Alaska’s glaciers melt faster as climate change speeds up

Alaska's glaciers melt faster as climate change speeds up

Climate change rather than natural causes is the main cause of Alaska’s glacier loss, which is set to speed up, US scientists say.

LONDON, 30 June, 2015 – The glaciers of Alaska are melting and retreating: the chief cause is climate change and the loss of ice is unlikely to slow, according to a new study by US scientists.

They calculate that the frozen rivers of the Pacific coast of America’s northernmost state are melting fast enough to cover the whole of Alaska with 30 cms of water every seven years.

Since Alaska is enormous – it covers 1.5 million square kilometres and is the size of California, Texas and Montana put together – this adds up to a significant contribution to sea level rise.

“The Alaska region has long been considered a primary player in the global sea level budget, but the exact details of the drivers and mechanisms of Alaska glacier change have been stubbornly elusive,” said Chris Larsen, a geophysicist at the University of Alaska Fairbanks, and lead author of a study in Geophysical Research Letters.

Taxonomy of change

Scientists from the University of Alaska and the US Geological Survey analysed studies of 116 glaciers in the Alaska region over a 19-year-period to estimate the rate at which ice melted and icebergs calved.

They used airborne lidar remote sensing technology and other techniques, historical data and a global glacier inventory to establish a kind of taxonomy of glacier change.

The Columbia Glacier in Prince William Sound had retreated more than 19 kilometres because of iceberg calving and had thinned by 450 meters in height since 1980. But, unexpectedly, tidewater glaciers – those that end in the ocean – seemed to make comparatively little contribution to sea level rise.

“Instead we show that glaciers ending on land are losing mass exceptionally fast, overshadowing mass changes due to iceberg calving, and making climate-related melting the primary control on mountain glacier mass loss,” Dr Larsen said.

Big contributor

He and his colleagues calculated that Alaska is losing ice at the rate of 75 billion metric tons a year. Such research is just one more piece of careful cross-checking in the great mosaic of climate research: another systematic confirmation that overall, glaciers are not losing ice in response to some natural cycle of change of the kind that occasionally confuses the picture for climate science.

The agency at work is largely global warming as a response to the steady rise in atmospheric carbon dioxide as a consequence of the burning of fossil fuels.

Mountain glaciers represent only 1% of the total ice on the planet: the other 99% is found in Greenland – which is melting fast – and in the great frozen continent of Antarctica, where ice mass is being lost at an increasing rate.

But although the mountains of the temperate and tropic zones bear only a tiny percentage of the planet’s ice, their melting accounts for almost a third of the sea level rise currently measured by oceanographers, and this melting will go on to become a big contributor to the sea levels later this century.

“Alaska will continue to be a major driver of sea level change in the upcoming decades”

Across the border in Canada, glaciologists have warned that the country will lose a huge volume of flowing ice, and while one team has confirmed that air pollution rather than global warming long ago began to strip Europe’s Alps of their glaciers, in general mountain peaks are warming faster than the valleys and plains below them.

Geophysicists and glaciologists have established that the glaciers of the tropical Andes are at risk, and in the Himalayan mountain chain glaciers seem to be in inexorable retreat with consequences that could be devastating for the many millions in the Indian subcontinent and in China who rely on seasonal meltwater for agriculture.

Glaciers are by definition hard to study – they are high, cold and in dangerous terrain – and such research is inevitably incomplete: the scientists for instance excluded glaciers smaller than three square kilometres. But together these small patches of flowing ice account for 16% of Alaska’s glaciated landscape. The 116 glaciers in the survey together added up to only 41% of the state’s glaciated area.

But the pattern established by the Fairbanks team suggests that melting will accelerate with climate change. “Rates of loss from Alaska are unlikely to decline, since surface melt is the predominant driver, and summer temperatures are expected to increase,” said Dr Larsen.

“There is a lot of momentum in the system, and Alaska will continue to be a major driver of sea level change in the upcoming decades.” – Climate News Network

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New flood alert as warming raises sea levels threat

New flood alert as warming raises sea levels threat

Scientists warn countries in northern Europe to plan for dramatic new worst-case scenarios as climate change increases the risk of seas sweeping inland.

