Aerosols may offer short-term lifeline to corals in crisis

Aerosols may offer short-term lifeline to corals in crisis

Reducing the bleaching of corals by blocking the sun’s rays might buy time to keep tropical reefs alive if efforts are increased to halt global warming.

LONDON, 29 May, 2015 − A new solution has been proposed for the forthcoming crisis of the coral reefs: blot out some of the sunlight.

Scientists from the US, UK and Australia suggest a form of climate engineering called solar radiation management, which involves pumping aerosols into the stratosphere to reduce global temperatures − and especially the warming of the tropic seas.

If sea temperatures rise just 1°C to 2°C above the normal summer high, something gruesome happens to the coral reefs: they bleach.

This is because they sicken, and expel the colourful algae with which they cohabit. It is a survival technique known to biologists as symbiosis. But if the bleaching goes on for long enough, they die.

Human-induced warming

Lester Kwiatkowski − a researcher with both the University of Exeter in the UK and the Carnegie Institution for Science in the US − and colleagues report in Nature Climate Change that human-induced global warming because of the burning of fossil fuels could raise temperatures enough by 2050 to bleach and degrade 90% of the world’s coral reefs.

So, the authors argue, the world must accept that the loss of the reefs is inevitable − or buy time to save them.

The latter option could be addressed by squirting massive quantities of sulphate aerosols into the stratosphere to reflect radiation and darken the skies, while humans get on with the much-delayed challenge of reducing atmospheric carbon dioxide concentrations by switching to renewable sources of energy.

The irony is that Dr Kwiatkowski has only lately dismissed at least one ocean geoengineering solution – to cool the sea surfaces by pumping up cold water from the ocean depths – because, in the long run, it might make the climate change crisis even worse. Nor is he the only scientist to make that point.

“We need to accept that the loss of a large percentage of the world’s reefs is inevitable,
or start thinking beyond conventional
mitigation of CO2 emissions”

Geoengineering has repeatedly been defined as the wrong answer to problems of soaring human numbers and uncontrolled economic growth.

So the real message of this latest study may be that the choices facing humankind have become increasingly unwelcome.

Coral reefs are the richest ecosystems in the oceans, and 500 million people depend on the living coral and its co-dependants for food, tourist income and coastal protection.

The tropical reefs have bleached before, in extremes of heat, but after a few years have recovered. Whether they could survive both a sustained rise in temperatures and the increasing acidification of the oceans that goes with higher carbon dioxide levels is another matter.

Ecosystem at risk

So the researchers decided to see what it would take to reduce the risk. They took some account of the impact of the debilitating effect of increasing ocean acidity. Then they considered the hypothetical fate of corals in a warming world.

There is no doubt that bleaching is a consequence of hotter seas, or that by 2100 the entire reef ecosystem will be at risk.

At least one other group has proposed that some form of solar protection could be an answer, but another has suggested that at least some corals might adapt.

“Coral reefs face a dire situation, regardless of how intensively society decarbonises the economy,” says Peter Cox, professor of climate system dynamics at the University of Exeter.

“In reality, there is no direct choice between conventional mitigation and climate engineering, but this study shows that we need to accept that the loss of a large percentage of the world’s reefs is inevitable, or start thinking beyond conventional mitigation of CO2 emissions.” – Climate News Network

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Rising temperatures mean fewer but fiercer hurricanes

Rising temperatures mean fewer but fiercer hurricanes

Climate change brings mixed prospects for people threatened by hurricanes: they are likely to occur less often, but when they do they will be even more destructive.

LONDON, 25 May, 2015 − Once again, scientists have confirmed the link between climate change and destructive hurricanes. The link is a simple one: a warmer world could mean fewer tropical storms, but those that arrive are likely to be more violent.

The conclusion is not new: other teams have already proposed that global warming linked to increases of carbon dioxide in the atmosphere as a consequence of fossil fuel combustion could drive tropical cyclones to higher latitudes and that the most destructive hurricanes could happen increasingly often. A British team has even linked better air quality – fewer sulphate aerosols and dust – to a greater probability of more violent winds.

But Nam-Young Kang, who now directs South Korea’s National Typhoon Center, and James Eisner, a geographer at Florida State University, set about a study of weather data and hurricane, cyclone and typhoon records between 1984 and 2012 to see if they could identify a pattern of change.

