Google Analytics Alternative

You are browsing the archive for Antarctic.

Whale dumps temper Antarctic warmth

March 25, 2014 in Antarctic, Carbon, Deep Ocean, Global Ocean Commission, Marine ecology, Whales


Whales play a key part in recycling iron and carbon in the Antarctic Image: US National Oceanic & Atmospheric Administration

Whales play a key part in recycling iron and carbon in the Antarctic
Image: US National Oceanic & Atmospheric Administration

By Alex Kirby

By enriching the seas with iron expelled from their digestive systems, sperm whales are helping to slow the warming of the Antarctic, scientists say.

LONDON, 25 March – There is plenty yet to learn about the causes and effects of climate change, and here is one fact you may perhaps not have known until now: defecating sperm whales are helping to slow the warming of the Southern Ocean.

A team of Australian scientists and colleagues based at Flinders University in Adelaide reported in Proceedings of the Royal Society B (in 2010) that the whales help to increase levels of iron in Antarctic waters (which are iron-deficient).

Iron is important for marine life, and the polar oceans are important for helping to regulate atmospheric CO2 levels. So the whales’ personal hygiene is helping vastly smaller lifeforms to thrive, which in turn keeps the ocean ecosystem in balance and able to recycle carbon safely to the seabed.

Scientists had believed that the whales’ breathing decreased the efficiency of the Southern Ocean’s biological pump by returning carbon from the depths to the surface and thence to the atmosphere, where it would add to the greenhouse gases already there.

But the Flinders team says that by consuming prey in deep water (the whales search for squid  at 1,200 metres or even further down) and then releasing iron-rich liquid faeces into the sunlit zone near the surface, the whales instead stimulate new primary production and return the carbon to deep water.

Damaged by whaling

“Primary production” is the scientific term used to describe the minute forms of life produced by the effect of light in the presence of nutrients and – crucially – iron.

The researchers say Southern Ocean sperm whales stimulate the return of 40,000 tonnes of carbon annually to the deep ocean but breathe out only half that amount. So by stimulating new primary production, the 12,000 Antarctic whales act as a carbon sink, removing twice as much carbon from the atmosphere as they add by their breathing.

The team adds that the ability of the Southern Ocean to act as a carbon sink has been diminished by the large-scale killing of sperm whales during the era of industrial whaling, which reduced the global populations of many whale species to a fraction of their historic levels.

The researchers say the killing of the whales, by decreasing iron inputs to the surface zone, has had a serious impact. “This nutrient loss has undoubtedly altered the dynamics and food-web structure of these environments and this has decreased carbon export to the deep ocean”, they conclude.

Not unique

News of the researchers’ conclusions, which have so far gone largely unreported, was given to journalists covering a recent meeting in Hong Kong of the Global Ocean Commission by Professor Alex Rogers, of the Department of Zoology at the University of Oxford, UK.

Goodbye to all that? Whaling - still continuing in the Antarctic - disrupts the carbon recycling Image: Courtesy of the International Whaling Commission

Goodbye to all that? Whaling – still continuing in the Antarctic – damages the recycling process
Image: Courtesy of the International Whaling Commission

Asked by the Climate News Network whether the findings might apply to other whale species in other oceans, he said: “Not for iron, as the Southern Ocean is a high-nutrient low-chlorophyll area and thus primary production in this region is specifically limited by iron. In most other parts of the ocean it is limited by nitrates.”

But a similar paper had shown that before industrial whaling began whales had been the primary source of nitrates through the same process in Chesapeake Bay, on the US Atlantic coast. So fertilisation through defecation was likely to be a common mechanism, although different constituents of the faeces were important, and in the Antarctic krill might also be important in iron release.

Professor Rogers said whales made other useful contributions to human welfare. Taken together, the toothed whales – a group including sperm whales, belugas and narwhals – were thought to contribute 0.5-1.0% of all the energy needed  for ocean mixing. – Climate News Network

Cold and warm polar water mixing slows

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


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

Penguins feel climate change’s impacts

February 1, 2014 in Antarctic, Climate, Extreme weather, Marine ecology, Rainfall, South America, Weather, Wildlife


Adélie penguin chicks chase an adult in the hope of finding food Image: Liam Quinn from Canada via Wikimedia Commons

Adélie penguin chicks chase an adult in the hope of finding food
Image: Liam Quinn from Canada via Wikimedia Commons

By Tim Radford

Scientists have identified climate change as the direct cause of rising mortality among penguin chicks hatched in Argentina.

LONDON, 1 February – Climate change is bad for penguin chicks. If rain doesn’t soak their feathers and kill them with cold, then extremes of heat could finish them off with hyperthermia.