LONDON, 22 June, 2015 − Europe could face a higher marine invasion than anybody anticipated. As polar ice melts, tides could be as much as 1.5 metres higher around the coasts of Scandinavia, Germany, the Netherlands and England, according to a new study.

This is considerably higher than the average sea level rise – driven by global warming as a consequence of burning fossil fuels – projected by the Intergovernmental Panel on Climate Change under a “business as usual” scenario and a global average temperature rise of 4°C.

But there is no contradiction. The discrepancy arises because the seas have never been level, and the land keeps moving too.

Aslak Grinsted, associate professor in the Centre for Ice and Climate at the Niels Bohr Institute of the University of Copenhagen, Denmark, and colleagues report in the journal Climate Research that they took a closer look at the dynamics of sea level change in the North Sea, the North Atlantic and the Baltic for the remainder of this century.

Land uplift

“Even though the oceans are rising, they do not rise evenly across the globe,” Dr Grinsted says. “This is partly due to changes in the gravitational field and land uplift.”

He and his colleagues started with the anomalies they knew best. These are in Greenland, which is covered by a sheet of ice so massive that it gathers up the sea around it. So, to reach Greenland, ships must sail uphill.

As the ice sheet melts – and there are studies that show it is melting at an accelerating rate that would heighten sea levels by 14 cms this century – the mass will be reduced and the sea levels will fall, even though more water has entered the oceans.

“In England . . . we cannot exclude a sea level rise of up to 1.75 metres this century”

But although waters are notionally lapping ever higher along coastlines, these too are changing. Northern Europe 12,000 years ago was covered by deep ice, and the bedrock below was depressed. Now the ice has gone, but the land once crushed by it is still rising.

Equipped with the latest research and measurements, the Copenhagen team began their reinterpretation of the local future. They found that what had once been considered “high” scenarios for the Netherlands and England will be surpassed.

Best estimate

Dr Grinsted says: “For London, the calculated best estimate is that sea level will rise by 0.8 metres. In England, a sea level rise of more than 0.9 meters in this century has been considered highly unlikely, but our new calculation shows that there is a 27% chance that this limit is surpassed, and we cannot exclude a sea level rise of up to 1.75 metres this century.”

For the Netherlands, the best estimate of sea level rise is 0.83 metres, but the calculations show that there is a 26% chance that it will exceed the existing high-end scenario of 1.05 metres, and could even reach 1.80 metres.

Dr Grinsted says: “Both countries have already established protections for the coasts with barriers, sluice gates and dikes, but is it enough? I hope that our calculations for worst-case scenarios will be taken into consideration as the countries prepare for climate change.”

The IPCC sea level projection is of 80 cms worldwide. Sea levels overall might change little in Scotland, Ireland and Norway. And in the Gulf of Bothnia, in Finland, where the land is rising even faster than the sea, tides could be as much as 10cms lower at the end of the century. − Climate News Network

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Glacier loss raises high concern over water supplies

Glacier loss raises high concern over water supplies

Massively increased ice melt in the high Himalayas because of climate change could seriously jeopardise the flow of water for billions of people in Asia.

LONDON, 2 June, 2015 − The glaciers of the Everest region of the Himalayan massif – home to the highest peak of all – could lose between 70% and 99% of their volume as a result of global warming.

Asia’s mountain ranges contain the greatest thickness of ice beyond the polar regions. But new research predicts that, by 2100, the world’s highest waters – on which billions of people depend for their water supply – could be at their lowest ebb because of the ice loss.

Many of the continent’s great rivers begin up in the snows, fed by melting ice in high-peak regions such as the Hindu Kush, the Pamir and the Himalayas.

Joseph Shea, a glacial hydrologist at the International Centre for Integrated Mountain Development in Kathmandu, Nepal, and French and Dutch colleagues report in The Cryosphere journal that they used more than 50 years of climate data and sophisticated computer models of predicted climate change to study the pattern of snowpack and seasonal melt in the Everest region.

Temperature increase

They found a decrease of 20% since 1961, and signs that most, if not quite all, of the stored ice could disappear in the next 85 years.

“The signal of future glacier change in the region is clear: continued and possibly accelerated mass loss from glaciers is likely, given the projected increase in temperatures,” Dr Shea says.

”Our results indicate that these glaciers may be highly sensitive to changes in temperature, and that increases in precipitation are not enough to offset the increased melt.”

