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Greenland’s icecap loses stability

April 13, 2014 in Arctic, Glaciers, Greenland, Ice Loss, Sea level rise, Warming

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The calving front of the Jakobshaven Glacier in western Greenland in April 2012 Image: NASA ICE via Wikimedia Commons

The calving front of the Jakobshaven Glacier in western Greenland in April 2012
Image: NASA ICE via Wikimedia Commons

By Tim Radford

Greenland is losing ice from part of its territory at an accelerating rate, suggesting that the edges of the entire ice cap may be unstable.

LONDON, 13 April – Greenland – the largest terrestrial mass of ice in the northern hemisphere – may be melting a little faster than anyone had guessed.

A region of the Greenland ice sheet that had been thought to be stable is undergoing what glaciologists call “dynamic thinning”. That is because the meltwater from the ice sheet is getting into the sea, according to a study in Nature Climate Change.

In short, Greenland’s contribution to sea level rise has been under-estimated, and oceanographers may need to think again about their projections.

Shfaqat Khan from the Technical University of Denmark and colleagues used more than 30 years of surface elevation measurements of the entire ice sheet to discover that overall loss is accelerating. Previous studies had identified melting of glaciers in the island’s south-east and north-west, but the assumption had been that the ice sheet to the north-east was stable.

Four times as fast

It was stable, at least until about 2003. Then higher air temperatures set up the process of so-called dynamic thinning. Ice sheets melt every Arctic summer, under the impact of extended sunshine, but the slush on the glaciers tends to freeze again with the return of the cold and the dark, and since under historic conditions glaciers move at the proverbial glacial pace, the loss of ice is normally very slow.

But global warming, triggered by rising levels of greenhouse gases in the atmosphere, has changed all that. Greenland’s southerly glaciers have been in retreat and one of them, Jakobshavn Isbrae, is now flowing four times faster than it did in 1997.
Now the Danish-led team has examined changes linked to the 600 kilometre-long Zachariae ice stream in the north-east.

This has retreated by about 20 kms in the last decade, whereas Jakobshavn has retreated about 35 kms in 150 years. The Zachariae stream drains around one-sixth of the Greenland ice sheet, and because warmer summers have meant significantly less sea ice in recent years, icebergs have more easily broken off and floated away, which means that the ice stream can move faster. The researchers used satellite studies to measure ice loss.

“North-east Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet,” said one of the team, Michael Bevis of Ohio State University in the US.

Deep impacts

“This study shows that ice loss in the north-east is now accelerating. So now it seems that all of the margins of the Greenland ice sheet are unstable.”

The scientists used a GPS network to calculate the loss of ice. Glacial ice presses down on the bedrock below it: when the ice melts, the bedrock rises in response to the drop in pressure, and sophisticated satellite measurements can deliver enough information to help scientists put a figure on the loss of ice.

They calculate that between April 2003 and April 2012, the region was losing ice at the rate of 10 billion tons a year.

“This implies that changes at the margin can affect the mass balance deep in the centre of the ice sheet,” said Dr Khan. Sea levels are creeping up at the rate of 3.2 mm a year. Until now, Greenland had been thought to contribute about half a mm. The real figure may be significantly higher. – Climate News Network

Climate science ‘is beyond argument’

March 17, 2014 in Arctic, Business, Carbon, Climate deniers, Deep Ocean, Economy, Fish, Food security, Global Ocean Commission, Ice Loss, Marine ecology, Ocean acidification, Ocean Warming, Polar ice, Pollution, Science

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Not as sunny as it seems: The ocean is under attack on many fronts, with climate change foremost among them Image: kein via Wikimedia Commons

Not as sunny as it seems: The ocean is under attack on many fronts, with climate change foremost among them
Image: kein via Wikimedia Commons

By Alex Kirby

The Global Ocean Commission says climate change is one of the key threats to the health of the world’s marine life, which it says faces multiple pressures in a warming world.

HONG KONG, 17 March - South Africa’s former Finance Minister, Trevor Manuel, has derided those who deny the scientific argument that climate change is an urgent problem caused largely by human activity.

