Joe Romm: Leading Climate Scientists: ‘We Have A Global Emergency,’ Must Slash CO2 ASAP!

by Joe Romm, Climate Progress, March 22, 2016

James Hansen and 18 leading climate experts have published a peer-reviewed version of their 2015 discussion paper on the dangers posed by unrestricted carbon pollution. The study adds to the growing body of evidence that the current global target or defense line embraced by the world — 2 °C (3.6 °F) total global warming — “could be dangerous” to humanity.

That 2 °C warming should be avoided at all costs is not news to people who pay attention to climate science, though it may be news to people who only follow the popular media. The warning is, after all, very similar to the one found in an embarrassingly under-reported report last year from 70 leading climate experts, who had been asked by the world’s leading nations to review the adequacy of the 2 °C target.

Specifically, the new Hansen et al. study — titled “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous” — warns that even stabilizing at 2 °C warming might well lead to devastating glacial melt, multimeter sea level rise and other related catastrophic impacts. The study is significant not just because it is peer-reviewed, but because the collective knowledge about climate science in general and glaciology in particular among the co-authors is quite impressive.

Besides sea level rise, rapid glacial ice melt has many potentially disastrous consequences, including a slowdown and eventual shutdown of the key North Atlantic Ocean circulation and, relatedly, an increase in super-extreme weather. Indeed, that slowdown appears to have begun, and, equally worrisome, it appears to be supercharging both precipitation, storm surge, and superstorms along the U.S. East Coast (like Sandy and Jonas), as explained here.

It must be noted, however, that the title of the peer-reviewed paper is decidedly weaker than the discussion paper’s “Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming is highly dangerous.” The switch to “could be dangerous” is reminiscent of the switch (in the opposite direction) from the inaugural 1965 warning required for cigarette packages, “Caution: Cigarette Smoking May Be Hazardous to Your Health” to the 1969 required label “Warning: The Surgeon General Has Determined that Cigarette Smoking Is Dangerous to Your Health.”

And yes I’m using the analogy to suggest readers should not be sanguine about the risks we face at 2 °C warning. Based on both observations and analysis, the science is clearly moving in the direction that 2 °C warming is not “safe” for humanity. But as Hansen himself acknowledged Monday on the press call, the record we now have of accelerating ice loss in both Greenland and West Antarctica is “too short to infer accurately” whether the current exponential trend will continue through the rest of the century.

Hansen himself explains the paper’s key conclusions and the science underlying them in a new video:

The fact that 2 °C total warming is extremely likely to lock us in to sea level rise of 10 feet or more has been obvious for a while now. The National Science Foundation (NSF) itself issued a news release back in 2012 with the large-type headline, “Global Sea Level Likely to Rise as Much as 70 Feet in Future Generations.”  The lead author explained, “The natural state of the Earth with present carbon dioxide levels is one with sea levels about 70 feet higher than now.” Heck, a 2009 paper in Science found the same thing.

What has changed is our understanding of just how fast sea levels could rise. In 2014 and 2015, a number of major studies revealed that large parts of the Antarctic and Greenland ice sheets are unstable and headed toward irreversible collapse — and some parts may have already passed the point of no return. Another 2015 study found that global sea level rise since 1990 has been speeding up even faster than we knew.

The key question is how fast sea levels can rise this century and beyond. In my piece last year on Hansen’s discussion draft, I examined the reasons the Intergovernmental Panel on Climate Change (IPCC) and scientific community have historically low-balled the plausible worst-case for possible sea level rise by 2100. I won’t repeat that all here.

The crux of the Hansen et al. forecast can be found in this chart on ice loss from the world’s biggest ice sheet:

Antarctic ice mass change from GRACE satallite data (red) and surface mass balance method (MBM, blue). From Hansen et al.

Hansen et al. ask the question: if the ice loss continues growing exponentially how much ice loss (and hence how much sea level rise) will there be by century’s end? If, for instance, the ice loss rate doubles every 10 years for the rest of the century (light green), then we would see multi-meter sea level rise before 2100? On the other hand, it is pretty clear just from looking at the chart that there isn’t enough data to make a certain projection for the next eight decades.

