Category Archives: Ocean Warming

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

No way back for West Antarctic glaciers

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Birth of an iceberg: a massive crack appears in the Pine Island glacier in West Antarctica Image: Nasa Earth Observatory via Wikimedia Commons

Birth of an iceberg: a massive crack in West Antarctica’s Pine Island glacier
Image: Nasa Earth Observatory via Wikimedia Commons

By Tim Radford

Satellite data analysis reveals the ominous news that the melting glaciers of West Antarctica have passed the ‘point of no return’ as the southern hemisphere gets warmer

LONDON, 22 May – The glaciers of the West Antarctic may be in irreversible retreat, according to the evidence of satellite data analysed by scientists at the US space agency Nasa.

The study of 19 years of data, due to be reported in the journal Geophysical Research Letters, confirms the ominous news that the southern hemisphere is not just warming − it is that it is warming in a way that speeds up the melting of the West Antarctic glaciers.

Long ago, glaciologists began to wonder whether the West Antarctic ice sheet was inherently unstable. The water locked in the ice sheet in the Amundsen Sea region – the area the Nasa researchers examined − is enough to raise global sea levels by more than a metre. If the whole West Antarctic ice sheet turned to water, sea levels would rise by at least five metres.

Steady change

What the latest research has revealed is a steady change in the glacial grounding line, which is the point in a glacier’s progress towards the sea where its bottom no longer scrapes on rock but starts to float on water. It is in the nature of a glacier to flow towards the sea, and at intervals to calve an iceberg that will then float away and melt. The puzzle for scientists has been to work out whether this process has begun to accelerate.

Eric Rignot, a glaciologist at the Nasa Jet Propulsion Laboratory and the University of California, Irvine, thinks it has. He and his research partners believe that European Space Agency satellite data has recorded the points at which the grounding lines can be identified in a series of West Antarctic glaciers monitored between 1992 and 2011, as the glaciers flexed in response to the movement of tides.

All the grounding lines had retreated upstream, away from the sea − some by more than 30 kilometres. The grounding lines are all buried under hundreds of metres of ice, and are difficult to identify.

The shift of ice in response to tidal ebb and flow provides an important clue. It also signals an acceleration of melting, because it is the glacier’s slowness that keeps the sea levels static. As it inches towards the sea, there is time for more snow and ice to pile up behind it.

Speeds up

But if the water gets under the ice sheet, it reduces friction and accelerates the passage of frozen water downstream. So the whole glacier speeds up, and the grounding line moves yet further upstream.

Something similar has been reported from the glaciers of Greenland. And once the process starts, there is no obvious reason why it would stop. The melting will still be slow, but the latest evidence indicates that it seems to be inexorable.

“We’ve passed the point of no return,” Prof Rignot says. “At current melt rates, these glaciers will be history within a few hundred years.

“The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.” – Climate News Network

Migrating cyclones pose new threat

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A washed out section of New York's Rockwell subway track after Hurricane Sandy hit in 2012 Image: Leonard Wiggins/MTA New York City Transit via Wikimedia Commons

Washed out track on New York’s Rockaway subway line after Hurricane Sandy hit in 2012
Image: Leonard Wiggins/MTA New York City Transit via Wikimedia Commons

By Tim Radford

The world’s most destructive storms are on the move – putting at risk coastal areas that would not expect to be hit by violent hurricanes or typhoons.

LONDON, 20 May − Tropical cyclones – hurricanes in the Caribbean, typhoons in the South China Sea – are moving further north and south, threatening to create new havoc in unsuspecting coastal areas.

New research published in the journal Nature reveals that, on average, the storms have been migrating towards the poles at the rate of 53 kilometres a decade in the northern hemisphere, and 62 kilometres in the southern.

This means that landfalls that in the past that would not have expected violent storms will become increasingly at risk − “with obvious effects on coastal residents and infrastructure”, the paper says.

Jim Kossin, an atmospheric research scientist at the US National Oceanic and Atmospheric Administration (NOAA), and colleagues looked at data for the last 30 years and measured the latitudes as which storms reached their peak intensity. They found an uneven but measurable shift of around half a degree of latitude every 10 years.