Over a 27-year research project in the world’s largest colony of Magellanic penguins, on the arid Argentine coast, researchers have seen a greater number of deaths directly attributable to climate change.

“We’re going to see years where almost no chicks survive if climate change makes storms bigger and more frequent during vulnerable times of the breeding season”, says Ginger Rebstock, who, with Dee Boersma, reports on the state of penguin survival in the Public Library of Science journal PLOS One.

The two scientists, biologists from the University of Washington, Seattle in the US, believe starvation and weather are going to make life harder for the offspring of the 200,000 pairs of penguins that breed each year at Punta Tombo, on Argentina’s Atlantic coast.

The number of storms during the first two weeks of December – when all the chicks are less than 25 days old and their downy coats are not yet waterproof – has increased between 1983 and 2010.

Every new chick is at hazard: over the span of study, the researchers calculate that 65% of chicks do not survive, 40% of them die by starvation. But climate change has begun to offer new dangers.

A Magellanic chick, still too young to have an adult's waterproofing, in the rain Image: D Boersma/University of Washington

A Magellanic chick, still too young to have an adult’s waterproofing, in the rain
Image: D Boersma/University of Washington

Some years up to half of all chicks die because of the weather. Punta Tombo is historically an arid region. In the last 50 years, the scientists report, rainfall has increased. The number of wet days has increased, the number of consecutive wet days has increased and the level of rainfall during those days has continued to increase.

Air temperatures changed too. The minimum temperatures decreased by up to 3°C and the number of these colder days increased. Storms, too, make it more difficult for foraging parents to gather enough food to feed their chicks.

Sea ice changes

“Starving chicks are more likely to die in a storm”, says Prof Boersma. “There may not be much we can do to mitigate climate change, but steps could be taken to make sure the Earth’s largest colony of Magellanic penguins have enough to eat by creating a marine protected reserve, with regulations on fishing, where penguins forage while raising small chicks.”

Further south, extreme weather is beginning to make life difficult for the Adélie penguins of Ross Island in Antarctica. Amélie Lescroël from the CNRS in France and colleagues report in the same edition of PLOS One that abnormal sea ice conditions reduce access to food.

Antarctic penguins are of course adapted to sea ice: it is their preferred habitat. But they must respond to short and long term changes in ice levels. For 13 years, scientists have monitored the feeding success of the Ross Island colony and observed that the birds could cope in those seasons when there was less sea ice.

But climate change in Antarctica, too, creates new problems for the birds and limits their foraging efficiency.

“Our work shows that Adélie penguins could cope with less sea ice around their summer breeding grounds”, said Dr Lescroël. “However, we also showed that extreme environmental events, such as the calving of giant icebergs, can dramatically modify the relationship between Adélie penguins and sea ice.”

If the frequency of such extreme events increases, then it will become hard to predict how penguin populations will get by, she thinks. – Climate News Network

Atlantic changes are warming Antarctic

January 31, 2014 in Antarctic, Atlantic, Atlantic Multidecadal Oscillation, Climate, El Niño, Ice Loss, Ocean Warming


Ice covering the Bellingshausen Sea in Antarctica - and feeling the impact of changes in the Atlantic Image: NASA/Michael Studinger via Wikimedia Commons

Ice covering the Bellingshausen Sea in Antarctica – and feeling the impact of changes in the Atlantic
Image: NASA/Michael Studinger via Wikimedia Commons

By Tim Radford

More evidence has emerged that changing climate in one region can have unpredictable effects many thousands of miles away.

LONDON, 31 January – The Antarctic Peninsula is now the strongest-warming region on the planet. Blame that on changes in the faraway North and tropical Atlantic Ocean.

Xichen Li of New York University in the US and colleagues matched sea surface temperature variations in the northern Atlantic over a three-decade period against long-term changes in the Antarctic. They found a clear correlation, they report in Nature.

They also observed that warming Atlantic waters were followed by changes in sea level pressure in the Antarctic’s Amundsen Sea, and these changes also preceded changes in sea ice between the Ross and Amundsen-Bellinghausen-Weddell Sea. Both stretches of water lie many thousands of miles south of the Atlantic.

Correlations are not causes, so the authors then followed up their observational data by experiments with computer models of the global atmosphere. When they simulated a warming of the North Atlantic, the model “changed” the climate in Antarctica.

That Pacific Ocean temperatures can affect Antarctica is no surprise: such things have been linked to the El Niño cycle, a periodic natural pulse of heat in the equatorial Pacific.