The authors write, “our conclusions suggest that a target of limiting global warming to 2 °C … does not provide safety.” On the one hand, they note, “we cannot be certain that multi-meter sea level rise will occur if we allow global warming of 2 °C.” But, on the other hand, they point out:

There is a possibility, a real danger, that we will hand young people and future generations a climate system that is practically out of their control.
We conclude that the message our climate science delivers to society, policymakers, and the public alike is this: we have a global emergency. Fossil fuel CO2 emissions should be reduced as rapidly as practical.

I have talked to many climate scientists who quibble with specific elements of this paper, in particular whether the kind of continued acceleration of ice sheet loss is physically plausible. But I don’t find any who disagree with the bold-faced conclusions.

Since there are a growing number of experts who consider that 10 feet of sea level rise this century is a possibility, it would be unwise to ignore the warning. That said, on our current emissions path we already appear to be headed toward the ballpark of 4-6 feet of sea level rise in 2100 — with seas rising up to one foot per decade after that. That should be more than enough of a “beyond adaptation” catastrophe to warrant strong action ASAP.

The world needs to understand the plausible worst-case scenario for climate change by 2100 and beyond — something that the media and the IPCC have failed to deliver. And the world needs to understand the “business as usual” set of multiple catastrophic dangers of 4 °C if we don’t reverse course now. And the world needs to understand the dangers of even 2 °C warming.

So kudos to all of these scientists for ringing the alarm bell: James Hansen, Makiko Sato, Paul Hearty, Reto Ruedy, Maxwell Kelley, Valerie Masson-Delmotte, Gary Russell, George Tselioudis, Junji Cao, Eric Rignot, Isabella Velicogna, Blair Tormey, Bailey Donovan, Evgeniya Kandiano, Karina von Schuckmann, Pushker Kharecha, Allegra N. Legrande, Michael Bauer, and Kwok-Wai Lo.

http://thinkprogress.org/climate/2016/03/22/3762111/climate-scientists-global-emergency/

Dr. Mauri Pelto discusses the Pine Island Glacier and the two recent papers on the Western Antarctic Ice Sheet, Part I

interview by Peter Sinclair, Climate Crocks, May 17, 2014


Link:  http://climatecrocks.com/2014/05/17/the-weekend-wonk-dr-mauri-pelto-on-antarctic-melt-part-1/

60% reduction in 40 years in the volume of Antarctic Bottom Water, the cold dense water that drives global ocean currents

Latest Southern Ocean research shows continuing deep ocean change

by John Hartz, Skeptical Science, May 21, 2012

This is a reprint of a press release posted by the Australian Commonwealth Science and Industrial Research Organization (CSIRO)  May 4, 2012.

New research by teams of Australian and US scientists has found there has been a massive reduction in the amount of Antarctic Bottom Water found off the coast of Antarctica.

 

Deploying a mooring carrying a suite of monitoring sensors into the sea ice. Credit: Steve Rintoul

Comparing detailed measurements taken during the Australian Antarctic program's 2012 Southern Ocean marine science voyage to historical data dating back to 1970, scientists estimate there has been as much as a 60% reduction in the volume of Antarctic Bottom Water, the cold dense water that drives global ocean currents.

In an intensive and arduous 25-day observing program, temperature and salinity samples were collected at 77 sites between Antarctica and Fremantle. Such ship transects provide the only means to detect changes in the deep ocean.

The new measurements, which have not yet been published, suggest the densest waters in the world ocean are gradually disappearing and being replaced by less dense waters.

 "The amount of dense Antarctic Bottom Water has contracted each time we've measured it since the 1970s," said Dr Steve Rintoul, of CSIRO and the Antarctic Climate and Ecosystems CRC. "There is now only about 40% as much dense water present as observed in 1970."

The ocean profiles also show that the dense water formed around Antarctica has become less saline since 1970.

"It's a clear signal to us that the oceans are responding rapidly to variations in climate in polar regions. The sinking of dense water around Antarctica is part of a global pattern of ocean currents that has a strong influence on climate, so evidence that these waters are changing is important," Dr Rintoul said.

The research was carried out by more than 50 scientists on the Australian Antarctic Division's research and resupply vessel Aurora Australis, which sailed to Commonwealth Bay, west along the Antarctic coast, and returned into Fremantle.

