Category Archives: Ocean Warming

Pre-history proof of climate’s see-saw sensitivity

The woolly rhinoceros once roamed wild on the plains of Europe Image: Public Library of Science via Wikimedia Commons
The woolly rhinoceros once roamed wild on the plains of Europe
Image: Public Library of Science via Wikimedia Commons

By Tim Radford

Computer simulations reaching back deep into the last Ice Age have enabled scientists to put a historic perspective on how even small variations in the climate system can lead to dramatic temperature change.

LONDON, 24 August, 2014 − It doesn’t take much to change a planet’s climate – just a little shift in the Northern hemisphere glacial ice sheet and a bit more carbon dioxide in the atmosphere. After that, the response is rapid. The tropical rain belt moves north and the southern hemisphere cools a bit, in some sort of bipolar see-saw response.

Sound familiar? It does, and it doesn’t. It all happened long before the internal combustion engine, or even the new Stone Age.

Researchers from the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research, Bremerhaven, the University of Bremen, Germany, and the University of Cardiff in the UK, report in Nature journal that they have made climate simulations that agree with observations of historical climate change that date back 800,000 years.

Long before the present alarms about global warming through the emission of carbon dioxide from fossil fuels, climate researchers were puzzled by the phenomenon of the Ice Ages and the “interglacials” that punctuated those long periods when the Arctic ice extended from the North Pole to the Atlantic coast of France, and over huge tracts of North America.

Vanished species

Mysteriously, and at great speed, the temperatures would rise by up to 10°C and the vast walls of ice would retreat. Lion, hyena and rhinoceros would invade the wild plains of what is now southern England, and now-vanished species of humans would hunt big game and gather fruit and seeds in the valleys and forests of Europe and America.

Since the end 10,000 years ago of the last ice age – itself a very rapid event – was the springboard for agriculture and civilisation, and eventually an Industrial Revolution based on fossil fuels, the story of climate change plays a powerful role in human history.

So any analysis of the tiny shifts in ice cover that seemed to trigger these dramatic, bygone events can be helpful in understanding the long story of the making of the modern world.

The researchers found a tentative scenario involving weak ocean currents, and prevailing winds that shifted the sea ice and allowed the oceans and atmosphere to exchange heat, pushing warmer water into the north-east Atlantic.

These changes precipitated a dramatic warming of the northern hemisphere in just a few decades, and the retreat of the glaciers for an extended period before the ice returned to claim much of the landmass again. But, overall, such changes tended to occur when sea levels reached a certain height.

“The rapid climate changes known in the scientific world as Dansgaard-Oeschger events were limited to a period of time from 110,000 to 23,000 years before the present,” said Xu Zhang, the report’s lead author.

“The abrupt climate changes did not take place at the extreme low sea levels, corresponding to the time of maximum glaciations 20,000 years ago, or at high sea levels such as those prevailing today. They occurred during periods of intermediate ice volume and intermediate sea levels”

Climate swings

Co-author Gerrit Lohmann, who leads the Wegener Institute’s palaeoclimate dynamics group, said: “Using the simulations performed with our climate model, we were able to demonstrate that the climate system can respond to small changes with abrupt climate swings.

“At medium sea levels, powerful forces − such as the dramatic acceleration of polar ice cap melting − are not necessary to result in abrupt climate shifts and associated drastic temperature changes.”

How much this tells anybody about modern climate change is open to debate. Right now, according to this line of evidence, the planet’s climate could be in one of its more stable phases of the Earth’s history.

But while the conditions for the kind of rapid change recorded in pre-history do not exist today, Prof Lohmann warns that “sudden climate changes cannot be excluded in the future”. – Climate News Network

Atlantic depths may hold key to heat hiatus

A jellyfish floats just above the seafloor of the deep Atlantic Image: NOAA/OAR/OER via Wikimedia Commons
A jellyfish floats just above the seafloor of the deep Atlantic Ocean
Image: NOAA/OAR/OER via Wikimedia Commons

By Tim Radford

Researchers analysing millions of oceanographic measurements believe they may finally have got to the bottom of the conundrum about why there is a slowdown in global warming despite greenhouse gas emissions rising.

LONDON, 22 August, 2014 − For years, researchers have puzzled over the temperature rises that haven’t happened – but scientists in China and the US believe they have cracked the mystery of the missing heat.

While calculations indicate that global average temperatures should be rising predictably, the planetary thermometers tell a different story.