He told journalists here: “The science is now incontrovertible. There are a few people in the world who deny it, but they are mainly in lunatic asylums.”

Mr Manuel is one of three co-chairs of the Global Ocean Commission, a panel of global leaders who have just ended a meeting here to finalise the proposals they will present to the United Nations in June.

The meeting agreed that another key threat to the world’s oceans is overfishing and the subsidies which help to make it possible. It says this, and the other factors causing ocean degradation, threaten the food security of as many as 500 million people.

It is deeply worried about pollution. With plastic remains now so pervasive that they are found even in deep seafloor sediments, Mr Manuel said, it sometimes seemed that “you might as well not bother to buy seafood at all – just buy the plastic bag it comes in and eat that.”

Shells corroded

The Commission says climate change threatens the oceans in three main ways: by raising the temperature of the water; by reducing its oxygen content; and by increasing its acidity. Antarctic pteropods, small sea snails also known as sea butterflies, are already being found with severely corroded shells because of acidification, and larger creatures, including bigger shellfish and corals, are likely to be seriously affected.

Another of the co-chairs, José María Figueres, the former president of Costa Rica, told the Climate News Network the Commission was concerned at the prospect of exploitation of the high seas in the Arctic as the region’s sea ice continues to melt.

He said: “Beyond Arctic countries’ EEZs (exclusive economic zones stretching 200 nautical miles from the coast), the melting will leave us with a doughnut-shaped hole in the Arctic high seas, which are not under international control.

“Some nations are now looking to explore there for fish, minerals, valuable biodiversity and other resources. I believe we should not go down that route.

We should listen to the science and follow the precautionary principle, keeping this pristine area off-limits for exploitation until we understand the consequences.

Coalition builders

“We’re already pushing the high seas to the limit. We don’t need to push them over the edge by a lack of proper precaution in the Arctic.”

He said: “The jury is still out on whether we have 20 or 30 years ahead as a window of opportunity to act. But why wait? Listen to the science, which is overwhelming, and to the economics, which are sound.”

Describing the Commission as “not just a bunch of treehuggers, but a group that’s grounded itself in good sound economics”, Mr Figueres said the recommendations it planned to present to the UN on 24 June would represent about 20% of its work. The other 80% would involve building coalitions around each recommendation: there are expected to be no more than 10 in total.

The Commission’s third co-chair is the UK’s former Foreign Secretary, David Miliband. He told the Network: “Answers that sit on a shelf are a waste of time, and people who are positively inclined to protect the oceans are held back by institutional inertia.

“But the interplay between climate change and ocean damage is rising, and it very much needs to. The science of most of the last half-century shows us how we’ve been playing tricks with nature.” – Climate News Network

India’s diesel fumes fuel glacier melt

March 6, 2014 in Black Carbon, Climate, Glaciers, Himalayas, Ice Loss, Mountains, Pollution

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Nanda Devi, one of the highest peaks in the Himalayas: Air pollution from the cities is affecting the mountain glaciers Image: Anirban c* via Wikimedia Commons

Nanda Devi, one of the highest peaks in the Himalayas: Air pollution from the cities is affecting the mountain glaciers
Image: Anirban c8 via Wikimedia Commons

By Kieran Cooke

As India’s economy expands, so does pollution, particularly in the country’s major cities. Kieran Cooke, one of our editors, has recently been in Kolkata, one of the country’s biggest and most polluted population centres: he says increasing pollution is not only harming Kolkata’s citizens – it’s also a likely contributor to climate change taking place in the Himalayan region.

KOLKATA, 6 March – Being a traffic policeman in Kolkata is a life-threatening business. Not only are you at risk of being run over on the traffic-clogged roads and streets of this chaotic city of 14 million – you’re also more than likely to suffer from serious health problems due to some of the worst air pollution not just in India, but in the world.

According to a 2012 report by the New Delhi-based Centre for Science and Environment on air quality in Kolkata, seven out of every ten people in the city suffer from some form of respiratory ailment: not surprisingly, traffic policemen and the city’s thousands of street dwellers are among the high risk groups.

