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by Kieran Cooke

Ground slows glacier ice loss

May 12, 2013 in Science

EMBARGOED until 2301 GMT on Sunday 12 May

One of the valley walls of the Petermann glacier in northern Greenland
Image: NASA/Michael Studinger

By Kieran Cooke

New understanding of some of Greenland’s major glaciers suggests they may not melt in the future nearly as fast as they are doing now.

LONDON, 13 May – Scientists tread very carefully when it comes to glaciers. While the consensus is that glaciers around the world are generally in retreat, there are the exceptions:

in the west of the Himalayas some glaciers have been found to be growing, not shrinking. In Antarctica some glaciers are gaining mass balance while others are losing it. Meanwhile glaciers in other parts of the world, particularly in the Andes, are disappearing at an ever increasing rate.

The impact of climate change on the Greenland ice sheet has been well documented: Arctic temperatures are rising at levels well above the global average, and ice-loss has been accelerating.

This has raised concerns that these constantly increasing rates of ice loss will lead to a rise in sea levels that could threaten coastal communities around the world. Yet the future contribution of Greenland’s glaciers to sea-level rise is uncertain.

A new study published in the journal Nature questions whether present trends of ice loss on the Greenland ice sheet will be maintained.

The report – Future Sea-level Rise from Greenland’s Major Outlet Glaciers in a Warming Climate – looks at the behaviour of the four major fast flowing glaciers in Greenland. The Petermann, Kangerdlugssuaq, Helheim and Jakobshavn glaciers together drain about 22% of the island’s ice sheet.

Lower loss expected

By building up a computer model of these four glaciers, scientists have revealed that the shape of the ground beneath the ice has a marked impact on the way the ice moves, with the rate at which the glaciers are losing ice depending critically on the shape of the fjords in which they sit and the topography of the rock below them.

In turn, this has led the scientists to doubt whether present rates of ice loss and the “calving” of icebergs from the glaciers will be maintained.

“…While these glaciers may show several bursts of retreat and periods of high iceberg formation in future, the rapid acceleration seen in recent years is unlikely to continue unchecked”, says the report.

The computer model suggests that, because of the influence of various topographical features, the projected sea level rise from ice loss of these four glaciers will be of the order of between 2cm and 5cm by 2200 – considerably lower than previous estimates which have been based solely on the extrapolation of current trends.

However, the rate of calculated ice loss will still be considerable: the model predicts that the combined ice loss of the four will amount to between 30 gigatonnes (Gt) and 47Gt per year over the present century. One Gt of ice is equivalent to one cubic kilometre of water. By way of comparison, Lake Geneva contains 90Gt of water.

More clarity needed

“I am excited by the way we have managed to create a detailed picture of the workings of the glaciers”, says Dr Faezeh Nick, of the Universite Libre de Bruxelles, lead author of the study.

“It turns out that if the fjord a glacier sits in is wide or narrow, it really affects the way the glacier reacts. The important role of the terrain below the ice shows we need to get a much clearer picture of the rest of Greenland’s glaciers before we have the whole story.”

Work on the modelling of the glaciers was carried out under the EU-funded Ice2sea programme which links scientific expertise among 24 institutions in Europe and elsewhere.

Professor David Vaughan, head of the programme, told Climate News Network that though there were various ways of analysing the behaviour of glaciers, the new computer modelling could be vital in assessing future levels of ice loss.

“The key point is that we actually need to know about the land beneath the ice if we are going to come up with really good projections on future ice loss and the contribution to sea level rise of these glaciers. This computer modelling could be a big step forward and adds to our understanding of how glaciers behave.” – Climate News Network

Tags: Glaciers, Greenland, Ice melt, Sea levels Comments Off

by Tim Radford

Clouds ’caused Greenland’s 2012 thaw’

April 5, 2013 in Science

FOR IMMEDIATE RELEASE

There were several factors which led to 2012′s dramatic thaw in Greenland
Image: Brocken Inaglory

By Tim Radford

Last year’s brief but startlingly rapid melting of the Greenland ice sheet probably had nothing to do with climate change. What it did reveal was the limits of our current knowledge.

LONDON, 5 April – US scientists think they can explain why the Greenland ice sheet started melting at an unexpected and alarming rate in the summer of 2012. They blame it on unusual clouds.

In four days during July last year, Nasa satellite measurements revealed that 97% of the surface of the Greenland ice sheet had begun to thaw. The slush was even recorded at the summit of the icecap, more than three kilometres above sea level. This sudden, dramatic thaw was brief, but without precedent.