But now Xianyao Chen, an oceanographer at the Ocean University of China in Qingdao, and Ka-Kit Tung, an atmospheric scientist at the University of Washington in Seattle, report in Science journal that they think they know where the notional extra heat has gone. It is at the bottom of the Atlantic Ocean.

And this time their conclusion isn’t based only on mathematical models and computer simulations. In their research − funded by the US National Science Foundation and the National Natural Science Foundation of China – they analysed millions of measurements of temperature and salinity taken by oceanographic instruments since 1970, and tracked the pathways that the heat must have taken since the beginning of the 21st century.

High temperatures

But first, a restatement of the conundrum. For more than a century, climate scientists have known that higher levels of carbon dioxide in the atmosphere mean higher atmospheric temperatures. For more than 30 years, every investigation has confirmed this link. And for the last 30 years of the 20th century, as greenhouse gas emissions increased, so did average temperatures.

This rise has continued, with 13 of the 14 warmest years ever recorded all falling in the 21st century, but the rate of increase unexpectedly slowed.

Researchers had expected that there would be some sort of heat hiatus, but not during the first years of the century, and they have been scratching their heads and examining the data again.

Some think that the measurements may be incomplete, or that natural cycles, such as the Pacific cooling event called La Niña, may be at play. Some have suggested that the pattern of trade winds may have a role in taking the warmth into the deep ocean, and some have suspected all along that the heat could be found far below the oceanic surface.

In the same week as the publication in Science, Reto  Knutti, a climate physicist at the federal technology institute ETH Zurich, and his colleague, Markus Huber, reported in Nature Geoscience that the apparent slowdown could be attributed to a cocktail of causes: a longer period of weaker solar irradiance – the sun has its own cycles of intensity − and to the cycle of El Niño and La Niña weather phenomena in the Pacific, and also to incompletely measured data.

“Many of the earlier papers had focused on
symptoms at the surface of the Earth”

But the Science report authors think they have an in-depth solution. “Every week, there’s a new explanation of the hiatus,” said Ka-Kit Tung. “Many of the earlier papers had focused on symptoms at the surface of the Earth, where we see many different and related phenomena. We looked at observations in the ocean to try to find an underlying cause.”

The oceans cover 70% of the planet, and are capable of storing 90% of the planet’s heat content. So the two Science report authors argue that a sudden shift in ocean salinity that corresponded with the slowdown of global warming could have triggered the movement of the heat to much deeper waters.

Saltier water is denser, sinks faster, and takes surface heat with it. As the two scientists see it, the depths of the North and South Atlantic have absorbed more heat in the last 14 years than the rest of the global ocean system put together.

This does not mean that global warming is not a problem: heat in the deep oceans is likely to come back to the surface, and to the atmosphere, sooner or later.

Natural cycle

The changes in the Atlantic ocean circulation system are part of a natural cycle that seems to date back many centuries. The surprise discovery by Chen and Tung is that the heat is tucked away in the Atlantic and Southern Oceans, rather than the Pacific − the suspected hiding place until now.

The argument is a complex one, and the latest research probably hasn’t settled the matter.

“All these analyses of ocean heat content are interpreting small changes in ocean temperature, and it will need to be picked over and repeated by others before being fully accepted,” said Professor Andrew Watson, head of the Marine and Atmospheric Science group at the University of Exeter, UK.

And Piers Forster, professor of climate change at the University of Leeds in the UK, said: “Most importantly, this paper is another nail in the coffin of the idea that the hiatus is evidence that our projections of long-term climate change need revising down.

“Variability in the ocean will not affect long-term climate trends, but may mean we have a period of accelerated warming to look forward to.” – Climate News Network

Antarctic warming could accelerate sea level rise

Warming would cause more Antarctic ice to break off and melt Image: PIK/R.Winkelmann
Rising concern: warming would cause more Antarctic ice to break off and melt
Image: PIK (R.Winkelmann)

By Alex Kirby

An international study says warming is affecting not only the Arctic but also the Antarctic – and that could significantly raise global sea levels much faster than previously predicted.

LONDON, 20 August, 2014 − The effect of climate change on the world’s two polar regions looks like a stark contrast: the Arctic is warming faster than most of the rest of the Earth, while most of Antarctica appears to remain reassuringly locked in a frigid embrace.

But an international scientific team says the reality is quite different. The Antarctic is warming too, it says, and the southern ice could become the main cause of global sea level rise during this century − far sooner than previously thought.

