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by Paul Brown

Arctic tundra ‘will turn to forest’

May 18, 2013 in Warming

EMBARGOED until 2301 GMT on Friday 17 May

Tundra will turn into fir forests at the current levels of carbon dioxide Photo by Jason Hollinger

Tundra will turn into fir forests at the current levels of carbon dioxide.             Image: Jason Hollinger

By Paul Brown

Two sets of scientists, working independently, come to the same conclusion: that the Arctic will soon become ice-free and forested.

LONDON, 18 May – An ice-free Arctic, the disappearance of tundra and forests up to the edge of the newly open ocean is how the north will look as the natural world reacts to the new climate caused by carbon dioxide reaching 400 parts per million (ppm) in the atmosphere, according to analysis of new lake sediments.

So far scientists have been guessing what a warmer world will look like, but lake bed cores from Russia provide evidence of the trees and plants that thrived north of the Arctic Circle last time CO2 was at 400 ppm – a barrier broken earlier this month.

There is a time lag of up to 30 years for the temperature to be forced up by the extra CO2 in the atmosphere, so the scientists’ findings give a clue to what to expect by the middle of the century.

Julie Brigham-Grette of the University of Massachusetts Amherst, who led a team of international scientists, says summer temperatures were about 8°C warmer in the Arctic than they are today, and the rainfall three times greater. At the same time the West Antarctic ice sheet did not exist, showing that both landscape and sea level were vastly different.

Underestimating the effects

 

She said the results showed that scientists might have badly underestimated the effect of existing carbon dioxide levels in altering the climate over time.

Another unconnected team of researchers has been studying how the temperature changes that are already occurring in the northern hemisphere are affecting plants. The two pieces of research appear to point to the same conclusions.

Hans Tømmervik at the Fram-High North Research Centre for Climate and the Environment and 21 scientists from 17 academic institutions have been looking at all the Arctic countries and how they are already reacting to increased temperatures.

He said: “Norwegian climate and vegetation as we know it today might be totally changed within some decades. The same process is happening in Siberia, in Alaska and in the northern parts of Canada. Mountain plateaus become forest land and the winter period is shorter and shorter every year”.

The growing season has increased by up to 40 days in some areas. The temperature difference between summer and winter is getting smaller because the winters are no longer so cold. Spring and autumn seasons are also shorter.

Tømmervik says the start and end period for vegetation growth are very dependent on threshold temperatures. When the trends of these temperatures change and thus change the start of photosynthesis, it will in time change the vegetation.

Pollen in the sediment

 

The result is that trees and bushes will be able to grow where only lichen and heather were living earlier. Species move slowly towards the north and up into the mountains. The increased vegetation in the north also gives an extra boost to global warming, because it reflects less sunlight back into space than the ice and snow it has replaced, and thus causes even more rapid changes.

The other team were looking at sediment layers and analysed cores collected in the winter of 2009 from under ice-covered Lake El’gygytgyn, the oldest deep lake in the northeast Russian Arctic. “Lake E” was formed 3.6 million years ago when a huge meteorite hit the Earth and blasted out an 11-mile (18 km) wide crater.

It has been collecting sediment layers ever since. Luckily for geoscientists, it lies in one of the few Arctic areas not eroded by continental glaciers, so a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geological time nearly 30 times farther than Greenland ice cores that cover the past 140,000 years.

“One of our major findings is that the Arctic was very warm in the Pliocene [~ 5.3 to 2.6 million years ago] when others have suggested atmospheric CO2 was very much like levels we see today. This could tell us where we are going in the near future.

“In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier models”, say the co-authors from Russia, Germany and the United States.

Also important to the story are fossil pollens extracted from the lake sediments, which allow scientists to reconstruct life around the lake in the past using modern habitat tolerances to reconstruct past winter and summer temperatures and precipitation.

Another significant finding to emerge from this first continuous, high-resolution record of the Middle Pliocene is the documentation of sustained warmth, with summer temperatures of about 59 to 61° F [15 to 16°C], about 8°C warmer than today, and regional precipitation three times higher than today.