Greenland is home to three million cubic kilometres of ice. If all of it melted, sea levels globally would rise by more than seven metres. So climate scientists have for decades taken a keen interest in Greenland, and report that such sudden periods of dramatic melting occur roughly only once in 150 years.

In July 2012, observers blamed the record North American heat waves, and even wild fires in the tundra that might have sent columns of sunlight-absorbing soot to darken the snow.

But now Ralf Bennartz of the University of Wisconsin-Madison thinks he has the answer. He and colleagues report in Nature that while there would be more than one cause for such a huge change in the pattern of summer thaw, they focused on the role of low-level clouds.

Snow keeps itself cool by reflecting sunlight back into space. Low-level clouds, too, should keep land masses cool, by reflecting sunlight back into space.

But the scientists calculated that, under particular temperature conditions, clouds could be thin enough to permit solar radiation to filter through, but thick enough to trap some of the Sun’s energy as infra-red radiation even if it was reflected by the snow and ice on the ground. The extra heat trapped close to the ice surface was enough to push temperatures above freezing.

Complex influences

There would have been other factors to consider: air pressure, regional temperatures, wind speeds, turbulence, ocean currents and so on. Nobody last year was inclined to blame global warming for such an entirely unexpected phenomenon.

The short, sudden and very unusual event was just that, an unusual event, to be reconstructed months later by a combination of observations on the ground, remote sensing data and computer models.

But it told meteorologists and climate scientists something about the complexities of the interplay of light, land, air, water and ice in those latitudes.

“We know that these thin, low-level clouds occur frequently. Our results may help to explain some of the difficulties that current global climate models have in simulating the Arctic surface energy budget”, said Professor Bennartz.

“Above all, this study highlights the importance of continuous and detailed ground-based observations over the Greenland ice sheet and elsewhere.” - Climate News Network

Tags: Arctic, Clouds, Greenland, Ice melt Comments Off

by Kieran Cooke

Glaciers on the slide

March 3, 2013 in Film reviews

EMBARGOED till 0001 GMT on Sunday 3 March

Greenland's glaciers face trouble - and so do many elsewhere Image: Christine Zenino

Greenland’s glaciers face trouble – and so do many others across the world
Image: Christine Zenino

By Kieran Cooke

If seeing really is believing, then James Balog’s film Chasing Ice is probably prompting a widespread outburst of faith. It shows the graphic evidence of how fast glaciers are melting worldwide.

LONDON, 3 March – You’d have to worry about James Balog’s knees. He has an operation on one leg and then, for a bit of gentle recuperation, goes walking on a glacier. Not surprisingly, before too long he needs to return to the surgeon’s table: then it’s back to the ice once more, only this time Balog is being lowered down into a crevasse, a cascade of freezing glacier melt water rushing within inches of his camera.

Balog is a photographer who has specialised for many years in what he describes as the “contact zone” between humans and nature. His work includes photos and documentaries on animals and forests, on the 2004 tsunami in Southeast Asia, on Hurricane Katrina and much, much more.

In 2006 he was given an assignment by National Geographic magazine to photograph glaciers and ice formations. He became a glacier groupie and the following year started the Extreme Ice Survey (EIS), photographing and filming glaciers round the world. Chasing Ice, released in the US last year and now doing the rounds of selected cinemas in the UK, captures the work of the EIS project.

Balog was once a climate change sceptic. Not any more. He and his team set up 28 time lapse cameras filming glaciers from Mount Everest in Nepal to Alaska, Greenland, Iceland and the Rockies in the US. Every half hour of daylight the cameras would click away, recording changes in glacier shape and size. The results, seen in the film, are startlingly clear.

“This is the memory of the landscape”, says Balog, standing by one of his cameras at a glacier in Greenland and holding up a small file of film. “I never imagined you could see glaciers this big disappearing in such a short space of time. That landscape is gone and may never be seen again in the history of civilisation.”

Balog now tours the world with his photos and film showing, in his words, “how extraordinary amounts of ice are disappearing with shocking speed.” He wants people to see for themselves the visual evidence of climate change. “Seeing is believing”, he says.

Up an ice field on crutches

Chasing Ice is visually stunning: at one point young members of the survey team are camped out on the ice overlooking the Illulissat or Jakobshavn glacier half way up the west coast of Greenland. They’ve been there for days – the wind its threatening to blow the tent away, the cold is intense.