Air pollution, particularly related to diesel-fuelled vehicles that jam Kolkata’s roads, is also linked to the city’s unusually high levels of lung cancer.

Meanwhile the government’s own Central Pollution Control Board gives Kolkata and New Delhi the unenviable status of being joint winners of India’s most polluted city prize.

All this is not just bad news for people living in Kolkata and India’s other major urban conglomerations. The increasing air pollution in India’s cities – particularly those in the northern parts of the country – also has an impact on the degree of melt taking place in glaciers in the Himalayas.

Soaking up the heat

Diesel fumes, along with smoke from coal burning, cooking fires and the burning of waste, are among the main sources of particulate matter called soot or black carbon. Recent studies suggest that funeral pyres and even the burning of incense at temples are also contributors to the accumulation of soot.

This black carbon rises into the atmosphere and is driven by winds on to the snow or ice in the Himalayas, darkening the surface and in the process reducing reflectivity and causing the surface to absorb more heat.

The International Centre for Integrated Mountain Development (ICIMOD), based In Kathmandu, Nepal, is the only transboundary organisation looking at climate developments across the Hindu Kush-Himalayan region.

According to ICIMOD estimates, black carbon is likely responsible for a large part – around 30% by some calculations – of glacial melt in the region. It says most of the black carbon deposited in the Himalayas and in the southern area of the Tibetan Plateau comes from the plains of India, while black carbon on the eastern and northern parts of the Plateau originates in central China.

Bigger harvests

ICIMOD says that while data is limited, studies suggest black carbon may not only be a factor in hastening the melt of mountain glaciers – it could also substantially alter rainfall patters and affect the behaviour of the monsoon.

While many well-organised environmental NGOs and other groups have formed in India in recent years, the environment – and climate change – does not come high on the political agenda.

A late 2013 study by the World Bank and the International Cryosphere Climate Initiative (ICCI) said that up to a million deaths could be avoided each year in the Himalayan region by cutting back on emissions of black carbon and methane. The study also said that regional yields of crops such as rice and wheat could be significantly improved by reducing black carbon.

“The health of people around the world will improve greatly if we reduce emissions of black carbon and methane”, says Jim Yong Kim, the World Bank president.

“Limiting these emissions will also be an important contributor to the fight against climate change.” – Climate News Network

Cold and warm polar water mixing slows

March 4, 2014 in Antarctic, Convection, Deep Ocean, Ocean Warming, Polar ice

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A large iceberg calved from an Antarctic glacier: Weakening convection will make it slower to melt Image: NASA ICE (uploaded by russavia) via Wikimedia Commons

A large iceberg calved from an Antarctic glacier: Weakening convection will make it slower to melt
Image: NASA ICE (uploaded by russavia) via Wikimedia Commons

By Tim Radford

The process that sends cold surface Antarctic water to the warmer depths, redistributing heat and storing carbon, is now faltering, scientists say – because of climate change.

LONDON, 4 March – Global warming could have dramatic consequences for ocean circulation in the Antarctic, according to new research in Nature Climate Change. It could reduce convection in the Southern Ocean.

Convection is the process that turns over a vast body of sea water, sending the fresh water from melted ice to the depths, while bringing warmer, more saline waters to the surface. Since the ocean is part of the global machinery for redistributing heat and storing carbon, any change in the pattern of movement could have profound significance.

Casimir de Lavergne and colleagues from McGill University in Canada and the University of Pennsylvania in the US analysed a 60-year sequence of satellite observations and direct measurements in the Ross and Weddell seas and coupled these with simulated studies of ocean behaviour. They found that the surface ocean had become less saline: cold fresh water now forms a kind of lid on the Southern Ocean surface to trap warmer salt water below.

What had historically been an upwelling of warmer water had dramatic consequences for the Weddel Sea ice pack: in the mid-1970s it permitted a 250,000 square kilometre stretch of open water called a polynya that stayed open for three full winters before it closed. The polynya has not re-opened in 40 years.

While it was open, the cold, surface dense waters of the polynya sank 3,000 metres, and became new deep ocean bottom water, and this sinking, while it lasted, was on a massive scale: at least twice the flow of all the rivers of the terrestrial world.