In the last 60 years or so, global average temperatures have risen, but are still less than 1°C above the average for the centuries before the Industrial Revolution. Hurricanes are linked to sea surface temperatures and the hurricane “season” does not start until ocean surface levels go beyond 26°C.

“We’re seeing fewer hurricanes, but the ones we do see are more intense. When one comes, all hell breaks loose”

The two scientists reckoned that even slightly higher average temperatures would mean more energy and therefore higher wind speeds at sea as well. They report in Nature Climate Change that they found what they were looking for: a pattern. On average, storm wind speeds had increased by 1.3 metres a second and there were 6.1 fewer tropical storms a year worldwide than there would have been if land and water temperatures had remained constant.

The research paper describes tropical cyclones – a term that for geographers also embraces Pacific typhoons and Atlantic hurricanes – as “perhaps the least welcomed natural phenomena on our planet” and points out that even well-developed, highly complex societies are exposed to them, and vulnerable. Superstorm Sandy, which began as an Atlantic hurricane, hit New York in 2012 with devastating consequences and even set the nation’s earthquake alarms ringing.

Professor Eisner has already established a link between temperatures and tornado hazard.  The new study delivers a statistical warning of a trade-off between frequency and strength offshore as well.“We’re seeing fewer hurricanes, but the ones we do see are more intense. When one comes, all hell breaks loose,” he said. − Climate News Network

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Antarctic ice is under attack from sea and air

Antarctic ice is under attack from sea and air

Satellite and radar studies show that twin forces causing the vast ice shelf to thin and become less stable could have a serious impact on global sea levels.

LONDON, 18 May, 2015 − Scientists have measured the rate of thinning of the great sea ice shelf of the Antarctic Peninsula and have identified the mechanisms at work above and below the shelf.

The collapse of floating sea ice makes no direct difference to global sea levels – but the effects could nevertheless lead to higher waters everywhere.

Paul Holland, of the British Antarctic Survey (BAS), and research colleagues from the US report in the journal The Cryosphere that they used satellite measurements and radar studies between 1998 and 2012 to confirm that the Larsen C ice shelf has lost four metres of ice, and is a metre lower at the surface.

Warmer waters

This is the largest of three shelves that have been under study for decades; the Larsen A and Larsen B shelves have already broken off and drifted north to warmer waters.

The Antarctic Peninsula is one of the fastest-warming regions of the world: 2.5°C in the last 50 years.

“What’s exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable,” says Dr Paul Holland, lead author of the BAS study.

“Air is being lost from the top layer of snow (called the firn), which is becoming more compacted, probably because of increased melting by a warmer atmosphere.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present”

“We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow. If this vast ice shelf − which is over two and a half times the size of Wales, and 10 times bigger than Larsen B − was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.”

A collapse of the shelf could occur within a century. When the two companion Larsen glaciers broke away, the glaciers that flowed from the ice-capped continent towards the sea began to accelerate.

Offshore ice, held fast to the shoreline, is a factor that helps keep glacier flow at its proverbially glacial pace. Once it has gone, the frozen rivers of ice onshore naturally begin to flow faster.

“We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present, and that will cause problems for coastal and low-lying cities,” says David Vaughan, director of science at the BAS.

“Understanding and counting up these small contributions from Larsen C and all the glaciers around the world is very important if we are to project, with confidence, the rate of sea-level rise into the future.”

The study is a confirmation of earlier research in which other groups, using different approaches, have already identified shelf ice loss and have warned that Antarctic melting could accelerate. Satellite-based measurements have also linked glacial melting with an acceleration in sea level rise.

Precision measurement of sea level rise is not easy. Oceans rise and fall with the tides, the water isn’t level anyway, and salinity and temperature differences in the oceans, and gravitational anomalies in the ocean basins, all mean that the ocean surfaces naturally undulate.

And the continents don’t keep still. Land surfaces from which researchers base their measurements also slowly rise or fall.

Accelerated rise

Christopher Watson, senior lecturer in the School of Land and Earth at the University of Tasmania, Australia, and colleagues report in Nature Climate Change that a different approach to the problem suggests that – contrary to previous estimates – sea level rise has accelerated in the last decade.

He and his colleagues searched not just global positioning satellite evidence from the surface waters but also from the land for signs of “bias” in the data. They also used evidence from hourly tide gauges from around the world and recalculated the rate of change.

What they found was that, overall, sea level rise in the last two decades has been at a rate just under, rather than just over, 3mm a year.