“We show that this warmth well north of the Arctic Circle occurred throughout both warm and cold orbital cycles and coincides, in part, with a long interval of 1.2 million years when the West Antarctic Ice sheet did not exist”, Brigham-Grette notes. Thus both poles share some common history, but the pace of change differed, she said  – Climate News Network

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by Tim Radford

Clouds ’caused Greenland’s 2012 thaw’

April 5, 2013 in Science

FOR IMMEDIATE RELEASE

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

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

By Tim Radford

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

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

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

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

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

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

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

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

Complex influences

 

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

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

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

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

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

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by Tim Radford

Warming ‘increases Antarctic ice’

March 31, 2013 in Science

EMBARGOED until 1700 GMT on Sunday 31 March

Some think global warming could be increasing Antarctic sea ice, while others are less sure Image: NASA

Some think global warming could be increasing Antarctic sea ice, while others are less sure
Image: NASA

By Tim Radford

The amount of ice in the Antarctic is increasing, scientists say – as a strange consequence of global warming. But at the other end of the world melting is proceeding apace.

LONDON, 31 March – The Arctic may be shrinking as the world warms but Antarctic sea ice is expanding. Blame global warming for that, too, say Dutch scientists.

The paradox is that increasing temperatures have set in motion a chain of events in the southern seas that have the opposite effect. Engineers call this negative feedback. So do Richard Bintanja and colleagues of the Royal Netherlands Meteorological Institute.

They report in Nature Geoscience that as the Antarctic ice shelves melt, the resulting cool fresh water has actually served to insulate the offshore sea ice from the warming ocean beneath the floating floes. So, as a consequence, in 2010 southern ocean sea ice reached a record extent.

The Arctic Ocean is mostly just that: ocean, which is getting warmer, and the northernmost parts of the globe have been warming at twice the global average rate.

So the north polar sea ice has been steadily thinning in depth and shrinking in area for more than 30 years. Ice reflects sunlight and keeps itself cold. Dark seas absorb sunlight and continue to get warmer.

As the Arctic ice shrinks, the feedback becomes positive. So the expectation is that sometime this century, in late summer, the Arctic ocean will for a few weeks be ice-free.

Plausible – and conclusive?

 

But Antarctica is an enormous, high continental landmass covered almost entirely by a huge depth of ice and snow, and it keeps itself cold very effectively. The oceans as a whole are warming – but in Antarctica, this warming has a counter-intuitive effect: thanks to the melt water, the total area of reflective sea ice is stable, or getting larger.

So although warm water is reaching the continental shelves, and creating some melting, the overall effect is to deliver a cold freshwater layer to the top hundred metres or so of the surrounding ocean. Fresh water freezes more quickly, so sea ice builds up quickly in the autumn and early winter.

“Our analyses indicate that the overall sea-ice trend is dominated by increased ice-shelf melt”, the Dutch scientists report.  “We suggest that cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise.”

That should be good news: there is enough ice on the southern continent to completely inundate most of the world’s great estuarine and sea level cities.  But the conclusions are tentative and not everybody is likely to agree.

Is this an effect that will last? The interaction of ocean and atmosphere is a complicated one, with a number of factors at work that influence the growth of sea ice. In the UK, Martin Siegert of the University of Bristol suspects that the process just described may not be significant in the long run.

Paul Holland of the British Antarctic Survey calls the freshwater concept “plausible” but thinks there are also plausible alternative explanations for the increase in sea ice around Antarctica, among them changes in the wind patterns that might deliver blasts of colder air to the surrounding seas.

Galloping change

 

And Andrew Russell of Brunel University agrees: he sees both wind pattern changes and ice shelf melting resulting in increased sea ice “which perhaps isn’t what you’d expect but is consistent with our best description of climate change.”

Meanwhile, scientists at the American Museum of Natural History have more bad news for polar bears and other creatures adapted to the frozen Arctic. It will get warmer, and greener.

Rising temperatures in the next few decades will lead to a “massive” increase in vegetation in the lands bordering the Arctic, with as much as 50% more tree cover.

Three weeks ago, an international team reported in Nature Climate Change that vegetation conditions had advanced hundreds of miles north in the last few decades.

Now a consortium of researchers from the New York museum, Woods Hole research centre, Cornell University and the University of York in the UK report in the same journal that the growth will continue.

They used climate models to simulate future conditions and they believe that positive feedback will guarantee the advance of mosses, dwarf shrubs, sedges, grasses and even trees towards the pole. As the ice and snow give way to green foliage, the rate of warming will step up.