The study, led by the Potsdam Institute for Climate Impact Research (PIK) in Germany, found that ice discharge from Antarctica could contribute up to 37 centimetres to global sea levels by 2100.

Computer simulations

The study is the first comprehensive estimate of the full range of Antarctica’s potential contribution to global sea level rise based on physical computer simulations. It combines state-of-the-art climate models and observational data with various ice models.

The results of the study − published in the European Geosciences Union’s journal, Earth System Dynamics − reproduce Antarctica’s recent contribution to sea level rise, as observed by satellites over the last two decades.

“If greenhouse gases continue to rise as before, ice discharge from Antarctica could raise the global ocean by an additional 1 to 37 centimetres this century,” says the study’s lead author, Anders Levermann, PIK professor of dynamics of the climate system.

“Science needs to be clear about the uncertainty,
so that decision-makers can consider the potential implications . . .”

“This is a big range – which is exactly why we call it a risk. Science needs to be clear about the uncertainty, so that decision-makers on the coast and in coastal mega-cities like Shanghai or New York can consider the potential implications in their planning processes.”

The scientists analysed how rising global average temperatures resulted in a warming of the ocean around Antarctica, influencing the melting of the Antarctic ice shelves.

Antarctica currently contributes less than 10% to global sea level rise and is a relatively minor player in comparison with the impact of the oceans’ increasing thermal expansion and the melting of glaciers.

But the major contributors to future long-term sea level rise are expected to be the huge volumes of ice locked up in Greenland and the Antarctic ice sheets. The marine ice sheets in West Antarctica alone could raise sea level by several metres over a period of several centuries.

The study’s computed projections for this century’s sea level contribution are significantly higher than the upper end of the latest projections by the Intergovernmental Panel on Climate Change. These suggest a probable rise by 2100 of around 60cm, although other estimates put the figure almost twice as high.

Even if governments can agree and enforce strict climate policies limiting global warming below the international target level of a maximum 2°C increase, Antarctica’s contribution to global sea level rise is expected still to range from 0 to 23cm this century.

Critical input

A co-author of the study, Robert Bindschadler, from the NASA Goddard Space Flight Center, said: “This paper is a critical input to projections of possible future contributions of diminishing ice sheets to sea level by a rigorous consideration of uncertainty of not only the results of ice sheet models themselves but also the climate and ocean forcing driving the ice sheet models.

“Billions of dollars, euros, yuan, etc, are at stake, and wise and cost-effective decision-makers require this type of useful information from the scientific experts.”

But major modeling challenges still remain. Datasets of Antarctic bedrock topography, for instance, are still inadequate, and some physical processes of interaction between ice and ocean cannot yet be sufficiently simulated.

The team also emphasises that the study’s results are limited to this century, while all 19 of the comprehensive climate models used show that the impacts of atmospheric warming on Antarctic ice shelf cavities will hit with a time delay of several decades.

However, Levermann says: “Earlier research indicated that Antarctica would become important in the long term. But pulling together all the evidence, it seems that Antarctica could become the dominant cause of sea level rise much sooner.” − Climate News Network

Climate changes ensnare Antarctic predator

Antarctic fur seals at Stromness on South Georgia island Image: Liam Quinn via Wikimedia Commons
Antarctic fur seals at Stromness on South Georgia island
Image: Liam Quinn via Wikimedia Commons

By Tim Radford

British scientists have recorded lower birth weights in female Antarctic fur seals as warming seas deplete their prime food source − but they have also observed genetic variations that could be crucial for survival.

LONDON, 29 July, 2014 − Climate change has begun to take its toll of one of Antarctica’s top predators. The Antarctic fur seal is being born with a lower weight and tends to breed later than earlier generations − almost certainly in response to the reduced availability of its prime food, krill.

But the fur seal (Arctocephalus gazelle) is also changing in other ways. British Antarctic Survey (BAS) scientists report in Nature that those females that survive to motherhood are more likely to have a higher level of genetic variation − a characteristic known as “heterozygous”, associated with higher fitness in many species.

In a world of environmental change – of warming seas and changing ocean chemistry – this confers a survival advantage, in that the individual is more likely to cope with the stresses of change.

Research such as this is based on long periods of observation, and the scientists gathered data from as far back as 1981 to assess the changes in a population of fur seals in South Georgia, in the southern Atlantic.