For decades, oceanographers and glaciologists regarded the event as naturally rare, a curiosity rather than an important part of the ocean ecosystem. The latest study however presents a different picture.

Few escape opportunities

The first orbiting satellites may have recorded, for the first time in 1974, a regular but steadily weakening feature of the Southern Ocean, a phenomenon that was  weakening because of climate change. It also means that heat stored in the deep ocean has been unable to melt the wintertime icepack.

“Deep ocean waters only mix directly to the surface in a few small regions of the global ocean, so this has effectively shut off one of the main conduits for the deep ocean heat to escape,” said de Lavergne.

The team’s models showed that, before the Industrial Revolution, significant ocean convection occurred in the region. Under a high emissions scenario, the models showed a decrease in the strength of this convection. In seven of the team’s 25 computer models, deep circulation stopped entirely by 2030.

The team’s computer simulations also predict greater snow and rainfall in the Southern Ocean as atmospheric carbon dioxide increases.

“A warming planet will see dryer regions become dryer and wetter regions become wetter. True to form, the polar Southern Ocean – as a wet place – has indeed become wetter,” said Jaime Palter of McGill, a co-author. “And as a response to surface ocean freshening, the polynyas simulated by the models also disappeared.” – Climate News Network

US urges fishing ban in melting Arctic

February 24, 2014 in Adaptation, Arctic, Fish, Indigenous peoples, Marine ecology, Ocean Warming

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A US Coastguard vessel patrols the Arctic Ocean: Once the ice goes, the trawlers will not be far behind Image: PA1 Timothy Tamargo via Wikimedia Commons

A US Coast Guard vessel patrols the Arctic Ocean: Once the ice goes, the trawlers will not be far behind
Image: PA1 Timothy Tamargo via Wikimedia Commons

By Alex Kirby

Washington is urging countries that share the Arctic to ban commercial fishing in the offshore Arctic Ocean, something that will soon be possible for the first time in human history as the ice melts.

LONDON, 24 February – The countries that ring the Arctic Ocean will soon face a dilemma: can they risk commercial fishing fleets shooting their nets in those soon-to-be-ice-free seas?

Before long – quite possibly before mid-century – the Arctic Ocean will be free of ice during part of each summer, scientists are now saying confidently. For better or worse that will open up huge opportunities for shipping and hydrocarbon exploitation. And for the first time in recorded history it will allow the fishing boats access to whatever has lived undisturbed until now beneath the ice.

A three-day meeting began today in Nuuk, the capital of Greenland, where US officials are hoping to persuade the other nations which border the Arctic Ocean to introduce a moratorium on high seas fishing there (the other members of the group are Canada, Russia and Norway).

David Benton, of the US Arctic Research Commission (USARC), said the Americans were proposing an agreement “that would close the international waters of the Arctic Ocean to commercial fishing until there is a good scientific foundation on which to base management of any potential fishing”.

All coastal countries control fisheries within 200 miles of their own coastlines. The high seas beyond that limit belong to no country and can be protected only by international agreement.

Once the five Arctic nations have agreed a fishing moratorium, Benton said, they would then approach other countries with major commercial fishing fleets, such as China, Japan and Korea, to negotiate full protection for the central Arctic Ocean.

Previous ban

The Arctic was experiencing a fairly rapid rate of change, said Benton, as the permanent ice melted. “That’s potentially causing large changes in the ecosystem, but we don’t understand what’s going on up there. If we want to do things right, this is the approach we should be taking.”

In 2009, the US adopted its own Arctic Fishery Management Plan, closing American waters north of Alaska to commercial fishing until scientific research proves that the fishery is sustainable. Scott Highleyman, director of the international Arctic program for the Pew Charitable Trusts, said that had been a precaution that took account of the way warming was changing the Arctic ecosystem faster than science could keep up with it.

He told the Los Angeles Times: “There are no stock surveys or scientific assessments for fish there. You don’t want to fish a place where you don’t know the fish population dynamics. Any time we’ve done that, it led to catastrophic overfishing.” One example, Highleyman said, is the New England Atlantic cod fishery, which was shut down in the 1980s due to overfishing, costing 50,000 jobs.