But the overestimate for the first six years of the survey had been much higher, which in turn suggested that the rate of rise had actually accelerated during this century, in a way that is consistent with the rate of glacial melting − at least from the Greenland and West Antarctic ice caps. – Climate News Network

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Plant growth may speed up Arctic warming

Plant growth may speed up Arctic warming

Arctic plants may absorb more greenhouse gases as the region warms – but scientists say this could intensify the warming rather than moderate it.

LONDON, 10 May, 2015 – Green may not automatically mean innocent or planet-friendly after all. Korean and German scientists have identified a mechanism that could encourage plants to take up more carbon dioxide – and at the same time amplify Arctic warming by 20%. This counter-intuitive finding is published in the Proceedings of the National Academy of Sciences.

Jong-Yeon Park of the Max Planck Institute for Meteorology and colleagues have been looking at the role of phytoplankton, those tiny marine plants that flourish around land masses, exploit the nutrients that flow from rivers and turn the blue ocean sea-green. Like any grass or shrub or tree, they exploit sunlight and employ photosynthesis to soak up atmospheric carbon dioxide.

So as the Arctic Ocean warms, because of increasing emissions of carbon dioxide from the burning of fossil fuels, the ice melts, the blue sea water absorbs more sunlight, and the green things get a chance to grow and soak up some of that greenhouse gas as organic carbon in plant tissues. This is what engineers call negative feedback.

But it may not work like that. The scientists matched up a model of the climate system with a model of the ecosystem and did all the sums again. And they found that instead of reducing warming, an explosion of phytoplankton growth could actually amplify it.

More warming

If the seas warmed and the ice melted, then the overall albedo – the reflectivity of the Arctic – would be changed. More high energy solar radiation would get into the sea, and the phytoplankton harvest would be greater and go on for longer.

But more phytoplankton would mean more biological activity, which would directly warm the surface layer of the ocean, “triggering additional positive feedbacks in the Arctic, and consequently warming the Arctic further,” the authors warn.

“We believe that, given the inseparable connection of the Arctic and global climate, the positive feedback in Arctic warming triggered by phytoplankton and their biological heating is a crucial factor that must be taken into consideration when projecting future climate changes,” said Jong-Seong Kug, a professor at Pohang University of Science and Technology in Korea.

Science like this is a reminder that the climate system is a subtle and complex machine driven by sunlight, atmosphere, water – and carbon. A British team has warned that rainforests could in fact be emitting much more carbon than climate modellers have accounted for. That’s because they haven’t allowed for all of the dead wood.

“A large proportion of forests worldwide are less of a sink and more of a source”

Marion Pfeifer of Imperial College and colleagues report in Environmental Research Letters  that they surveyed a large area of forest in Malaysian Borneo to make their calculations.

Pristine, untouched forest is rare. Most forests provide an income for someone, and increasingly parts of the great forests are exploited by loggers and planters. In untouched forests, dead wood makes up less than 20% of the biomass. Dr Pfeifer and her colleagues found that in partially-logged forests, the dead wood could account for 64% of the biomass.

Details such as this could send climate modellers back to the drawing board. That is because the great riddle of climate science is: where does all the carbon go? The assumption has been that forests are “sinks” that collect atmospheric carbon. But that depends on the forest.

“I was surprised by how much of the biomass dead wood accounted for in badly-logged forests. That such logged forests are not properly accounted for in carbon calculations is a significant factor. It means that a large proportion of forests worldwide are less of a sink and more of a source, especially immediately following logging, as carbon dioxide is released from dead wood during decomposition,” Dr Pfeifer said.

“Selectively-logged tropical forests now make up about 30% of rainforests worldwide. That means such global calculations are wrong at least 30% of the time.” – Climate News Network

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Familiar fish find northern seas too warm for comfort

Familiar fish find northern seas too warm for comfort

Fish accustomed to shallow northern waters will search in vain for cooler depths as climate change warms the seas where they thrive.

LONDON, 18 April, 2015 – Some of Northern Europe’s favourite suppers may be about to swim off the menu altogether. Global warming could change the future catch, according to new research.

British scientists report in the journal Nature Climate Change that popular species such as haddock, lemon sole and plaice could become less common as the climate changes and the North Sea warms.

The North Sea is relatively shallow – during the height of the Ice Age, much of the sea bed was dry land – which means that fish that would otherwise find deeper waters to keep cool have nowhere to go.