“These impacts would extend far beyond the Arctic region,” said Richard Pearson of the American Natural History Museum. “For example some species of birds seasonally migrate from lower latitudes and rely on finding particular polar habitats, such as open space for ground nesting.” – Climate News Network

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by Tim Radford

Greening tundra shows Arctic heat

March 10, 2013 in Warming

EMBARGOED until 1800 GMT on Sunday 10 March

Vegetables can't be fooled: The tundra shows the effects of spreading warmth Image: ADialla

Vegetables can’t be fooled: The tundra shows the effects of spreading warmth
Image: ADialla

By Tim Radford

The Arctic is warming faster than many other parts of the planet, and plants are providing some of the clearest signs of the impacts, with vegetation now growing nearly 500 miles further north than it did a few decades ago.

LONDON, 10 March – The Arctic is on the move. The North Pole is in the same place, but Arctic conditions have begun to shift. A study of 30 years of satellite data confirms that the difference in temperatures between the seasons has diminished.

Conditions now have shifted the equivalent of four or five degrees of latitude southward. At the same time, vegetation has moved north, colonizing the thawing permafrost.

A team of 21 scientists from 17 institutions in seven nations reports in Nature Climate Change that as the cover of snow and ice has diminished and retreated in the Arctic Circle, the temperatures have begun to increase – at differing rates – during the four seasons. Although conditions differ from region to region, overall the growing season is beginning earlier, and the autumn freeze is starting later.

Conditions in northern latitudes now increasingly resemble those found several hundred miles further south 30 years ago. One of the authors, Bruce Forbes of the University of Lapland in Finland, told the Climate News Network that in his own research region of north-west Siberia “we are seeing more frequent and longer-lasting high pressure systems. In winter, the snow cover comes later, is deeper on average than in the 1960s, but is melting out earlier in spring.”

Climate is a complicated business, and there is always legitimate room for argument about the validity of one selected set of measurements, a potential bias in the observations, or the reliability of comparison data collected two generations earlier.

But vegetables can’t be fooled. Plants grow where they can. If deciduous shrubs are growing taller, and colonizing sites ever further north, then conditions must be getting warmer, and staying warmer.

Winners – and losers

 

Professor Forbes says that indigenous reindeer herders report that alder and willow, normally stunted by the polar winter, are growing taller: his own research team has confirmed this with dendrochronology, the science of tree ring measurement.

“In a few decades, if the current trends continue, much more of the existing low shrub tundra will start to resemble woodlands as the shrubs become tree-sized”, he says.

This enhanced warming over a longer ground-thaw season has changed the landscape: it has, says Compton Tucker of the Goddard Space Flight Center in the US, “created during the past 30 years large patches of vigorously productive vegetation, totaling more than a third of the northern landscape – over nine million km2, which is roughly about the area of the USA -  resembling the vegetation that occurs further to the south.”

This warming of the high latitudes is not necessarily good news for all plants. As the tundra turns green at an accelerating rate, the growth of the boreal forests – those mighty stands of conifer species that cover northern Canada and northern Eurasia and enclose the Arctic Circle – may even be decelerating.

Boreal forest species are adapted to cold. “Some areas of boreal forest will be negatively impacted by warming temperatures, from increased drought stress as well as insect and fire disturbance”, says Scott Goetz of Woods Hole Research Center in the US, another of the co-authors.

“But this work shows that in most high latitude regions we see increased productivity resulting from a reduced range of seasonal temperature variability.”

Driving more warming

 

Since relative temperatures are dictated by latitude, the researchers used latitude as a measure. They selected reference sites and studied both change, and the rate of change, using three decades of Nasa satellite data, and reports from researchers and nomad observers.

One of these sites was at 64° N. Now, 30 years on, it has plant cover characteristic of 57° N. It is as if growing conditions had shifted seven degrees north, or very nearly 750 km, according to Terry Chapin, of the University of Fairbanks, Alaska.

By the end of the century, at the present rate of change, temperature seasonality will have diminished substantially, and – once again using latitude as a yardstick – will be the equivalent of a 20 degrees shift, relative to measurements made between 1951 and 1980.

Such warming is all too likely to feed back into even more global warming, as the frozen soils of the north come to life, peat and vegetation begin to decompose, and yet more reservoirs of buried methane and carbon dioxide are released into the atmosphere.

What it will mean to the peoples and the creatures of the north is hard to guess, because ecosystems will change with seasonal temperature and plant growth.