That mountain glaciers in the temperate zones and the tropics are in retreat is not in doubt. In the last two years, researchers have established patterns of ice loss in Nepal, in the tropical Andes of South America, and in the Canadian highlands.

“The signal for future glacier change in the region is clear and compelling”

Other teams have stepped back to look at the big picture, and one calculation is that around 160,000 glaciers in Europe, Asia, and the Americas are shedding 260 billion tonnes of ice each year. This is roughly as much as is now being lost from the Greenland and Antarctic ice sheets.

The consequences for sea level rise are obvious, and ominous. But glaciers have local importance too: their spring and summer meltwater drives hydroelectric power, nourishes industrial growth in the cities, and irrigates the rice and wheat crops on which billions of people depend.

The rate and extent of glacial retreat, the scientists say, depends on the levels of greenhouse gases emitted from the burning of fossil fuels in future. And some of the loss depends on the changes in the altitude at which water freezes.

Freezing levels

Right now, in the Everest region, ice forms at 3,200 metres in January, but at 5,500 metres in August. But according to Walter Immerzeel, assistant professor of physical geography at the University of Utrecht in the Netherlands, these freezing levels could rise by between 800 and 1,200 metres by 2100.

“Such an increase would not only reduce snow accumulation over the glaciers, but would also expose 90% of the current glacier area to melt in the warmer months,” he says.

Research at high altitudes is difficult, dangerous, and subject to error. The scientists focused their study on four large glaciers in Nepal’s Dudh Kosi river basin, which holds 400 square kilometres of glacial ice. They then tested eight future climate scenarios to construct the pattern of the future.

In 2007, the Intergovernmental Panel on Climate Change reported that the Himalayan glaciers could vanish as early as 2035 − but three years later had to apologise for what was described as an “unfounded” claim.

The Cryosphere authors say their own results should also be treated cautiously. But, their paper concludes, “the signal for future glacier change in the region is clear and compelling”. – Climate News Network

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Science puzzles over recent rapid Antarctic thaw

Science puzzles over recent rapid Antarctic thaw

Part of Antarctica has begun thawing unusually fast, leaving scientists unsure whether a natural cycle or human-caused climate change is responsible.

LONDON, 31 May, 2015 − Antarctic glaciers once thought relatively stable are starting to melt. Evidence from a five-year satellite study of the frozen rivers on the southern Antarctic Peninsula now reveal that these are shedding ice at the rate of 60 cubic kilometres a year: altogether around 300 trillion litres of water has moved from the frozen continent to the oceans.

Bert Wouters of the University of Bristol, UK, and colleagues report in the journal Science  that they used data from two very different research satellites to confirm their findings.

The European Space Agency’s CryoSat-2 has been orbiting the polar world since April 2010, bouncing radar signals off the surface and measuring the return travel time. An examination of five years of results shows that the glacial surfaces are sinking, in some places by as much as four metres a year. There could be two reasons for that: either the snow is compacting or the ice is flowing faster.

“The glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings”

But results from the US space agency Nasa’s GRACE mission – the acronym stands for Gravity Recovery and Climate Experiment – settle the matter. The mass of ice lost in the region is so large that it changes the local gravity field, and the changes in the sheer weight of 750 kilometres of glaciers in the region can be measured from space.

“To date, the glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” Dr Wouters said.

“The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us. It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted.”

Melting maintained

That the southern continent is responding to climate change of some kind is not in doubt: another study has put the overall mass loss at 92 billion tons a year, and twin assaults of warmer air above, and warmer waters around the continent, continue the attrition.

What is not yet certain is whether scientists are looking at the consequences of human-made global warming or at the see-saw conditions inherent in some kind of as-yet-unidentified natural cycle.

But ice loss on that scale cannot be easily explained by changes in snowfall or air temperatures, so suspicion falls on the effect of warmer waters. The glaciers flow into seas that are surrounded by ice shelves. The ice shelves have lost one fifth of their thickness in recent decades, so they offer less resistance to the land-based ice, allowing the glaciers to accelerate.

There is a second factor: some of the glaciers are grounded on continental bedrock that is depressed below sea level, which means that warmer ocean waters can penetrate further inland and melt the glaciers from below.