The North Atlantic is warming fast. The mean annual North Sea surface temperatures have increased by 1.3°C in the past 30 years. This is four times faster than the global average. But fish evolved to make a living in the temperatures that suit them best, and the evidence is that the North Sea is increasingly host to species that were once characteristic of the Mediterranean.

Changing abundance

Fishing is big business: landings in 2007 in the region reached $1.2 billion, and accordingly the ecology of the North Sea has been intensively monitored. Cold-adapted landings have halved in the last 30 years, but landings of warm-adapted species have increased 2.5 times. With a baseline of very detailed data from the past, the researchers were able to use computer models to build up a picture of things to come in northern waters.

And the result is this: the demersal or bottom-feeding fish that were the basis of fish-and-chip suppers from Cornwall in the UK to northern Norway are likely to dwindle over the next 50 years. Many of them cannot move north to get away from the heat, because there is no suitable habitat, and they can’t go deeper, because there isn’t any depth. So the abundance of species will change with time.

“Our study suggests that we will see proportionately less of some of the species we eat most of as they struggle to cope with warming conditions in the North Sea,” said Louise Rutterford of Exeter University, the first author.

Squeezed out

“We provide new insight into how important local depths and associated habitats are to these commercial species. It’s something that is not always captured in existing models that predict future fish distributions.”

Other studies have found that fish in many regions are changing to new latitudes as climates change in response to greenhouse gas emissions from fossil fuel combustion. The same man-made global warming has brought a greater number of sardines, for instance, to northern waters, and in the US fishermen have had to sail ever further north to pursue the black bass. There has even been a warning that the retreat of the Arctic ice means that Atlantic halibut could actually migrate into the North Pacific.

So the latest message is confirmation of an increasingly familiar finding. “We will see a real changing of the guard in the next few decades,” said Steve Simpson, a marine biologist at Exeter, and another of the authors.

“Our models predict cold water species will be squeezed out with warmer water fish likely to take their place. For sustainable UK fisheries, we need to move from haddock and chips and look to southern Europe for our gastronomic inspiration.” – Climate News Network

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Threat to marine life adds to California’s woes

Threat to marine life adds to California’s woes

Unusually high water and air temperatures off the US West Coast as climate patterns shift mean bad news for sea lions, sea birds and the fishing industry.

LONDON, 22 March, 2015 – California, currently in the grip of a devastating drought and facing an increasingly parched future, has just been dealt another blow. Not only is the land less productive, but the state’s fisheries could also be about to feel the heat.

A new report warns that the climate seems to be shifting to warmer, less productive conditions. And that’s bad news for seabirds, salmon, sea lions − and sea fishermen.

At play, according to the National Atmospheric and Oceanic Administration Regional Fisheries Science Centres, is the effect of unusually high coastal water and air temperatures over the last year, and changes in the California Current that washes the West Coast of the US.

The consequence is a dip in what ecologists call “primary productivity” – in this case, the tiny copepods and other microscopic creatures that are the first level of the food chain.

Higher death rates

This means less for salmon and other marine species to eat, and higher death rates among sea lion pups in Southern California, and among sea birds on the Washington and Oregon coasts.

Commercial fisheries so far have been good, but California’s fishermen have begun to specialise, and could see catches fluctuate and revenues fall as their target species start to feel the effects.

Toby Garfield, director of environmental research atthe NOAA Southwest Fisheries Science Centre, says: “We are seeing unprecedented changes in the environment.”

John Stein, who directs the Northwest Fisheries Science Centre, adds: “We’re seeing some major environmental shifts taking place that could affect the ecosystem for years to come. We need to understand and consider their implications across the ecosystem, which includes communities and people.”

The changes are partly cyclic: the sea surface temperatures are at record heights, and these have combined with shifts in meteorological cycles, such as the Pacific Decadal Oscillation, and the North Pacific Gyre Oscillation.

“We’re seeing some major environmental shifts taking place that could affect the ecosystem for years to come”

The consequence is that the normal upwelling of deep cold waters has weakened in recent years, and so has the supply of nourishing copepods. Sea lion pups and a species of seabird called Cassin’s auklet have been found dying and emaciated, which suggests problems with the food supply.

Since 2014, blobs of warm water have been observed in the Gulf of Alaska and all the way down the coast, and these conditions tend to be accompanied by lower productivity.

In the past, this has meant poorer catches of salmon, anchovy and squid, although better catches of sardines, tuna and marlin. But lately, both anchovy and sardine hauls have been at lower levels.