The Australian Antarctic Division's Chief Scientist, Dr Nick Gales, said the findings of the oceanographic study are profoundly important.

"Not only will this research improve our understanding of ocean currents, but will also feed into our knowledge of how the Southern Ocean and the Antarctic continent drives the world's climate processes," Dr Gales said.

Dr Rintoul was Chief Scientist on the recent voyage and has made a dozen voyages to the Southern Ocean. "When we speak of global warming, we really mean ocean warming: more than 90% of the extra heat energy stored by the earth over the last 50 years has gone into warming up the ocean.

The Southern Ocean is particularly important because it stores more heat and carbon dioxide released by human activities than any other region, and so helps to slow the rate of climate change" Dr Rintoul said. "A key goal of our work is to determine if the Southern Ocean will continue to play this role in the future."

The causes of the observed changes in the Southern Ocean are not yet fully understood. Changes in winds, sea ice, precipitation, or melt of floating glacial ice around the edge of Antarctica may be responsible. Data collected on the latest voyage will help unravel this mystery.

A major challenge is the lack of observations at high latitude, where much of the ocean is covered by sea ice in winter. During the voyage scientists deployed nine drifting profilers, called Argo floats, which will transmit profiles of temperature and salinity every 10 days for the next five years. These ice-capable floats in the seasonal ice zone in the Australian sector of the Southern Ocean are funded through Australia's Integrated Marine Observing System.

"The Argo floats have revolutionised our ability to measure the ocean, particularly in winter when ship observations are very rare," said Dr Rintoul. "On this voyage, we deployed a new kind of float designed to survive encounters with the sea ice. These floats will allow us to see how dense water forms in winter for the first time."

The Aurora Australis visited Commonwealth Bay as part of a celebration of the centenary of Sir Douglas Mawson's Australian Antarctic Expedition. Dr Rintoul's team had the opportunity to repeat oceanographic measurements made by Mawson's team 100 years ago, obtaining one of the few century-long records obtained anywhere in the ocean.

"Our measurements collected in 2012 are quite different to those collected by Mawson in 1912," Dr Rintoul said. "This is an indication of a change in the ocean currents that may be related to a reduction in the amount of dense water formed near Antarctica."

"Mawson's expedition really marked the transition from the "Heroic Age" of Antarctic exploration to a period where science was the primary motivation for Antarctic expeditions. I think he would have gotten a real kick out of the idea that measurements made by his team a century ago are still useful and that Australian scientists are continuing his legacy by studying Antarctica and its connection to the rest of the globe."

http://www.skepticalscience.com/Southern-Ocean-research-shows-continuing-deep-ocean-change_CSIRO.html

Different magnitudes of projected subsurface ocean warming around Greenland and Antarctica by Yin et al., Nature Geoscience (2011)

Nature Geoscience (2011); doi:10.1038/ngeo1189

Different magnitudes of projected subsurface ocean warming around Greenland and Antarctica

Jianjun Yin,

Jonathan T. Overpeck,

Stephen M. Griffies,

Aixue Hu,

Joellen L. Russell and

 

Ronald J. Stouffer

Abstract

The observed acceleration of outlet glaciers and ice flows in Greenland and Antarctica is closely linked to ocean warming, especially in the subsurface layer. Accurate projections of ice-sheet dynamics and global sea-level rise therefore require information of future ocean warming in the vicinity of the large ice sheets. Here we use a set of 19 state-of-the-art climate models to quantify this ocean warming in the next two centuries. We find that in response to a mid-range increase in atmospheric greenhouse-gas concentrations, the subsurface oceans surrounding the two polar ice sheets at depths of 200–500 m warm substantially compared with the observed changes thus far. Model projections suggest that over the course of the twenty-first century, the maximum ocean warming around Greenland will be almost double the global mean, with a magnitude of 1.7–2.0 °C. By contrast, ocean warming around Antarctica will be only about half as large as global mean warming, with a magnitude of 0.5–0.6 °C. A more detailed evaluation indicates that ocean warming is controlled by different mechanisms around Greenland and Antarctica. We conclude that projected subsurface ocean warming could drive significant increases in ice-mass loss, and heighten the risk of future large sea-level rise.” 