“Think of the migration of birds to the Arctic in the summer and the hibernation of bears in the winter”, says Dr Goetz. “Any significant aberrations in seasonality are likely to impact life not only in the north, but elsewhere, in ways that we do not know.” – Climate News Network

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by Paul Brown

Arctic oil and gas will exact high price

March 6, 2013 in Energy

EMBARGOED until 0001 GMT on Wednesday 6 March

No Arctic drilling, thank you: Norway's Young Friends of the Earth make their point Image: Natur og Ungdom

No Arctic drilling, thank you: Norway’s Young Friends of the Earth make their point
Image: Natur og Ungdom

By Paul Brown

As the ice melts in the Arctic, opening up the possibility of exploiting new oil and gas reserves, there are conflicting views on whether that will be commercially viable. The future of this pristine environment apparently depends not so much on whether it is good or bad for the planet that more fossil fuels are burnt, but on the price of gas. The stakes could not be higher or the uncertainty greater. Here the Climate News Network explores two conflicting views.

LONDON, 6 March – First, there’s a new assessment report by Ernst & Young, the international accountancy firm. It says the high-cost, high-risk resources of oil and gas available inside the Arctic Circle are both commercially exploitable and affordable.

After analysis of the tax and incentive schemes offered by the eight countries with hopes of drilling oil and gas wells in the Arctic, the firm concludes that Russia is a good investment opportunity with massive Arctic gas reserves.

However Alaska is the best bet for oil, with the largest untapped Arctic reserves. Norway, because of the stability of its government, and the opening up of Greenland for exploration also present good business opportunities.

This assessment contrasts with an influential American view – that international gas prices will fall because of an energy glut, making Russian gas too expensive to sell.

The US Council on Foreign Relations says that countries in Europe, currently dependent on high-priced Russian gas, will be able to exploit cheap shale gas within their own borders. Some will no longer need to import Russian gas at all.

The Ernst and Young report argues that with 20% of the planet’s remaining oil and gas reserves lying in the Arctic, and still to be located and exploited, the potential is enormous.

Already 61 large oil and natural gas fields have been discovered within the Arctic Circle – 43 are in Russia, 11 in Canada, six in Alaska and one in Norway.

Expensive and uncertain

 

However, the report warns: “The quest for Arctic oil and gas resources is not for the faint of heart nor for those with less-than-deep pockets. Rather, Arctic resource development is both high-cost and high-risk.”

It says that apart from the harsh climate other challenges are lack of infrastructure, pipelines and ports. Special tankers and icebreakers will be needed, and if there are spills they will be difficult to control and clear up.

There are overlapping sovereignty claims, which lead to uncertainty about the environmental rules in any particular area. The firm also says that environmental campaigners wishing the Arctic to be left alone can be troublesome.

Although the report is generally positive about exploiting the Arctic it does emphasise the long lead times of projects and says only the five or six largest oil and gas companies with the deepest pockets will be able to afford the investment.

“These operations are clearly on the outer limits of both safety and commercial viability for the industry”, it says, “and a spill or accident there would be catastrophic. The economics of Arctic development are also looking forward to even higher oil prices which may or may not happen in the near term.”

Prohibitive production costs

 

Ernst and Young’s cautious but optimistic approach to the prospects of investment in the Arctic contrasts with the Council on Foreign Relations’ assessment of future energy supplies, particularly the Russian prospects.

While it accepts that Russia has vast gas reserves, the expense of extracting and transporting the gas from the far north will make it uncompetitive in world markets, the Council says.

Aviezer Tucker, writing on the website of Foreign Affairs, published by the Council, says the energy map of the world is being redrawn, and the fall in gas prices in America as a result of vast new discoveries of shale gas is about to be repeated in Europe.

Ukraine and Poland are among the countries currently dependent on Russian gas which have the potential to produce all their own supplies of much cheaper shale gas. If they did, the effect would be an energy glut and falling gas prices severely damaging the Russian economy.

Tucker quotes some estimates that 60% of Russian federal income comes from energy exports. Russia’s other potential market for gas, China, is also discovering that it too has large shale gas reserves.

If this assessment is right, then much of the Arctic gas will stay beneath the Earth’s crust, just too expensive to exploit. – Climate News Network

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by Tim Radford

Fast boat to China?

March 4, 2013 in Science

EMBARGOED until 2000 GMT on Monday 4 March

Safety will be just one problem for Arctic mariners Image: Ansgar Walk

Safety will be just one problem for Arctic mariners
Image: Ansgar Walk

By Tim Radford

In less than 50 years from now the north-west passage through the Arctic should be open to suitable vessels for a short time every other year, scientists have calculated.