Double jeopardy

Salmon in particular face double jeopardy in California. Not only is the food supply in the sea threatened, but low snowfalls and greater drought mean that the rivers up which the salmon jump to spawn are less hospitable.

The California drought, the worst in the state’s history, has been tentatively linked to global warming. The changes in the California Current may be a coincidence of natural cycles.

Reports such as these are intended to alert communities to changing conditions. They are not so much prescriptions for doom as practical warnings of potential problems ahead. But the tone may well have become more urgent.

“We are in some ways entering a situation we haven’t seen before,” says Cisco Werner, who directs the Southwest Fisheries Science Centre at La Jolla. “That makes it all the more important to look at how these conditions affect the entire ecosystem.” – Climate News Network

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More Antarctic warmth creates heavier snowfall

More Antarctic warmth creates heavier snowfall

Rising temperatures may result in more snow falling in Antarctica, with the ice that builds up flowing to the ocean and raising sea levels.

LONDON, 16 March, 2015 – It may sound unlikely, but the evidence is mounting that the more the Antarctic warms under the impact of climate change, the more snow will fall on it.

Not only that, says a team of European and US scientists, but as the snow turns to ice it is going to flow downhill, borne by its own weight, and contribute to rising sea levels.

The impact of this paradoxical process is likely to be significant. The team, led by scientists from Germany‘s Potsdam Institute for Climate Impact Research (PIK), says each degree Celsius of warming in the region could increase Antarctic snowfall by about 5%.

Ice-core data

The research, published in Nature Climate Change, builds on high-quality ice-core data and fundamental laws of physics captured in global and regional climate model simulations.

The suggestion that Antarctic snowfall is increasing is not itself new, though not all scientists accept the data without qualification.

What the Potsdam scientists have done is important, not simply because they provide new evidence to support the contention, but because they explore its potential consequences.

Katja Frieler, climate impacts and vulnerabilities researcher at PIK, and lead author of the report, says: “Warmer air transports more moisture, and hence produces more precipitation. In cold Antarctica, this takes the form of snowfall. We have now pulled a number of various lines of evidence together and find a very consistent result: temperature increase means more snowfall on Antarctica.”

To reach a robust estimate, the PIK scientists collaborated with colleagues in the Netherlands and the US.

“Ice-cores drilled in different parts of Antarctica provide data that can help us understand the future,” says co-author Peter U. Clark, professor of geology and geophysics at Oregon State University.

“The Antarctic ice sheet could become a major contributor to future sea-level rise, potentially affecting millions of people in coastal areas” 

“Information about the snowfall spanning the large temperature change during the last deglaciation [the uncovering of land by the melting of glaciers], 21,000 to 10,000 years ago, tells us what we can expect during the next century.”

The researchers combined the ice-core data with simulations of the Earth’s climate history and comprehensive future projections by different climate models, and were able to pin down temperature and accumulation changes in warming Antarctica.

The increasing snowfall on the continent will add to the mass of the ice sheet and increase its height.

But the researchers say it won’t stay there. On the basis of another previous PIK study, they say the extra snow will also increase the amount of ice flowing to the ocean.

Dr Frieler says: “Under global warming, the Antarctic ice sheet, with its huge volume, could become a major contributor to future sea-level rise, potentially affecting millions of people living in coastal areas.”

Additional snowfall

As snow piles up on the ice, its weight presses down – the higher the ice, the greater the pressure. Additional snowfall elevates the grounded ice-sheet on the Antarctic landmass, but has less of an effect on the floating ice shelves at the coast, allowing the inland ice to flow more rapidly into the ocean and raise sea levels, the researchers say.

The 5% increase in Antarctic snowfall that they expect for every 1°C rise in temperature would mean an estimated drop in sea-level of about three centimetres after a century.

But they say other processes will cause an eventual rise in sea-level. For example, relatively slight warming of the ocean could cause coastal ice to break off more easily, allowing more of the continental ice mass to discharge into the ocean.

Another co-author is Anders Levermann, PIK professor of dynamics of the climate system, and also a lead author of the sea-level rise chapter in the latest report by Intergovernmental Panel on Climate Change.

