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by Tim Radford

Glaciers are melting slowly – but surely

May 20, 2013 in Warming

EMBARGOED until 2301 GMT on Sunday 19 May

Glacier in the Tian Shan mountains of Central Asia, where ice loss is considerable
Image: Andrzej Barabasz (Chepry)

By Tim Radford

Although hundreds of the world’s glaciers are shrinking fast, far more are losing ice much more slowly, new research has established. But it shows that, almost everywhere, the glaciers are in retreat.

LONDON, 20 May – Forget, for the moment, the Greenland and Antarctic ice sheets: what about all the other stuff? What kind of difference does the melting of glaciers in Scandinavia, or Alaska, or the Himalayas make to the ocean levels?

Alex Gardner of Clark University, Massachusetts, and 15 colleagues from the US, Canada and Europe decided to take a closer look: their answer is that shrinking glaciers lost 259 billion tonnes (259 gigatonnes) of mass in the form of meltwater every year between 2003 and 2009, give or take 28 gigatonnes, an amount equal to around 30% of observed sea level rise.

This equals the combined losses from the permanent ice sheets that blanket, in layers thousands of metres thick, the two vast land masses of Greenland and Antarctica.

The scientists report their findings in the journal Science. They used both measurements on the ground – necessarily selective – and measurements from orbiting satellites, which naturally give a bigger picture, but also a more imprecise one.

The satellites carried instruments specifically designed to study ice loss: one was called GRACE, short for gravity recovery and climate experiment, and the other was called ICEsat – an ice, cloud and land elevation satellite. The first measured tiny changes in gravity as the ice melts away. The second used lasers to measure changes in height, and therefore volume.

The scientists also consulted an authoritative store of geographical data, the Randolph Glacier Inventory, which defines 19 glacier regions with a total area under flowing ice of 729,400 square kilometres. They chose the dates under study because for those six years, ICEsat and GRACE were both in orbit, and sending back data, and thus providing a record of both seasonal and overall ice loss during that time.

Long-term concern

The conclusion was that although the 300 most closely-observed glaciers, the ones that have caused the most alarm, are indeed losing mass at a disturbing rate, this is not the whole picture. The other 160,000 glaciers distributed across the planet are losing ice overall at a slower rate.

This sounds like relatively good news, considering that global anxiety about retreating glaciers was based mostly on direct measurements of famous or easy-to-observe ice flows. But the research confirms the big picture: that glaciers are in retreat almost everywhere.

And this spells problems in the long run everywhere: glaciers store winter water for summer irrigation, city water supplies and hydroelectric power. They keep rivers navigable, and they maintain mountain ecosystems.

If they shrink, that’s not good news for mountain creatures or the people, forests, plains and settlements downstream. The largest losses were from Arctic Canada, Alaska, coastal Greenland, the southern Andes and the high peaks of Asia. There was little loss from Antarctica’s glaciers. – Climate News Network

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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 Paul Brown

Antarctic Peninsula’s thaw speeds up

April 14, 2013 in Warming

EMBARGOED until 1700 GMT on Sunday 14 April

James Ross Island: Scientists worked in shifts to drill to the base of the ice sheet.
Image: Nerilie Abram

By Paul Brown

Ice in parts of the Antarctic Peninsula is now melting during the summer faster than at any time in the last thousand years, and the most marked speed-up in the thaw has occurred since 1960, scientists say.

LONDON, 14 April – Summer ice melt in the Antarctic Peninsula has increased almost 10-fold in the last 600 years, weakening the area’s large ice shelves and reducing glacier size, scientists have discovered.

The findings explain a series of sudden collapses of ice shelves in the last 20 years, which scientists studying them had not expected. The researchers say the melting that is now occurring could lead to further dramatic events, making the loss of large quantities of ice on the Peninsula more likely, and adding to sea level rise.

The results are significant because in the last two decades scientists have been divided on whether the Antarctic would gain mass through extra snow falling and so reduce sea level rise, or would lose ice because of higher sea and air temperatures and so multiply the effect. The new data come from a 1,000-year Antarctic Peninsula climate reconstruction published in the journal Nature Geoscience.

In 2008 a UK-French team drilled a 364-metre ice core from James Ross Island, near the northern tip of the Peninsula, with the idea of measuring past temperatures in the area. What surprised them was that the core also gave an unexpected insight into ice melt in the region over that period.

