Replies to post #434420 on Zeev's Turnips Talk Politics (ZTTP)

[StephanieVanbryce]

Antarctic Ice Sheet Is Melting Rapidly
New Study Warns Of Rising Sea Levels

........in 2006

The Antarctic ice sheet is losing as much as 36 cubic miles of ice a year in a trend that scientists link to global warming, according to a new paper that provides the first evidence that the sheet's total mass is shrinking significantly.

The new findings, which are being published today in the journal Science, suggest that global sea level could rise substantially over the next several centuries.

It is one of a slew of scientific papers in recent weeks that have sought to gauge the impact of climate change on the world's oceans and lakes. Just last month two researchers reported that Greenland's glaciers are melting into the sea twice as fast as previously believed, and a separate paper in Science today predicts that by the end of this century lakes and streams on one-fourth of the African continent could be drying up because of higher temperatures.

The new Antarctic measurements, using data from two NASA satellites called the Gravity Recovery and Climate Experiment (GRACE), found that the amount of water pouring annually from the ice sheet into the ocean -- equivalent to the amount of water the United States uses in three months -- is causing global sea level to rise by 0.4 millimeters a year. The continent holds 90 percent of the world's ice, and the disappearance of even its smaller West Antarctic ice sheet could raise worldwide sea levels by an estimated 20 feet.

"The ice sheet is losing mass at a significant rate," said Isabella Velicogna, the study's lead author and a research scientist at Colorado University at Boulder's Cooperative Institute for Research in Environmental Sciences. "It's a good indicator of how the climate is changing. It tells us we have to pay attention."

Richard Alley, a Pennsylvania State University glaciologist who has studied the Antarctic ice sheet but was not involved in the new research, said more research is needed to determine if the shrinkage is a long-term trend, because the new report is based on just three years of data. "One person's trend is another person's fluctuation," he said.

But Alley called the study significant and "a bit surprising" because a major international scientific panel predicted five years ago that the Antarctic ice sheet would gain mass this century as higher temperatures led to increased snowfall.

"It looks like the ice sheets are ahead of schedule" in terms of melting, Alley said. "That's a wake-up call. We better figure out what's going on."

Velicogna acknowledged that it is hard to predict how fast the ice sheet will melt in the future but said, "I don't expect it's going to stop in the next couple of years."

Scientists have been debating whether the Antarctic ice sheet is expanding or shrinking overall, because the center of the sheet tends to gain mass through snowfall whereas the coastal regions are more vulnerable to melting.

Velicogna and her co-author, University of Colorado at Boulder physics professor John Wahr, based their measurements on data from the two GRACE satellites that circle the world more than a dozen times a day at an altitude of 310 miles. The satellites measure variations in Earth's mass and gravitational pull: Increases or decreases in the Antarctic ice sheet's mass change the distance between the satellites as they fly over the region.

"The strength of GRACE is that we were able to assess the entire Antarctic region in one fell swoop to determine if it was gaining or losing mass," Wahr said.

But some scientists remain unconvinced. Oregon state climatologist George Taylor noted that sea ice in some areas of Antarctica is expanding and part of the region is getting colder, despite computer models that would predict otherwise.

"The Antarctic is really a puzzle," said Taylor, who writes for the Web site TSCDaily, which is partly financed by fossil fuel companies that oppose curbs on greenhouse gases linked to climate change. "A lot more research is needed to understand the degree of climate and ice trends in and around the Antarctic."

At the other end of the temperature spectrum, two South African researchers are reporting today in Science that their computer models indicate that by 2100 climate change may rob the south and west of Africa and areas in the upper Nile region of a significant portion of their current water supply. Warming may reduce the rainfall needed to replenish up to 25 percent of Africa's surface water, said Maarten de Wit and Jacek Stankiewicz at the University of Cape Town in Rondebosch, South Africa.

"Water is essential to human survival," they wrote, "and changes in its supply can potentially have devastating implications, particularly in Africa, where much of the population relies on local rivers for water."

Congressional Democrats, including Sen. John F. Kerry (Mass.) and Rep. Henry A. Waxman (Calif.) said yesterday that the two new papers show that the United States must act quickly to impose mandatory limits on carbon dioxide and other greenhouse gases. The Bush administration opposes such curbs on the grounds that they could hurt the country's economy and has instead invested money on new technology to limit greenhouse emissions and further climate science research.

"Climate change is not just someone else's concern but a very real threat to the lives and livelihood of people across the globe," Kerry said.


http://www.washingtonpost.com/wp-dyn/content/article/2006/03/02/AR2006030201712.html

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[StephanieVanbryce]

Increasing Amounts Of Ice Mass Have Been Lost From West Antarctica

ScienceDaily (Jan. 14, 2008) — Increasing amounts of ice mass have been lost from West Antarctica and the Antarctic peninsula over the past ten years, according to research from the University of Bristol and published online recently in Nature Geoscience.

Meanwhile the ice mass in East Antarctica has been roughly stable, with neither loss nor accumulation over the past decade.

