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Early springs surprise many species

April 7, 2014 in Adaptation, Arctic, Climate, Polar ice, Species loss, Warming, Wildlife

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Roe deer numbers have been particularly hard hit by seasonal disruption.  Image: Marek Szczepanek via Wikimedia Commons

Roe deer numbers have been particularly hard hit by seasonal disruption.
Image: Marek Szczepanek via Wikimedia Commons

By Tim Radford

As seasonal change suffers ever more disruption, many species are struggling to adapt quickly enough.

LONDON, 7 April – Spring is arriving earlier. This is not necessarily welcome news for Arctic creatures or the roe deer of France. It could be awkward for flower festival organisers as well.

Julienne Stroeve of the US National Snow and Ice Data Centre and colleagues will report in Geophysical Research Letters that the length of the Arctic melt season is growing by several days each decade. When the melt starts earlier, the Arctic Ocean absorbs more radiation: enough in some places to melt four feet in thickness from the Arctic ice cap.

“The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the oceans and increase ice melt during the summer, overall weakening the sea ice cover,” says Stroeve. The Arctic sea ice has now been in decline for four decades.

The seven lowest September sea ice extents in the satellite record have all occurred in the last seven years. A new examination of satellite imagery and data from 1979 to the present shows that the Beaufort and Chukchi Seas are freezing up between six and 11 days later per decade. But the earlier melt is more ominous than the later freeze: the sun is higher and brighter, and delivers more warmth to the seas.

Festival disruption

The earlier spring presents no problems for many plants but it may not be much fun for the organisers of flower festivals who like to announce their events well in advance. Tim Sparks of Coventry University reports in the journal Climate Research that over its 46-year history, the Thriplow Daffodil Weekend in Cambridgeshire in eastern England has been forced to bring its dates forward by 26 days.

The event can attract up to 10,000 visitors, and has raised £300,000 (US $500,000) for charity, so it clearly helps the organisers to set up some advance publicity. Since 1969, mean temperatures in March and April in the UK have risen by 1.8°C.

“The study represents one of the first solid pieces of evidence of flower tourism having to adapt to climate change,” said Professor Sparks. “The issues faced by Thriplow are a microcosm of the wider picture.”

Flower festivals may be able to adapt. Sadly, the roe deer of Champagne have yet to get the message about climate change. To flourish, both nectar seekers and herbivores have to time their breeding patterns to the surge in plant growth.

Three French scientists looked at records of a population of roe deer in the Champagne region of France, and found that although spring has been arriving increasingly earlier, the fawns are being born at around the same dates as they were 27 years ago, and their survival rate is falling, they report in the Public Library of Science journal PLOS Biology. Overall, the roe deer population in the region is also in decline.

Great tits have kept up with climate change, because reproduction is cued by temperature, so they are around at the same time as the explosion in food sources. What sets the biological pace for roe deer is day length, the authors think, and this is not affected by climate change. - 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

Arctic melt speeding up

March 9, 2014 in Arctic, Climate Sensitivity, Deep Ocean, Greenland, Marine ecology, Ocean Warming, Polar ice, Solar energy

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Measuring the sun's reflectivity in the Arctic Image: NASA/Kathryn Hansen via Wikimedia Commons

Measuring the sun’s reflectivity in the Arctic
Image: NASA/Kathryn Hansen via Wikimedia Commons

By Tim Radford

It’s long been established that Arctic ice is on the retreat but it’s the pace of change that’s surprising scientists: latest studies show the region is at its warmest for 40,000 years. 

LONDON, 9 March - Ice in the Arctic continues to retreat. The season without ice is getting longer by an average of five days every 10 years, according to a new study in Geophysical Research Letters.  And in some regions of the Arctic, the autumn freeze is now up to 11 days later every decade.

This means that a greater proportion of the polar region for a longer timespan no longer reflects sunlight but absorbs it. This change in albedo – the scientist’s term for a planet’s reflectivity – means that open sea absorbs radiation, stays warmer, and freezes again ever later.