LONDON, 4 March – The great Elizabethan explorer Martin Frobisher tried three times to get from Europe to China by sailing across the Arctic circle. In the summer of 1578 he steered his ships between the Canadian mainland and Baffin Island, in an attempt to find the fabled north-west passage.

He was soon defeated by tempest, snow and ice. “There fell so much snow, with such bitter cold air, that we could not scarce see one another for the same, nor open our eyes to handle our ropes and sails”, says the account recorded in Hakluyt’s famous Principal Navigations, Traffiques and Discoveries of the English Nation.

Tomorrow’s mariners may have an easier time of it, according to Laurence Smith, a geographer at University of California, Los Angeles. He reports in the Proceedings of the National Academy of Sciences that by 2059 ships, especially if reinforced for polar waters, should be able to manage the north-west passage from the east coast of America to the west, one year in two. Right now, it is navigable perhaps one year in seven.

The north-east passage, or northern sea route along the coast of Siberia, is already in regular use, and 46 ships made the journey in 2012. The Arctic ice sheet is expected to thin with global warming to a point where polar icebreakers will be able to go straight over the North Pole between the Pacific and Atlantic Oceans, he calculates.

Smith and his co-author Scott Stephenson considered seven different forecasts for sea ice cover in the Arctic between 2040 and 2059, and took an average. They studied the emerging navigation routes and the degree of sea ice melting that has made them possible.

They then considered two scenarios for climate change: one that assumed a 25% increase in carbon dioxide emissions, and one that assumed a 35% rise. And then they looked ahead to mid-century. To their surprise, the choice of scenarios made no difference to the outcome.

“No matter which carbon emission scenario is considered, by mid-century we will have passed a crucial tipping point – sufficiently thin sea ice – enabling moderately capable icebreakers to go where they please”, Smith said.

Seasonal shipping only

 

The attraction of the polar route is that it is shorter: substantially shorter than the traditional routes through the Suez or Panama Canals. Ships heading from New York for Yokohama, or from Bremen to Vancouver, via the Arctic Ocean, could save days at sea and cut running costs.

But the possibility also raises concerns about safety, suitable ports of call, and hazard to the Arctic environment. It also raises sovereignty issues, with increasing disputes about who “owns” the polar waters.

Such questions were, until 2007, largely hypothetical. But that year the Arctic sea ice, which has been shrinking and thinning gradually for decades, hit a record low.

Some glaciologists now think – though there is plenty of room for argument – that the Arctic may have reached a tipping point, and is about to enter a new and less stable state, in which ice cover will go on shrinking in the summer months.

One day, Frobisher’s unhappy voyage will be possible and may even become routine, but only in the late summer. “This will never be a year-round operation”, says Smith. – Climate News Network

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by alex kirby

Arctic ice loses volume fast

February 16, 2013 in Science

EMBARGOED until 0001 GMT on Saturday 16 February

Not just what you see: the volume of ice is shrinking too Image: Patrick Kelley

Not just what you see: the volume of sea ice is shrinking too            Image: Patrick Kelley

By Alex Kirby

Researchers say the Arctic sea ice is not only undergoing seasonal shrinkage in area, but that it is also thinning and losing much of its volume.

LONDON, 15 February – The seasonal shrinkage of the area of Arctic sea ice is now well-established. But a new study has found that it is also undergoing thinning and a pronounced loss of volume all year round.

Between 2003 and 2012 the volume of the ice declined by 36% in the autumn and 9% in the winter, a UK-led team of scientists has discovered.

They used data from NASA’s ICESat satellite from 2003 to 2008, and new data from the European Space Agency’s CryoSat-2 satellite between 2010 and 2012, to estimate the volume of sea ice.

From 2003 to 2008, they found, autumn ice volumes averaged 11,900 cubic kilometres. But from 2010 to 2012 the average had dropped to 7,600 km3 – a decline of 4,300 km3. The average winter volume from 2003 to 2008 was 16,300 km3, dropping to 14,800 km3 between 2010 and 2012 – a difference of 1,500 km3.

“While two years of CryoSat-2 data aren’t indicative of a long-term change, the lower ice thickness and volume in February and March 2012, compared with same period in 2011, may have contributed to the record minimum ice extent during the 2012 autumn,” says Professor Christian Haas of York University, Canada, a co-author of the study.