Professor Jonathan Bamber at the University of Bristol and colleagues estimated the flux of ice from the ice sheet into the ocean from satellite data that cover 85% of Antarctica's coastline, which they compared with simulations of snow accumulation over the same period, obtained using a regional climate model.

They arrived at a best estimate of a loss of 132 billion tonnes of ice in 2006 from West Antarctica -- up from about 83 billion tonnes in 1996 -- and a loss of about 60 billion tonnes in 2006 from the Antarctic Peninsula.

Professor Bamber said: "To put these figures into perspective, four billion tons of ice is enough to provide drinking water for the whole of the UK population for one year."

The authors conclude that the Antarctic ice sheet mass budget is more complex than indicated by the evolution of its surface mass balance or climate-driven predictions.

Changes in glacier dynamics are significant and may in fact dominate the ice sheet mass budget. This conclusion is contrary to model simulations of the response of the ice sheet to future climate change, which conclude that it will grow due to increased snowfall.

The ice loss is concentrated at narrow glacier outlets with accelerating ice flow, which suggests that glacier flow has altered the mass balance of the entire ice sheet.

Over the 10 year time period of the survey, the ice sheet as a whole was certainly losing mass, and the mass loss increased by 75% during this time. Most of the mass loss is from the Amundsen Sea sector of West Antarctica and the northern tip of the Peninsula where it is driven by ongoing, pronounced glacier acceleration. In East Antarctica, the mass balance is near zero, but the thinning of its potentially vulnerable marine sectors suggests this may change in the near future.



http://www.sciencedaily.com/releases/2008/01/080113143438.htm

[StephanieVanbryce]

Greenland And Antarctic Ice Sheet Melting, Rate Unknown

ScienceDaily (Feb. 25, 2009) — The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.

In the past, the Greenland ice sheet has grown when its surroundings cooled, shrunk when its surroundings warmed and even disappeared completely when the temperatures became warm enough. If the ice sheet on Greenland melts, sea level will rise about 23 feet, which will inundate portions of nearly all continental shores. However, Antarctica, containing much more water, could add up to another 190 feet to sea level.

"We do not think that we will lose all, or even most, of Antarctica's ice sheet," said Alley. "But important losses may have already started and could raise sea level as much or more than melting of Greenland's ice over hundreds or thousands of years," Alley told attendees Feb 16 at the annual meeting of the American Association for the Advancement of Science.

Warming is expected to cause more precipitation on Greenland and Antarctica, adding snow. Previously, many scientists suggested that this would offset increasing melting. However, recent studies show that the ice sheets on both Greenland and in Antarctica are melting faster than the snow is replacing the mass.

A number of things can contribute to the increased rate of melting in Greenland and Antarctica. Large lakes of water on the ice in Greenland pose a problem. This water, by wedging open a crack or crevasse in the ice, quickly flows through to the bottom, melting the bottom of the ice sheet and causing it to move more rapidly toward the ocean. Observers have seen lakes on the Greenland ice sheet drain at the speed of Niagara Falls.

All ice sheets spread due to their large mass, but friction from the rocks beneath slows the ice's motion. Water beneath the ice allows the ice to move more rapidly.

"Right now, the center of the Greenland ice sheet is frozen to the rocks," says Alley. "If the melt water moves inland as the world warms and gets to the bottom, it will thaw the bottom and unstick the ice from the rocks."

Another contributor to the melting ice sheets is the warming of the ocean. When ice shelves -- ice still connected to the ice sheet but floating over water -- melt, they also cause the ice sheet to flow faster. In Greenland, the Jakobshavn ice shelf has retreated more than 5 miles since 1992. Rocks and cliffs on the sides of fiords or inlets slow the seaward movement of the ice shelves. If these shelves break up and melt, the ice streams behind them move more rapidly.

Ice shelf failures have also occurred on Antarctica where, for example, most of the Larsen B ice shelf disintegrated in March of 2002 and increased the rate of ice stream flow eight times.

"Water temperature is more important than air temperature in melting the ice shelves," says Alley. "However, both contribute."

Warmer oceans, caused by general global warming or local events can trigger more breakups of ice shelves and faster flow of ice streams in Antarctica. In Greenland, sustained increase in temperatures of only a few degrees will remove the ice.

Alley believes he knows the direction to go to gain a better understanding of the ice sheets, how they work and the effect they have on climate change. Although those who study ice sheets have long modeled ice sheet behavior, simulations of the whole earth system typically have not included ice sheets along with the atmosphere, oceans and clouds, in their models. Past atmospheric modelers usually treated the ice sheets simply as white mountains.

"They are not white mountains and they need to be modeled," said Alley. "We need to have them in the models to figure out how the system works."

Alley notes that a collaboration of government and academic scientists created the atmospheric and ocean models, but collaborations to model the ice are only just being developed.

http://www.sciencedaily.com/releases/2009/02/090216131158.htm

[BuckeyeMike]

Artic Ice Increasing :-D

http://www.ecoworld.com/blog/2009/04/30/antarctic-ice-increasing/