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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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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Scientists zero in on only solution to climate crisis

Scientists zero in on only solution to climate crisis

Panel of international climate scientists says the world has only until 2050 to become a zero-carbon society − but the rewards for doing so would be immense.

LONDON, 22 April, 2015 – If you want to know what we have to do to avoid catastrophic climate change, 17 of the world’s leading climate scientists have worked out a simple but challenging solution: the world, they say, must turn by mid-century into a zero-carbon society.

The signatories to today’s “Earth Statement” say: “This trajectory is not one of economic pain, but of economic opportunity, progress and inclusiveness. It is a chance too good to be missed.

“The latest science indicates that there are critical thresholds in the Earth system. Transgressing them may lead to dramatic and irreversible environmental changes.

“We are probably edging very close to such thresholds, and may already have crossed one with regard to melting of parts of Antarctica. Sea-level rise of more than one metre due to this event alone may be inevitable.”

Window of opportunity

They are convinced that time is short. “The window of opportunity is closing fast,” says Johan Rockström, chair of the Earth League, an international group of scientists from leading research institutions working on issues caused by climate change, natural resource depletion, land degradation and water scarcity.

“We are on a trajectory that will leave our world irrevocably changed, far exceeding the 2°C mark. This gamble risks disaster for humanity, with unmanageable sea-level rise, heat waves, droughts and floods.

“We would never consider this level of risk in any other walk of life, yet we seem prepared to take this risk with our planet. Conversely, the scientific evidence shows that we can create a positive future, but only with bold action now.”

The 2°C threshold is the limit beyond which world leaders have agreed to prevent global temperatures rising as climate change intensifies.

“For the sake of fairness, rich countries and progressive industries can and should take the lead and decarbonise well before mid-century”

The Earth League’s first Earth Statement is issued as a warning ahead of the UN climate conference in Paris in December − referred to by the UN Framework Convention on Climate Change as COP21, the 21st conference of the parties to the original climate treaty.

The League is supported in its statement − published today to mark Earth Day, an annual reinvigoration of the global environmental movement − by the Global Challenges Foundation.

Professor Jeffrey Sachs, director of the Earth Institute at Columbia University, US, and one of the authors of the statement, says: “COP21 is the moment of truth − the last chance to stay within the 2°C upper limit.

Quality of life

“The key to success is deep decarbonisation by mid-century. Our studies show that this can be accomplished, at modest cost, and with a significant improvement in the quality of life.”

The Earth Statement lists what it calls “eight essential elements of climate action”, which it says any agreement achieved in Paris in December should achieve in order to provide the world with a good chance of avoiding dangerous climate change.

They include the need for the process of deep decarbonisation to start immediately. One of the eight points, which may prove contentious, reads: “Equity is critical. Every country must formulate an emissions pathway consistent with deep decarbonisation.

“For the sake of fairness, rich countries and progressive industries can and should take the lead and decarbonise well before mid-century.”

Prof Rockström and Prof John Schellnhuber, a fellow Earth League member and director of the Potsdam Institute for Climate Impact Research, will present the Earth Statement tomorrow at the fourth Nobel Laureates Symposium on Global Sustainability in Hong Kong. – Climate News Network

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Permafrost holds key to release of trapped carbon

Permafrost holds key to release of trapped carbon

The frozen soil of the northern polar regions holds billions of tonnes of organic carbon – and global warming could speed its escape into the atmosphere.

LONDON, 14 April, 2015 − Three sets of scientists in the same week have helped narrow the uncertainties about how the natural world will respond to extra carbon dioxide in the atmosphere caused by the burning of fossil fuels.

Carbon locked in the frozen earth will escape gradually as the Arctic permafrost melts – but the scientists say the process could accelerate.

As greenhouse gas levels soar, and soils warm, and plant roots tap down into the carbon stored there by centuries of ancient growth, they will release potent chemicals that will accelerate microbial attack – and speed up the release of carbon dioxide into the atmosphere.

The soil carbon cycle is one of the great headaches of climate science. And the Arctic is the first place to look for answers about it, and about how the Earth and oceans that store atmospheric carbon will respond to global warming.

