freaks can't do math?

The earth is cooling from 2001:

http://woodfortre...01/trend
ryggesogn2
2 / 5 (8) Jun 27, 2011
"but how do we overcome this problem?" - Gilbert

A national razor.

Violence is always the final solution for the socialist.
Argon
1 / 5 (2) Jun 27, 2011
thermodynamics
4.6 / 5 (9) Jun 27, 2011
NotParker: Do you have a clue as to how statistics works? Do you realize that by cherry picking a noisy signal you can make it say almost anything? The process of picking a signal out of noise requires a strong background in mathematics and statistics. It also requires some integrity. Your example of cherry picking data above:

"Or is it just that your fellow AGW/paranormal freaks can't do math?

The earth is cooling from 2001:"

With your reference: http://woodfortre...01/trend

Is an amazingly blatant example of disingenuous cherry picking. Please tell us how you chose the start and end to be statistically important and how that shows a trend Mathematically? Your example is embarrassing to you if you think it is statistically valid and subterfuge if you know it is not.
NotParker
1.5 / 5 (8) Jun 27, 2011
Ten years of cooling is not cherry picking when the 10 year period is the last 10 years.

How can anyone claim the earth is warming when it hasn't for the last 10 years?

Antarctica is cooling at a rate of -1.27 °C / century.
The continental USA is cooling at a rate of -4.84 °C / century.

Those are not trivial amounts.
ryggesogn2
1.9 / 5 (9) Jun 27, 2011
cherry picking data

That's what Mann did to create his hockey stick.

BTW, what is 'normal'?
MikPetter
5 / 5 (1) Jul 03, 2011
Notes from the Wood for Trees site author
"Temperature trends - pick a timescale, any timescale!
After many requests, I finally added trend-lines (linear least-squares regression) to the graph generator. I hope this is useful, but I would also like to point out that it can be fairly dangerous...
Depending on your preconceptions, by picking your start and end times carefully, you can now 'prove' that:
Temperature is falling!Temperature is static!Temperature is rising!Temperature is rising really fast!
Personally, I prefer the long view, and now we have trendlines, and adjusted anomaly baselines, we can throw it all together into one monster plot:....If you look at the trend data, you can see the current trends in °C, between 0.13-0.17°C/decade, or, if it continues at the same rate, between 1.3 and 1.7°C per century."
Cin5456
5 / 5 (1) Jul 03, 2011
Mik, I like your idea of using the variance adjusted global mean, but some might object to the adjustment. Instead, use the same graph and set the date to 1950. This gives a long view with a 0.6 rise in global temps. If you set it to 1939, near the beginning of the military industrial complex that geared up for war, you still get a 0.4 rise in global temps. If you go all the way back to 1850, the time limit on records, you will see three periods of rising, and falling temps. Overall, the time delimited data shows discontinuous rise in global temperatures of about 0.7 degrees since 1850. This is what happens when you don't restrict the data to small increments. Personally, I prefer the 1950 to present graph, because it demonstrates the trend.

Aren't graphs fun?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.