Then, in little over an hour, a piece of glacier more than half the size of Manhattan Island breaks or “calves” away. It’s the first time such a large-scale calving event has been captured on film. Giant pieces of ice shoot 600 feet up in the air, the glacier doing cartwheels, the deep, roaring sound echoing like the last breath of some giant, fatally wounded animal.

“The only way that you can really try to put it into scale with human reference is if you imagine Manhattan, and all of a sudden, all of those buildings just start to rumble, and quake, and peel off, fall over, and roll around”, says one of the film-makers. “This whole massive city just breaking apart in front of your eyes.”

The film was not an easy one to make, with delicate electronic equipment being placed in some of the harshest conditions on the planet. Cameras would have to be secured by elaborate systems of anchors and wires. At one point Balog’s team return to the cameras to find the equipment has failed and months of filming has been lost.

And then there are those knees. Towards the end of the film Balog is seen struggling up an ice field on crutches. There’s a postcript saying his knees have been repaired once again, this time with the aid of stem cell surgery. The EIS project is ongoing. Let’s hope the knees keep going as well. – Climate News Network

Tags: Glaciers, Greenland, Ice melt Comments Off

by alex kirby

Ice melt means uneven sea-level rise

February 20, 2013 in Science

FOR IMMEDIATE RELEASE

Greenland’s ice will have distant impacts Image: Christine Zenino

By Alex Kirby

Research shows that some parts of the world are likely to experience much more sea-level rise than others this century, with parts of the Pacific Ocean particularly affected.

LONDON, 20 February – Scientists say the sea-level rise caused by climate change during the rest of this century will not affect all parts of the world equally, because of the ways sea, land and ice interact.

They say parts of the Pacific are likely to see the highest rise. This region is where many low-lying island countries most vulnerable to sea level rise are already struggling. In the Indian Ocean the Seychelles face a similar plight. Their peoples will need evacuation if the scientists’ high-end predictions are correct. Northern Europe, on the other hand, will experience a below-average increase.

The team, from Italy’s University of Urbino and the University of Bristol, UK, report their findings in a paper, The gravitationally consistent sea-level fingerprint of future terrestrial ice loss, published in Geophysical Research Letters online.

Scientists have known for some time that sea level rise around the globe will not be uniform. The team investigated how ice loss will continue to add to rising sea levels until the year 2100. The researchers, from the European Union’s Ice2sea project, show in detail the global pattern of sea-level rise that would result from two scenarios of ice-loss from glaciers and ice sheets.

Improved projections of the contribution of ice to sea-level rise produced by Ice2sea will feed into the fifth assessment report of the Intergovernmental Panel on Climate Change. In 2007, the IPCC’s fourth report highlighted ice-sheets as the most significant remaining uncertainty in projections of sea-level rise.

The researchers found that ice melt from glaciers and from the Greenland and Antarctic ice sheets is likely to be critically important to regional sea-level change in the equatorial Pacific ocean.

Legacy of the Ice Age

There the rise will be greater than the global average increase, affecting in particular western Australia, Oceania and the small atolls and islands in the region, including Hawaii. Another area which should expect an above-average increase is the east coast of South Africa and Madagascar.

The study focussed on three effects that lead to the unequal distribution of sea-level rise. First, land is both subsiding into and emerging from the sea because of a massive ice loss at the end of the last Ice Age 10,000 years ago, when billions of tonnes of ice covering parts of North America and Europe melted.

This caused a major redistribution of mass on the Earth, but the crust responds to such changes so slowly that it is still changing shape. Secondly, the warming of the oceans changes the distribution of water across the globe.

The third effect is the way the sheer mass of frozen water on Antarctica and Greenland exerts a gravitational pull on the surrounding liquid water, pulling in enormous amounts and raising the sea-level close to the coasts. As the ice melts its pull decreases and the water previously attracted pours away, to be redistributed around the globe.

Co-author Professor Giorgio Spada said: “The most vulnerable areas are those where the effects combine to give the sea-level rise that is significantly higher than the global average.” In Europe the level would rise, but it would be slightly lower than the average.

“We believe this is due to the effects of the melting polar ice relatively close to Europe – particularly Greenland’s ice”, he said. “This will tend to slow sea-level rise in Europe a little, but at the expense of higher sea-level rise elsewhere.”

The team considered two scenarios in its modelling. One was the “most likely” or “mid-range” and the other closer to the upper limit of what could happen.