Locked away

Around half of the world’s buried organic carbon is locked away in the soils of the northern circumpolar permafrost, and this huge vault of deep-frozen peat and leaf litter – more than 1,000 billion metric tonnes in the top three metres, at the latest estimate − contains twice as much carbon as is held in the atmosphere.

But the Arctic is the fastest-warming region on the planet, so what will happen as the permafrost thaws and plants begin to move north? Would it all be surrendered to the atmosphere in one devastating exhalation, triggering an explosion in global warming and causing trillions of dollars in economic damage?

An international team within the Permafrost Carbon Network thinks not. Their verdict, published in Nature journal, is that the current evidence suggests “a gradual and prolonged release of greenhouse gas emissions in a warming climate”. That is, humankind would have time to adapt.

“The data from our team’s syntheses don’t support the permafrost carbon bomb view,” says one of the team members, David McGuire, professor of landscape ecology at the University of Alaska Fairbanks.

“What our syntheses do show is that permafrost carbon is likely to be released in a gradual and prolonged manner, and that the rate of release through 2100 is likely to be of the same order as the current rate of tropical deforestation in terms of its effects on the carbon cycle.”

Since the tropical forests are already under pressure, this is hardly good news. And the picture is not a simple one.

“Even small changes will have serious effects on carbon concentrations in the atmosphere, and by extension on climate”

As the permafrost thaws, the soil microbes will get to work on the buried carbon, which will inevitably add to the soil warming, and provide an instance of what engineers call positive feedback, according to a team led by Jøgen Hollesen, senior researcher at the University of Copenhagen’s Centre for Permafrost.

He and colleagues report in Nature Climate Change that when they measured heat production in 21 contrasting organic permafrost soils, they found it to be between 10 and 130 times higher than in mineral soils measured in Greenland − and this would have “crucial implications for the amounts of carbon being decomposed”.

And in the same issue of Nature Climate Change, a team led by researchers from Oregon State University have confirmed that any kind of warming or plant growth is likely to get the soil microbes working as hard as they can – partly because the plants use chemistry to free the soil carbon so the bacteria can start to turn it back into carbon dioxide.

Neither of the two Nature Climate Change studies was directly concerned with climate change. The Danish scientists’ findings sprang from concern about what warming might do to the ancient middens that hold as-yet-unexamined evidence of early human settlement in the Arctic. The Oregon team were more concerned about the interactions that go on in the soil, and how they could be measured.

Chemical bonds

They found that plant roots released an exudate that acted to release the chemical bonds that keep a carbon bound to non-organic minerals in the soil. Warming could only speed the process, so more carbon dioxide will get into the atmosphere from the soil because of global warming.

This, again, is positive feedback at work. And it suggests climate scientists might be underestimating carbon loss from the soil by as much as 1% a year.

“Our main concern is that this is an important mechanism, and we are not presently considering it in global models of carbon cycling,” says soil and environmental geochemist Markus Kleber, one of the authors of the Oregon report.

“There is more carbon stored in the soil, on a global scale, than in vegetation, or even in the atmosphere. Since this reservoir is so large, even small changes will have serious effects on carbon concentrations in the atmosphere, and by extension on climate.” – Climate News Network

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Canada will lose many glaciers as climate warms

Canada will lose many glaciers as climate warms

Climate change could cause many glaciers in western Canada to start to disappear by 2040, affecting people and places that depend on their water.

LONDON, 10 April, 2015 − As the world warms, many of the great frozen rivers of Canada will not just retreat, but could vanish altogether.

New research suggests that maritime glaciers in the far northwest might survive, but more than two-thirds of Canada’s existing glaciers in British Columbia and Alberta could be lost altogether by 2100.

Garry Clarke, a glaciologist at the University of British Columbia in Vancouver, says: “Soon our mountains could look like those in Colorado or California, and you don’t see much ice in those landscapes.”

The consequences for the forests, grasslands, animals and communities that depend on glacial meltwater could be serious. The disappearance of the glaciers will also create problems for Canada’s hydroelectric industry, for agriculture and grazing, for the mining industry, for the salmon fishery, and for tourism.

