(Also see “Manhattan-Size Ice Island Cracks in Half.”)

The crevasse stretches 19 miles (30 kilometers) long and up to 260 feet (80 meters) wide, as shown in a picture taken by NASA’s Terra satellite in October and featured this week as a NASA Image of the Day.

Snaking across the floating tongue of the Pine Island Glacier in West Antarctica, the crack is expected to create an iceberg 350 square miles (907 square kilometers)—versus 303 square miles (785 square kilometers) for Manhattan, Brooklyn, Queens, Staten Island, and the Bronx combined, according to NASA.

As for when the iceberg might shove off, “that is very difficult to predict,” said oceanographer Eric Rignot of NASA’s Jet Propulsion Laboratory, “but in the coming months for sure.”

Glacier “Contributing Most to Sea Level”

Usually there’s nothing extraordinary about a glacier calving, said glaciologist Ted Scambos of the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado.

Glaciers that flow into the sea, like the Pine Island Glacier, go through a normal cycle in which the floating section grows, stresses mount, and an iceberg breaks off, Scambos said.

“That is nothing unusual in most cases.”

But when the pattern deviates, glaciologists take notice. In this case, the crack is forming significantly farther “upstream” than has previously been the case. That “signifies that there are changes in the ice,” he said.

When “that point of rifting starts to climb upstream, generally you see some acceleration of the glacier.” That means that the ice will flow into the ocean at a faster rate, contributing even more to sea level rise.

(Related: “Hundreds of Glaciers Melting Faster in Antarctica.”)

 Such an acceleration is of particular concern at the Pine Island Glacier, because, among Antarctic glaciers, it’s “the one that’s contributing the most to sea level rise.”

In fact, he said, ice flows from that glacier alone account for a quarter to a third of Antarctica’s total contribution to sea level rise.

“It’s moving at about three kilometers [almost two miles] per year,” Scambos said. And, he noted, “it’s been accelerating quite a bit.”

(Pictures: Antarctica Warming.)

Cracking Glacier “Really Important”

As far as sea levels are concerned, changes in the Pine Island Glacier and other West Antarctic glaciers are far more important than shifts among the continent’s other glaciers, such as East Antarctica’s Mertz Glacier—despite Mertz’s much publicized release of a Luxembourg-size iceberg in early 2010.

That’s because the “Luxembourg” iceberg came from a glacial ice tongue that had just been “sitting there,” said oceanographer Doug Martinson of Columbia University’s Lamont-Doherty Earth Observatory.

By contrast, “West Antarctica has ice streams, of which Pine Island is one. Those are fast-flowing streams of ice,” said Martinson, who specializes in polar oceans.

When ice breaks off the Pine Island Glacier, he said, more ice can flow in faster from the mountains above—ice that will eventually wind up contributing to sea level rise.

“This glacier,” NSIDC’s Scambos added, “is really important.”

Source National Geographic

The map, along with an associated animation (below) developed by NASA, reveals that ice is flowing fastest in coastal ice shelves and their tributaries, shown in this illustration in bright purple and blue. Though it’s ice that’s moving, not water, “you can imagine it like a river system,” says Bernd Scheuchl, one of the map’s creators. The fastest ice flows out to sea at a rate of a few kilometers a year. Pine Island and Thwaites Glaciers on the west coast are the most active.

The team was surprised by how far inland they found fast-moving ice, Scheuchl says. So, if Antarctica loses a great deal of its coastal ice to climate change in the coming decades, large quantities of interior ice could follow. “That’s critical knowledge for predicting future sea level rise,” NASA polar scientist Thomas Wagner said in a prepared statement.

To create this view of Antarctic ice flow, the UC Irvine researchers relied on data from satellites operated by Canada, Japan and the European Space Agency. Flow was tracked from 2007 to 2009 during a period of intense scientific monitoring of Earth’s poles that researchers all over the world had agreed to do. A report on the map was published online August 18 in Science.

Source Scientific America

New University of Washington research shows that rising sea surface temperatures in the area of the Pacific Ocean along the equator and near the International Date Line drive atmospheric circulation that has caused some of the largest shifts in Antarctic climate in recent decades.

The warmer water generates rising air that creates a large wave structure in the atmosphere called a Rossby wave train, which brings warmer temperatures to West Antarctica during winter and spring.