Cautious response

There are questions that have yet to be resolved. As usual in science, the interpretations are open to debate. “Although these latest CryoSat measurements of Antarctic thinning agree with findings from two studies reported last year, I think the new estimates of ice loss computed from them are far too high, because the glaciers in this sector just haven’t speeded up that much,” said Andy Shepherd, professor of earth observation at the University of Leeds in the UK and principal scientific advisor to the CryoSat mission.

“It could be that a bigger chunk of the thinning is down to snowfall fluctuations than the authors have accounted for, and so I would be cautious about the new numbers until more information is to hand.”

Dr Wouters agrees that more research is necessary. “It appears that some time around 2009, the ice shelf thinning and the subsurface melting of the glaciers passed a critical threshold which triggered the sudden ice loss. However, compared to other regions in Antarctica, the Southern Peninsula is rather understudied, exactly because it did not show any changes in the past, ironically,” he said.

“To pinpoint the cause of the changes, more data need to be collected. A detailed knowledge of the geometry of the local ice shelves, the ocean floor topography, ice sheet thickness and glacier flow speeds are crucial to tell how much longer the thinning will continue.” − Climate News Network

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Antarctic ice is under attack from sea and air

Antarctic ice is under attack from sea and air

Satellite and radar studies show that twin forces causing the vast ice shelf to thin and become less stable could have a serious impact on global sea levels.

LONDON, 18 May, 2015 − Scientists have measured the rate of thinning of the great sea ice shelf of the Antarctic Peninsula and have identified the mechanisms at work above and below the shelf.

The collapse of floating sea ice makes no direct difference to global sea levels – but the effects could nevertheless lead to higher waters everywhere.

Paul Holland, of the British Antarctic Survey (BAS), and research colleagues from the US report in the journal The Cryosphere that they used satellite measurements and radar studies between 1998 and 2012 to confirm that the Larsen C ice shelf has lost four metres of ice, and is a metre lower at the surface.

Warmer waters

This is the largest of three shelves that have been under study for decades; the Larsen A and Larsen B shelves have already broken off and drifted north to warmer waters.

The Antarctic Peninsula is one of the fastest-warming regions of the world: 2.5°C in the last 50 years.

“What’s exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable,” says Dr Paul Holland, lead author of the BAS study.

“Air is being lost from the top layer of snow (called the firn), which is becoming more compacted, probably because of increased melting by a warmer atmosphere.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present”

“We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow. If this vast ice shelf − which is over two and a half times the size of Wales, and 10 times bigger than Larsen B − was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.”

A collapse of the shelf could occur within a century. When the two companion Larsen glaciers broke away, the glaciers that flowed from the ice-capped continent towards the sea began to accelerate.

Offshore ice, held fast to the shoreline, is a factor that helps keep glacier flow at its proverbially glacial pace. Once it has gone, the frozen rivers of ice onshore naturally begin to flow faster.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present, and that will cause problems for coastal and low-lying cities,” says David Vaughan, director of science at the BAS.

“Understanding and counting up these small contributions from Larsen C and all the glaciers around the world is very important if we are to project, with confidence, the rate of sea-level rise into the future.”

The study is a confirmation of earlier research in which other groups, using different approaches, have already identified shelf ice loss and have warned that Antarctic melting could accelerate. Satellite-based measurements have also linked glacial melting with an acceleration in sea level rise.

Precision measurement of sea level rise is not easy. Oceans rise and fall with the tides, the water isn’t level anyway, and salinity and temperature differences in the oceans, and gravitational anomalies in the ocean basins, all mean that the ocean surfaces naturally undulate.

And the continents don’t keep still. Land surfaces from which researchers base their measurements also slowly rise or fall.

Accelerated rise

Christopher Watson, senior lecturer in the School of Land and Earth at the University of Tasmania, Australia, and colleagues report in Nature Climate Change that a different approach to the problem suggests that – contrary to previous estimates – sea level rise has accelerated in the last decade.

He and his colleagues searched not just global positioning satellite evidence from the surface waters but also from the land for signs of “bias” in the data. They also used evidence from hourly tide gauges from around the world and recalculated the rate of change.

What they found was that, overall, sea level rise in the last two decades has been at a rate just under, rather than just over, 3mm a year.

