Last edge of Greenland ice sheet to resist global warming is now unstable

March 17, 2014 by admin  
Filed under Global Warming

The last edge of the Greenland ice sheet that had resisted global warming has now become unstable, adding billions of tonnes of meltwater to rising seas, scientists said.

In a study published on Sunday in the journal Nature Climate Change, they said a surge in temperature from 2003 had eased the brakes on a long “river” of ice that flows to the coast in northeastern Greenland. Known as an ice stream, the “river” takes ice from a vast basin and slowly shifts it to the sea.

In the past, the flow from this ice stream had been constrained by massive buildups of ice debris choking its mouth. But a three-year spell of exceptionally high temperatures removed this blockage - and like a cork removed from a bottle helped accelerate the flow, the study said.

The stream, called Zachariae, is the largest drain from an ice basin that covers 16 per cent of the Greenland ice sheet.

From 2003 to 2012, northeastern Greenland disgorged 10 billion tonnes of ice annually into the ocean, the study found.

“Northeast Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet,” said Michael Bevis, an earth sciences professor at Ohio State University who led the study. “This study shows that ice loss in the northeast is now accelerating. So, now it seems that all the margins of the Greenland ice sheet are unstable.”

Greenland is estimated to contribute 0.5mm to the 3.2 mm annual rise in global sea levels.

The study’s main tool was data from a network of 50 Global Positioning System (GPS) sensors along the Greenland coast.

They use earth’s natural elasticity as a stethoscope of the ice sheet. When the ice melts in massive quantities the land rebounds and the sensor positions change.

To get a wider picture, the GPS data was then overlaid with data from four satellites that measured ice thickness from space.

“The Greenland ice sheet has contributed more than any other ice mass to sea level rise over the last two decades and has the potential, if it were completely melted to raise global sea level by more than seven metres,” said Jonathan Bamber, a professor at Britain’s University of Bristol.

Article source: http://www.scmp.com/news/world/article/1451095/last-edge-greenland-ice-sheet-resist-global-warming-now-unstable

Greenland Ice Sheet Experiences Record Melt

January 22, 2011 by admin  
Filed under Featured, Global Warming

New research shows the ice sheet is melting

The Greenland ice sheet, a vast body of ice covering 80% of the country, experienced a record melt in 2010.

The remote island of Greenland is at the coal face of global warming. The Greenland ice sheet makes up around one-twentieth of the worlds ice. In 2010 much of Greenland experienced unusually warm weather, extending the annual melting season by 50 days.

Research published by the City College of New York’s Cryospheric Processes Laboratory shows that since 1979 the area subject to melting in Greenland has been increasing at a rate of 17,000 kilometers square each year. This means that an area the size of France melted in 2010 which would not have melted three decades ago.

Greenland's icesheets experience record melt - M. Tedesco/WWFThe Greenland ice sheets annual melt started exceptionally early in 2010 and extended exceptionally late, lasting from the end of April to mid-September. The studys co-author Marco Tedesco, director of the Cryospheric Processes Laboratory, explained that this was caused by above-normal near-surface air temperatures.

The teams research was based on satellite data and ground observations, as well as data collected by automated weather stations installed by the Institute of Marine and Atmospheric Research Utrecht in 2003.

If the entire 2,850,000 km3 of the Greenland ice sheet were to melt, global sea levels would rise by a catastrophic 7.2 meters. The 2010 melt beats the previous record set in 2007. Eight of the largest melts on record happened between 1998 and 2010.

2010 was the warmest year on record for Nuuk, Greenlands capital city. It is projected that local warming in Greenland will exceed 3 degrees Celsius (5.4 degrees Fahrenheit) before the end of this century. Continued warming such as this would see the Greenland ice sheet cross a threshold where long-term melting is inevitable.