He says: “If we look at the big picture, these new findings don’t change the fact that Antarctica will lose more ice than it will gain, and that it will contribute to future sea-level change.” – Climate News Network

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Satellite link puts sharper focus on ocean acidity rise

Satellite link puts sharper focus on ocean acidity rise

Global data network could provide scientists with an easy and cheaper way of finding answers to crucial questions on the oceans’ changing chemistry.

LONDON, 25 February, 2015 − Climate scientists are looking for a new perspective on the increasingly acidic oceans through a suite of satellites 700 km out in space, watching over parts of the seas that research ships cannot reach.

They report in the journal Environmental Science and Technology that thermal cameras could measure ocean temperatures, while microwave sensors could measure ocean salinity. Together, the two sets of data could help answer, cheaply and easily, questions about the chemistry of the oceans – and in particular changes in pH, the index of acidity.

Until now, researchers have depended on specialist instruments or shipboard samples to provide answers to huge questions about the oceans’ increasing uptake of carbon dioxide. Such research is costly and limited.

But ocean science has become ever more important. Each year, 36 billion tonnes of CO2 are released into the atmosphere, and about a quarter of this gets into the oceans.

Greenhouse gas

That’s a good thing: if it did not, global warming would accelerate at an even greater rate. But the same global transfer of greenhouse gas also delivers a stronger solution of carbonic acid to the oceans, and ocean acidity levels have risen by 26% over the last 200 years.

The consequences for all those sea creatures that evolved to exploit ocean chemistry to build shells or skeletons are uncertain, but the evidence so far is that changes can affect fish behaviour, shellfish reproduction, and coral growth.

The changes could almost certainly affect fisheries in the short term, and in the long term could possibly alter the continuous and vital exchanges between atmosphere and ocean that controls the climates of continents.

So marine scientists launched a Global Ocean Acidification Observing Network to assemble worldwide expertise and find new ways to monitor change.

“We are pioneering these techniques so that we can monitor large areas of the Earth’s oceans”

“Satellites are likely to become increasingly important for the monitoring of ocean acidification especially in remote and dangerous waters like the Arctic,” says one of the report’s authors, Jamie Shutler, an oceanographer at the University of Exeter. UK.

“It can be difficult and expensive to take year-round direct measurements in such inaccessible locations. We are pioneering these techniques so that we can monitor large areas of the Earth’s oceans, allowing us to quickly and easily identify those areas most at risk from the increasing acidification.”

The European Space Agency’s SMOS satellite in orbit. Image: ESA

The European Space Agency’s SMOS satellite in orbit.
Image: ESA

The new approach will exploit a number of existing satellites, along with the European Space Agency’s Soil Moisture and Ocean Salinity sensor (SMOS), launched in 2009, and the US space agency NASA’s Aquarius satellite, launched in 2011.

The satellites cannot, of course, directly measure ocean pH values, but the capacity of CO2 to dissolve in water is controlled by ocean temperatures.

Salinity levels

On the other hand, salinity levels play into the capacity to form carbonates. Chlorophyll levels in the oceans also indicate the rates at which biology can exploit any of the dissolved carbon dioxide.

If the scientists have temperature and air pressure data as well, they have enough to begin to calculate the rates at which any stretch of sea might be acidifying.

Although such measurements are indirect, and involve complex mathematical calculation, the results can be checked in some places against real-time data from a network of autonomous instruments called Argo, and by shipboard laboratory studies.

But satellites are about the only way of making consistent measurements of the desolate and hostile Arctic and Indian Oceans. They could also help researchers understand the changes taking place in complex stretches of sea such as the Bay of Bengal and the Greater Caribbean.

The research is in its infancy. But the authors say that satellite studies − supported by good measurements taken directly at sea − could become a key element in understanding and assessing the acidification of the oceans. – Climate News Network

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Sardines swim into northern waters to keep cool

Sardines swim into northern waters to keep cool

Fish species in subtropical European waters are migrating north to escape warming seas − leaving fishermen who rely on them for a living with empty nets.

LONDON, 20 February, 2015 − Several important fish species that for centuries have been part of the staple diet of people in the Mediterranean region are abandoning sub-tropical seas because the water is too warm and are heading north.

Sardines, which for generations have been the most abundant commercial fish species in Portugal, are moving away. They are now established in the North Sea, and are being caught in the Baltic – a sea that until recently was normally frozen over in the winter.

Sardines, anchovies and mackerel − three fish species that are important in the diet of many southern European and North African countries − have been studied by scientists trying to discover how climate change and warming seas are affecting their distribution.