But the overestimate for the first six years of the survey had been much higher, which in turn suggested that the rate of rise had actually accelerated during this century, in a way that is consistent with the rate of glacial melting − at least from the Greenland and West Antarctic ice caps. – Climate News Network

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Permafrost thaw’s runaway effect on carbon release

Permafrost thaw’s runaway effect on carbon release

Arctic warming is causing organic carbon deep-frozen in the soil for millennia to be released rapidly into the air as CO2, with potentially catastrophic impacts on climate.

LONDON, 14 May, 2015 − An international team of scientists has settled one puzzle of the Arctic permafrost and confirmed one long-standing fear: the vast amounts of carbon now preserved in the frozen soils could one day all get back into the atmosphere.

Since the Arctic is the fastest-warming place on the planet, such a release of greenhouse gas could only accelerate global warming and precipitate catastrophic climate change.

That the circumpolar regions of the northern hemisphere hold vast amounts of deep-frozen carbon is not in question.

The latest estimate is 1,700 billion tonnes, which is twice the level of carbon dioxide in the atmosphere and perhaps 10 times the quantity put into the atmosphere by burning fossil fuels since the start of the Industrial Revolution.

Hazard underlined

In recent weeks, researchers have already underlined the potential hazard. But the big question has been that if some of the trapped carbon must be escaping now, where is it going?

Researchers have checked the mouths of the Arctic rivers for the telltale evidence of ancient dissolved organic carbon – partly-rotted vegetable matter deep-frozen more than 20,000 years ago − and found surprisingly little.

Now Robert Spencer, an oceanographer at Florida State University, and colleagues from the US, UK, Russia, Switzerland and Germany report in Geophysical Research Letters that the answer lies in the soil − and in the headwater streams of the terrestrial Arctic regions.

Instead of flowing down towards the sea, the thawing peat and ancient leaf litter of the warming permafrost is being metabolised by microbes and released swiftly into the atmosphere as carbon dioxide.

“We found that decomposition converted 60% of the carbon in the thawed permafrost to carbon dioxide in two weeks”

The scientists conclude that the microbes, once they get a chance to work at all, act so fast that half of all the soil carbon they can get at is turned into carbon dioxide within a week. It gets into the atmosphere before it has much chance to flow downstream with the soil meltwater.

The researchers centred their study on Duvanny Yar in Siberia, where the Kolyma River sluices through a bank of permafrost to expose the frozen organic carbon.

They worked at 19 different sites − including places where the permafrost was more than 30 metres deep − and they found tributary streams made entirely of thawed permafrost.

Measurement of the carbon concentration confirmed that it was indeed ancient. The researchers analysed its form in the meltwater, then they bottled it with a selection of local microbes, and waited.

Used by microbes

“We found that decomposition converted 60% of the carbon in the thawed permafrost to carbon dioxide in two weeks,” says Aron Stubbins, assistant professor at the University of Georgia’s Skidaway Institute of Oceanography. “This shows that permafrost carbon is definitely in a form that can be used by the microbes.”

The finding raises a new – and not yet considered – aspect of the carbon cycle jigsaw puzzle, because what happens to atmospheric and soil carbon is a huge element in all climate simulations.

At he moment, permafrost carbon is not a big factor in projections by the Intergovernmental Panel on Climate Change.

Dr Spencer says: “When you have a huge frozen store of carbon and it’s thawing, we have some big questions. The primary question is, when it thaws, what happens to it?

“Our research shows that this ancient carbon is rapidly utilised by microbes and transferred to the atmosphere, leading to further warming in the region, and therefore more thawing. So we get into a runaway effect.” – Climate News Network

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Plant growth may speed up Arctic warming

Plant growth may speed up Arctic warming

Arctic plants may absorb more greenhouse gases as the region warms – but scientists say this could intensify the warming rather than moderate it.

LONDON, 10 May, 2015 – Green may not automatically mean innocent or planet-friendly after all. Korean and German scientists have identified a mechanism that could encourage plants to take up more carbon dioxide – and at the same time amplify Arctic warming by 20%. This counter-intuitive finding is published in the Proceedings of the National Academy of Sciences.

Jong-Yeon Park of the Max Planck Institute for Meteorology and colleagues have been looking at the role of phytoplankton, those tiny marine plants that flourish around land masses, exploit the nutrients that flow from rivers and turn the blue ocean sea-green. Like any grass or shrub or tree, they exploit sunlight and employ photosynthesis to soak up atmospheric carbon dioxide.