The news makes sense, as researchers have previously identified a steady “expansion” of the tropics as a result of global warming.

More hostile

“We’ve identified changes in the environment in which the deep tropics have become more hostile to the formation and intensification of tropical cyclones, and the higher latitudes have become less hostile,” Dr Kossin said. “This seems to be driving the poleward migration of storm intensity.”

Kerry Emanuel, professor of atmospheric science at the Massachusetts Institute of Technology and co-author of the report, said: “The trend is statistically significant at a pretty high level.”

Another of the report’s authors, Gabriel Vecchi, also of NOAA, said: “Now we see this clear trend, it is crucial that we understand what caused it – so we can understand what is likely to occur in the years and decades to come.”

There seems to be an ideal ocean surface temperature of between 28°C and 30°C at which tropical cyclones are most likely to happen. As temperate seas begin to warm, the hazard zone widens.

Not prepared

The superstorm Hurricane Sandy, which devastated New York in 2012, slammed into a coast not prepared either for the force of the wind or for the storm surge that washed through the coastal structures.

But storms are capricious, and notoriously hard to map accurately, so the researchers decided that the surest guide to any pattern of migration would be the latitude at the point of maximum intensity.

They identified regional differences, but found that every ocean basin except the northern Indian Ocean had experienced such a change. Changes in vertical wind shear – which plays a role in cyclone formation – may be involved.

The incidence of cyclones in the tropics actually fell between 1982 and 2012. The suspicion is that although tropical cyclones may become more intense in a warmer climate, it may also be harder to generate them. – Climate News Network 

Reefs merit protection money

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Waves crash ashore on the Southern Pacific island of Niue Image: Gadfium via Wikimedia Commons

Waves sweep in across coral reefs surrounding the Southern Pacific island of Niue
Image: Gadfium via Wikimedia Commons

By Tim Radford

The great natural protective barriers that coral reefs provide for millions of people in coastal communities are seriously threatened, but scientists calculate that restoration projects would cost 20 times less than building artificial breakwaters to keep pounding waves at bay

LONDON, 19 May − Coral reefs, under threat around the tropics from the double menace of global warming and ocean acidification, are also natural protection systems for million people. And the importance of that protection is shown in a new scientific study confirming that a coral reef can reduce the energy of a pounding wave by up to 97%.

It is widely known that reef systems offer a natural barrier. But Filippo Ferrario, from the University of Bologna in Italy, and an international team of researchers report in Nature Communications that they decided to try to put a figure on the effectiveness of a living limestone rampart maintained by a tiny animal that is the basis for a rich submarine ecosystem.

They found that the shallowest part of a reef – the crest where the waves break first – dissipates 86% of the wave’s energy, while the whole reef can reduce the sea’s impact by 97%.

And the cost of maintaining a reef − that is, the cost of a reef restoration project − is US$1,290 per metre, compared with an average $19,791 per metre to build an artificial breakwater. That’s almost 20 times cheaper.

First line of defence

“Coral reefs serve as an effective first line of defence to incoming waves, storms and rising seas,” says study co-author Michael Beck, lead marine scientist of the US Nature Conservancy. “Two hundred million people across more than 80 nations are at risk if coral reefs are not protected and restored.”

Dr Ferrario adds “The study illustrates that the restoration of coral reefs is an important and cost-effective solution to reduce risks from coastal hazards and climate change.”

Marine scientists have argued for decades that natural systems such as mangrove forests, sandspits, water meadows and reefs offer protection for coastal cities. A huge proportion of humanity now lives in cities, and many cities have grown up on estuaries, around natural harbours, or on beach fronts − that is, at or near sea level.

Extreme weather

Sea levels will rise inexorably with global warming, and climate change threatens to increase the frequency and the magnitude of extreme weather events. There have been warnings that, by the end of the century, coastal flooding could cost up to a trillion dollars a year.

But the natural reefs that have offered shelter for so many people – for example, an estimated 41 million in Indonesia, 36 million in India, and 23 million in the Philippines – are under stress from pollution and overfishing.