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1189.html

Justin Gillis, Green, NYT: A Big Surprise Beneath the Ice (Antarctica)

A Big Surprise Beneath the Ice

by JUSTIN GILLIS, Green blog, The New York Times, March 3, 2011

Courtesy Bell et al, via ScienceA radar image of the Gamburtsev Mountains, overlain by the Antarctic ice sheet, which has been deformed by a bulge of refrozen ice (center).

Only rarely do researchers discover an entirely new physical mechanism that forces them to rethink a branch of science. But some new results from Antarctica promise to do exactly that in the field of glaciology.

A scientific study summarized online on Thursday in the journal Science shows that ice melts and re-freezes extensively at the base of the Antarctic ice sheet. This process apparently creates huge chunks of fresh ice that disrupt the usual layer-cake structure of the ice sheet, and the chunks can grow big enough that they change the shape and elevation of the ice sheet at the surface, the researchers reported.

The findings are a surprise. While scientists have long known that ice can melt at the base of miles-thick ice sheets from a combination of friction and pressure, their working assumption has been that this melt water functioned mainly as a layer of lubricant, sometimes speeding movement of glaciers.

The new findings suggest it is far more important than that. They imply that, at least in some places, melt water is a prime mechanism for contributing to the overall topography of the ice sheets, and may also govern important aspects of the behavior of the glaciers that ultimately empty ice into the sea.

Assuming that the findings stand up to scrutiny, glaciologists are now confronted with a new task: mapping the re-frozen chunks beneath thousands of square miles of ice and figuring out how they, and the process that created them, might alter the behavior of the ice sheets as greenhouse gases warm the planet. The new paper covers only a section of Antarctica but it is setting off a rush to find the same kind of ice chunks in the Greenland ice sheet.

Robin E. Bell, a scientist at Columbia University’s Lamont-Doherty Earth Observatory who led the research, said the results were so unexpected that at first, her team could not believe it. The team, from seven nations, flew planes over a section of the ice sheet in eastern Antarctica in 2008 and 2009, shooting radar waves into the ice to map the hidden structure. This sort of thing had been done before, but improved equipment allowed the scientists to see more detail than in the past.

Ice sheets generally grow in layers year by year, as snow falls and gradually gets compressed by the weight of new snow on top. The layers can be seen clearly in radar images, draped over the mountains that underlie parts of eastern Antarctica, “kind of like if you dropped a giant tortilla onto mountain ranges,” Dr. Bell said.

Yet some of the detailed new radar images obtained by the team showed huge chunks of ice that appeared to have melted and re-frozen, looking nothing like the usual layers. When the images began to come in, “at first we thought there were errors in the data,” Dr. Bell said. “Or that the people on the planes were so tired they were seeing things.”

But the results proved to be solid, resulting in the paper that was released Thursday and is scheduled for future publication in the journal Science.

“In the last 15 years, we’ve gone from thinking there’s a little water under ice sheets, to thinking there are lakes the size of New Jersey under ice sheets, to thinking water can move around underneath ice sheets,” Dr. Bell said. “Now, we know that water can modify the basic structure of the ice sheets.”

The work was supported by the National Science Foundation, a leading American agency financed by taxpayers, and by other governments. Scientists from the United States, Britain, Germany, China, Australia, Japan and Canada took part in the work.

Scientists flew geophysical instruments over a section part of the East Antarctic ice sheet to image what lay below.http://green.blogs.nytimes.com/2011/03/03/a-big-surprise-beneath-the-ice/#more-93738

Antarctic melting as deep ocean heat rises. Big melting along the Antarctic coast shows the deep sea has been holding the Earth's warming

ANTARCTIC MELTING AS DEEP OCEAN HEAT RISES

Big melting along the Antarctic coast has researchers realizing that the deep sea has been holding Earth's warming

by Larry O'Hanlon, DiscoveryNews, December 14, 2010

Global warming is sneaky. For more than a century it has been hiding large amounts of excess heat in the world's deep seas. Now that heat is coming to the surface again in one of the worst possible places: Antarctica.

New analyses of the heat content of the waters off Western Antarctic Peninsula are now showing a clear and exponential increase in warming waters undermining the sea ice, raising air temperatures, melting glaciers and wiping out entire penguin colonies.