Professor Clarke and his colleagues report in Nature Geoscience that they devised a model – a high-resolution computer simulation – of the glaciers of western Canada that explicitly mimicked glacial flow. Then they tested it with a range of scenarios for climate change, driven by human combustion of fossil fuels and rising atmospheric carbon dioxide levels in the last two centuries.

“Once the glaciers are gone, the streams will be a lot warmer and this will hugely change freshwater habitat”

There are more than 17,000 glaciers in British Columbia and Alberta, covering more than 26,000 square kilometres of the two provinces, and holding an estimated 2,980 cubic kilometres of ice. This puts western Canada as more glaciated than the Himalayas (which have less than 23,000 sq kms of glacier): the entire continent of South America has only 31,000 sq kms of glacier.

The researchers found that maritime glaciers in the northwest would endure, in a diminished state. But overall, the volume of the glaciers in western Canada would shrink by 70%, give or take 10%.

Right now glaciers, most of them between 100 and 200 metres thick, are thinning at a rate of about a metre a year. The peak flow of meltwater would most likely occur between 2020 and 2040. Thereafter, the rivers would be in decline.

Potential sea level rise as a consequence of this, the scientists say, would be “modest” at around 6mm, but the consequences for that part of Canada would be substantial.

The Columbia River, which flows from the interior to the Pacific coast of Washington and Oregon, yields the largest hydroelectric production of any river in North America. And the impact on freshwater ecosystems could be considerable.

“These glaciers act as a thermostat for freshwater systems,” said Professor Clarke. “Once the glaciers are gone, the streams will be a lot warmer and this will hugely change freshwater habitat. We could see some unpleasant surprises in terms of salmon productivity.” – Climate News Network

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Changing climate causes weather chaos in Chile

Changing climate causes weather chaos in Chile

What is being described as an environmental catastrophe is hitting Chile as torrential rains batter the north while the south suffers prolonged drought and wildfires.

LONDON, 30 March, 2015 − The Atacama desert region of northern Chile, one of the driest areas on Earth, has been hit in recent days by torrential rains and floods that have caused deaths, swept away homes and left much of the region without power.

Meanwhile, in the usually lush southern parts of the country, wildfires are raging across lands and forests parched by the longest period of drought in living memory, endangering some of the world’s richest flora and fauna.

“We are witnessing a massive environmental catastrophe,” Luis Mariano Rendon, head of the Accion Ecologica environmental group, told the AFP news agency.

Irreparable loss

“There have been whole species lost, such as the Araucaria araucana (monkey puzzle tree). They are trees that take hundreds of years to reach maturity, so this is a practically irreparable loss for current generations.”

The trees, a distant relative of the pine, are considered sacred by indigenous Mapuche people, and have been declared part of Chile’s unique natural heritage.

Scientists say the drought in the southern region – which is the powerhouse of Chile’s multi-billion dollar agricultural sector, and site of many of its famous vineyards – is a long-term trend, linked to climate change.

“There is no choice but to assume that the lack of water resources is a reality that is here to stay”

Chile’s president, Michelle Bachelet, says millions of dollars will have to be invested in desalination plants and new reservoirs to cope with the continuing drought. Canals and irrigation systems will also have to be upgraded.

“Faced with this critical situation,” he says, “there is no choice but to assume that the lack of water resources is a reality that is here to stay, and that puts at risk the development of important regions of the country.”

The Maipo river basin − which includes Santiago, Chile’s capital − contains nearly 40% of the country’s population and is an important area for agriculture, mining, and for power generation, much of which comes from hydroelectric sources.

Researchers, led by the Centre for Global Change at the Pontifical Catholic University of Chile, have been mapping the impact that climate change is likely to have on the Maipo basin.

Projections so far indicate that rainfall is likely to drop by 10% in the area over the period up to 2040, and by up to 30% by the end of the century. Meanwhile, temperatures will rise by 1˚C above the historical average over the next 25 years, and by between 2.5˚C and 3.5˚C by 2100.

Power source

The researchers have also been investigating glacier mass and melt in the Andes − the source of the bulk of the country’s water supply for millions of people in the region, and a crucial power source.