Antarctica is somewhat isolated by the vast Southern Ocean, but the new results “show that it is still affected by climate changes elsewhere on the planet,” said Eric Steig, a UW professor of Earth and space sciences and director of the UW Quaternary Research Center.

Steig is the corresponding author of a paper documenting the findings that is being published April 10 in the journal Nature Geoscience. The lead author is Qinghua Ding, a postdoctoral researcher in the UW Quaternary Research Center. Co-authors are David Battisti, a UW atmospheric sciences professor, and Marcel Küttel, a former UW postdoctoral researcher now working in Switzerland.

The scientists used surface and satellite temperature observations to show a strong statistical connection between warmer temperatures in Antarctica, largely brought by westerly winds associated with high pressure over the Amundsen Sea adjacent to West Antarctica, and sea surface temperatures in the central tropical Pacific Ocean.

They found a strong relationship between central Pacific sea-surface readings and Antarctic temperatures during winter months, June through August. Though not as pronounced, the effect also appeared in the spring months of September through November.

The observed circulation changes are in the form of a series of high- and low-pressure cells that follow an arcing path from the tropical Pacific to West Antarctica. That is characteristic of a textbook Rossby wave train pattern, Ding said, and the same pattern is consistently produced in climate models, at least during winter.

Using observed changes in tropical sea surface temperatures, the researchers found they could account for half to all of the observed winter temperature changes in West Antarctica, depending on which observations are used for comparison.

“This is distinct from El Niño,” Steig said. That climate phenomenon, which affects weather patterns worldwide, primarily influences sea-surface temperatures farther east in the Pacific, nearer to South America. It can be, but isn’t always, associated with strong warming in the central Pacific.

Steig noted that the influence of Rossby waves on West Antarctic climate is not a new idea, but this is the first time such waves have been shown to be associated with long-term changes in Antarctic temperature.

The findings also could have implications for understanding the causes behind the thinning of the West Antarctic Ice Sheet, which contains about 10 percent of all the ice in Antarctica.

Steig noted that the westerly winds created by the high pressure over the Amundsen Sea pushes cold water away from the edge of the ice sheet and out into the open ocean. It is then replaced by warmer water from deeper in the ocean, which is melting the seaward edge of the ice sheet from below.

The work was funded by the National Science Foundation.

Source Science Daily

It is natural to be rattled by these observations. There is no immediately obvious reason why the rate of ice loss should not continue to increase. Indeed, the recent observations might presage even faster acceleration, perhaps involving the discharge of a substantial fraction of the 1500 mm of sea-level equivalent still stored in Pine Island Glacier and its neighbours. And we have a serious enough problem even if Pine Island Glacier simply maintains its present rate of loss.

Knowing what they know and what they don’t know, “alarmist” is therefore not a label about which glaciologists need to be embarrassed. But they also know that alarmist projections have a way of turning out to be exaggerated.

Consider the energy-balance models, that describe how the climate responds to changes in radiative forcing. The two first such models, published independently by Mikhail Budyko and William Sellers in 1969, projected that the Earth’s surface temperature would drop to tens of degrees below freezing if the output of the Sun were to decrease by only two percent. That made people sit up, and yielded a flurry of publications showing that there are plenty of ways in which the climate system moderates the severity of the negative feedback which was the basis for the original findings.

Even though they are based on measurement rather than on modelling, might our concerns about the recent behaviour of outlet glaciers in Antarctica and Greenland be similarly exaggerated? In a recent modelling study, Ian Joughin and co-authors suggest that the answer is “Probably, but not necessarily”.

The model is not quite state-of-the-art, in that it does not solve the full Stokes equation but a simpler form of the dynamical system that is appropriate for ice shelves and ice streams. The authors were obliged to handle the grounding line, where the grounded ice stream feeds into the floating ice shelf, somewhat roughly. Nevertheless the calculations allow for careful treatment of the rapid sliding at the base of the ice stream, and the implied very large rates of basal melting. And the model does a good job of reproducing the documented behaviour of Pine Island Glacier up to 2009.

Most of the ice in the Pine Island Glacier catchment is flowing very slowly indeed, at a few metres per year at most. But as it converges on the outlet of the catchment it accelerates spectacularly, and is moving at thousands of metres per year by the time it starts to float at the grounding line. Most of the speed is the result of basal sliding, so the ice stream is not unlike a rigid plug, punching its way through the much slower ice on its flanks. This peculiar setup is the core of the problem.