"In the area I work there is the highest increase in temperatures of anywhere on Earth," said physical oceanographer Doug Martinson of the Lamont-Doherty Earth Observatory. Martinson has been collecting ocean water heat content data for more than 18 years at Palmer Island, on the western side of the Antarctic Peninsula.

"Eighty-seven percent of the alpine glaciers are in retreat," said Martinson of the Western Antarctic Peninsula. "Some of the Adele penguin colonies have already gone extinct."

Martinson and his colleagues looked not only at their very detailed and mapped water heat data from the last two decades, but compared them with sketchier data from the past and deep ocean heat content measurements worldwide. All show the same rising trend that is being seen in Antarctica.

"When I saw that my jaw just dropped," said Martinson. The most dramatic rise has happened since 1960, he said.

What the rising water heat means, he said, is that even if humanity got organized and soon stopped emitting greenhouse gases, there is already too much heat in the oceans to stop a lot of impacts -- like the melting of a huge amount of Antarctic ice.

"There's the potential that we're locked into long term sea level rise for a long time," Martinson told Discovery News. Martinson presented his latest ocean heat results on Monday at the meeting of the American Geophysical Union in San Francisco.

As for how fast the ice will melt and in what locations, that depends largely on whether the upwelling warm water comes in contact with the thick ice shelf that crowds the coast and holds the block the glaciers from reaching the sea.

That, in turn, depends on the winds which drive away the surface waters and make it possible for the deeper waters to rise to the surface, said senior researcher Robert Bindschadler of NASA's Goddard Earth Science and Technology Center and the University of Maryland-Baltimore County.

"It can destroy the ice shelf if that heat can get to it," said Bindschadler, who at the same meeting presented his work from the melting Pine Island Ice Shelf in Antarctica.

Now that the upwelling deep sea water is the clear cause of the melting ice shelf, rather than summer melt water, as had been thought in the past, it's a question of how winds will change in a warming world and whether they will drive more warm water into the ice shelves.

"So we have thrown the problem back over the fence to the climate modelers," said Bindschadler.

Link:  http://news.discovery.com/earth/antarctica-melting-warming-penguins-101214.html

Ted Scambos, Eric Steig, Tom Neumann, IPY, U.S.-Norwegian South Pole Traverse

ANTARCTICA NEWS ARCHIVES

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Photo credit:Lou Albershardt

