Tag Archives: Oceans

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

Data adds to confusion over polar sea ice

The expansion of Antarctic sea ice may have been overestimated. Image: Jason Auch via Wikimedia Commons
The expansion of Antarctic sea ice may have been overestimated.
Image: Jason Auch via Wikimedia Commons

By Tim Radford

Possible errors in the interpretation of satellite data may help to explain scientists’ puzzlement over indications that sea ice cover is apparently increasing in the Antarctic, but is shrinking visibly in the Arctic.

LONDON, 26 July, 2014 − Scientists believe they may have found explanations for two inconsistencies in their understanding of global warming.

One cause for head scratching is in the Antarctic, where the sea ice seems to be getting bigger when it ought to be shrinking, and another has been the apparent slowdown overall in the rate of global warming for the last decade.

Climate scientists around the world have been picking away at both puzzles, and not just because climate sceptics and energy industry lobbyists use them as ammunition to argue that global warming is not a problem at all. Scientists are naturally unhappy when data doesn’t match their predictions − and they want to know the reason why.

The Antarctic problem is hard to miss. The Arctic Ocean sea ice is shrinking visibly, and the entire sea could be ice-free most summers in a few decades. But even though there is clear evidence from separate sources that West Antarctica is responding to climate change, the southern hemisphere ice cover, overall, has been increasing.

Or has it? Ian Eisenman, a climatologist at the Scripps Institution of Oceanography at the University of California San Diego, begs to differ. He and colleagues report, in The Cryosphere journal, that it could be due to an error in the way satellite data is processed.

Spliced together

Scientists have been using satellite data to check sea ice cover for 35 years. But the data does not come from one instrument on just one satellite: observations transmitted from a series of satellites have been spliced together.

One report from the Intergovernmental Panel on Climate Change said the sea ice cover was more or less constant, but a later report said it had grown by 16,500 square kilometers a year between 1979 and 2012.

“When we looked at how the numbers reported for the trend had changed, and we looked at the time series of Antarctic sea ice, it didn’t look right,” Dr Eisenman said.

The researchers think that the difference between the two datasets might be linked to a change in satellite sensors in 1991, and the way the data collected by the two instruments was calibrated. What the Scripps team has done is identify a source of possible error, but it hasn’t settled the question one way or the other.

Since the Arctic and Antarctic are very different places, it would be unrealistic to expect the patterns of melting to be the same. And it may still be that southern hemisphere sea ice is growing.

However, while that question remains open, there is less doubt about the long slowdown in the rate of average global warming during the 21st century.

Missing heat

Separate teams of researchers have proposed a series of possible explanations for the failure of the climate to keep up with the projections of the climate scientists. These have included the suggestion that the missing heat may be “concealed” in the deep oceans, and that a pause in warming was going to happen anyway, but it just happened earlier than anyone expected.

Shaun Lovejoy, professor of physics at McGill University in Canada, reports in Geophysical Research Letters that there is yet another explanation. He argues, from statistical analysis, that coincidentally with the increase in man-made emissions of greenhouse gases, there has been a natural cycle at work, and that the most recent human impact on climate has been damped down by a cooling phase.

He had already ruled out with 99% certainty the possibility that natural variation could explain all the ups and downs of global average temperatures since 1800. This time he used the same statistical approach to the data for the 15 years from 1998 to the present.

His research suggests that there has been a natural cooling of 0.28°C to 0.37°C since 1998, which is in line with natural variations that occur every 20 to 50 years. “The pause has a convincing statistical explanation,” Lovejoy says. – 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

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

Icebergs strip away rich Antarctic habitat

Icy waters near the Rothera research station in Antarctica Image: Vincent van Zeijst via Wikimedia Commons
Icy waters near the Rothera research station in West Antarctica
Image: Vincent van Zeijst via Wikimedia Commons

By Tim Radford

The scouring effect of drifting icebergs that are increasingly breaking free from Antarctic ice shelves as a result of global warming is wiping out fauna that cling to the boulders in shallow waters

 LONDON, 23 June, 2014 − A once-rich habitat in the Antarctic has become an impoverished zone as icebergs, increasingly breaking free from the surrounding sea ice because of global warming, scour the shallow-water rocks and boulders on which a diversity of creatures cling to life.

A report in the journal Current Biology says that researchers who carried out a survey dive in 2013 at Lagoon Island, off the West Antarctic Peninsula, discovered that “no live mega or macro-fauna can be found, the first time this has been observed there, despite being regularly visited by scientific divers since 1997”.

David Barnes, of the British Antarctic Survey, and colleagues report that boulders on the seabed near the Rothera research station had once been richly encrusted with creatures that competed for living space. Now such rocks might only support a single species.