Joughin and his co-authors simulated responses of the glacier to a variety of scenarios that might or might not represent the next hundred years. Even the more extreme scenarios, featuring basal melting at four times the present rate, did not lead to flotation of the entire 200-kilometre length of the ice stream, as one earlier study had suggested. Nor did the model come anywhere close to an even simpler extrapolation of current behaviour, based on kinematics rather than dynamics.

Don’t breathe out yet, however. The results considered by the authors to be the most probable have Pine Island Glacier continuing to lose mass at rates comparable to the recent rates. It doesn’t continue to accelerate, but it doesn’t slow down either. The grounding line doesn’t continue to migrate inland, but the inland thinning implied by the fast flow does continue.

It would be wrong to write off this heroic but tentative modelling effort, which is an important step towards the goal of understanding Pine Island Glacier. Models like this one, and like the energy-balance models that followed up on Budyko and Sellers, are part of the learning process. They suggest that doomsday isn’t going to happen just yet. But, in short, doomsday scenarios are educational.

Source Environmental research web

Footnote – This situation and the broader picture of the grounding lines under the Pine Island Glacier and the Ross Ice Shelf are cover in the book ZERO Greenhouse Emissions – get the ebook here.

Named by the French in 1792 the Peak stands 262 metres above sea level. At the base of the impressive rock formation, signs point the way to what is described as a two hour round trip to the summit. Being a very hot and humid day and with the suggestion that it should only be attempted by fit hikers, I decided to give the summit climb a miss!

There was another sign at the base that caught my attention. The origins of the rock. Geologists had established that the massive granite formation was formed 120 million years ago; a long time. The sign went on to detail how the cave on the top of Frenchman’s Peak was formed by waves over thousands of years, 40 million years ago during the Middle Eocene period, when sea level was 250 metres higher than today.

Excerpt from SkepticalScience.com

Around 40 million years ago, sea surface temperatures rose around 5°C in a period called the Middle Eocene Climatic Optimum (MECO). A new study Transient Middle Eocene Atmospheric CO₂ and Temperature Variations (Bijl et al 2010) has found atmospheric CO2 was the primary driver of this global warming event. During this period, CO2 levels rose dramatically to 2 to 3 times previous levels. This study gives us further insight into how climate responds to changing CO2 levels and provides evidence for strong climate sensitivity. Read more Skeptical Science article

As you watch the following YouTube videos, it may strike you as it did me that everything viewed from the top of Frenchman’s Peak by these visitors; 40 million years ago was below the sea! A very different world!

With continuing rises in greenhouse emissions Frenchman’s Peak may one day return to its origins.

ERICE, Italy—If you think of Earth’s poles as fraternal twins, the Arctic has been the wild one in recent years, while the Antarctic has been a steady plodder. Withered by summer heat, Arctic sea ice has shrunk to record low coverage several times since 2005, only to rebound to within 95 percent of its long-term average extent this winter. By comparison, Antarctica, with some 90 percent of the world’s glacial reserves, has generally shed ice in more stately fashion.
   
However, emerging evidence from an Antarctic geological research drilling program known as ANDRILL suggests that the southernmost continent has had a much more dynamic history than previously suspected—one that could signal an abrupt shrinkage of its ice sheets at some unknown greenhouse gas threshold, possibly starting in this century. Especially troubling, scientists see evidence in the geological data that could mean the vast East Antarctic Ice Sheet, which holds at least four-fifths of the continent’s ice, is less resistant to melting than previously thought.
   
ANDRILL, a collaboration among scientists from Germany, Italy, New Zealand and the U.S., obtained the evidence from a 3,734-foot-long core extracted in 2007 from the seafloor on the southern McMurdo Sound, near Antarctica’s Ross Island.
   
A prior core, extracted from the McMurdo Ice Shelf between October 2006 and January 2007, indicated that the West Antarctic Ice Sheet has frequently advanced and retreated. As ANDRILL scientists met here April 6-11 to integrate core results, the geologists and climate modelers pondered the hints of dynamism observed in the much larger East Antarctic Ice Sheet.
   
Contrary to what climate simulations suggest, David Harwood, the program’s co-chief scientist, says, “nature seems to give us a record that the ice sheets are coming and going.”
   