An open letter to the Arctic governments, signed by 2,000 scientists from around the world, says that if the Ocean is overfished that will damage species that live there, including seals, whales and polar bears, and the people who use them for food.

“Until recently, the region has been covered with sea ice throughout the year, creating a physical barrier to the fisheries,” the scientists wrote. “A commercial fishery in the central Arctic Ocean is now possible and feasible.” – Climate News Network

Arctic ‘is set to reach 13°C by 2100′

February 20, 2014 in Arctic, Climate risk, Feedbacks, Ice Loss, NOAA, Polar ice, Temperature Increase

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Iceberg in Rødefjord (Scoresby Sund), Greenland: Arctic sea ice volume has shrunk by 75% since the 1980s Image: Hannes Grobe 20:05, 16 December 2007 (UTC)

Iceberg in Rødefjord (Scoresby Sund), Greenland: Arctic sea ice volume has shrunk by 75% since the 1980s
Image: Hannes Grobe 20:05, 16 December 2007 (UTC) via Wikimedia Commons

By Alex Kirby

There is wide political agreement that global average temperatures should not rise more than 2°C above their level several centuries ago. The rise some scientists expect in the Arctic by 2100 is more than six times as great.

LONDON, 20 February – US scientists say that by the end of this century temperatures in the Arctic may for part of each year reach 13°C above pre-industrial levels. Global average temperatures have already risen by about 0.8°C over the level they were at in around 1750.

The Intergovernmental Panel on Climate Change said in its 2013 Fifth Assessment Report that it thought the probable global temperature rise by 2100 would be between 1.5 and 4°C under most scenarios. Most of the world’s governments have agreed the global rise should not be allowed to exceed a “safety level” of 2°C.

But James Overland, of the US National Oceanic and Atmospheric Administration, and colleagues, writing in the American Geophysical Union’s journal Earth’s Future, say average temperature projections show an Arctic-wide end of century increase of 13°C in the late autumn and 5°C in late spring for a business-as-usual emission scenario.

By contrast, a scenario based on climate mitigation would reduce these figures to 7°C and 3°C respectively. The team say they consider their estimates “realistic”, and they have used a large number of models in reaching them.

Ice fall

The Arctic is known to be warming fast, much faster than regions further south. The mean Arctic temperature is 1.5°C higher today than it was between 1971 and 2000, double the warming that occurred at lower latitudes during the same period.

The authors say Arctic sea ice volume has decreased by 75% since the 1980s. Reasons for the rapid warming include feedback processes linked to changes in albedo, which have caused a big drop in the ability of the Arctic’s snow and ice to reflect sunlight back into space.

As they melt they are replaced by darker rock and water, which, instead of reflecting the warmth away from the Earth, absorb it and help to raise the temperature. There are also changes taking place in ocean and land heat storage. These all help to amplify the effect of greenhouse gases in warming the Arctic.

Professor Overland and his colleagues say it is very likely that the Arctic Ocean will become nearly free of sea ice at some seasons of the year before 2050, and possibly within a decade or two. This in turn will further increase Arctic temperatures, economic access (for oil and gas exploitation and by shipping), and ecological shifts.

No agreement

The greenhouse gas emissions mitigation scenario the authors use (known as RCP4.5) assumes atmospheric concentrations of carbon dioxide (CO2) of about 538 parts per million (ppm). Before the Industrial Revolution concentrations were at about 280 ppm, and had changed little over many millennia. They are now at their highest in 15 million years, and rising at about 2 ppm annually, reaching almost 400 pp

Greenhouse gas emissions continue to rise, and so far world leaders have not managed to agree how to reduce them. Their efforts are now concentrated on next year’s UN climate change convention meeting, to be held in the French capital, Paris.

Professor Overland and his colleagues conclude that major changes in the Arctic climate are “very likely” over the decades until 2040, including “several additional months of open water in the Arctic Ocean, ever earlier snow melt, further loss of permafrost, increased economic access, and dramatic impacts on ecological systems.”