So as the Arctic Ocean warms, because of increasing emissions of carbon dioxide from the burning of fossil fuels, the ice melts, the blue sea water absorbs more sunlight, and the green things get a chance to grow and soak up some of that greenhouse gas as organic carbon in plant tissues. This is what engineers call negative feedback.

But it may not work like that. The scientists matched up a model of the climate system with a model of the ecosystem and did all the sums again. And they found that instead of reducing warming, an explosion of phytoplankton growth could actually amplify it.

More warming

If the seas warmed and the ice melted, then the overall albedo – the reflectivity of the Arctic – would be changed. More high energy solar radiation would get into the sea, and the phytoplankton harvest would be greater and go on for longer.

But more phytoplankton would mean more biological activity, which would directly warm the surface layer of the ocean, “triggering additional positive feedbacks in the Arctic, and consequently warming the Arctic further,” the authors warn.

“We believe that, given the inseparable connection of the Arctic and global climate, the positive feedback in Arctic warming triggered by phytoplankton and their biological heating is a crucial factor that must be taken into consideration when projecting future climate changes,” said Jong-Seong Kug, a professor at Pohang University of Science and Technology in Korea.

Science like this is a reminder that the climate system is a subtle and complex machine driven by sunlight, atmosphere, water – and carbon. A British team has warned that rainforests could in fact be emitting much more carbon than climate modellers have accounted for. That’s because they haven’t allowed for all of the dead wood.

“A large proportion of forests worldwide are less of a sink and more of a source”

Marion Pfeifer of Imperial College and colleagues report in Environmental Research Letters  that they surveyed a large area of forest in Malaysian Borneo to make their calculations.

Pristine, untouched forest is rare. Most forests provide an income for someone, and increasingly parts of the great forests are exploited by loggers and planters. In untouched forests, dead wood makes up less than 20% of the biomass. Dr Pfeifer and her colleagues found that in partially-logged forests, the dead wood could account for 64% of the biomass.

Details such as this could send climate modellers back to the drawing board. That is because the great riddle of climate science is: where does all the carbon go? The assumption has been that forests are “sinks” that collect atmospheric carbon. But that depends on the forest.

“I was surprised by how much of the biomass dead wood accounted for in badly-logged forests. That such logged forests are not properly accounted for in carbon calculations is a significant factor. It means that a large proportion of forests worldwide are less of a sink and more of a source, especially immediately following logging, as carbon dioxide is released from dead wood during decomposition,” Dr Pfeifer said.

“Selectively-logged tropical forests now make up about 30% of rainforests worldwide. That means such global calculations are wrong at least 30% of the time.” – Climate News Network

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Scientists weigh up new evidence on Antarctic ice melt

Scientists weigh up new evidence on Antarctic ice melt

Southern continent’s mysteries start to unfold as satellite data is used to measure the extent and pattern of increased ice loss that threatens to be a “runaway problem”.

LONDON, 7 May, 2015 − Antarctica has been losing its ice cover at an average rate of 92 billion tons a year since at least 2003, according to new research.

And while the scientists can’t yet say for certain that human-made climate change is the main cause, they warn that the ice loss has the potential to have serious impacts on sea level rise.

The southern continent is the Earth’s largest store of fresh water, but is also its least studied area, having had no known human visitors until the late 18th century. So while scientists have a clear idea of processes at work in the Arctic, the big picture at the other end of the planet has been uncertain.

Heavier snowfalls

West Antarctica has been losing vast chunks of ice, but greater average warmth has meant there have been heavier snowfalls, and the icepack in east Antarctica has been on the increase.

Now Christopher Harig and Frederik Simons, geoscientists at Princeton University in the US, report in the journal Earth and Planetary Science Letters that gravitational satellite data has delivered a method of “weighing” the ice sheet, and identifying a pattern of change.

Most of the loss has been from the West Antarctic region, where the glaciers are increasingly unstable. In 2008, the region was shedding ice at the rate of 121 billion tons a year. By 2014, this rate of loss had doubled.

At the same time, the ice sheet in East Antarctica had thickened – but  the gain made up for only about half the ice lost from the west.