The southern McMurdo Sound core yielded clear evidence of some 74 cycles of ice sheet buildup and retreat during a 6-million-year stretch starting in the Miocene Epoch some 20 million years ago. The unexpected ice-sheet dynamism has ANDRILL climate modelers considering what input or software adjustments would make the simulation produce the kind of dynamism seen in the geological record. Their model currently indicates that even if the imperiled West Antarctic Ice Sheet succumbs to current warming trends, the much larger East sheet should stubbornly resist melting. According to the simulation, the East ice sheet melts only when atmospheric carbon dioxide levels are at least eight times higher than preindustrial levels. The ice sheet’s so-called hysteresis, or resistance to change, is now in doubt.
  
Modeler and geologist Robert DeConto of the University of Massachusetts, Amherst, says the policy implications are grim. “Our models may be dramatically underestimating how much worse it’s going to get,” he says, noting that many population centers worldwide are within a few meters of sea level. Looking at signs of meltwater in the early Miocene, DeConto says, “we’re seeing ice retreat faster and more dramatically than any model predicts.”
  
Antarctica’s ice sheets contain roughly two-thirds of the world’s fresh water. A meltdown of the West Antarctic Ice Sheet alone would boost sea levels by an estimated 20 feet, but if the East sheet were to also succumb, along with the Greenland ice sheet, sea levels could rise by more than 200 feet. This would be catastrophic for major population centers near sea level, such as New York City, much of Florida and nearly all of Bangladesh. No one expects the ice sheets to disappear overnight—even the worst timelines span centuries—and uncertainty about their fate remains, but radar altimetry from NASA satellites indicates that melting is under way in some parts of the East sheet, as well as in much of the West sheet. Researchers say the effects of melting ice sheets could be apparent within a lifetime as undersea currents are disrupted and weather patterns shift.
  
DeConto’s collaborator, climate modeler David Pollard of Pennsylvania State University, says the answer to the puzzling disparity between model predictions and the core data could lie in an erroneous assumption about Antarctica itself. For example, Pollard says, some parts of the land underlying the East ice sheet might be much lower than currently believed. In that case, if warming oceans strip away the surrounding ice shelves, significant chunks of the ice sheet could slide into the ocean. Subglacial lakes, which form as glaciers slide over depressions, may have an underappreciated role, he added. DeConto says polar stratospheric clouds also need further study. There are indications, he says, that they act as infrared reflectors, which might contribute to ice sheet melting in ways not yet accounted for in models.
  
Whatever the cause, the key evidence for ice sheet dynamism in the Antarctic comes from the core’s lithographic record. Sedimentologists have studied its facies, the visible characteristics that distinguish each stratum, for indications of how warm or cold the surrounding environment was. The McMurdo Sound facies repeatedly vary from “ice proximal,” where fractures, scraping and larger grain size indicate a glacier rumbling by, to “ice distal,” where laminated sediments and marine fossils speak of lapping waves in an ice-free marine environment.
  
Numerous other lines of evidence from the core support the idea of wide climate swings in Antarctica’s past. There are spikes in the amount of pollen found within the core, for example, indicating flowering plants nearby. Levels of various organic molecules repeatedly rise and fall in the column, showing that microorganisms and shellfish flourished in the warmer periods and receded during cold times. The presence or absence of clasts—chunks of sedimentary rock carried along and deposited by glaciers—also indicates a fluctuating Antarctic climate. Co-chief scientist Fabio Florindo of Italy’s National Institute of Geophysics and Volcanology notes that surges of magnetic mineral in the core may also mark warming trends. Reviewing the record, sedimentologist Christopher Fielding of the University of Nebraska-Lincoln says that in its warmest periods Antarctica must have resembled Patagonia today, where winters average a few degrees below freezing and summertime highs occasionally reach 80 degrees Fahrenheit.
  
However, Fielding, DeConto and others agree the core data is not conclusive. The McMurdo Sound core offers a pinhole view of East and West Antarctic Ice Sheet behavior, but at the price of extreme difficulty of interpretation. Scientists expect that firmer answers will emerge from other Antarctic research, including a hoped-for third ANDRILL project planned for Coulman High, also in the vicinity of Ross Island.
  
Harwood, a University of Nebraska geoscientist, says there is already evidence enough for policymakers to take action against global warming in hopes of preventing a dramatic Antarctic meltdown. “This core is going to be studied for the next 20 to 30 years,” he notes, but already, he adds, the Miocene-age evidence it contains strongly suggests that it would be a mistake to count on ice-sheet stability in the Antarctic. “We see two or three periods of ice-sheet collapse, including one that looks abrupt, with very rapid deglaciation.”
Source Scientific America

“During the summer of 2005 we got started on breaking some records for melting of the Greenland ice sheet. Offering to destabilize large parts of the ice sheet on timescales measured in years or decades, not millennia. Just to emphasize the point,” said the super salesman, “in 2007 the summer melt on Greenland broke the 2005 record by 10 percent making it the largest melt recorded since satellite measurements began in 1979.”