They say the large difference in surface air temperatures in the Arctic at the end of the century, which they are confident will happen, “makes a strong case to begin mitigation activities for greenhouse gases”. – Climate News Network

Cat litter killer in the whales of the North

February 14, 2014 in Adaptation, Arctic, Atlantic, Disease, Ice Loss, Indigenous peoples, Marine ecology, Ocean Warming, Polar ice, Wildlife

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Blissful domesticity: But even domestic cats can spread Toxoplasma gondii

Blissful domesticity: But even domestic cats can spread Toxoplasma gondii

By Tim Radford

One consequence of a warming climate is new patterns of disease, and researchers have identified two parasites formerly unknown in the Arctic in marine mammals.

CHICAGO, 14 February – The great Arctic thaw – up to 50% of sea ice by area and 75% by volume in the summer season – could be offering new opportunities for one of the planet’s most successful parasites. Toxoplasma gondii, an infection spread by almost all cat species, has been identified for the first time in the western Arctic Beluga whale.

Toxoplasma is found almost everywhere that cats settle: domestic pets, ocelots, cougar, wild cats all carry and spread oocysts of the parasite (structures it uses to transfer to new hosts) in their faeces, to be spread further with discarded cat litter.

The parasite is notoriously hard to kill. Scientists store their samples in sulphuric acid, and the creature can survive unharmed in bleach. It is, however, routinely killed by freezing conditions, or boiling water.

The suspicion is that with the steady, sustained warming of the Arctic over the past 30 years, chiefly because of a buildup of carbon dioxide in the atmosphere, the retreat of the ice has begun to allow new traffic in parasite infections.

Another parasitic killer, a new strain called Sarcocystis pinnipedi, normally found only in the highest, iciest latitudes, has been linked with mass deaths too: 406 grey seals died in 2012 in the north Atlantic. It has also been observed to kill Steller’s sea lions, Hawaiian monk seals, walruses, grizzly bears and polar bears as far south as British Columbia.

In the case of Toxoplasma, warming polar summers could have created conditions in which the parasite could find new warm-blooded hosts further north. In the case of the second parasite, the loss of ice has meant a greater mixing of species, and allowed Sarcocystis to find new hosts in warmer waters.

Cause of blindness

“Ice is a major barrier for pathogens”, Michael Grigg, of the US National Institutes of Health told the American Association for the Advancement of Science annual meeting here. “What we are seeing with the big thaw is the liberation of pathogens gaining access to vulnerable new hosts and wreaking havoc.”

Toxoplasma can also infect people: it is the leading cause of infectious blindness in humans, and can be dangerous to unborn children and to people with compromised immunity.

It has been found in human communities in northern Quebec, perhaps spread by the consumption of dried seal meat. The discovery of Toxoplasma in Beluga whales has begun to worry health officials. Belugas are part of the traditional diet of the Inuit hunters of the far North.

Seals, walruses and polar bears are all what scientists like to call “ice obligate animals”: the ice sheet provides them with their preferred habitat. With the loss of the ice, new species are colonizing the Arctic, and those creatures that cannot now use the ice sheet have been forced to invade new habitats.

“Marine mammals can act as ecosystem sentinels because they respond to climate change through shifts in distribution, timing of their movements and feeding locations”, said Sue Moore of the US National Oceanic and Atmospheric Administration. “These long-lived mammals also reflect changes to the ecosystem in their shifts in diet, body condition and physical health.” – Climate News Network

Greenland’s fastest glacier picks up pace

February 6, 2014 in Arctic, European Space Agency, Glaciers, Greenland, Ice Loss, Lakes, Sea level rise

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An iceberg calved from the rapidly accelerating Jakobshavn Isbræ floats in Greenland's Disko Bay Image: Courtesy of Ian Joughin, PSC/APL/UW

An iceberg calved from the rapidly accelerating Jakobshavn Isbræ floats in Greenland’s Disko Bay
Image: Courtesy of Ian Joughin, PSC/APL/UW

By Tim Radford

Research from the Arctic shows Greenland’s fastest-flowing glacier has doubled its summer flow pace in a decade, and ice cover on Alaskan lakes is declining.