Genetic samples

They measured age, body length, weight, counted the numbers of sea pups, noted the diet, and recorded climate data. They also took genetic samples from 1,728 seals.

“Compared with 20 years ago, we can see that female fur seals are now born with a lower weight, those that survive and return to breed tend to be the bigger ones, and they have their first pup later in life than they used to,” said the report’s lead author, Jaume Forcada, BAS marine mammal leader.

“Such changes are typically associated with food stress. An important food source for the seals is Antarctic krill, and decades of data collected at South Georgia show how changes in the seal population have occurred over time with krill availability.

“Even if krill is very abundant, environmental variation determines its availability in the seals’ feeding grounds. This variation is driven by climate, which impacts local atmospheric, sea ice and oceanographic conditions.”

If the climatic conditions are adverse, then krill is harder to find, which makes it tough on fur seals and, directly or indirectly, all other Antarctic predators. But the picture for the moment remains uncertain.

Recently, other researchers pronounced that the population in Antarctica of the Adélie penguin – another greedy consumer of krill – is higher than all previous estimates, which suggests that some species at least are, for the moment, finding enough for supper.

But the krill population is sensitive to a south polar phenomenon called the southern annular mode (SAM), a seasonal pattern of winds and pressures that changes from time to time.

Survival fitness

The BAS team found that the seal population responded to the notorious El Niño cycle in the Pacific, and to the SAM, and that the data from this population clearly showed a response to climate change. Overall, the number of heterozygous seals has increased by 17%, but other indicators of survival fitness are not so encouraging.

“Over the last two decades, the proportion of breeding females that are highly heterozygous has increased, as these individuals are more likely to survive the changing conditions,” said the report’s co-author, Joe Hoffman, reader in population genetics at Bielefeld University, Germany.

“Strong selection by the environment can drive rapid evolution. However, in this case the seals do not appear to be evolving because surviving females do not pass their heterozygosity on to their offspring.

“Therefore, with each new generation the process of selection has to start all over again, with only those individuals that happen to be born heterozygous having a good chance of survival. As the climate continues to change, many fur seal pups are not surviving to adulthood, and the population is declining.” – Climate News Network

Hi-tech quest for Arctic sea ice answers

Walrus surfacing through sea ice off the Alaska coast Image: Joel Garlich Miller/USFWS via Wikimedia Commons
Breakthrough: walrus surfacing in sea ice off the coast of Alaska
Image: Joel Garlich Miller/USFWS via Wikimedia Commons

By Tim Radford

A sophisticated array of automatic sensors will allow scientists to conduct the longest ever monitoring programme to determine the precise physics of summer sea ice melt in the Arctic.

LONDON, 20 July, 2014 − An international team of scientists plan to spend months watching ice melt. But although it will take longer and cost a lot more than watching paint dry, it will be much more interesting and rewarding.

They plan to discover just how the Arctic ice retreats, the rate at which it melts, and the oceanographic processes at work.

The Arctic ice cap is a vital part of the climate machine, and the basis of an important ecosystem. But although the polar ice once stretched far further south, it has been both thinning and shrinking for more than three decades. This melting shows signs of accelerating, with consequences for nations far to the south, but researchers still don’t know much about the physics of the process.

Suite of technologies

So the US Naval Research Laboratory, oceanographers from France and the US, the British Antarctic Survey, the Korean Polar Research Institute, the Scottish Association for Marine Science, and the Universities of Cambridge in the UK and Yale in the US have co-ordinated a suite of technologies to monitor every detail of this summer’s ice retreat from the Alaskan shoreline, northwards.

They will use an array of floats, buoys, sensors, thermometers, tethers, GPS receivers and automated weather stations to measure every detail, such as the flow of warmer water, growth and pattern of waves, the wind speed and direction, air pressure, and humidity.

There will be buoys fixed in the ice to record both the melting and – later in the year – its refreezing, and an array of ice-tethered profilers to monitor the changes in the upper ocean. Autonomous sea gliders, too, will be released to explore below the ice shelf and report back every time they surface.

The Arctic summer ice is an example of positive feedback. Ice reflects sunlight, so it is its own insulator, and keeps itself cold. But as it melts and retreats, the exposed darker ocean waters can absorb more radiation, and bring more warmth to the edges of the retreating ice, thus accelerating the process.

It freezes again, but – on average – each year the ice cap becomes thinner, and the total area frozen continues to shrink. Researchers think they understand the big picture, but now they want the confirmatory fine detail.