Warming accelerates

None of this is news: sea ice in the Arctic has been both retreating and thinning in volume for four decades. Researchers have tracked the retreat of the snow line to find tiny plants exposed that had been frozen over 40,000 years ago: the implication is that the Arctic is warmer now than it has been for 40 millennia.

This warming threatens the animals that depend for their existence on a stable cycle of seasons  and is accelerating at such a rate that the polar ocean could be entirely free of ice in late summer in the next four decades.

So Julienne Stroeve, of University College London and her colleagues have provided yet further confirmation of an increasing rate of change in the region in their latest study.

The scientists examined satellite imagery of the Arctic for the last 30 years, on 25 square kilometer grid, to work out the albedo of each square for every month they had data.

Their headline figure of five days is an average: in fact the pattern of freeze and thaw in the Arctic varies. In one region the melt season has been extended by 13 days, in another the melt season is actually getting shorter.

Energy increases

This increasing exposure to summer sunlight means that ever greater quantities of energy are being absorbed: several times the energy of the atomic bomb dropped on Hiroshima hits every square kilometer of the open Arctic Ocean.

“The extent of sea ice in the Arctic has been declining for the last four decades,” said Professor Stroeve, “and the timing of when melt begins and ends has a large impact on the amount of ice lost each summer.

With the Arctic region becoming more accessible for longer periods of time, there is a growing need for improved prediction of when the ice retreats and reforms in the water.” - 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

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

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

Bears pay price of Arctic ice melt

November 7, 2013 in Arctic, Marine ecology, Polar ice, Predation, Wildlife

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By Tim Radford

The Arctic lost less sea ice this year than last, and that is good news for many polar bears, if not for their preferred prey, the ringed seals.

LONDON, 7 November – Churchill, Manitoba is about to lose its star performers, but paradoxically nobody will be sorry to see them go. And, even more paradoxically, the whole world can now watch them, courtesy of a set of web cameras set up by the media organisation Explore [Live cam footage courtesy of explore.org, Polar Bears International and Frontiers North Adventures].

The story is a simple one: somewhere between 900 and 1,000 polar bears make up the Western Hudson Bay population of Ursus maritimus, the Arctic’s top terrestrial predator, and many of them will have not eaten properly for eight months. Polar bears will if there is no choice forage for goose eggs, berries, carrion and town rubbish, which is why so many gather near Churchill, Manitoba while waiting for the seas to freeze.

The polar bear is adapted to the Arctic ice as perfectly as the African lion is at home on the savannah. But as the Arctic summers lengthen, and the ice dwindles, the southernmost polar bear population is under threat.

Only as Hudson Bay ices over will the Churchill bears be able to hunt their favoured prey, the ringed seal, Phoca hispida, an energy source so rich that – when the hunting is good – polar bears will eat only the blubber, and leave the rest for other Arctic carnivores and scavengers.

Precarious foothold: More ice, more bears Image: Agrant141 via Wikimedia Commons

Precarious foothold: More ice, more bears
Image: Agrant141 via Wikimedia Commons

The polar bear needs at least two kilograms of seal blubber a day; a hungry polar bear has enough room in its stomach for up to a fifth of its bodyweight. A kilo of seal blubber could deliver up to 5,000 kilocalories which means a 500 kg bear could in theory gorge on up to 500,000 kilocalories a day, in a voracious bid to build up enough fat to see it through the next cycle of spring births and summer fasting.

But to gorge, the bears must get to the ice. During the summer of 2012, Arctic ice contracted to its lowest ever recorded level. If the pattern of summer ice loss continues, the bears could be in trouble.

Fewer cubs survive

Pregnant female bears generally enter their dens in November or December and then emerge with their cubs in April or May, having eaten nothing for four or five months, only to be forced off the ice in July. “So by the time they head out to the ice again, they’ve been without food for up to eight months,” says Barbara Nielsen of Polar Bears International, which declared Polar Bear Week, beginning on 4 November.

