The first comprehensive survey of all Antarctic ice shelves discovered that basal melt, or ice dissolving from underneath, accounted for 55 percent of shelf loss from 2003 to 2008 — a rate much higher than previously thought. Ice shelves, floating extensions of glaciers, fringe 75 percent of the vast, frozen continent.

The findings, to be published in the June 14 issue of Science, will help scientists improve projections of how Antarctica, which holds about 60 percent of the planet’s fresh water locked in its massive ice sheet, will respond to a warming ocean and contribute to sea level rise.

It turns out that the tug of seawaters just above the freezing point matters more than the breaking off of bergs.

“We find that iceberg calving is not the dominant process of ice removal. In fact, ice shelves mostly melt from the bottom before they even form icebergs,” said lead author Eric Rignot, a UC Irvine professor who’s also a researcher with NASA’s Jet Propulsion Laboratory in Pasadena. “This has profound implications for our understanding of interactions between Antarctica and climate change. It basically puts the Southern Ocean up front as the most significant control on the evolution of the polar ice sheet.”

Ice shelves grow through a combination of land ice flowing to the sea and snow falling on their surfaces. The researchers combined a regional snow accumulation model and a new map of Antarctica’s bedrock with ice shelf thickness, elevation and velocity data captured by Operation IceBridge — an ongoing NASA aerial survey of Greenland and the South Pole. (Rignot will host a planning session of Operation IceBridge scientists at UC Irvine on June 17 and 18.)

Ocean melting is distributed unevenly around the continent. The three giant ice shelves of Ross, Filchner and Ronne, which make up two-thirds of Antarctica’s ice shelves, accounted for only 15 percent of the melting. Meanwhile, less than a dozen small ice shelves floating on relatively warm waters produced half the total meltwater during the same period.

The researchers also compared the rates at which the ice shelves are shedding ice with the speed at which the continent itself is losing mass and found that, on average, the shelves lost mass twice as fast as the Antarctic ice sheet did.

“Ice shelf melt can be compensated by ice flow from the continent,” Rignot said. “But in a number of places around Antarctica, they are melting too fast, and as a consequence, glaciers and the entire continent are changing.”

Other authors are Jeremie Mouginot and Bernd Scheuchl of UC Irvine and Stanley Jacobs of Columbia University. Funding was provided by NASA, the National Science Foundation, and the National Oceanic & Atmospheric Administration.

The Critical Decade

Cars are parked on an overpass on a flooded street in Bangkok, Thailand. Projections on the rise of sea levels show Bangkok could be at risk of inundation in 100 years. (Associated Press file photos)

From Bangkok to Miami, cities and coastal areas across the globe are already building or planning defenses to protect millions of people and key infrastructure from more powerful storm surges and other effects of global warming. • Some are planning cities that will simply adapt to more water. • But climate-proofing a city or coastline is expensive, as shown by New York Mayor Michael Bloomberg’s $20 billion plan to build floodwalls, levees and other defenses against rising seas. • The most vulnerable places are those with the fewest resources to build such defenses, secure their water supplies or move people to higher ground. How to pay for such measures is a burning issue in U.N. climate talks, which just wrapped up a

FILE – In this Wednesday, March 28, 2012 file photo, amphibious homes float on the harbor in the IJburg neighborhood in Amsterdam. IJburg is a new district in the eastern part of town completely surrounded by water. The Netherlands, a third of which lies below sea level, has been managing water since the Middle Ages. (AP | Margriet Faber)

session in the German city of Bonn. • A sampling of cities around the world and what they are doing to prepare for the climatic forces that scientists say are being unleashed by global warming:ROTTERDAM, Netherlands

In a country where two-thirds of the population lives below sea level, the battle against the sea has been a matter of life and death for centuries.

The focus in the 20th century was on a spectacular series of sea defenses, including massive steel and concrete barriers that can be quickly moved to protect against storm surges. But current techniques embrace a philosophy of “living with water.”

Thousands of waterways are being connected so the country can act as a sponge and absorb influxes of water. Some areas have been designated as flood zones. Houses that can float have been a building sensation.

VENICE, Italy

Sea-level rise is a concern for this flood-prone city. It’s in the process of realizing an expensive and oft-delayed system of underwater barriers that would be raised in the event of flooding over 43 inches.

Venice, a system of islands built into a shallow lagoon, is extremely vulnerable to rising seas because the sea floor is also sinking. Plans for the new

FILE – A tourist sits outside a cafe in a flooded St. Mark square as high tides reached 1.05 meters above sea level, partly flooding the city of Venice, Italy on Monday, Oct. 15, 2012. The Lagoon City, a system of islands built into a river delta, is extremely vulnerable to rising sea levels. At the same time it is experiencing a lowering of the sea floor. The constant flooding puts the city’s considerable architectural treasures at risk. (AP | Luigi Costantini)

so-called Moses barriers will cost more than 4 billion euro. The first of these have been moved into place in recent days. Many Venetians remain skeptical of the project due to the high costs and concerns over environmental risks.MIAMI

Southern Florida is one of those places that show up as partially under water in many sea-level projections for this century. So it’s no surprise local leaders are seeking ways to adapt. Four counties of South Florida, including Miami-Dade, have collaborated on a plan to respond to climate change. Their overarching goal: keeping fresh water inland and saltwater away.