Melt season

“This has never been done at this level, over such a large area and for such a long period of time,” said Craig Lee, of the University of Washington, who leads the Marginal Ice Zone Programme project. “We’re really trying to resolve the physics over the course of an entire melt season.”

The project began in March, when researchers planted an array of sensors along a line 200 miles to the north of Alaska. In August, a Korean icebreaker will install more equipment, and a team from Miami is studying high resolution satellite pictures of ice floes in the region. Biologists will also want to understand the effect of temperature changes on marine micro-organisms.

“The field programme will provide unique insight into the processes driving the summer melt of Arctic ice,” Dr Lee said. “It’s the automation and unprecedented collaboration that allows us to be out there for the entire season. You couldn’t afford to be out there at this intensity, for this length of time, any other way.” − Climate News Network

New clue to Antarctic food-web puzzle

Strength in numbers: thousands of Adélie penguins at a rookery Image: Michael Van Woert/NOAA NESDIS, ORA via Wikimedia Commons
Strength in numbers: thousands of Adélie penguins in an Antarctic rookery
Image: Michael Van Woert/NOAA NESDIS, ORA via Wikimedia Commons

By Tim Radford

A landmark research study that shows one species of penguin is thriving while other populations are in rapid decline offers new insight into how climate change is affecting Antarctica.

LONDON, 16 July, 2014 − Good news from Antarctica: the continent may be warming, the ice shelf may be at risk, and the food chain may ultimately become precarious, but the Adélie penguin population – at least for the moment − is higher than ever before.

The news does not suggest that global warming and climate change are actually good for this important indicator species, which has certainly been in decline on the Antarctic Peninsula. But it does represent an advance: for the first time, a comprehensive study has concluded with a full census of the species.

Heather Lynch, assistant professor of ecology and evelotion at Stony Brook University in New York, and Michelle La Rue, research fellow at the University of Minnesota’s Polar Geopspatial Center, used high resolution satellite imagery to measure levels of penguin guano – the fertiliser industry’s preferred term for seabird excrement – on the continent.

They then used that as the basis for calculating the numbers of birds in a colony necessary to account for all that digested and evacuated seafood.

They report in a journal called The Auk: Ornithological Advances that they identified at least 17 populations of Adélie penguins not previously known to exist, but failed to pinpoint 13 already-recorded colonies, and declared eight of them eradicated.

Their estimate for the total Adélie population in and around the Southern Ocean stands at 3.79 million, which is 53% higher than all previous estimates.

Useful evidence

The researchers call their work a “landmark” study, and see it not as evidence that climate change is going to work for the benefit of one particular species, but more as a useful piece of the great food-web puzzle in a changing climate.

Penguins have been in rapid decline in the West Antarctic Peninsula, which has become one of the fastest-warming regions on the planet. Warmer weather and increased rain have already started to take toll of Magellanic penguins in Argentina, and researchers recently predicted long-term decline for the iconic Emperor penguin on Antarctica itself.

But this is only long-term decline. As long as Antarctica stays cold and the ice shelf stays stable, the researchers say, the population could, in the short term, actually rise.

That is because what matters most to the species that nest in Antarctica is the supply of fish and krill around the continent’s edge. The health and resilience of the Adélie population – and the Emperor penguin, the leopard seal, the cetaceans, and so on – ultimately depend on how the krill and fish populations respond to climate change.

Humans, too, fish for commercial supplies of Antarctic krill, which provides a source of food for fish farms.

“Our finding of a 53% increase in Adélie penguin breeding abundance, compared to 20 years ago, suggests that estimates of krill consumption by this species may be seriously underestimated,” Dr Lynch said. “Leaving enough prey for natural krill predators is an important element in ensuring fisheries proceed sustainably.”

But a second team confirms in Nature Communications that there are strong links between climate and marine life, and that changes in factors such as wind speed and sea ice can have knock-on effects right around the Antarctic food web.

Since 1990, scientists aboard US research vessels have been conducting annual surveys along the western side of the Antarctic Peninsula, measuring populations of photosynthetic algae.

These peak every four to six years, according to changes in atmospheric pressure between the mid-latitudes and Antarctica itself.

Glacial meltwater

In winter, when cold southerly winds blow across the Peninsula, the winter ice extends. Winds drop from spring to summer, reducing the retreat of the ice. So the water column in summer then is stable, and the phytoplankton multiply, fed by iron-rich glacial meltwater.