Canyon over the ice sheet formed by meltwater - M. Tedesco/WWFThese new findings come as the United States grapples with its funding of international climate change initiatives. A recently released budget plan prepared by the Republican Party includes a provision to eliminate all taxpayer subsidies to the United Nationals Intergovernmental Panel on Climate Change. According to New York Times environment reporter Andrew C. Revkin, dont look for the vital 21st-century energy quest, let alone a reality-based approach to global warming, to begin within the borders of the United States.

The ice in the Greenland ice sheet is up to 130,000 years old, making it an important record of past climatic conditions. Scientists have been able to drill 4 kilometers deep ice cores, providing an accurate snap shot of global climate changes, ocean volumes and volcanic eruptions.

By area Greenland is the worlds largest island. Its population totals less than 57,000, making it the least densely populated country or dependency in the world.

Article source: http://www.suite101.com/content/greenland-ice-sheet-experiences-record-melt-a336236

Greenland ice sheet future ‘grim’

December 28, 2010 by admin  
Filed under Global Warming

Dr Alun Hubbard and his team camped about 70 miles (112km) up the ice sheet in Greenland

A glaciologist is warning that the Greenland ice sheet is “retreating and thinning extensively” after a year of record-breaking high temperatures.

Dr Alun Hubbard on Aberystwyth University says its future is “grim” but disputes claims by other experts that it could collapse within 50 years.

He maintains it would be at least 100 to 1,000 years before it “potentially passes any point of no return leading to any widespread collapse”.

Dr Hubbard and his team have been analysing the results of a summer-long expedition.

His team of 15 from Aberystwyth and Swansea universities spent five months on the ice sheet from the beginning of May.

The group camped about 70 miles (112km) up the sheet, and measured the thickness, speed, climate, and other vital statistics using radar, seismic and geophysical equipment.


Large melt lakes form on the Greenland ice sheet

They found rising temperatures had caused extensive melting in new upper parts of the ice sheet in this “very sensitive polar region of the planet”.

This has generated at least double the quantity of melt water, compared with 2009, which runs off the ice sheet into the Atlantic and Arctic oceans.

There are fears the melting of the entire sheet could raise sea levels globally by about 7m (20ft), and a study last year found it was losing its mass faster than in previous years.

Dr Hubbard said his expedition had proved enhanced melting was more than just replenishing the oceans, it was now “directly contributing to global sea-level rise”.

He said global warming - at least local Greenland warming - was “worse than ever”.

“This year was another record-breaking year marked by very warm temperatures across Greenland and the Arctic,” he said.

“This warming enhanced and extended melting into new northern and upper parts of the ice sheet generating huge quantities - at least double that compared with the previous year - of melt water which runs off the ice sheet into the ocean.”

Dr Hubbard has spent four years researching the effects of climate change on the country. He has also worked on other glaciers and spent five years working in Antarctica before the Greenland project started.

It’s much like the ice is suddenly aquaplaning or slipping on a banana skinĀ  -Alun Hubbard

The team of scientists and students monitored the build up and drainage of a series of large melt lakes - up to five miles (8km) across - which form on the ice sheet surface during the summer and can drain rapidly to the bed through more than 1000m of ice.

He said the effect of this rapid drainage was to “lubricate and hydraulically lift up” the base of the ice sheet, “overcoming friction with underlying rock”, thereby allowing the sheet to flow much faster.

“It’s much like the ice is suddenly aquaplaning or slipping on a banana skin,” he explained.

“What we observed using methods borrowed from earthquake monitoring, is that the ice sheet slides and accelerates massively when these lakes drain, but the effect is relatively short lived and that the flow does regulate as further melt water drains to the bed.”

His work is part of a wider project involving researchers from Bristol, Cambridge, Edinburgh, Denmark, Sweden, the Netherlands, Germany and the United States.

Dr Hubbard and his team plan to return to the Greenland ice sheet next year to study the effect that reduced winter sea ice has on ice sheet flow and ice berg calving.

Funding for the research has come from the Natural Environment Research Council.

Article source: http://www.bbc.co.uk/go/rss/int/news/-/news/uk-wales-mid-wales-11993455