Scientists say that accelerated melting of Andean glaciers is being caused by atmospheric warming.

Water shortages are hitting not only the agricultural sector, but also mining – one of Chile’s major industries. The country is the world’s biggest producer of copper, and mining companies say they are having to invest in costly desalination plants in order to get water for processing copper concentrate from milled rock.

A drop in river levels feeding hydroelectric facilities is also leading to an increase in coal-fired power plants – a major source of climate-changing greenhouse gases.

Despite the recent rains in the north of the country, scientists are warning of the dangers of desertification in the region, with the northern desert advancing further south each year. – Climate News Network

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Shrinking of ice shelves raises sea level concerns

Shrinking of ice shelves raises sea level concerns

Evidence of rapid reduction of West Antarctica’s shelf ice could have serious implications for global sea levels in a warming world.

LONDON, 29 March, 2015 – Scientists in the US report that the volume of Antarctic shelf ice is diminishing, and that there has been an 18% shrinkage in the mass of some ice floating on coastal waters over the last 18 years.

And because much of the loss has been off West Antarctica, where shelf ice helps to keep the ice sheet stable, it could mean that global sea levels will rise even faster as a result of increased glacial flow into the ocean.

The findings once again raise concern about the link between man-made emissions of greenhouse gases and the dangerous new world of global warming, climate change and sea level rise.

Fernando Paolo, a researcher at the Scripps Institution of Oceanography at the University of California, San Diego, and colleagues report in the journal Science that they used continuous radar altimetry measurements − taken from three European Space Agency satellites between 1994 and 2012 − to compose a high-resolution record of shelf ice thickness.

Declined swiftly

They found that the total volume of shelf ice – the thickness multiplied by the shelf area – around Antarctica stayed more or less the same from 1994 to 2003, but then declined very swiftly.

The ice shelves of West Antarctica lost ice during the entire period, and although East Antarctica had been gaining shelf ice, these gains ceased after 2003. Some shelves had lost 18% of their volume.

“Eighteen per cent over the course of 18 years really is a substantial change,” Paolo says. “Overall, we show not only that the total ice shelf volume is decreasing, but we see an acceleration in the last decade.”

Shelf ice is frozen sea, so when it melts, it makes no difference to sea levels. But there could be an indirect effect.

“The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea levels rise, so that’s a key concern from our new study,” says co-author Helen Fricker, a glaciologist at the Scripps Institution.

In climate science, one such study is never enough: such conclusions need support from other studies. But the ice volume measurements are likely to add to growing concern about West Antarctica.

“The ice shelves buttress the flow from
grounded ice into the ocean, and that
flow impacts sea levels rise”

One earlier study looked at the potential loss of ice from West Antarctica by examining the “grounding lines” of the terrestrial glaciers, and found evidence of continuous and accelerating retreat. In effect, the West Antarctic ice sheet could be approaching a point of no return, scientists reported.

And a second group used other satellite measurements to calculate that ice was being lost from the southern continent at an increasing rate – around 150 cubic kilometres a year from West Antarctica.

So the Scripps study indirectly backs up earlier findings. It calculates that most mass has been lost from ice shelves in the Amundsen and Bellingshausen seas, off the coast of West Antarctica. These account for less than 20% of the total West Antarctic ice-shelf area, but contribute more than 85% of the total ice-shelf volume loss from West Antarctica.

Slow process

Were the West Antarctic ice sheet to melt completely – a long, slow process at almost any temperatures – sea levels would rise by more than three metres worldwide.

At current rates, a couple of the ice shelves off the western coast of the continent could disappear completely within 100 years, the Scripps team says.

Although the Arctic is one of the fastest-warming places on the planet, and although this warming has been directly linked to man-made climate change, the pattern of temperature shifts in the southern hemisphere has been more ambiguous.

The Scripps team have now begun to think about possible reasons for the loss of shelf ice in the far south, and one factor might be the cycle of El Niño events – natural and periodic bubbles of Pacific ocean warmth that have waxed and waned at intervals and changed the prevailing weather patterns worldwide through history.