The blooms of phytoplankton are what the krill need to multiply, and when the krill are around in huge volumes, the Adélie and other penguins, fur seals, baleen whales and albatross don’t have to go so far to find food.

But marine scientist Grace Saba, who did her research while with the Virginia Institute of Marine Science, before moving to Rutgers University, New Jersey, reports that these ideal conditions – negative phases of the Southern Annular Mode (SAM), to give it the technical terminology – are not guaranteed in future. If the world goes on burning fossil fuels, conditions will probably change.

“Projections from global climate models under business-as-usual emission scenarios up to the year 2100 suggest a further increase in temperature and in the occurrence of positive-SAM conditions,” Dr Saba said.

“If even one positive SAM episode lasted longer than the krill lifespan – four to six years with decreased phytoplankton abundance and krill recruitment – it could be catastrophic to the krill population.”  − Climate News Network

Arctic warming upsets birds’ breeding calendar

 

A chick of the Arctic migrant bird, the red-necked phalarope Image: US Fish and Wildlife Service via Wikimedia Commons
Early bird: a chick of the Arctic migrant, the red-necked phalarope
Image: US Fish and Wildlife Service via Wikimedia Commons

By Tim Radford

As global warming increasingly causes Arctic snow to melt earlier, researchers warn that it could have a long-term adverse effect on the breeding success of migrant birds.

LONDON, 8 July, 2014 − Arctic migrants are nesting up to seven days earlier as the world warms. The sandpiper makes a beeline for the Alaskan shores, to join the phalarope on the beach and the songbirds in the woods − and all because the winter snows are melting earlier.

Conservation scientists Joe Liebezeit and Steve Zack – both then of the Wildlife Conservation Society (WCS) – and colleagues report in the journal Polar Biology that they looked into nearly 2,500 nests of four shorebird species in Alaska – two sandpipers, two phalaropes − and a songbird called the Lapland songspur over a nine-year period.

Nest timing

They recorded when the first eggs were laid. And they also assessed snow melt in nesting plots at different times in the early spring, and took note of predator abundance and the seasonal flush of vegetation − both of which can affect nest timing − to see what mattered most in terms of breeding.

“It seems clear that the timing of the snow melt in Arctic Alaska is the most important mechanism driving the earlier and earlier breeding dates we observed in the Arctic,” said Liebezeit, now of the Audubon Society of Portland, Oregon.

“The rates of advancement in earlier breeding are higher in Arctic birds than in other temperate bird species, and this accords with the fact that the Arctic climate is changing at twice the rate.”

During the nine years in which the scientists conducted their study, they found that nesting advanced by between four and seven days.

“Migratory birds are nesting earlier in the changing Arctic, presumably to track the earlier springs and abundance of insect pray,” said Steve Zack, who is the WCS co-ordinator of bird conservation.

“Many of these birds winter in the tropics and may be compromising their complicated calendar of movements to accommodate this change. We’re concerned that there will be a threshold where they will no longer be able to track the emergence of these earlier springs, which may impact breeding success or even population viability.”

Ecology changing

The calendar of Arctic life is shaped by ice, and the ecology of the region is beginning to change as the area of sea covered by ice shrinks with successive summers.

But Ingrid Onarheim, of the University of Bergen’s Geophysical Institute, and colleagues warn in the journal Tellus − published by the International Meteorological Institute at Stockholm University − that the Arctic ocean is losing ice even in winter, at least north of the island of Svalbard, Norway.

A study of satellite records shows that this region is losing winter ice at the rate of almost 10% per decade, and the north Atlantic water that enters the Arctic ocean at this point has been warming at 0.3°C per decade. At the same time, the surface air temperature has been warming at 2°C per decade, and researchers have recorded an average rise in winter temperatures of 6.9°C in the last 34 years.

They believe that winds have not caused the long-term warming or loss of ice, so it must be warmer ocean temperatures pushing into the region west of Svalbard. The ice, furthermore, has thinned with the decades, making it more likely to melt and retreat with each succeeding winter. – Climate News Network

Emperor penguin’s Antarctic realm is in peril

 

Iconic pose: emperor penguins' habitat is under serious threat Image: John Landis/NSF via Wikimedia Commons
Iconic pose: emperor penguins’ habitat is seriously threatened by climate change
Image: John Landis/NSF via Wikimedia Commons

By Tim Radford

Loss of Antarctic sea ice through climate change threatens the emperor penguin’s habitat to such an extent that scientists say it should now be made an iconic symbol – like China’s endangered giant panda – of the wildlife conservation movement.