“The longer ice free periods are really hard on mothers with cubs and scientists are seeing a drop in cub survival rates as a result.” Some of the population have been fitted with radio collars and tracked by satellite: the first tracked bear came ashore on 4 July of this year, a month earlier than was normal 30 years ago.

Polar bears are powerful swimmers, and have been tracked swimming for huge distances; on land they can move at speed, but not for long, because they overheat. So their best hope of a full meal is on the ice, used by ringed seals as a nursery every spring.

Although summer ice loss in 2013 was much less dramatic than in 2012, Arctic ice has been retreating at an accelerating rate for the last 30 years.  Conservationists and zoologists have repeatedly warned that the polar bear population of Hudson Bay is at risk. So the people of Churchill will be happy to see them go, because the sooner they go, the more likely it is that many of them will be back. – Climate News Network

Arctic is warmer than in 40,000 years

October 24, 2013 in Arctic, Climate, Permafrost, Polar ice, Science, Warming

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Gifford MIller collecting the now-exposed tundra plants on Baffin Island, Canada. These climate clocks suggest unprecented warmth in the Arctic Image: Gifford Miller via AGU

The now-exposed tundra plants on Baffin Island, Canada suggest exceptional warmth in the Arctic
Image: Gifford Miller via AGU

By Tim Radford

Average summer temperatures in the Canadian Arctic are now at the highest they’ve been for approaching 50,000 years, new evidence suggests.

LONDON, 24 October - Good news for Arctic mosses, if not for any other Arctic creatures: little tundra plants that have been buried under the Canadian ice can feel the sunlight for the first time in at least 44,000 years.

The implication is that the Arctic is now, and has been for the last 100 years, warmer than at any time in the last 44,000 years and perhaps for the last 120,000 years.

This also means that the Arctic is warmer now than it was in what geologists call the early Holocene, the end of the last Ice Age – when the peak summer sunlight was roughly nine per cent greater than it is today, according to Gifford Miller of the University of Colorado Boulder, in the US.

The mosses studied by Dr Miller, of course, could feel nothing: they were dead. But they could tell a story, all the same.

The Arctic ice cap has been in constant retreat for the last century, and glaciers almost everywhere have been melting: there are fears that the process has begun to accelerate as greenhouse gases concentrate in the atmosphere.

But as the ice recedes, it exposes evidence of the past, preserved over the millennia in the natural deep freeze.

Creating a timeline of climate change

The researchers used a technique called radiocarbon dating to establish that the mosses had been screened from the elements for at least 44,000 to 51,000 years. Since radiocarbon dating is only accurate for about 50,000 years, the mosses could have been buried for perhaps 120,000 years, since the last “interglacial” when the polar regions experienced a natural thaw.

Miller and colleagues report in Geophysical Research Letters that they did their fieldwork on Baffin Island in the Arctic Circle, and measured the radiocarbon ages of the dead mosses in at least four different locations.

They were careful to pick their 145 samples within one metre of the receding ice cap. Since the ice is receding at two or three metres a year, they could be sure the plant tissues had just been exposed that season.

Since the plants could only have taken root in sunlight, they were evidence that the exposed terrain was once free of ice. They became silent witnesses, telling researchers about the changes through time in the frozen North.

“The key piece here is just how unprecedented the warming of Arctic Canada is. This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere,” said Miller.

Recent decades critical

Since radiocarbon clocks can only tick for so long, the Colorado team used ice cores to provide clues to the climate history of Baffin Island: each winter’s snowfall and summer melt is preserved in the icepack and like the growth rings in a tree provides a calendar of annual change.

The last time temperatures on Baffin Island were as high as today was about 120,000 years ago. About 5,000 years ago, after a mellow period in the early Holocene, the Arctic began to cool again, and stayed cool until the beginning of the last century.

“Although the Arctic has been warming since about 1900, the most significant warming in the region didn’t really start until the 1970s,” said Dr Miller.