“We’re looking into connections between El Niño events in the tropical Pacific and changes in the Antarctic ice sheet,” Paolo says. “It’s very far apart, but we know these teleconnections exist. That may ultimately allow us to improve our models for predicting future ice loss.” – Climate News Network

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Eyes in the sky see seas rising alarmingly faster

Eyes in the sky see seas rising alarmingly faster

Scientists analysing sophisticated satellite data warn that rises in sea level more rapid than expected are increasing threats to coastal cities and food security.

LONDON, 27 March, 2015 − Satellite observations show that sea level rise may have been underestimated, and that annual rises are increasing.

A collaborative effort between maritime organisations and space agencies in measuring sea level rise has come to the conclusion that it has been increasing by 3.1 millimetres a year since 1993 – higher than previous estimates.

The evidence is growing from a number of recent studies of the ice caps that sea level rise is accelerating, posing a threat to many of the world’s largest and most wealthy cities − most of which are also important ports.

Many of these in the developing world have little or no protection against rising sea levels. Some in Europe – such as London and Rotterdam − already have flood barriers to protect areas below high tide or storm surge level, but  these will need to be replaced and raised in the next 30 years.

Delta areas in Egypt, Vietnam, Bangladesh and China – vital to each of the nation’s food supply – are already losing land to the sea.

Difficult to measure

One of the problems scientists have had in getting accurate worldwide data is that the sea does not rise evenly around the globe. This, added to the fact that in some places the land is sinking and in other places is rising, makes exact information difficult to measure from tide gauges.

Since 1991, it has been possible to measure the surface of the oceans across the entire globe by using satellite altimetry, whereby the satellite emits a signal towards the ocean’s surface and receives the reflected echo. The sea level is calculated from the round-trip time between the satellite and the sea surface and the position of the satellite along its trajectory.

While the data from tide gauges provides information about local changes relative to the land, the use of altimeter satellites enables the recording of data on a global basis.

Luciana Fenoglio-Marc, a scientist specialising in physical and satellite geodesy at the Technical University of Darmstadt, Germany, uses these and other satellite geodetic observation data in her research.

She is working with the European Space Agency and the European Organisation for the Exploitation of Meteorological Satellites, and in close consultation with the German Federal Institute of Hydrology and the Federal Maritime and Hydrographic Agency of Germany.

This lends credibility to the report that European coastal cities are not sufficiently prepared for the threats that climate change poses

The increase of around 3.1mm per year since 1993 indicates a marked rise in the average sea level when compared to previously recorded values, which show a sea level rise of between 1mm and 2mm per year in the 20th century.

In its fifth Assessment Report (AR5, 2013), the Intergovernmental Panel on Climate Change (IPCC) predicted a further increase in the global sea level of 30cm to 70cm by the end of the 21st century, based on a scenario involving a medium rate of global warming.

The report predicted that increases will not be even, but will have a greater impact on some regions than on others. The result could be coastal flooding and rising groundwater levels – an outlook that makes it essential to have a reliable data basis for dealing with the dangers this poses.

Protecting coasts from the rising seas will require considerable adaptations, particularly in such low-lying coastal regions as the North Sea coast of Germany and the many low-lying islands in the tropics.

Another aspect of the work with satellites is measuring ocean density to see how much water expansion − because of warming − is leading to sea level rise. A direct estimation of mass changes in the Mediterranean Sea show expansion to be the cause of an average sea level rise of about 2.1mm per year since 1993.

According to the IPCC, about 35% of the sea level increase between 1993 and 2010 was the result of thermal expansion, and the rest was due to melting ice and increasing run-off from land. But the latest observation shows this may not be true of the Mediterranean.

Too cautious

There is wide debate about whether the IPCC estimates of sea level rise have been too cautious, suggesting that the sea level will rise more than a metre this century – and some have even suggested that the rise could be two metres.

This is mainly because there has been uncertainty about how much of the huge icecap in Greenland, and most of all in Antarctica, would contribute to sea level rise by 2100 – if at all.

Research published since the IPCC estimates were made show that both icecaps will be large net contributors to sea level rise, and possibly much quicker than previously thought.