 

LONDON, 3 July, 2014 − Global warming will this century take its toll of Antarctica’s most regal predator, the emperor penguin. There are now 45 colonies of this wonderful bird, but by 2100 the populations of two-thirds of these colonies will have fallen by half or more.

Stéphanie Jenouvrier, a biologist at the Woods Hole Oceanographic Institution in the US, and colleagues from France and the Netherlands report in Nature Climate Change that changes in the extent and thickness of sea ice will create serious problems for a flightless, streamlined ,survival machine that can live and even breed at minus 40°C, trek across 120 kilometres of ice, and dive to depths of more than 500 metres.

The researchers took all the data from 50 years of intensive observation of one colony in Terre Adélie and used climate models to project a future for the other 44 colonies known in the Antarctic.

Decisive factor

They found that the decisive factor in emperor penguin survival was the sea ice. If the seas warmed and there wasn’t enough ice, then that affected the levels of krill in the southern ocean, and therefore reduced the available prey. It also made the penguins more vulnerable to other predators.

If the opposite happened and there was too much sea ice, then foraging trips took longer and penguin chicks were less likely to survive.

Aptenodytes forsteri – the Linnean name for the emperor – is not in trouble yet, and its numbers may even grow in the years up to 2050. But this growth won’t last, and decline is likely everywhere. Climate change has already begun to affect penguin species much further north, in Argentina, by taking toll of young chicks.

Endangered class

For different reasons, the average rise in global temperatures forecast by the Intergovernmental Panel on Climate Change (IPCC) could push the emperor into the endangered class.

“If sea ice declines at the rates projected by the IPCC climate models, and continues to influence emperor penguins as it did in the second half of the 20th century in Terre Adélie, at least two-thirds of the colonies are projected to have declined by greater than 50% from their current size by 2100,” Dr Jenouvrier said.

“None of the colonies, even the southernmost locations in the Ross Sea, will provide a viable refuge by the end of the 21st century.”

The researchers end their paper by arguing that the emperor should – like the giant panda in China – become an icon for the conservation movement.

They conclude: “We propose that the emperor penguin is fully deserving of Endangered status due to climate change, and can act as an iconic example of a new global conservation paradigm for species threatened by future climate change.” – Climate News Network

Coastal warning for vital Atlantic habitats

Kelp fringes the coast of Jura off north-east Scotland. Image: Patrick Mackie/geograph.org.uk via Wikimedia Commons
Thick kelp beds fringe the rocky coast of the Scottish island of Jura
Image: Patrick Mackie/geograph.org.uk via Wikimedia Commons

 By Tim Radford

Some of the world’s most productive marine habitats are seriously at risk as scientists say that CO2-related changes and human activities threaten to destroy vital kelp fields and maerl beds in the north-east Atlantic’s coastal waters

 

LONDON, 26 June, 2014 − Rising temperatures, increasingly acidic seas and human destruction will drastically change the nature of the coastal seas of the north-east Atlantic over the next century, scientists predict.

According to new research in the journal Ecology and Evolution, it will completely alter the forests of kelp and the maerl beds of coralline algae that serve as shelter and nurseries for baby cod and juvenile scallops. These are some of the most productive habitats on Earth − habitats that also soak up carbon from the atmosphere and deliver the primary production for thriving communities of sea creatures.

Juliet Brodie, research chair of the Department of Botany at the Natural History Museum, London, reports with colleagues that their study considered changes in water chemistry, the steady rise in water temperatures, and the pattern of destruction in the northern seas − by fishermen, dredgers and pollutants. They then calculated the likely outcomes.

Invasive species

“We predict that, by 2100, warming will kill off the kelp forest in the south, ocean acidification will remove maerl beds in the north, and invasive species will thrive,” the report warns.

The sea grasses will survive only if they are protected from dredging and other human impacts. As habitats disappear, native species will perish with them, and invasive species will thrive.

Jason Hall-Spencer, a study team member and professor of marine biology at Plymouth University, UK,, said: “What we find most staggering is how fast warming and the spread of corrosive waters will alter marine life around out coasts. Our shores will look very different in coming years, affecting people who make a living from the seas.”

The scientists built up a picture of the future from a study of existing research, and they concentrated on the primary producers: the plants that build up tissues from atmospheric carbon, and provide the provender and protection for a host of other species.