Icy paradox

But until this study, no-one had thought to link Antarctica with long-term changes in the North Atlantic,and  in particular, a climatic phenomenon known as the Atlantic multidecadal oscillation, a cycle of natural warming and cooling that can last for 20 to 40 years.

“Our findings reveal a previously unknown – and surprising – force behind climate change that is occurring deep in our southern hemisphere: the Atlantic Ocean”, says Li. “Moreover, the study offers further confirmation that warming in one region can have far-reaching effects in another.”

The Antarctic presents a paradox: the sea ice in the Arctic is declining rapidly; but conditions in the Antarctic don’t seem to have been changing at the same rate or in the same pattern. Concentrations of ice have changed but there seems to be as much sea ice or more, overall.

David Holland of New York University, a co-author, says: “From this study, we are learning just how Antarctic sea ice redistributes itself, and also finding that the underlying mechanisms controlling sea ice are completely distinct from those in the Arctic.” – Climate News Network

Some lose, some win in warming world

December 25, 2013 in Adaptation, Antarctic, Vegetation changes, Wildlife


The Alpine ibex will be a clear winner, its horns growing in the warmer weather Image: User:Nino Barbieri via Wikimedia Commons

The Alpine ibex will be a clear winner, its horns growing in the warmer weather
Image: User:Nino Barbieri via Wikimedia Commons

By Tim Radford

Not all species will be damaged by climate change. Recent research has identified some of those who will benefit from a warmer world, as well as some of the losers.

LONDON, 25 December – And now for the good news: climate change could actually make life better for some creatures. The ibex in the Swiss Alps may find an extra spring in its step. The roly-poly pika of the American northwest might find it has gained an edge over its predators because it is adapted to a high fibre diet.

The news is not uniformly good: climate change is already taking its toll of Arctic peregrine falcons and chinstrap penguins on the Antarctic peninsula. But change is not always for the worse.

A team of scientists led by the Swiss Federal Institute of Forest, Snow and Landscape Research reports in Ecology Letters that they used dendrochronological techniques (the scientific method of dating based on the analysis of patterns of tree rings) to monitor the response of the mammal Capra ibex to patterns of climate change.

Climate scientists have been using these growth rings in tree trunks to read evidence of seasonal and annual change; the growth rings in the large, curved horns of the male Alpine ibex or wild goat would also tell a story.

They analysed more than 42,000 increments of horn growth from more than 8,000 male ibex, collected since 1964, in annual culls and hunting programmes regulated by the Swiss government. The ibex is a protected species, so careful records are kept of each kill.

Warmer weather, longer horns

To make sense of the data, the researchers had to allow for the age of the animal at death, and the year of its death. But a pattern began to emerge: horn growth is affected by changes in European springtime temperatures.

Warmer temperatures between March and May mean an earlier snowmelt and more and tastier alpine grasses and herbs for the ibex – and thus better vitality.

Such research was intended primarily to check on the health of the ibex population: the creature was once hunted almost to extinction.

The roly-poly pika of Oregon state is a little lagomorph – a member of the rabbit family – that tends to live in rockslides near sea level. In hot weather, most animals would be forced to leave the shade and shelter to go in search of food – and become easy prey for weasels or hawks or death from overheating.

The moss-eating, fibre-loving roly-poly pika has a bright future Image: Courtesy of Mallory Lambert, University of Utah

The moss-eating, fibre-loving roly-poly pika has a bright future
Image: Courtesy of Mallory Lambert, University of Utah

But the roly-poly pika has, according to a new study in the Journal of Mammalogy, one thing in its favour: it can flourish on a diet of moss. “Mosses are 80% fibre. It’s a bit like eating paper”, says the research author Jo Varner. “By consuming mosses that grow on the rockslides where they live, the pikas are released from foraging outside the safety and shady heat buffer of the rocks.

“Few herbivores consume moss because it’s so nutritionally deficient. The pikas in our study set a new record for moss in a mammal’s diet: 60%”.

Successful adjustment

The pika is sensitive to heat: the animal is almost spherical, with a thick fur coat and a high metabolic rate which should make it peculiarly at risk from global warming – either it moves higher up the mountain with each rise in temperature, or it dies. The Oregon state pikas seem to have adjusted to change by staying on the warmer, wetter slopes and adapting their diet.

Chinstrap penguins of the Antarctic peninsula, however, have been conspicuous victims of a warming world, according to US researchers who have been tracking population changes.

The Antarctic peninsula has warmed by 3°C in summer and 5°C in winter in the last 60 years. The researchers had started with the hypothesis that tourism – on the increase in the region – might be affecting penguin populations: however, they found that even at sites that experienced little or no tourism, there had been declines of as much as 50% in the population.