Stark contrast

Professor Spada said: “The total rise in some areas of the equatorial oceans worst affected by the terrestrial ice melting could be 60cm if a mid-range sea-level rise is projected, and the warming of the oceans is also taken into account.”

Another co-author, Jonathan Bamber, professor of physical geography at Bristol University, UK, told the Climate News Network: “Northern Europe will be influenced by mass loss from Greenland, and places like Scotland and Scandinavia will probably see close to zero sea-level rise from the melting ice, leaving aside thermal expansion of the sea.

“But if you take the high-end scenario, there’s a reasonable chance the rise could reach a metre in the western Pacific.”

Professor David Vaughan, Ice2sea programme coordinator, said: “The urgent job now is to understand how the global sea-level rise will be shared out around the world’s coastlines. Only by doing this can we really help people understand the risks and prepare for the future.”

A spokesman for the Association of Small Island States (Aosis), told a UN climate conference two years ago that whole nations would be washed away by sea level rise.

He said the people of Kiribati, Tuvalu, most of the Cook Islands, the Marshall Islands and the Maldives, which are just a few metres above sea level now, could be lost. – Climate News Network

Tags: Antarctica, Glaciers, Greenland, Sea levels Comments Off

by Tim Radford

Researchers unravel Greenland ice riddle

January 28, 2013 in Science

EMBARGOED until 0001 GMT on Monday 28 January

By Tim Radford

Why, scientists are wondering, did warmer temperatures in the far-distant past allow Greenland’s ice cap to remain stable while sea levels rose significantly? They think there could be lessons for us in this century.

LONDON, 28 January – Scientists examining ice cores from deep in the glaciers of northwest Greenland have identified a period around 120,000 years ago when temperatures were 8°C warmer than today, they report in the journal Nature.

The good news is that despite this dramatic rise in temperature, the Greenland ice cap remained stable: it shrank to about 130 metres below the present level but the island remained covered by a thick blanket of ice.

The bad news is that – since at the time global sea levels were between four and eight metres higher than today – much of the meltwater that raised sea levels must have come from somewhere else.

Greenland has always been at the heart of concerns about global warming: climate scientists have for decades suspected that the massive ice sheets that cover Greenland and West Antarctica must have melted during the warm periods between the ice ages.

A pointer to the present

A team of 300 researchers from 14 nations has been studying the record of global temperatures preserved in the layers of ice during the Eemian period, a warm spell in the last great Ice Age. Locked in each annual snowfall is a ratio of oxygen isotopes that provides a measure of the atmospheric temperatures prevailing at the time.

With careful analysis of cores from Antarctica and Greenland – backed up by independent evidence from muds from the sea floor and pollens found in old lake beds – climatologists have been able to reconstruct the patterns of temperature for hundreds of thousands of years.

They see the Eemian period as a guide to what might happen as carbon dioxide levels in the atmosphere rise in the present century, driving global warming and climate change: during those few thousand years of warming, temperatures were between 5°C and 8°C warmer than the average of the last 1,000 years.

During the Eemian period the glacial surface melted, sank into the underlying snow, and froze again. This is a rare event at such latitudes, but in 2012, while the researchers were camped on the ice, it happened again.

“It was even raining, and just like in the Eemian, the meltwater formed refrozen layers of ice under the surface,” said Dorthe Dahl-Jensen of the Niels Bohr Institute at the University of Copenhagen, leader of the project.

“Although it was an extreme event, the current warming over Greenland makes surface melting much more likely, and the warming that is predicted to occur over the next 50-100 years will potentially have Eemian-like climatic conditions.”

The scientists drilled for, and recovered, more than 2,500 metres of ice core, a frozen record of more than 130,000 years of precipitation. The study confirms that, although the glacier at the peak of the 6,000 year warm period was shrinking by six centimetres a year, the island remained sheathed by a huge depth of ice.

The suspicion now must be that colossal melting in west Antarctica may have delivered much of the then-higher sea levels.

“A thick Greenland ice sheet connected to much warmer conditions is astounding but no reason to relax and watch what the future of man-made warming has in store for us,” said Hubertus Fischer of the University of Bern.

“The warming was accompanied by a sea level rise of four to eight metres. Such a sea level rise would be a disaster for the more than seven billion people living on this planet today, even if it takes a thousand years to be reached.” – Climate News Network

Tags: Antarctic, Greenland, Ice cores, Sea levels Comments Off

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