Most scientists would be hard-pressed to find mechanisms that do not include human-made climate change”

In the period since 2003, ice loss over the whole continent increased at the rate of six billion tons a year. West Antarctica’s melting rate, however, accelerated by 18 billion tons a year during the same timespan.

So the researchers did the sums and arrived at an annual average loss of 92 billion tons a year. This could be envisaged as an iceberg the size of Manhattan Island in New York, and more than 1,600 metres high.

What the researchers cannot be sure of is the cause: is a natural cycle of climate at play, or is it a consequence of global warming because  of greenhouse gas emissions from the burning of fossil fuels?

“We have a solution that is very solid, very detailed and unambiguous,” Dr Simons says. “A decade of gravity analysis alone cannot force you to take a position on this ice loss being due to anthropogenic global warming. All we have done is take the balance of the ice on Antarctica and found that it is melting – there is no doubt.

Rapidly accelerating

“But with the rapidly accelerating rates at which the ice is melting, and in the light of other, well-publicised lines of evidence, most scientists would be hard-pressed to find mechanisms that do not include human-made climate change.”

The two scientists used data from a US-German research satellite called GRACE − short for Gravity Recovery and Climate Experiment.

The agency linked to the ice loss is a measured warming of the southern ocean that is reducing the sea ice, which in turn holds back the flow of ice on land. So glaciers are melting, and flowing towards the sea at a faster rate.

“The fact that West Antarctic ice melt is still accelerating is a big deal because it’s increasing its contribution to sea level rise,” Dr Harig says. “It really has the potential to be a runaway problem.

“It has come to the point that if we continue losing mass in those areas, the loss can generate a self-reinforcing feedback, whereby we will be losing more and more ice, ultimately raising sea levels.” – Climate News Network

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No green light for whitening Arctic’s melting ice

No green light for whitening Arctic’s melting ice

Scientists pour cold water on the idea of preventing ice melt by using geo-technology to keep it white so that it reflects sunlight and stays frozen.

LONDON, 4 May, 2015 – Yet another geo-engineering solution to climate change has been proven potentially useless: even if you could paint the Arctic white, the world would still get warmer.

For the second time in months, scientists at the Carnegie Institution for Science in the US have shown that some technological solutions won’t work even in principle, let alone in practice.

Geo-engineering is, for some, the simple technological answer to climate change: if humans have inadvertently warmed the planet’s climate through technological change, then surely they can cool it again intentionally through technological ingenuity.

But Carnegie global ecologist Ken Caldeira and research colleagues − having already demonstrated that piping cold deep waters to the ocean surface would accelerate global warming, rather than reduce it − now report in Environmental Research Letters that changing the reflectivity of the northern hemisphere won’t have the intended consequences either.

Climate machinery

Caldeira, Ivana Cvijanovic, now at the Lawrence Livermore National Laboratory, and Douglas MacMartin, of the California Institute of Technology, decided to consider an aspect of the climate machinery known as albedo. This is a measure of the planet’s reflectivity.

It works like this: dark colours, such as blue oceans and green rainforests, absorb more sunlight, while white and pale surfaces – snow caps and ice sheets, for instance  – reflect most sunlight.

So the Arctic and Antarctic keep cold simply by staying frozen. But any consistent thawing pattern will make an icy region warmer, at an increasing rate.

This is happening at measurable speed, in the northern hemisphere. “By the middle of the century, the Arctic Ocean is predicted to be ice-free during part of the year,” Dr Cvijanovic says. “This could create substantial ecological problems in the Arctic, including habitat range and loss of biodiversity.

“However, the problem is not only local. A number of studies have indicated that Arctic sea ice loss can affect weather patterns across the northern mid-latitudes, including Europe, most of North America and much of Asia.”

“Even if you could do it, the direct negative consequences of reducing the amount of sunlight available to marine ecosystems could be huge”

So it would make sense to keep the Arctic cold and white − perhaps by filling the ocean with floating reflective grains, or the air above it with tiny bubbles to bounce back the incoming sunlight.

But the Carnegie team decided to work out, with help from computer models, what a whiter Arctic would achieve in a world in which humans went on burning fossil fuels in ever-increasing quantities, in which the atmosphere eventually held four times the carbon dioxide levels recorded at the start of the Industrial Revolution, and in which average planetary temperatures went up by a devastating 10°C.