“And it really is in the last 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to disappear, even if there is no additional warming.” - Climate News Network

Poles apart: sea ice melts – and grows

October 4, 2013 in Antarctic, Arctic, Polar ice, Science, Warming

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Ice on the Bellingshausen Sea in Antarctica: It's growing - but why? Image: NASA/Michael Studinger via Wikimedia Commons

Ice on the Bellingshausen Sea in Antarctica: It’s growing – but why?
Image: NASA/Michael Studinger via Wikimedia Commons

By Alex Kirby

While climate change is clearly strongly affecting Arctic sea ice, scientists are uncertain what links the rise in global temperatures and the continuing small increase in the Antarctic ice sheet.

LONDON, 4 October – It’s one of the most closely-watched questions in climate science: how fast is the Arctic sea ice melting?

The definitive answer is that it is still melting rapidly, though not quite as fast it did in 2012, when the extent of the ice sheet was lower than ever recorded.

At the other end of the world, though, the Antarctic ice sheet has continued to grow, reaching a new record extent. Some experts believe this is the result not of cooling but of stronger polar winds pushing the ice further outward from the pole.

Others have suggested that increased fresh water from summer icecap melting means the sea ice can form at a higher temperature in winter since the salt water is diluted.

The details are published by the US National Snow and Ice Data Center (NSIDC), based at the University of Colorado Boulder, in Arctic Sea Ice News and Analysis.

This September, sea ice covering the Arctic Ocean fell to its sixth lowest extent in the satellite record, which dates from 1979. All of the seven lowest extents have occurred in the last seven years. The NSIDC says cooler conditions in the Arctic this summer helped to retain more sea ice.

Satellite data analysed by NSIDC scientists shows the sea ice cover at its lowest extent on 13 September. Averaging the extent for the whole of September also showed it to be the sixth lowest in the satellite record.

Julienne Stroeve, an NSIDC scientist, says: “A relatively cool and stormy summer helped slow ice loss compared to the last few summers. This summer’s extent highlights the complex interaction between natural climate variability and long-term thinning of the ice cover.”

Mark Serreze, the director of the NSIDC, said: “For Earth’s ice and snow cover taken as a whole, this year has been a bit of a bright spot within a long-term sobering trend.”

Thinning ice

But the Arctic sea ice continues to be thinner than in past years, as confirmed both by direct satellite observations and estimates of ice age, and so it is more vulnerable to breakup by storms, circulating currents and thawing.

“While Earth’s cryosphere, its snow and ice cover, got a shot of hope this year, it’s likely to be only a short-term boost,” Serreze said.

The NSIDC says that although most of the ice cover now consists of young, thin ice, a pack of multi-year ice (ice that has survived more than one melt season and is thicker than first-year ice) remains in the central Arctic.

At its lowest point this year on 13 September sea ice extent dropped to 5.10 million square kilometers (1.97 million square miles). September ice extent was 1.17 million sq km (452,000 sq m) below the 1981 to 2010 average.

This summer’s low ice extent continues the downward trend seen since 1979, with September sea ice extent declining by 13.7% per decade. Summer sea ice extent is important because, among other things, it reflects sunlight, keeping the Arctic region cool and tempering global climate.

As well as declining in extent the ice cover has grown thinner and less resistant to summer melt. Recent data on the age of sea ice, which scientists use to estimate the thickness of the ice cover, shows that the youngest, thinnest ice, which has survived only one or two melt seasons, now makes up most of the cover.

But in the Antarctic the sea ice has reached record high levels – a Southern Hemisphere winter maximum extent of 19.47 million sq kms (7.52 million sq m) on 22 September. The September monthly average was also a record high, at 19.77 million sq kms (7.63 million sq m), slightly higher than last year’s previous record.

Antarctic September sea ice has been increasing at 1.1% a decade relative to the 1981 to 2010 average. “The tiny gain in Antarctica’s ice is an interesting puzzle for scientists,” said NSIDC lead scientist Ted Scambos. “The rapid loss of ice in the Arctic should be ringing alarm bells for everyone.” – Climate News Network