Corals are also sensitive to rising water temperatures. And, although there is some evidence that some corals can adapt, there are serious concerns about the consequences of change in water chemistry as more and more atmospheric carbon dioxide dissolves in the oceans. – Climate News Network

Plankton loss threatens marine food web

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Zooplankton such as Hyperia macrocephala are vital sources of nutrients for marine life Image: Uwe Kils via Wikimeadia Common s

Zooplankton such as Hyperia macrocephala are vital sources of nutrients for fish
Image: Uwe Kils via Wikimedia Commons

By Alex Kirby

Researchers warn that marine life could be dramatically affected as climate change threatens to cause severe reduction of plankton – the key source of nutrients − in some ocean regions by the end of the century

LONDON, 12 May − There are plenty more fish in the sea − but not for too much longer in some parts of the world, researchers say. And the reason is very simple: the food on which they all depend faces a marked decline.

Researchers from AZTI-Tecnalia, a Spanish-based technology centre specialising in marine and food research, report in the journal Global Change Biology that the warming of the oceans will cause phytoplankton biomass to decrease by 6% by the end of this century.

Phytoplankton are the single-celled plants that are the basic building blocks of most marine life. In particular, they sustain zooplankton − tiny animals that are eaten in turn by fish. The study found evidence that, by 2100, zooplankton biomass will be 11% less than it is today, with obvious implications for the fish that feed on them.

The report says that sea surface temperature is predicted to increase by 2ºC on average globally by 2080-2100. The consequences of this increase will include changes in ocean circulation and higher water column stratification, where water of different densities forms distinct layers instead of mixing, affecting the availability of nutrients.

Biomass reduction

The depletion expected in the amount of plankton in the marine food web could reduce fish biomass in 47% of the total global ocean area, especially in tropical oceans.

But phytoplankton and zooplankton reduction will affect different regions in different ways. In the North Sea and temperate north-east Atlantic, higher stratification and lower nutrient levels will reduce phytoplankton growth. In the Baltic, Barents and Black Seas, it is expected to increase.

Guillem Chust, an Azti-Tecnalia researcher and the lead author of the paper, said: “In the ocean regions that lose more phytoplankton and zooplankton biomass, fish biomass may also decrease dramatically.” He said this would especially affect pelagic species − deep-sea fish that are not bottom dwellers.

He said the oceans’ role in moderating climate change would also be damaged: “As there will be less phytoplankton, absorption of CO2 from the atmosphere by the oceans will be lower, as plankton is responsible for half of the planet’s photosynthetic activity. This in turn will reduce the ocean’s capacity to regulate the climate.”

The research was undertaken as part of Marine Ecosystem Evolution in a Changing Environment (MEECE), a European Union project to explore the impact of climate and human activities on marine ecosystems.

One of the project’s concerns is the growing evidence of damage from ocean acidification, the process by which emissions of carbon dioxide are making the seas increasingly acid and hostile to some forms of marine life.

Emission limits

A group which works to protect seafood supplies and marine ecosystems, Global Ocean Health, has welcomed a move by the US Environmental Protection Agency  intended to lead to the introduction of performance-based emission limits for new power plants, which would help to reduce the threat of acidification.

“The rule would help protect productive fisheries and oceans,” GOH says. “Although it cannot single-handedly staunch the flow of carbon emissions that drive ocean acidification, the rule would make a good start.”

Capping CO2 emissions per unit of power produced would, GOH says, effectively block any new coal plants in the US, ensuring a continued shift towards natural gas, which is cheaper than coal. In the last six months, it says, more than 80% of the new electricity capacity added to the US grid was renewable energy.

It also believes the rule would dampen global investors’ appetite for coal projects by demonstrating that the US is no longer willing to tolerate unlimited CO2 emissions from coal.

“With this policy, the world’s most influential economic superpower would signal to global capital markets that coal is no longer a safe investment,” GOH says.

This would add to the growing argument that fossil fuel reserves risk becoming unusable “frozen assets” because of their climate impact. − Climate News Network