The research was funded by the UK’s Natural Environment Research Council (NERC), the European Space Agency, the German Aerospace Center, Alberta Ingenuity, NASA, the Office of Naval Research and the National Science Foundation.

“The data reveals that thick sea ice has disappeared from a region to the north of Greenland, the Canadian Archipelago, and to the northeast of Svalbard,” said Dr Katharine Giles, a NERC-funded research fellow at the Centre for Polar Observation and Modelling (CPOM) at University College London, and another co-author of the report, published online in Geophysical Research Letters.

NERC says: “The findings confirm the continuing decline in Arctic sea-ice volume simulated by the Pan-Arctic Ice-Ocean Modelling & Assimilation System (PIOMAS), which estimates the volume of Arctic sea ice and had been checked using earlier submarine, mooring, and satellite observations until 2008.”

Ice volume a crucial indicator

 

PIOMAS was developed at the University of Washington’s Polar Science Center, which says of the part of the Arctic it studied: “Monthly averaged ice volume for September 2012 was 3,400 km3. This value is 72% lower than the mean over this period, [and] 80% lower than the maximum in 1979…”

Other satellites have already shown drops in the area covered by Arctic sea ice as the climate has warmed, and its extent reached a record minimum in September 2012.

But CryoSat-2, launched in April 2010, differs in its ability to allow scientists to estimate the volume of ice, a much more accurate indicator of the changes taking place in the Arctic.

NERC says the satellite measures ice volume using a high-resolution radar altimeter, which fires pulses of microwave energy down towards the ice.

The energy bounces off both the top of sections of ice and the water in the cracks in between. The difference in height between these two surfaces lets scientists calculate the volume of the ice cover.

The team confirmed CryoSat-2′s estimates of ice volume using measurements from three independent sources – aircraft, moorings, and NASA’s Operation IceBridge.

The decline in Arctic sea ice may have serious implications both regionally and globally. While much of the Sun’s heat is reflected back into space by light-coloured ice, more of it will be absorbed by the darker water exposed as the ice melts, speeding up the process of global warming.

The melting may also accelerate the thawing of the permafrost, allowing methane, a potent greenhouse gas, to escape to the atmosphere. It could also help to destabilise the Greenland ice cap.

The research findings were the result of collaboration between teams from UCL, the European Space Agency, the Jet Propulsion Laboratory, the University of Washington, York University, Alfred Wegener Institute for Polar & Marine Research, Woods Hole Oceanographic Institution, Morgan State University and the University of Maryland. – Climate News Network

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by Tim Radford

Thawing tundra threat to frozen carbon

February 11, 2013 in Science

 

Svalbard tundra - how fast it thaws is crucial Image: Billy Lindblom

Svalbard tundra – how fast it thaws is crucial            Image: Billy Lindblom

By Tim Radford

The melting of Arctic ice frozen for many thousands or even millions of years is speeding up, a potential route for carbon frozen deep below ground level to seep into the atmosphere.

LONDON, 12 February – The first kiss of sunlight on the frozen soils of the Arctic could spell increasing trouble as the world warms.

The return of the spring sun melts domes and lakes of frozen water called thermokarsts – karst is a word usually linked to limestone country, but it has been pressed into service as a label for the hard surfaces caused by ice.

Within this ice is dissolved organic carbon. Once the ice melts, microbes get to work releasing carbon dioxide into the air. The soil thaws, the surface collapses, lakes form, water flows, land surfaces erode which in turn releases more carbon dioxide to create more warming, to make the tundra even more vulnerable to spring thaw, and of course to accelerated warming.

This is not a scare story. It is happening now, according to Rose Cory of the University of North Carolina and colleagues who report in the Proceedings of the National Academy of Sciences.

They analysed water from 27 undisturbed sites in Alaska, and seven unique thermokarst failures – a polite word for landslides – near Toolik Lake in Alaska. The places they examined had been frozen for at least 10,000 years, and in some places two million years.

Speed the key factor

 

The team found dissolved organic carbon in all of them, and they found that newly-exposed muddy water was liable to surrender 40% more CO2 to the atmosphere.

This has of course been going on at the fringe of the Arctic permafrost for at least 10,000 years. The hazard is not in the process itself, but in its potential acceleration: nobody knows how much carbon is stored in the Arctic tundra as a greenhouse gas source, and nobody can guess what proportion of this will be released as the world warms. Thermokarsts are also found on a smaller scale in the Himalayas and the Swiss Alps.