Before writing the plan, the counties reviewed regional sea-level data and projected a rise of 9 to 24 inches in the next 50

FILE – In this Saturday, Oct. 8, 2005 file photo, boats sail in Miami’s Biscayne Bay at the start of the annual Columbus Day Regatta. Southern Florida is one of the places that shows up as partially under water in many sea level projections for the 21st century. (AP | Lynne Sladky)

years along a coastline that already has documented a rise of 9 inches over the past 100 years.BANGLADESH

Bangladesh is one of Asia’s poorest countries and one that faces extreme risks from rising sea levels. Its capital, Dhaka, is at the top of a list of world cities deemed most vulnerable to climate change, according to risk analysis company Maplecroft.

The World Bank says a sea-level rise of 5 inches would affect 20 million people along the 440-mile coast. Many of these people would be homeless.

Bangladesh is implementing two major projects worth $470 million that involve growing forests on the coastal belt and building more multistory shelters to house people after cyclones and tidal surges.

BANGKOK,

FILE – In this Sunday, May 31, 2009 file photo, floodwaters flow to a lower area as villagers rebuild an embankment at Protap Nagar in Shatkhira, Bangladesh, about 176 kilometers (109 miles) southwest of Dhaka after Cyclone Aila. The low-lying delta nation of 153 million people is one of Asia’s poorest countries, and one that faces extreme risks from rising sea levels. (AP | Pavel Rahman)

ThailandSea-level rise projections show Bangkok could be at risk of inundation in 100 years unless preventive measures are taken. But when the capital and its outskirts were affected in 2011 by the worst flooding in half a century, the immediate trigger was water runoff from the north, where dams failed to hold very heavy rains.

The government recently announced winning bids totaling $9.38 million by Chinese, South Korean and Thai firms to run the flood and water management schemes, including the construction of reservoirs, floodways and barriers.

Solutions to the problem of rising seas are still being studied.

“Construction alone is not sustainable,” said Seree Supratid, director of a climate and disaster center at Rangsit University. “People have to adapt to nature.”

Date

June 17, 2013

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Ben Cubby

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Taking action: Professor Lesley Hughes. Photo: Peter Morris

Most of Australia’s coal reserves will have to be left unburned if the world is to avoid catastrophic global warming, according to a major new report from the federal government’s Climate Commission.

The report puts the key science advisory body on a collision course with some of the nation’s biggest export industries, and marks the first time a government agency has endorsed calls for fossil fuel industries to be phased out because of their contribution to climate change.

Its findings mean that most of Australia’s known coal, oil and gas reserves – many of which are already subject to minerals production licences held by companies such as BHP Billiton and Rio Tinto – must somehow be left alone if the world is to avoid dangerous climate change.

Climate Change Minister Greg Combet says coal use has already decreased by 7%. Photo: Louie Douvis

The Climate Commission acknowledged its conclusions were “sobering” and that the potential for economic disruption could be serious, but said there was no alternative if the world was to avoid dangerous climate change.

“How people react to this is up to the policymakers and governments, as well as investors,” said Professor Lesley Hughes, co-author of the report The Critical Decade 2013 – Climate change science, risks and responses, to be released on Monday.

“It isn’t our job to reconcile the politics of this with the science,” she said. “We are simply presenting the facts as best we know them. Just because the facts may be unpalatable to some people doesn’t make them any less important.”

Australia’s fossil fuel resources are the equivalent of about 51 billion tonnes of greenhouse gases, about one twelfth of the world’s entire “carbon budget” of about 600 billion tonnes – the amount of carbon that scientists estimate can be burned by 2050 if the world is to stop temperatures rising more than two degrees.

If that carbon budget is exceeded, the build-up of heat-trapping gases in the atmosphere is likely to trigger dangerous global warming of up to five degrees this century, the report said.

And the world is still eating into its budget far too fast, with average global emissions still rising at about 3 per cent a year, the report said.

“If emissions could somehow peak in 2015, just two years away, the maximum rate of emission reductions thereafter would be 5.3 per cent, a very daunting task,” it said.

“However, if we allow emissions to continue to rise through the rest of this decade and don’t reach the peaking year until 2020, the maximum rate of emission reductions thereafter is 9 per cent, a virtually impossible task unless economies around the world prioritise emission reductions above all other economic and technological goals.”

Climate Change Minister Greg Combet said the government’s carbon price had already driven coal use down 7 per cent, and most countries that bought Australian fossil fuels would soon have similar carbon prices.

Countries are responsible for the carbon emissions generated within their borders, a spokesman for Mr Combet said.

“When it comes to exports, the majority of Australia’s coal exports go to Japan, South Korea, China and the European Union,” he said.

“All these countries have introduced, or plan to introduce, a price on carbon through emissions trading schemes or carbon taxes that will apply to coal consumption.”