Cooling effect

The whitening of the Arctic would restore a percentage of the ice – about three-quarters of a square kilometre for every whitened square kilometre. But the cooling effect would be much more modest.

And the return of the ice would not preserve the permafrost – home to colossal quantities of organic carbon that could, if released, become carbon dioxide – or prevent escapes of another potent greenhouse gas, methane.

While it might work to keep a bay or inlet frozen, it would not, in principle, save a frozen ocean, or save the world from catastrophic climate change.

“Simply put, our results indicate that whitening the surface of the Arctic Ocean would not be an effective tool for offsetting the effects of climate change caused by atmospheric greenhouse gases,” Professor Caldeira says.

“Furthermore, it is not clear to me that there is a technologically feasible way of actually doing this. And even if you could do it, the direct negative consequences of reducing the amount of sunlight available to marine ecosystems could be huge.” – Climate News Network

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High anxiety that mountain peaks are warming faster

High anxiety that mountain peaks are warming faster

Scientists call for international efforts to determine why temperatures on high-altitude mountains appear to be rising faster than in nearby lowlands.

LONDON, 28 April, 2015 − Temperatures could be climbing on mountains − with new research suggesting that the highest altitudes may be warming at a rate greater than expected.

Members of the Mountain Research Initiative collective report in Nature Climate Change that they found evidence that mountain peak regions were warming faster than the surrounding plateaus and lowlands.

The study − by Nick Pepin, leader of the Environmental Processes and Change Research Group at Portsmouth University in the UK, and colleagues from the US, Switzerland, Canada, Ecuador, Pakistan, China, Italy, Austria and Kazakhstan − comes with more than the usual set of health warnings.

The authors concede that the evidence is “extremely sparse”. But just as the Arctic region – the high latitudes of the northern hemisphere – is warming faster than anywhere else in the world, so the high altitude could also be at risk. The important thing is to find out.

No long-term data

There are few weather stations above 4,500 metres, and no long-term data for peaks higher than 5,000 metres anywhere in the world. The summit of Kilimanjaro, Africa’s highest mountain, has been monitored longest of all, but measurements have been recorded there on a systematic basis only for the last decade.

Other indications come from the Tibetan plateau, where temperatures recorded at 139 stations have risen steadily over the past 50 years, and the rate of change is accelerating.

“There is growing evidence that high mountain regions are warming faster than lower elevations,” Dr Pepin say. “Such warming can accelerate many other environmental changes, such as glacial melt and vegetation change, but scientists urgently need more and better data to confirm this.

“The social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought”

“If we are right, and mountains are warming more rapidly than other environments, the social and economic consequences could be serious, and we could see much more dramatic changes sooner than previously thought.”

Kilimanjaro’s snow-covered peak in 1938. Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

Kilimanjaro’s snow-covered peak in 1938.
Image: Mary Meader/American Geographical Society Library via Wikimedia Commons

There are two obvious causes for concern, the first being the simple problem of biodiversity. Plants and animals that occupy the highest elevations are at the optimum limits of their climatic tolerance, and if the climate gets warmer, they must move uphill to survive.

There is already evidence from alpine Switzerland that this is indeed happening. But those species already at the highest altitudes have nowhere else to go −  and so face extinction.

The second concern relates to an even more immediate impact. The highest mountain regions are glaciated, and this store of winter snow and ice becomes a source of spring and summer meltwater on which farmers, cities and even whole nations have grown to depend.

There is also good evidence that glaciers are in retreat, almost everywhere in the world. So the economic consequences could be considerable.

Endangered species

“This alone requires that close attention be paid to the issue,” the authors write. “In addition, mountains provide habitat for many of the world’s rare and endangered species, and the presence of many different ecosystems in close proximity enhances the ecological sensitivity of mountains to environmental change.”

In essence, the study incorporates a warning: more evidence is needed.

Raymond Bradley, who directs the Climate System Research Centre at the University of Massachusetts Amherst, spells it out: “We are calling for special efforts to be made to extend scientific observations upwards to the highest summits to capture what is happening across the world’s mountains.

“We also need a strong effort to find, collate and evaluate observational data that already exists wherever it is in the world. This requires international collaboration.” – Climate News Network

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