But, as the soils warm, and the microbes get a chance to draw breath and get to work, say the authors, “the ultimate fate of deep, frozen soil carbon will be affected by coupled photobiological processing, by the available light field in streams that receive thermokarst drainage, and eventually by the landscape configuration of lakes and streams.”- Climate News Network

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by Tim Radford

Arctic predator faces migration or death

January 18, 2013 in Science

EMBARGOED till 2200 GMT on Friday 18 January

By Tim Radford

There will be winners and losers among Arctic creatures trying to survive intensified climate change, which is already leaving its mark on some plants found far further south.

LONDON, 18 January – Climate change, with associated extremes of cold, rain and warmth, could make life very tricky for some of the Arctic’s most charismatic animals.

Those with somewhere to go could survive migration to more suitable climates, according to new research in three journals. But those that depend on others for their daily supper could find periodic difficulties. Spring already arrives earlier and flowers are blooming at unprecedented dates, but one or two rare blooms may be extinguished altogether.

Conservation biologists at the Norwegian University of Science and Technology report in Science that they examined the dynamics of a simple ecosystem on the island of Spitsbergen in the Svalbard archipelago, at 78 degrees North latitude.

The components were the wild Svalbard reindeer, a bird called the Svalbard rock ptarmigan, a European rodent called the sibling vole – and a predator, the Arctic fox. What caused population fluctuations, they found, were simple events: rain on snow, followed by extreme cold.

Arctic fox

Arctic foxes in Svalbard will have more than enough food during rainy and icy winters because there will be many reindeer carcasses for them to eat. The next winter, however, the fox population size will be reduced because a robust and small reindeer population will mean many fewer deaths and hence, very little carrion. Image: Brage B. Hansen, NTNU Centre for Conservation Biology

The snow cover would freeze, preventing the reindeer, the ptarmigan and the vole from grubbing for food beneath the snow.  Many would die, populations would crash.

However, the Arctic fox – perfectly happy to eat carrion – would do very well on dead reindeer carcasses and flourish. But the following winter, reindeer would be scarce, birds and voles difficult to find and the foxes would starve, one year out of step.

Rain on snow, followed by ice, is rare in much of the Arctic, but Svalbard has an oceanic climate: such events could be more common as the high Arctic warms with climate change.

Ice on top of snow can damage vegetation and reduce the richness of life in the soil. The Norwegian team think that damage to a community forced to overwinter could cascade through the food web.

“The die-offs among resident herbivores shape predator abundance, which could in turn affect the migratory prey that reside in the area in the summer, such as sea birds and barnacle geese,” says Brage Bremset Hansen, lead author of the paper.

But some creatures will cope with change, according to ecologists at Umeå University in Sweden. They modelled the distribution of species in northern Europe’s Arctic and sub-arctic land areas and predicted that the climate change expected by 2080 could benefit most mammals – with the exception of the lemming and the Arctic fox, both cold climate specialists.

“…even well-protected and even relatively abundant species may succumb to climate-induced stresses.”

But the “winners” would survive only if they could safely move to new ranges with climates to which they were adapted. “It is highly improbable that all mammals will be able to do so, owing partly to the increased fragmentation of their living environment caused by human beings,” said Christer Nilsson, one of the authors, in PLoS ONE (the Public Library of Science One).

One creature with nowhere to go as the world warms could be a rare flowering plant called the Haleakalā silversword, which makes its home high on just one Hawaiian volcanic crater.

It grows for between 20 and 90 years before flowering, just once, at the end of its life. Its survival was first endangered by humans who picked the flowers, and by introduced grazing animals: protection arrangements were introduced and the population recovered but, scientists warn in Global Change Biology, it could succumb to global warming.

“The silversword example foreshadows trouble for biodiversity in other biological hotspots,” said Paul Krushelnycky of the University of Hawaii, “and it illustrates how even well-protected and even relatively abundant species may succumb to climate-induced stresses.”

But there is more benign news from the eastern United States where, on average, spring blossoms appear 11 days earlier than they did when the great American writer and naturalist, Henry David Thoreau, began keeping records at Walden Pond, near Concord, Massachusetts 161 years ago.

And a thousand miles away in Wisconsin, in 2012 and during the warmest spring on record, plants bloomed on average a month earlier than 67 years ago, when the pioneer conservationist Aldo Leopold began keeping notes, researchers report in PLoS ONE. The research has important implications for predicting plant responses to climate change. – Climate News Network

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