“Pop in for a visit to Swiss Camp, a research station established in 1990, and take a trip over to the newly expanding ‘Greenland Lake District’ where some lakes cover six kilometers. We could set up a bit of water skiing for those interested. These have been set up by Mother Nature as reservoirs for the destruction of the ice sheet, so you’ll have to be quick if you want to get in some sailing. The lakes grow until they find a crevasse that provides an opportunity for them to drain into the extensive river systems beneath the ice and the hard bedrock, providing lubrication for the ice sheet before emerging at the glacier’s snout. On your trip you might like to view one of the waterfalls that run as much as 3 kilometers high taking the meltwater all the way to the bedrock. We once thought this would take ten thousand years but we can now see the lakes empty into moulins (vertical shafts) in just ten seconds. You’ll need to book your trip soon while we have some ice left for the gin and tonic. On offer is a day trip to the Jakobshavn Isbrae glacier. You can spot her on the 700-kilometer trip west to Baffin Bay.”

“This we think has some history, providing the nudge that sank the Titanic in 1912,” said the super salesman. “Who says you can’t make money from disaster, the film made millions!”

Since 1997 the speed has doubled and now at 15 kilometers per year it claims the world land speed record for glaciers. At that rate Baffin Bay can have the whole glacier within approximately sixty years. In the meantime from the Jakobshavn Isbrae glacier we can offer meltwater of somewhere in the region of 50 cubic kilometers per year, enough to fill up the Nile as it responds to climate change, if you can get it there. The heater is working well on glacial speed all over the Greenland ice sheet and the thinning of the ice sheet for some, has reached a critical point and begun to drastically change the glacier’s dynamics.

Get a copy of the Book in e-book format for only $9.99 and start reading today ‘What they would rather you didn’t know!’

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The ice has retreated so far from the land mass that Charcot Island, which has long been connected to the peninsula by an ice bridge, emerged as a real island again last year, a USGS scientist said.
“This is the first time since people have been observing the area, since the 1800s, that that ice shelf has not hitched together Charcot Island and the peninsula,” scientist Jane Ferrigno said in a telephone interview.
The Antarctic Peninsula extends further northward than the rest of the roughly circular ice-covered continent, and it is warmer than the rest of Antarctica. But even in the peninsula’s coldest, southern part, ice shelves are vanishing.
Research by the USGS was the first to show that every ice front on the southern section of the peninsula has been retreating from 1947 to 2009, with the most dramatic changes since 1990.
A study of the phenomenon by the USGS in collaboration with the British Antarctic Survey and assistance from the Scott Polar Research Institute and Germany’s Bundesamt fur Kartographie and Geodasie was posted at pubs.usgs.gov/imap/i-2600-c/ in February; a statement was released on Monday.
ICE SHELVES ACT AS GLACIER DAMS
Ice shelves act as dams to keep land-based glaciers from flowing unimpeded into the sea; when ice shelves melt, glaciers can move more quickly into ocean waters.
If all the land-based ice in Antarctica melted, scientists have estimated sea levels worldwide could rise from 213 to 240 feet, according to the study. If just the ice in West Antarctica melted, there would be a sea level rise of about 20 feet, threatening coastal communities and low-lying islands.
The land-based ice on the Antarctic peninsula is not enough to fuel a major rise in sea level, Ferrigno said. However, the dramatic disappearance of ice shelves there could give a clue of what could happen when glaciers are free to flow seaward.
This is important because the Antarctic ice sheet contains 91 percent of Earth’s glacier ice, Ferrigno said.
Unlike Antarctic land-based ice, the ice that covers much of the Arctic Ocean would not contribute to sea level rise if it all melted, in much the way that a melting ice cube in a glass of water would not make the glass overflow.
But both the Arctic and Antarctic have major impact on weather in the temperate parts of the world.

Source Reuters

Want a weekly update of all the greatest posts on the web? Subscribe for the weekly VOICE FOR CHANGE Newsletter and never miss a story! CLICK Bob Williamson and in the subject line type SUBSCRIBE

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