Layers in the ice core showed periods when summer snow on the ice cap thawed and then refroze. By measuring the thickness of these melt layers the scientists were able to examine how the history of melting compared with changes in temperature at the ice core site over the last thousand years.

In the last 600 years the temperature has increased by 1.6C, but only in the last 50 years has it reached a level at which summer melting has increased dramatically.

Lead author Dr Nerilie Abram of the Australian National University and the British Antarctic Survey (BAS) said: “We found that the coolest conditions on the Antarctic Peninsula and the lowest amount of summer melt occurred around 600 years ago.

“At that time temperatures were around 1.6°C lower than those recorded in the late 20th century and the amount of annual snowfall that melted and refroze was about 0.5%. Today, we see almost ten times as much (5%) of the annual snowfall melting each year.

“…even small changes in temperature can result in large increases in the amount of melting…”

“Summer melting at the ice core site today is now at a level that is higher than at any other time over the last 1,000 years. And whilst temperatures at this site increased gradually in phases over many hundreds of years, most of the intensification of melting has happened since the mid-20th century.”

Dr Robert Mulvaney from the BAS led the ice core drilling expedition and co-authored the paper. He said: “Having a record of previous melt intensity for the Peninsula is particularly important because of the glacier retreat and ice shelf loss we are now seeing in the area.

“Summer ice melt is a key process that is thought to have weakened ice shelves along the Antarctic Peninsula leading to a succession of dramatic collapses, as well as speeding up glacier ice loss across the region over the last 50 years.”

The changes in the Peninsula do not necessarily apply to other parts of Antarctica, for example the West Antarctic Ice sheet, where melting is occurring and there is potentially an even greater risk of large-scale sea level rise.

It is not yet clear that the levels of recent ice melt and glacier loss in West Antarctica are exceptional or are caused by human-driven climate changes.

However, Dr Abram said: “This new ice core record shows that even small changes in temperature can result in large increases in the amount of melting in places where summer temperatures are near to 0°C, such as along the Antarctic Peninsula, and this has important implications for ice instability and sea level rise in a warming climate.” – Climate News Network

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by alex kirby

Canadian glaciers are melting fast

March 7, 2013 in Warming

FOR IMMEDIATE RELEASE

Canada's far north is melting - and there's probably no going back Image: David

Canada’s far north is warming – and there’s probably no going back
Image: David

By Alex Kirby

Many of the Canadian far north’s glaciers are likely to have melted by the end of the century, researchers believe, making significant sea-level rise inevitable.

LONDON, 7 March – Canada’s Arctic Archipelago glaciers will melt faster than ever in the next few centuries, research by European-funded scientists has shown.

They say 20% of the Canadian Arctic glaciers may have disappeared by the end of this century, which would mean an extra sea level rise of 3.5cm

The results of the research, part of the EU-funded ice2sea programme, will be published in Geophysical Research Letters this week, and the paper, Irreversible mass loss of Canadian Arctic Archipelago glaciers, is now available online.

The researchers developed a climate model for the island group in the north of Canada in which they simulated the shrinking and growing of glaciers in this area.

The model correctly “predicted” the ice mass loss measured over the last ten years, and the researchers then used it to look forward to project the effect of future climate change on the Arctic Archipelago glaciers.

The most important result of the research is that it shows that the melting will probably be irreversibie, according to lead author Dr Jan Lenaerts of Utrecht University.

He says: “Even if we assume that global warming is not happening quite so fast, it is still highly likely that the ice is going to melt at an alarming rate. The chances of it growing back are very slim.”

One main reason for this expected irreversibility is that snow melting on tundra, and sea ice loss from around the glaciers, will intensify regional warming.

Snow and sea ice reflect the sunlight, and when they disappear a large part of the sunlight will instead be absorbed by the land and the sea, raising the local temperature significantly.

Successful backcasting

In one scenario considered by the scientists 20% of the volume of the glaciers disappears by the end of this century. This would be accompanied by an average global temperature rise of 3°C.

But the regional rise around the Canadian ice caps - a form of glacier in which the ice flows to the sea in many directions – would be 8°C. And this is not an extreme scenario, Dr Lenaerts says.

Canada’s Arctic Archipelago glaciers are one of the largest ice bodies in the world after Greenland and the Antarctic. If they melted completely, global average sea level would rise by 20 cms. Since the year 2000 the temperature in this area has risen by 1-2°C and the ice volume has already decreased significantly.