IPY Traverse Posted: May 6, 2009 Courtesy: Antarctic Sun

by Peter Rejcek The 12 scientists and support staff who made a slow crawl across a vast, blank stretch of East Antarctica this past austral summer for three months to study how regional climate variability relates to global climate change expected to encounter brutally cold storms and other challenges on the high polar plateau. They didn’t expect to come across other travelers in the relatively unexplored area known as Queen Maud Land. But they did — three times in one day. “We were astonished because we were supposed to be all alone,” said Ted Scambos , a member of the Norwegian-U.S. science team that crossed a large slice of the Antarctic continent using tracked vehicles pulling sleds. “I don’t know where you can go in order to be on the edge of the Earth anymore.” The encounters, all involving people taking part in a commercial race to the South Pole, occurred near a fuel depot in an area where the ice sheet was more than 3,000 meters thick, hiding at least four distinct subglacial bodies of water called the Recovery Lakes. “Fuel depots in Antarctica are kind of the equivalent of watering holes in Africa,” mused Scambos, lead scientist at the Boulder, Colo.-based National Snow and Ice Data Center. “Everybody has to come to the fuel depot, and you see all kinds of people, all kinds of groups, gathered at the fuel depot.” But for most of the roundtrip journey between Norway’s Troll research station on the coast and the U.S. Antarctic Program’s South Pole Station , the scientists and crew were on their own. They took measurements of the snow and ice in areas that virtually no one had visited since the late 1960s, when the United States primarily used tractor trains to conduct deep-field science work. Living and working out of bright red, boxed buildings mounted on sleds, the team collected ice cores at various depths and locations, used radar to map the ice sheet layers and dug snow pits — all in an effort to understand the climate in this area for the last thousand years and how it may be changing today. The project was part of the International Polar Year , a 60-nation effort to better understand the Antarctic and Arctic, which officially ended last month. “It’s really been a blank spot on the map — on both the literal map as well as the metaphoric map of climate change in Antarctica,” said Tom Neumann , leader of the traverse team during the second leg of the two-year project that began in 2007-08 and covered nearly 7,000 kilometers including a few side trips. “[The traverse] should help fill in the picture of how Antarctica overall is changing.” Scientists had believed that Antarctica was largely bucking the global warming trend. While West Antarctica was undoubtedly heating up — particularly the outstretched tip of the Antarctic Peninsula where ice shelves are disappearing at historic rates — studies of the much larger East Antarctic Ice Sheet suggested a cooling trend. Some researchers have suggested the depletion of stratospheric ozone over Antarctica — the ozone hole that appears each austral spring — is affecting atmospheric circulation and westerly winds around the continent, effectively shielding it from global warming. But a paper in the journal Nature earlier this year said warming in West Antarctica is greater than whatever cooling may be occurring on the rest of the ice-covered continent. “Simple explanations don’t capture the complexity of climate,” explained Eric Steig , lead author of the Nature paper and a professor at the University of Washington , in a statement back in January. “The thing you hear all the time is that Antarctica is cooling, and that’s not the case,” added Steig, a collaborator on the IPY traverse project. “If anything it’s the reverse, but it’s more complex than that. Antarctica isn’t warming at the same rate everywhere, and while some areas have been cooling for a long time, the evidence shows the continent as a whole is getting warmer.” Antarctica is roughly the size of the United States and Mexico: Snow in Denver doesn’t mean a blizzard stretches all the way down to Mexico City. “Antarctica is a huge place, and I would be surprised if it was all doing the same thing,” said Neumann, a scientist now with NASA Goddard Space Flight Center . Yet there’s even a hint that East Antarctica — well, at least one spot on that incomplete map — may be warming based on one initial experiment by the traverse team. Scambos deployed strings of highly sensitive “thermometers” called thermistors into two of the deeper ice core holes. The temperature on the ice sheet surface changes with the weather, but the temperature deeper down changes very slowly as the climate changes. Neumann likens it to throwing a frozen turkey into the oven — not the best way to cook a turkey, for sure, but eventually the center starts to thaw and cook based on the long-term outside temperature. “It takes a while for the ice at 90 meters to notice how the surface temperature has changed,” Neumann explained. At that depth, the ice temperature is determined by the average temperature of the last 50 years or so. The instruments will operate for the next several years, allowing the scientists to determine how surface temperature changes through time. “The initial results do say these areas are warming,” Neumann said, stressing that the measurements are in the hundredths of a degree per year and the data still raw. Scambos: Recovery Lakes region was likely marine embayment in distant past Most of the scientific analysis is yet to come. Neumann and others on the team will use the ice core samples to conduct stable isotopic measurements. By studying the isotopic ratios of oxygen 16 and oxygen 18, for instance, researchers can figure out what the climate was doing at a particular time because different ratios indicate different types of climate. The chemistry will help the team calibrate the radar returns of the ice layers, a key step to nailing the snow accumulation rates in East Antarctica — one part of the equation to whether the ice sheet is overall losing or gaining mass. Loss of mass would indicate a rise in sea level. “The chemistry from the core helps because it tells you the accumulation rate at a point,” Neumann explained. “For example, how deep is the fallout from the 1960s above-ground nuclear testing? That information helps to calibrate the radar layers that intersect the core site. “If a radar layer is shallower, then it has had relatively less accumulation; a deep layer reflects relatively more accumulation. The information form the core lets you quantify the ‘relative’ statements above.” The scientists also took the opportunity to explore the Recovery Lakes, an area of at least four lakes at the head of one of the largest ice streams draining East Antarctica. Ranging in size from 600 to 1,500 square kilometers, at depths well below sea level, the lakes were likely part of a deep marine embayment millions of years ago when the ice sheet was much smaller, according to Scambos. “It was probably dynamic in the past,” he said. “In the distant future, if the Earth gets a great deal warmer, it would be dynamic again. I would prefer to think that we’ll stabilize climate change before we have to worry about this part of Antarctica disintegrating.” There is still a lot of uncertainty about what the Antarctic ice sheets may do in the future because so little of it has been measured, particularly compared to Greenland, according to Neumann. “The uncertainties in Greenland are getting quite a lot smaller as we get more and more data about ice velocity, ice thickness and accumulation rate. It’s certainly negative [mass balance] and we know roughly how negative it is in Greenland,” he said. “Antarctica is a bit of a different story, because it is so much larger and there’s places with so much less data, such as in East Antarctica. “The physical insight is coming along and the model development is coming along, but I think it’s going to be a quite a while before we really have confidence in the large-scale predictive models of ice sheet change,” he added. More ground-based studies like the traverse would help to continue filling in the blank spots of the climate change map, according to the scientists. “Most of that uncertainty [about Antarctica] can be beaten down with more and more measurements of accumulation rates,” Neumann said. “The traverse system that the Norwegians have put together is fantastic, state-of-the-art. It’s the best in the world right now in terms of supporting a science crew over long distances,” Scambos said. “They essentially have a mobile, 12-person base that provides them relatively easy access to a large area. … [Queen Maud Land is] one of the least-explored areas of Antarctica, and I think that’s going to change, in part, thanks to this traverse system they’ve got.”