A study of Arctic peregrines in Canada, however, found an unequivocal connection between declines in falcon numbers and global warming. A team monitored nestboxes near Hudson Bay, and found that more than one third of peregrine chick deaths were caused by rain, linked to warmer summer temperatures.

“The nestlings died from hypothermia and in some cases from drowning in their flooded nests. Without constant parental care, they are most vulnerable to cold and wet conditions in the first three weeks of life”, said the research author, Alistair Franke of the University of Alberta. – Climate News Network

Researchers study shellfish success

December 24, 2013 in Adaptation, Antarctic, Europe, Fish, Marine ecology, Ocean acidification


Scottish musel beds: The European research will be globally relevant Image: Copyright and courtesy of SAMS

Scottish mussel beds: The European research will be globally relevant
Image: Copyright and courtesy of SAMS

By Alex Kirby

The British Antarctic Survey is leading a research programme aimed at helping the European fishing industry and monitoring the effects of climate change on several shellfish species.

LONDON, 24 December – If you like the occasional plate of grilled scallops or fancy an oyster now and then, read on and ponder. The health of several species of European shellfish is under threat.

The bad news is that the shellfish face an uncertain future as the oceans become warmer and more acidic because of the changing climate. But there is some better news too: the European Union is funding an international research team to work out how these changes will affect several species vital to the European fishing economy and to marine biodiversity.

Scientists do not fully understand how shellfish like oysters, mussels, scallops and clams produce their shells, or how a change in environment will affect their populations. To address this the EU is funding a €3.6 million (£3 m) programme called CACHE (Calcium in a Changing Environment). Shellfish are an important part of the European marine economy which provides an estimated 5.4 million jobs.

Coordinated from the British Antarctic Survey (BAS) in Cambridge, UK, the programme will research how the animals produce their shells. The scientists will also try to identify populations which are resilient to climate change.

These relatively small animals are important as part of the wider pattern of marine biodiversity. And, as they make their shells from calcium carbonate, they also help to absorb the greenhouse gas CO2 from seawater.

Biotech applications

The risk to them comes from their dependence on calcium carbonate – a substance which dissolves under acidic conditions.  As the oceans become warmer and more acidic their shells will either thin, or the animals will have to expend more energy on producing thicker shells.  This will affect their population sizes and the quality of their flesh, directly affecting fisheries and consumers.

How shellfish produce their shells also matters to the biotech industry, which is interested in imitating (in a process known as bio-mimicry) the way in which shellfish take a soluble compound like calcium to make solid, robust structures.

A better understanding of this could reduce the carbon footprint of producing construction materials and create the potential for “fixing” CO2 into the building process.

The species the research team is looking at are the king scallop, the Pacific oyster, the blue mussel and the soft shell clam. It will also study the native oyster to help conservation plans, as it is listed as a priority species in the UK.

Iceberg protection

Dr Melody Clark of BAS, the programme coordinator, told the Climate News Network: “The programme is driven by the science. We really don’t know the fundamentals of how shellfish respond to changing environments.

“We do know that, in response to environmental conditions, they can change how much shell they produce, for example growing thicker shells in response to predators. In the Antarctic, inter-tidal limpets grow much thicker shells than sub-tidal ones, because they are bashed by icebergs.

“And we don’t know just how they make their shells, whether with calcium from their food, or from the seawater.

“On bio-mimicry, this research may let us start to develop ways of producing more robust structures without carbon, and with little energy.

“We’re researching shellfish in European waters, but we’re recruiting the researchers worldwide, and the results will be relevant beyond Europe.” – Climate News Network

West Antarctic ice loss speeds up

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


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

Antarctic fjord life puzzles science

December 14, 2013 in Antarctic, Marine ecology, Ocean Warming


Giant bristle worm from Andvord Bay, Antarctica, a fjord hotspot for biodiversity Image: Craig Smith. University of Hawaii at Mānoa

Giant bristle worm from Andvord Bay, Antarctica, a fjord hotspot for biodiversity
Image: Craig Smith. University of Hawaii at Mānoa

By Tim Radford

To the surprise of researchers, the warming waters of the fjords of the Antarctic Peninsula have an abundant and diverse population of marine life.

LONDON, 14 December – Arctic fjords are poor places, low in marine life and muddied by glacial meltwater. In the southern ocean, where everything is upside down, it’s a different story. Scientists from the University of Hawaii report that they found unexpected riches deep in the fjords of the Antarctic Peninsula.

The Peninsula is one of the fastest-warming places on the planet. On land, researchers have used 150 years of moss growth as a kind of archive of change, and recorded a warming of 0.56°C per decade since the 1960s.