Significant role

Kelp forests are among the most productive habitats in the seas. Studies have found that these great, fleshy algae can consume more than a kilogram of carbon per square metre per year, so they play a significant role in the carbon cycle, and help to modify climate change.

Kelps and other seaweed species are adapted to cool waters and, as the seas warm, are predicted to become increasingly stressed. As these weaken, they will steadily be replaced by invaders from other climates. Researchers have already identified 44 species of non-native algae in the north-east Atlantic.

“Carbon dioxide emissions are causing rates of global warming and ocean acidification that will profoundly affect marine flora worldwide,” the scientists conclude.

And they warn that, unless action is taken, societies will “sleepwalk through radical ecological changes” to the plantlife of the European coasts. – Climate News Network

Dark shadow falls on melting icecap

 

Signs of melting as darkness falls on the Greenland icecap Image: Matthew Hoffmann/NASA ICE via Wikimedia Commons
Signs of melting can be seen as darkness descends on the Greenland icecap
Image: Matthew Hoffmann/NASA ICE via Wikimedia Commons

By Tim Radford

Dust blowing in from warming areas of the Arctic is causing the Greenland icecap to melt faster by reducing the whiteness that reflects light and keeps it cool 

LONDON, 13 June − French scientists have identified a new mechanism that could cause the Greenland icecap to melt even faster – because dust is making its surface darker.

Marie Dumont, of the French national meteorological service, Météo-France, reports with colleagues in Nature Geoscience that, since 2009, the snows of the Arctic region’s biggest single permanent white space have been steadily darkened by “light-absorbing impurities” − known to the rest of the world simply as dust.

The Arctic has always been cold and white, simply because it is not just cold but is also white. The phenomenon is called albedo. Regions with a high albedo reflect light and stay cooler, so ice is a form of self-insulation.

Conversely, things that absorb light become warmer − and satellite data analysed by Dr Dumont and her fellow researchers shows that the Greenland ice is getting darker in the springtime.

They think the dust is blowing in from areas of the Arctic that are losing snow cover much earlier in the season as the climate warms. And, they calculate, this steady darkening alone has led to “significant” melting of the icecap.

This finding is ominous. What the researchers have identified is yet another case of what engineers call positive feedback. In the last 30 years, the Arctic sea ice has been in retreat, and researchers expect that, later in the century, the Arctic ocean will be entirely free of ice most summers.

Insulating layers

That means that there will be more atmospheric dust each spring, landing on the snows of Greenland and lowering its albedo even more, so the insulating layers of ice on the huge island will continue to retreat.

Researchers have twice in the last few months had to revise their predictions for the melting of the Greenland glaciers. The continued melting of the ice sheet is expected to raise global sea levels by 20cm by 2100, and since the whole ice sheet – which would take much longer to melt − holds enough frozen water to raise sea levels by more than seven metres, what happens in Greenland matters very much to maritime cities as far apart as Miami and Mumbai.

The French researchers have backed up their observations with a computer model of potential surface melt in Greenland. If a perfect reflecting surface would have a value of one, then meteorologists allot a value of 0.9 to the albedo of fresh snow. They calculate that a decrease in the albedo of even a very small ratio, such as 0.01, could lead to the melting of 27 billion tons of ice every year.

They are not saying that this is already happening, but they do argue that “future trends in light-absorbing impurities should therefore be considered in projections of Greenland’s mass loss”.

Accelerating warming

This is not the only newly-identified potential mechanism for positive feedback. A report by Laetitia Pichevin, of the University of Edinburgh’s School of GeoSciences, Scotland, and fellow researchers, was published in the same issue of Nature Geoscience. It says that rising global temperatures could decrease the amount of carbon dioxide naturally taken up by the world’s oceans, thus also accelerating global warming. This, too, is another process that could go on accelerating.

The researchers analysed sediments laid down 26,000 years ago in the Gulf of California and measured the abundance of silicon and iron in tiny marine fossils. They found that those periods when silicon was least abundant in ocean waters coincide with relatively warmer climates, low levels of atmospheric iron, and reduced carbon dioxide uptake by the plankton in the oceans.

“We were surprised by the many ways in which iron affects the CO2 given off by the oceans,” Dr Pichevin said. “If warming climates lower iron levels at the sea surface, as occurred in the past, this is bad news for the environment.” – Climate News Network