LONDON, 6 February – A fast-moving Arctic glacier which has earned a place in history is now accelerating even more quickly. The Jakobshavn Isbrae (the Danish word for glacier) is a massive river of ice from the Greenland ice sheet to an Atlantic ocean fjord and is thought – there is no way of proving this – to be the source of the giant iceberg that sank the Titanic in 1912.

According to research published in the European Geosciences Union journal The Cryosphere, summer flow speeds have doubled yet again since a Nasa measurement in 2003. And that in turn represented a doubling of flow speeds since 1997.

The Jakobshavn glacier is Greenland’s fastest-flowing glacier. It now moves at 17 kilometres a year. That works out at 46 metres a day. With accelerations like this, phrases like “glacial pace” may no longer serve as clichés of lethargic movement. These speeds are recorded in the summer, when all glaciers are more likely to be a bit friskier. But even when averaged over the whole year, the glacier’s flow has accelerated threefold since the 1990s.

Icebergs “calve” from glaciers – they break off and drift out to sea. The Arctic ice sheet is thinning, and most of the planet’s glaciers are retreating as climates warm, so the Jakobshavn glacier is carrying less ice, at a faster rate, over shorter distances than ever before, and by the end of the century could have shifted 50 kilometres upstream. But right now it is also contributing to sea level rise at a faster rate.

“We know that from 2000 to 2010 this glacier alone increased sea level by about 1mm”, said Ian Joughin, of the Polar Science Centre at the University of Washington, who led the research. “With the additional speed it will likely contribute a bit more than this over the next decade.”

The scientists used satellite data to measure the rate of summer change in Greenland. But other satellite radar imagery has begun to reveal an ominous picture of change elsewhere in the Arctic, on the north slope of Alaska. Even during the winter months, ice on the lakes of Alaska has begun to decline. Warmer climate conditions means thinner cover on shallow lakes and a smaller fraction that freeze entirely during the winter months.

“We were stunned to observe such a dramatic ice decline during a period of only 20 years”

Cristina Surdu of the University of Waterloo in Canada and colleagues report in The Cryosphere that there has been a 22% fall in grounded ice – frozen from surface to lakebed – between 1991 and 2011.

They expected to find a decline in ice thickness when they embarked on a study of radar observations of 402 lakes near Barrow in Alaska from the European earth resources satellites ERS-1 and ERS-2. That was because they already had temperature and precipitation records from Barrow dating back five decades.

Freeze dates in the region are now occurring on average six days later than in the past, and the ice is breaking up on average around 18 days earlier.

“At the end of the analysis, when looking at trend analysis results, we were stunned to observe such a dramatic ice decline during a period of only 20 years”, Surdu said. – Climate News Network

West Antarctic ice loss speeds up

December 20, 2013 in Antarctic, European Space Agency, Ice Loss

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CryoSat-2, keeping a weather eye open whatever the weather Image: ESA

CryoSat-2, keeping a weather eye open whatever the weather
Image: ESA

By Tim Radford

The rate of ice loss from the West Antarctic appears to have accelerated sharply in the last four years, European scientists say.

LONDON, 20 December – Ice is being lost over the West Antarctic ice sheet at a faster rate. The European Space Agency’s Cryosat – a satellite with a radar altimeter that can peer through the clouds and see in the dark – has confirmed  that 150 cubic kilometres of ice are drifting into the Southern Ocean each year: a much faster rate than the calculation for 2010.

After observations between 2005 and 2010, gathered by 10 different satellite missions, Antarctic scientists and oceanographers calculated that the melting of ice from the West Antarctic peninsula was causing global sea levels to rise by 0.28mm a year. The latest survey suggests this rate is 15% higher.

The figures were revealed at the autumn meeting of the American Geophysical Union in San Francisco. Most of the ice loss comes from glaciers flowing into the Amundsen Sea.

“We find that ice thinning continues to be most pronounced along fast-flowing ice streams of this sector and their tributaries, with thinning rates of between four to eight metres per year near the grounding lines – where the ice streams lift up off the land and begin to float out over the ocean – of the Pine Island, Thwaites and Smith glaciers”, said Malcolm McMillan of the University of Leeds in the UK.

