East Antarctic ice sheet may be losing mass-on yougestindia.blogspot.com

East Antarctic ice sheet may be losing mass

The East Antarctic ice sheet has been losing mass for the last three years, according to an analysis of data from a gravity-measuring satellite mission.

The scientists involved say they are "surprised" by the finding, because the giant East Antarctic sheet, unlike the west, has been thought to be stable.

Other scientists say ice loss could not yet be pinned on climate change, and uncertainties in the data are large.

The US-based team reports its findings in the journal Nature Geoscience.

The data comes from Nasa's Gravity Recovery and Climate Experiment (Grace) mission.

Grace has previously shown that the smaller West Antarctic and Greenland ice sheets are losing mass.

These two bodies of ice contain enough water to raise sea levels by about six to seven metres (20ft) each if they melted completely.

Melting the East Antarctic sheet would raise sea levels by much more - about 50-60m.

But scientists have generally discounted the possibility of it happening because the region is so cold.

The Grace measurements suggest there was no net ice loss between 2002 and 2006.

But since then, East Antarctica has been losing 57 billion tonnes (Gt) per year.

"We felt surprised to see this change in East Antarctica," study leader Jianli Chen from the Centre for Space Research at the University of Texas in Austin told BBC News.

The loss still looks small by contrast with West Antarctica, which is losing 132Gt per year, and with Greenland, where a recent analysis combining Grace data with other measurements indicated an annual figure of 273Gt.

Previous Grace analyses - and those from other satellites - had given an inconclusive picture for the giant ice body.

The twin Grace satellites fly in close formation, detecting minute changes in the Earth's gravity through the marginal changes this causes in their relative positions.

Eastern energy

Measuring Antarctic ice loss is a tricky issue because the continent itself is rising and deforming.

Its ice cover was significantly thicker during the last Ice Age; as the ice melted, the weight pressing down on the rock abated, and the rock is "isostatically rebounding".

Readings from satellite missions have to be adjusted to allow for this rebound - and that is one source of uncertainty when trying to assess the significance of the new research, according to Richard Alley, one of the world's leading glaciologists.

"The first thing is that lots of this is dependent on the isostatic [rebound] model, and (recent work has) cast some doubt on the istostatic models that people are using," commented the Penn State University researcher (who was not involved in the paper).

"And then you get into the age-old question of 'is it climate or is it weather?'

"So it energises me as a scientist, but I'm not convinced that as yet it should energise anyone else."

Rising potential

The Grace data gives a picture of where ice is being lost across the continent; and these areas are mainly on the coast.

It is not clear what physical processes could be driving any loss of mass here, although it is not simply melting due to high air temperatures, because temperatures are well below zero.

One clue could lie in research published last year by Leigh Stearns and colleagues, showing that lakes under the ice sheet can periodically overflow, with the liquid water then acting as a lubricant to speed glaciers on their way towards the sea.

Commenting on the new research, Dr Stearns told BBC News: "In these coastal regions the ice loss could be driven by some interaction with the oceans or some weather patterns, or it could be a sub-glacial lake that drained and caused some thinning - so it might not be climate-related.

"It's easy to jump to the conclusion that it's exceptional because it's the first time we've recorded it, but we do need a baseline of how things have been in the past so we do need to be cautious," said the University of Kansas researcher.

"Nevertheless, it awakens us to the fact that the East Antarctic sheet is more dynamic than we thought, and we do need to pay attention to it because its potential for sea level rise is so much greater than in West Antarctica or Greenland."

Dr Chen said that one of his team was currently conducting airborne surveys of one of the regions where mass loss had been detected, hoping to shed some light on the mechanisms involved.

US healthcare bill clears Senate test-on yougestindia.blogspot.com

The US Senate has narrowly voted to hold a full debate on a landmark bill designed to overhaul the country's healthcare.

All 58 Democrats, plus two independent senators, approved it. All but one of 40 Republican senators voted against.

Two Democratic senators whose support had been in doubt earlier said they would back the package, a key election pledge of President Barack Obama.

The White House said Mr Obama was "gratified" by the result.

A full Senate debate on healthcare reform will now begin on 30 November.

The House of Representatives narrowly passed its own version of the reforms earlier this month.

The legislation - designed to secure coverage for millions of uninsured Americans - could lead to the biggest changes in US healthcare in decades, if approved.

Senate Democratic leader Harry Reid says his $849bn (£508bn) bill would extend coverage to another 31 million people, or 94% of eligible citizens.

The legislation, which was outlined in a 2,074-page document, is said by Democratic aides to reduce deficits by $127bn (£76bn) over a decade and by as much as $650bn (£389bn) in the 10 years after that.

'Historic'

But Republicans say it will be too expensive, and have vowed to block it. Fewer than 60 votes for the initial measure would have left the bill vulnerable to Republican delaying tactics.

A White House spokesman said President Obama was "gratified that the Senate has acted to begin consideration of health insurance reform legislation".

"Tonight's historic vote brings us one step closer to ending insurance company abuses, reining in spiralling health care costs, providing stability and security to those with health insurance, and extending quality health coverage to those who lack it," said Robert Gibbs.

Speaking after the vote, Mr Reid said he was looking forward to the coming debate and to "finally bringing quality health care to the American people".

But Republican Senate leader Mitch McConnell said he would continue to oppose the motion.

"The American people are asking us to stop this bill and we're going to do anything and everything we can to prevent this measure from becoming law," he said.

Efforts to get the vote passed had focused on three centrist Democrats - Ben Nelson of Nebraska, Blanche Lincoln of Arkansas and Mary Landrieu of Louisiana - who expressed doubts about the bill.

Sen Nelson said on Friday he would back the procedural vote, but Senators Lincoln and Landrieu declared themselves available only hours before it was due to take place.

'Deep reservations'

After confirming her support, Sen Lincoln said that it was important to start debating the issue and that Saturday's vote would "mark the beginning of consideration of this bill by the US Senate, not the end".

Senator Landrieu said there were "enough significant reforms and safeguards in this bill to move forward, but much more work needs to be done".

All three Democrats continue to have deep reservations about the bill.

Under the Senate bill, most Americans would have to have health insurance, while private insurers would be banned from refusing to provide insurance because applicants had pre-existing medical conditions.

Insurance would be made more affordable with subsidies available to help those in lower income bands, the Democrats say.

People would also be able to take part in new insurance market places and be able to choose to buy government-sold insurance from 2014, a provision intended to help regulate the prices charged by private companies.

Large companies would be required by law to provide coverage to staff. The costs would be covered by government cuts on future Medicare spending.

If the Senate eventually passes its bill, it must then be reconciled with the House of Representatives bill and voted on again before the programme can become law.

Mr Reid's bill differs to the House bill in that he calls for an increase of a half percentage point in Medicare payroll tax for people with an income of over $200,000 (£119,779) per annum - rising to $250,000 (£149,724) for couples.

There is also a tax on high-value insurance policies that is not contained in the House version of the bill.