But researchers who photographed the sea floor found an abundance of bristle worms, sea spiders, sea cucumbers, crustaceans, jellyfish and of krill, they report in the journal PLOS One.

This is precisely what they had not expected: on the evidence of the rapidly-warming Arctic waters, these Peninsula fjords should have been much less lively.

“There appears to be something special about these fjords that stimulates sea floor productivity”, says Laura Grange, of the UK National Oceanography Centre at the University of Southampton, who collaborated in the study.

Change on the way?

“Seafloor ecosystems at the bottom of fjords rely on detritus for food, so these Antarctic fjords must be getting some sort of enhanced food input, most likely from phytoplankton blooms, micro-algal debris or even from krill – their moulted carapaces or the dead bodies that sink to the bottom.”

Humpback whales forage in those waters, and their excrement, too, may fertilise life at the sea bottom. But although the fjords are rich in life, they may not stay that way.

The Antarctic Peninsula warming is at a much earlier stage than the Arctic warming, and so far the fjords show little disturbance from glacial melting. Icebergs drift out so sea without dropping much sediment, which keeps the waters clear, and permits phytoplankton and algae to bloom. As the climate warms, these conditions could change.

“The extraordinary ecosystems, which provide habitat and foraging areas for krill and baleen whales and are hotspots of seafloor diversity, are very likely to be negatively impacted by the very rapid warming occurring along the Antarctic Peninsula”, says Craig Smith of the University of Hawaii Mānoa. The guess is that such marine communities play an important role in providing food for fish, penguins and whales.

“We urgently need to develop a better understanding of the structure, function and climate sensitivity of these fascinating and imperilled seafloor communities.” – Climate News Network

Poles apart: sea ice melts – and grows

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


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

Ocean warming narrows climate options

September 28, 2013 in Antarctic, Arctic, Climate, Global Ocean Commission, Greenland, Marine ecology, Ocean acidification, Polar ice, Sea level rise


Sunrise at Southwold in eastern England: What is happening in the deep oceans? Image: Brenda and Ken Bent via Wikimedia Commons

Sunrise at Southwold in eastern England: What is happening in the deep oceans?
Image: Brenda and Ken Bent via Wikimedia Commons

Professor Chris Rapley is a former director of both the British Antarctic Survey and  the Science Museum in London. What the IPCC’s Fifth Assessment Report, AR5, says about the oceans alarms him.

LONDON, 28 September – The messages are ever clearer: climate change is real, we humans are the driver, and we need to act resolutely and soon to reduce the risk of serious disruption.

The IPCC’s latest report took over 250 experts from 39 countries to sift 9,000 pieces of scientific research and address over 54,000 comments under the close scrutiny of 190 governments. The result: a fresher and sharper image of the physical state of our planet and the changes it is undergoing.

It confirms that each of the most recent three decades has been warmer than its predecessor and that the change – almost 1°C since the beginning of the last century – is significant on a timescale of ten thousand years.

In the context of an unabated planetary energy imbalance, and evidence that the 93% of the energy build-up taken up by the oceans continues to accumulate, the recent slow-down in the rise of surface temperatures, much heralded by the climate dismissers, appears a minor and temporary fluctuation.

In the meantime, the melting and retreat of polar ice shocks experts such as myself – with the loss of ice from Greenland and Antarctica both having increased by a factor of 5-6 over the decades 1990-1999 and 2000-2009.

“…we are fast losing the possibility of restricting warming to 2°C.”

The consequence? In combination with ocean thermal expansion, an accelerating rise in global mean sea level, currently running at 35 cm per century. This is already approaching one third of the rate sustained for 10,000 years during the transition from the last Ice Age to the current warm period, when sea level rose by 120 metres.

The predictions? That we are fast losing the possibility of restricting warming to 2°C. We have at most half a trillion tons of carbon left that can be burned, after which we will be committed to temperature rises outside those experienced by the planet for hundreds of thousands of years.

The scientists have done their job; now is the time for politicians to take a lead, and everyone to act.

Professor Chris Rapley CBE
Department of Earth Sciences
University College London


Note: The Global Ocean Commission says the IPCC report “shows that the ocean is shielding humanity from climate change impacts at significant cost to its own health”. Specifically, AR5 says:

- the upper part of the ocean is warming by about 0.1°C per decade
– the deep ocean is warming too, and will continue to do so for centuries even if emissions are curbed immediately
– sea levels are rising, currents are changing, the rapid shrinking of Arctic sea ice is freshening water around the region, and concentrations of dissolved oxygen are declining
– acidification will make up to half of the Arctic ocean uninhabitable for shelled animals by 2050.Climate News Network