Wide-ranging view

The increase could be due to faster thinning – or it could be down to more accurate measurement, because Cryosat has more advanced instruments and circles the planet in a near-polar orbit, to cross territory no other observers could hope to see.

Cryosat will be followed by another series of European satellites, to be launched from 2014 onwards. Each of these Sentinels – that is their name – will have synthetic aperture radar instruments that will monitor a 250 kilometre-wide strip of the globe with each orbit.

They will work in pairs and not just keep an eye on polar ice but will cover Europe and Canada as well every one to three days, and watch, too, the main shipping routes, whatever the weather. – Climate News Network

Arctic melting ‘affects temperate zones’

December 18, 2013 in Arctic, Extreme weather, Polar ice, Weather, Weather Systems

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Bear on the ice near Svalbard: Arctic warming appears to be having effects far to the south Image: Hannes Grobe via Wikimedia Commons

Bear on the ice near Svalbard: Arctic warming appears to be having effects far to the south
Image: Hannes Grobe via Wikimedia Commons

By Tim Radford

Weather extremes in temperate countries may be the consequence of the melting of Arctic snow and ice, according to Chinese and American scientists.

LONDON, 18 December – The shrinking Arctic sea ice – a loss of 8% per decade during the last 30 years – isn’t just bad news for polar bears. It could be bad news for citizens of Europe and the United States who like to think they live in a temperate zone.

Qiuhong Tang of the Chinese Academy of Sciences and colleagues from Beijing and the US report in Nature Climate Change that they have identified a link between declining snow and ice in the polar north, and catastrophic heat waves, droughts and floods in the mid-latitudes.

Recent years have been marked by devastating extremes of heat in Russia, Europe and the US, and by unprecedented floods in the UK and in East Asia. Over the same period, snow cover and sea ice in the Arctic have been in retreat.

The link, the scientists say, could be changes in atmospheric circulation triggered by the loss of snow cover.

There are perfectly good reasons to expect some impact on weather systems from a retreat of the snow line. In the first place, snow and ice are white – that is, they reflect sunlight, and its warmth – while ocean and forest and tundra are dark, and absorb heat.

Closer link established

Good snow fall means lots of soil moisture in the summer months while dry ground tends to be warmer. So temperatures change, overall. Air currents flow because of pressure differences, which are linked to temperature. So winds would inevitably be affected.

But the researchers went beyond this loose generalisation, to match satellite observations of the snow cover and sea ice extent in the Arctic with atmospheric data, to explore the effects further south.

They found a distinct set of patterns of circulation associated with the loss of snow and ice.

The upper atmospheric winds in the north become weaker, and the jet stream shifts northwards, which means that weather systems become more stable. The longer a weather system stays in one location, the greater the probability that the conditions will become extreme.

In 2012, in the continental United States, it was the hottest summer ever recorded and the second worst for floods, hurricanes and droughts. In September 2012, the Arctic sea ice fell to its lowest level ever. It could be just chance, it could be just two aspects of the same big picture, but Tang and colleagues think not.

Hotter future

They think the link is clear. They even see a closer link between the loss of sea ice and a change in circulation pattern, even though the area of sea ice lost is only half of the total area of snow lost in the months of May and June.

That could be because much of the northern hemisphere snow cover is over land which is forested anyway – that is, partly dark – whereas the Arctic sea can only be white or dark.

The link is not certain – they are putting the idea out there for others to challenge or confirm, which is the way science advances – but the three authors argue that their research builds on studies by others which spell out the same conclusion.

And they don’t see things getting better, either for polar bears who need the sea ice to hunt, or for farmers in the great plains of the US or city dwellers on floodplains and river estuaries in the temperate world.

“As greenhouse gases continue to accumulate in the atmosphere and all forms of Arctic ice continue to disappear, we expect to see further increases in summer heat extremes in the major population centres across much of North America and Eurasia where billions of people will be affected”, they conclude. – Climate News Network