Early warning system

“The Antarctic Peninsula can be considered an early warning system, like a canary in a coal mine,” Dr Barnes said. “Physical changes there are among the most extreme and the biology considered quite sensitive, so it was always likely to be a good place to observe impacts of climate change.

“But impacts elsewhere are likely to be not too far behind. A lot of the planet depends on the near shore environment, not least for food. What happens there to make it less stable is important.”

A research diver surveys the shallow waters of West Antarctica Image: British Antarctic Survey
A research diver surveys the shallow waters off the West Antarctic Peninsula
Image: British Antarctic Survey

Climate change has already begun to affect Antarctica in different ways. Researchers last year found that as icebergs broke free, the surviving ice shelf had begun to melt from underneath from underneath. The effect of the drifting bergs was mixed: at depth in the fjords of the Peninsula, for instance, the species variety seemed to have got richer, according to one set of observations.

But no such effect was observed in the ocean shallows that are being scraped and scoured by drifting icebergs. The researchers say that although no species has disappeared entirely from the region, the numbers are so low as to be negligible.

In 2013, most of the observations seemed to involve just one opportunistic or pioneer species, a suspension feeder called Fenstrulina rugula. What had once been a rich habitat had become one of the simplest seabed systems to be found anywhere.

Ecological roles

“Reduction of complex systems into very simple ones, where many (formerly important) species become too rare to maintain meaningful ecological roles, is a common reaction to anthropogenic disturbance such as overfishing, pollution, introductions of non-indigenous species, and habitat destruction,” the report’s authors say.

“Across West Antarctica, the levels of these disturbances are among the lowest globally, apart from greenhouse contributions to climate change.”

The scientists conclude: “We expect the deeper seabed to become richer in benthic colonisation with more ice shelf collapses and fast ice losses, but hard surfaces in the shallows are likely to become deserts dominated by rapidly-colonising pioneers and responsive scavengers.” − Climate News Network

May days’ heat sets up record El Niño

 

Flooding in California during the “El Niño of the century” in 1998 Image: Dave Gatley/FEMA via Wikimedia Commons
Flooding in California during the “El Niño of the century” in 1998
Image: Dave Gatley/FEMA via Wikimedia Commons

By Tim Radford

Scientists believe that soaring global temperatures during an unusually hot month of May may have created the ideal conditions to provide a warm welcome for an El Niño weather phenomenon that will break records

LONDON, 20 June, 2014 − Last month was the third warmest May since NASA satellites began taking the temperature of the planet 35 years ago, and was also the warmest May that did not fall within an El Niño Pacific warming event – which could mean a record-breaking appearance this year by the fearsome “Child”.

Scientists in the US says the global average was 0.33°C warmer than the seasonal norms for the month. The warmest May ever was in 1998 during the “El Niño of the century”, when global average temperatures rose by 0.56°C, and the second warmest at 0.45°C was in 2010, another El Niño year.

So if indications are correct that an El Niño event is taking shape in the Pacific right now off the equatorial coast of South America, then it could become a record-setter − even if it isn’t a very spectacular event − just because it will get a warmer start, according to John Christy, professor of atmospheric science at the University of Alabama in Huntsville, US.

Temperature patterns

An El Niño (Spanish for The Child, because it was first observed by Peruvian fishermen around Christmas) is a shift in the temperature patterns of the Pacific, as a blister of equatorial ocean heat moves eastwards. It is a natural cyclic event that tends to reverse the prevailing Pacific weather patterns, often damagingly, and is not connected with climate change  although its effects could be made worse by climate change.

“The long-term baseline temperature is about three tenths of a degree warmer than it was when the big El Niño of 1997-1998 began, and that event set the one month record,” Christy said. “With the baseline so much warmer, this upcoming El Niño won’t have very far to go to break that 0.66°C record. That isn’t to say it will, but even an average-sized warming event will have a chance to get close to that level.”

Meanwhile, according to new research in Nature Climate Change, people in the northern hemisphere can also expect warmer temperatures in autumn and winter – in spite of last winter’s spectacular ice storms in the US north-east that shut down cities from the Atlantic to the Midwest, and where − to the joy of headline writers − the town of Hell in Michigan froze over.

Extremes of cold

The report’s author, James Screen, Natural Environment Research Council research fellow at the University of Exeter, UK, says that even though there will be extremes of cold, these will be less frequent and less severe. The Arctic is warming, and a study of autumn and winter temperature variations shows that variability in the temperate zone overall has in fact decreased.

“Autumn and winter days are becoming warmer on average, and less variable from day to day,” Dr Screen said. “Both factors reduce the chance of extremely cold days.

“Cold days tend to occur when the wind is blowing from the north, bringing Arctic air south into the mid-latitudes. Because the Arctic air is warming so rapidly, these cold days are now less cold than they were in the past.” – Climate News Network