This lends credibility to the report last week that European coastal cities are not sufficiently prepared for the threats that climate change poses. The report − titled Underfunded, Unprepared, Underwater? Cities at Risk – is by the E3G non-governmental organisation, and it says governments across the European Union are leaving their major cities exposed to danger from climate change, including floods, heat waves and sea level rise.

Since it takes an average of 30 years from planning to complete construction of a major flood barrier to protect a city, the report warns that the problem needs to be given urgent consideration and funding. – Climate News Network

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More Antarctic warmth creates heavier snowfall

More Antarctic warmth creates heavier snowfall

Rising temperatures may result in more snow falling in Antarctica, with the ice that builds up flowing to the ocean and raising sea levels.

LONDON, 16 March, 2015 – It may sound unlikely, but the evidence is mounting that the more the Antarctic warms under the impact of climate change, the more snow will fall on it.

Not only that, says a team of European and US scientists, but as the snow turns to ice it is going to flow downhill, borne by its own weight, and contribute to rising sea levels.

The impact of this paradoxical process is likely to be significant. The team, led by scientists from Germany‘s Potsdam Institute for Climate Impact Research (PIK), says each degree Celsius of warming in the region could increase Antarctic snowfall by about 5%.

Ice-core data

The research, published in Nature Climate Change, builds on high-quality ice-core data and fundamental laws of physics captured in global and regional climate model simulations.

The suggestion that Antarctic snowfall is increasing is not itself new, though not all scientists accept the data without qualification.

What the Potsdam scientists have done is important, not simply because they provide new evidence to support the contention, but because they explore its potential consequences.

Katja Frieler, climate impacts and vulnerabilities researcher at PIK, and lead author of the report, says: “Warmer air transports more moisture, and hence produces more precipitation. In cold Antarctica, this takes the form of snowfall. We have now pulled a number of various lines of evidence together and find a very consistent result: temperature increase means more snowfall on Antarctica.”

To reach a robust estimate, the PIK scientists collaborated with colleagues in the Netherlands and the US.

“Ice-cores drilled in different parts of Antarctica provide data that can help us understand the future,” says co-author Peter U. Clark, professor of geology and geophysics at Oregon State University.

“The Antarctic ice sheet could become a major contributor to future sea-level rise, potentially affecting millions of people in coastal areas” 

“Information about the snowfall spanning the large temperature change during the last deglaciation [the uncovering of land by the melting of glaciers], 21,000 to 10,000 years ago, tells us what we can expect during the next century.”

The researchers combined the ice-core data with simulations of the Earth’s climate history and comprehensive future projections by different climate models, and were able to pin down temperature and accumulation changes in warming Antarctica.

The increasing snowfall on the continent will add to the mass of the ice sheet and increase its height.

But the researchers say it won’t stay there. On the basis of another previous PIK study, they say the extra snow will also increase the amount of ice flowing to the ocean.

Dr Frieler says: “Under global warming, the Antarctic ice sheet, with its huge volume, could become a major contributor to future sea-level rise, potentially affecting millions of people living in coastal areas.”

Additional snowfall

As snow piles up on the ice, its weight presses down – the higher the ice, the greater the pressure. Additional snowfall elevates the grounded ice-sheet on the Antarctic landmass, but has less of an effect on the floating ice shelves at the coast, allowing the inland ice to flow more rapidly into the ocean and raise sea levels, the researchers say.

The 5% increase in Antarctic snowfall that they expect for every 1°C rise in temperature would mean an estimated drop in sea-level of about three centimetres after a century.

But they say other processes will cause an eventual rise in sea-level. For example, relatively slight warming of the ocean could cause coastal ice to break off more easily, allowing more of the continental ice mass to discharge into the ocean.

Another co-author is Anders Levermann, PIK professor of dynamics of the climate system, and also a lead author of the sea-level rise chapter in the latest report by Intergovernmental Panel on Climate Change.

He says: “If we look at the big picture, these new findings don’t change the fact that Antarctica will lose more ice than it will gain, and that it will contribute to future sea-level change.” – Climate News Network

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