Professor David Vaughan, the programme leader of ice2sea, who is based at the British Antarctic Survey in Cambridge, UK, says: “Added to glaciers in Alaska, the Russian Arctic and Patagonia, these apparently small contributions add up to significant sea-level rise.

“A key success of this study was in showing that the model performed well in reproducing recently observed changes. That success gives us confidence in how the model predicts future changes”.

Glaciers in many parts of the world are undergoing rapid melting, although some experts argue that natural variability needs to be taken into account as well as climate change (and see our story of 3 March, Glaciers on the slide.) – Climate News Network

Tags: Canada, Glaciers, Ice melt, Sea levels 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

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by Paul Brown

Europe’s climate forecast: unsettling

February 1, 2013 in Economy

EMBARGOED until 0001 GMT on Friday 1 February

By Paul Brown

Climate change will mean winners and losers in Europe, with the effects likely to be more acute nearer the Mediterranean. But across the continent countries will have to find ways to adapt.

LONDON, 1 February – With the European land surface warming rapidly, rainfall patterns changing and sea levels rising ever faster, southern Europe will suffer most from climate change. But there is an urgent need for countries across the continent to adapt to change, according to the European Environment Agency (EEA).

Temperatures are already 1.3C above the pre-industrial average and are expected to go on rising. This brings gains to some countries in northern Europe, with higher crop yields and lower heating costs, while the south loses.

It is the countries currently struggling most at the moment economically, Greece, Spain and Portugal, that will fare worst under climate change. The EEA says all three countries will lose both harvests and tourists, two of their main economic props, as a result of rising heat and low summer rainfall.

Northern Europe does not escape unscathed. River flooding is already a problem and annual sea level rise, which has already doubled in the last 20 years, and is currently at 3 mm a year, is expected to rise further. All the countries around the North Sea are now vulnerable to storm surges.

It’s real and it’s now

The latest assessment of how climate change is affecting Europe, published every four years by the Agency and due out in March, is the main evidence being used by the European Union to underpin its policy of adapting to a warming world.

Billions of euros will be spent trying to stave off the worst effects of climate change, which the Agency says are already going to happen whatever we do now to mitigate carbon emissions. Temperatures in Europe are expected to rise as much as 4C this century.

Professor Jacqueline McGlade, EEA Executive Director, has said: ”Climate change is a reality. The extent and speed of it is becoming ever more evident. This means every part of the economy, including households, has to adapt.”

While in some places changes are beneficial, for example an earlier spring and longer growing season, the overall effects are negative. The further south in Europe climatologists investigate, the more they see climate change affecting both human and natural populations.

Changes ahead for tourism

Health effects, tick-borne diseases, mosquitoes and heat waves are serious threats. There is evidence that butterflies and other species adapted to living in cooler climes cannot move north fast enough to survive.

Among the predictions is a change in where Europeans will take their holidays, and when. As temperatures increase, more people will take their summer breaks in northern and central Europe, leaving it till the winter to travel south. This, along with loss of snow cover in the lower skiing resorts, is likely to have severe economic impacts in some regions.

The number of days people need to turn on their central heating has already gone down by 16 days a year since 1980. The number of days when air conditioning is needed in the summer has risen.

The increased electricity demand in the summer is likely to cause a power crisis in southern Europe. Low river flows will probably face nuclear and thermal power plants with difficulties because both need large quantities of cooling water to operate efficiently.

The lack of summer hydropower, already a problem in some countries, will become far more noticeable because of the demand for electricity for cooling in the heat.

Crop yields will increase dramatically in some northern and eastern European countries and decrease in the south. The countries worst affected will be Spain, Portugal and Greece, which stand to lose between 15% and 25% of all crops because of a lack of summer rainfall. France, Italy, Albania, Macedonia, Serbia, Bosnia and Bulgaria will also suffer losses of between 5% and 15%.

The gains are mostly in the north, with the Scandinavian countries and Russia increasing yields – more than 5% and perhaps as much as 35% in parts of Norway and Sweden. The Ukraine, already one of the largest grain producers in Europe, is also going to have improved yields.

Along with the effect on agriculture, less rainfall will cause species loss in the Mediterranean, partly due to more forest fires and heat waves. The health of rivers will be affected by low summer rainfall. – Climate News Network

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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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