Link to this article:
http://antarcticsun.usap.gov/science/contenthandler.cfm?id=1758

Gregory Johnson of NOAA, CLIVAR Project, finds warming of abyssal water in the Southern Ocean, perhaps responsible for 20% of sea level rise

Global warming reaches the Antarctic abyss

by Catherine Brahic, Copenhagen, New Scientist, March 11, 2009

Even the deepest, darkest reaches of the Antarctic abyss are feeling the heat, according to new results presented at the climate change congress in Copenhagen, Denmark, on Tuesday.

Gregory Johnson, of the US National Oceanic and Atmospheric Agency, says even he was surprised by the findings. He says the changes could be responsible for up to 20% of the observed global sea-level rise.

As part of the CLIVAR project, Johnson and a team of international colleagues have been spending weeks at a time at sea, tracing straight lines across all of the world's oceans. As they make these traverses, they measure the temperatures of the water from the very bottom right up to the surface.

The team takes its measurements along the same routes as expeditions carried out in the 1990s, which provides a picture of how things have changed in roughly one decade.

Global influence

The researchers are particularly interested in the masses of cold water that sink down to the abyss along the shores of Antarctica before moving north along the ocean floor into the Atlantic, Pacific and Indian Oceans.

These three flows of Antarctic abyssal water overwhelmingly influence the deep waters of the world, says Johnson. Water sinks off the coast of Greenland too, but the Antarctic abyssal water volume is twice that of the north Atlantic.

Early results from CLIVAR show that abyssal water is warmer now than it was in the 1990s. The water that travels from Antarctica into the south-eastern Indian basin is roughly 0.1 °C warmer. The deep ocean current travelling from Antarctica into the Pacific is 0.03 °C warmer.

In the northern hemisphere, the deep abyssal Atlantic water, which sits between the ocean floor and the layer of deep water that sinks off the coast of Greenland and travels south, is 0.04 °C warmer.

What surprises Johnson most is that the warmer deep Antarctic water is apparently carried all the way to the north Pacific, too. Other vessels that have monitored what happens to the abyssal water as it moves north have also noticed a warming, albeit a smaller one.

Diluted oceans

The researchers have also looked at the salinity -- important because it affects water buoyancy -- of the deep Antarctic waters. They found that here, too, there is change: in both the southeast Indian Ocean and in the Pacific, the water is less salty today than it was in the 1990s. Most likely, says Johnson, this is a direct result of dilution from the melting Antarctic ice.

He is very reluctant, however, to say what is warming the abyss. Two possibilities present themselves: either the water is being warmed more at the surface near Antarctica before sinking into the abyss, or it is taking longer to sink and therefore has a longer time to soak up the surrounding temperatures.

As for whether human-driven climate change has anything to do with it: "It's just too early to say," Johnson says.

Either way, the changes are significant. On average, over the last decade, water at the surface of the oceans has gained 0.35 watts per square metre -- a measure of the amount of heat absorbed from the warming atmosphere. Johnson's measurements in the abyss are, in some regions, nearly three times that.

Johnson estimates that the warming and consequent expansion of the deep water flows may be responsible for between 10% and 20% of the global sea-level rise seen during that time.

Link to article: http://www.newscientist.com/article/dn16740-global-warming-reaches-the-antarctic-abyss.html