A spokeswoman for opposition climate spokesman Greg Hunt said he would “consider the report carefully but we do not support shutting down Australia’s major export industry”.

If elected to government at the September poll, the opposition has pledged to abolish the Climate Commission.

“The Coalition has been consistent in arguing that the role of the Climate Commission on providing advice on addressing climate change is best undertaken by a merged department of environment and climate change,” Mr Hunt’s spokeswoman said. “There needs to be a continued focus on reducing emissions as is outlined in this report.”

The opposition plans to abolish the carbon price and replace it with a suite of measures it calls “direct action”, involving paying industries to reduce their emissions.

Both of the main parties have committed to reducing Australia’s emissions to 5 per cent below their 2000 levels by the year 2020 – a target that now looks achievable, but which falls well short of the much deeper cuts outlined in the Climate Commission’s report.

“To stay within the two degrees limit, the trend of increasing global emissions must be slowed and halted in the next few years and emissions must be trending downwards by 2020 at the latest,” the report said. “Investments in and installations of renewable energy must therefore increase rapidly. And, critically, most of the known fossil fuel reserves must remain in the ground.”

The noble gases get their collective moniker from their tendency toward snobbishness. The six elements in the family, which includes helium and neon, don’t normally bond with other elements and they don’t dissolve into minerals the way other gases do. But now, geochemists from Brown University have found a mineral structure with which the nobles deign to fraternize.

Researchers led by Colin Jackson, a graduate student in geological sciences, have found noble gases to be highly soluble in amphibole, a mineral commonly found in oceanic crust. “We found remarkably high solubility,” said Stephen Parman, assistant professor of geological sciences at Brown and Jackson’s Ph.D. adviser. “It was three or four orders of magnitude higher than in any other mineral than had been measured.”

The findings, which are published in Nature Geoscience, are a step toward answering puzzling questions about how noble gases are cycled between the atmosphere and the depths of the Earth.

Completing the cycle

Gases in the air we breathe are on a geological conveyor belt of sorts, cycled from the Earth’s mantle to the atmosphere and back again. Carbon dioxide, water vapor and other gases are released into the atmosphere and oceans from molten magma during volcanic eruptions, and then returned to depths through subduction, when one tectonic plate slides underneath another. The subducting crust is injected deep into the mantle, taking water and any other volatiles it may carry along for the ride.

Noble gases are also released during volcanic activity, but the amount of those gases returned to the mantle through subduction was long thought to be minimal. After all, if noble gases don’t dissolve in minerals, they would lack a vehicle to make the trip. Recent research, however, has suggested that some noble gases are indeed recycled, leaving scientists at a loss to find a mechanism for it. By showing definitively that noble gases are soluble in amphibole, Jackson and his colleagues have shown how noble gases could be carried in subducting slabs.

The key to amphibole’s ability to dissolve noble gases, the researchers say, is its lattice structure. Amphibole and other silicate minerals are made up of tetrahedral and octahedral structures linked together in a way that creates a series of rings. It’s those rings, called A-sites, that provide a home for otherwise finicky noble gases, the research suggests.

Jackson performed a series of experiments to see if the number of empty rings in different types of amphibole were correlated to its ability to dissolve noble gases. He placed cut amphibole gems into a tube with helium or neon under high pressure and temperature, and then used a mass spectrometer to see how much of the gas had dissolved in each gem over the duration of each experiment. The experiments showed that noble gas solubility was highest in types of amphibole with the most unoccupied ring structures.

“This was the meat of the paper,” Parman said. “It’s telling us a specific site where we think the noble gases are. It might be the first time anyone has made a positive identification of where noble gases are going into a mineral.”

Importantly, the researchers said, amphibole isn’t the only crustal mineral with these ring structures. Ring structures are actually quite common in crustal minerals, and could provide a wide variety of potential vehicles that could take noble gases back to the depths via subduction.

A high-fidelity fingerprint

Understanding how noble gases are cycled between the Earth’s surface and interior could shed new light on how other volatiles are recycled, the researchers said.

Scientists are particularly interested in tracking the cycling of water and carbon. Water is obviously vital for life, and carbon cycling has an important impact on the climate. Scientists try to track the cycle by looking at isotope ratios, which can provide a fingerprint that helps to identify where elements originated. Butarbon and the hydrogen in water have only a few isotopes that scientists can use for tracking, and in the case of hydrogen, the isotope ratios are easily thrown off by all kinds of natural processes.

The noble gases, on the other hand, have lots of isotopes, giving scientists ways to track them with great specificity. So if noble gases are cycled in the same minerals that cycle other volatiles like water and carbon, they could be used as a marker to track those other volatiles. “It’s a very high-fidelity fingerprint because you have so many isotopes to play with,” Jackson said.

There’s more work to be done before noble gases could be used as such a fingerprint, but this work does provide a first step: showing which kinds of minerals could be responsible for noble gas recycling.

Other authors on the paper were Simon Kelley of The Open University in the United Kingdom and Reid Cooper, professor of geological sciences at Brown. The work was funded by the National Science Foundation’s Division of Earth Sciences (1019229).