Fishing industry

As well as the affect on the fishing industry, the abundance or disappearance of these species is crucial for many other marine species that rely on them for food.

A pioneering study, published in Global Change Biology, analysed 57,000 fish censuses conducted over 40 years, and has tracked the movement of these fish during this period.

It confirms that the continued increase in water temperature has altered the structure and functioning of marine ecosystems across the world. But it also shows that the effect has been greater in the North Atlantic, with increases of up to 1.3 ºC in the average temperature over the last 30 years.

This variation in temperature directly affects the frequency and range of pelagic fish, which live in the middle of the water column and are directly influenced by temperature, rather than habitat. It includes the sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus), horse mackerel (Trachurus trachurus) and mackerel (Scomber scombrus), among others.

Sardines and other fish represent “an exceptional bioindicator to measure the direction and speed of climate change expected in the near future”

They feed off phytoplankton and zooplankton, and are themselves the staple diet of large predators, such as cetaceans, large fish and marine birds. These fish occur off the shores of many coastal countries in the world and are important sources of protein.

Scientists have known that fish were moving to new areas, but did not know whether it was in response to their main food supply plankton moving first or whether it was a simple response to changing temperatures.

The new study has developed statistical models for the North Sea area, and confirms the great importance of sea temperatures.

“Time series of zooplankton and sea surface temperature data have been included to determine the factor causing these patterns,” Ignasi Montero-Serra, lead author of the study and researcher in the department of Ecology at the University of Barcelona, explains to the Scientific Information and News Service.

To demonstrate the consequences of the warming of the seas, the research team analysed fish censuses from commercial fishing performed independently along the European continental shelf between 1965 and 2012, extracted from data provided by the International Council for the Exploration of the Sea.

The study, which is the first to be carried out on such a large timescale and area, allows for the dynamics of this species to be understood in relation to the rapid warming of the oceans that has been happening since the 1980s.

The results reveal that sardines and other fish with fast life cycles, planktonic larval stage and low habitat dependence are highly vulnerable to changes in ocean temperature, and therefore represent, Montero-Serra says, “an exceptional bioindicator to measure the direction and speed of climate change expected in the near future”.

Accelerated increase

Montero-Serra says that accelerated increase in temperature of the continental seas has resulted in sardines and anchovies − with a typically subtropical distribution − increasing their presence in the North Sea and “even venturing into the Baltic Sea”. And the presence of species with a more northern distribution, such as the herring and the sprat, has decreased.

The analysis is therefore a clear sign that species in the North Sea and Baltic Sea are “becoming subtropical”.

This is due to the pelagic fish being highly dependent on environmental temperatures at different stages of their life cycle − from reproductive migrations and egg-laying, to development and survival of larvae.

According to the researchers, the changes in such an important ecological group “will have an effect on the structure and functioning of the whole ecosystem”, although they still do not know the scale of the socio-economic and ecological repercussions. – Climate News Network

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Climate change triggers threats to marine ecosystems

Climate change triggers threats to marine ecosystems

A two-way migration of fish species between the northern Pacific and Atlantic as oceans warm could have drastic ecological and commercial impacts.

LONDON, 7 February, 2015 − The Atlantic halibut is about to go where no Atlantic halibut has gone before – into the Pacific. And it could meet the Alaska pollock coming in the other direction.

Just as marine commerce could soon exploit the opening of the fabled north-west or north-east passages between the two great oceans, so could at least 80 species of fish.

Mary Wisz, an ecologist now with the Danish DHI group, but formerly at the Arctic Research Centre of Aarhus University in Denmark, reports with colleagues in Nature Climate Change that as sea temperatures increase, and food sources begin to flourish at the highest latitudes, shoals of fish from the Atlantic could reach the Pacific along once almost impassable seaways north of Arctic Canada and Siberia.

Northerly species

The last such large-scale transfer was nearly three million years ago, with the opening of the Bering Strait. But climate conditions that were once harsh have begun to open migration opportunities for the northerly species in both oceans, the researchers say.

Such changes have happened before. Since the opening of the Suez Canal in 1869, the Mediterranean has been invaded by 55 Red Sea species, with a “drastic impact” on commercial fisheries.

Fish are already moving north in response to climate change, and Dr Wisz and her colleagues modelled what would happen to 515 species of fish under predicted conditions of global warming later this century.

By 2050, the scientists believe, trans-Arctic traffic will accelerate, and by 2100, 41 Atlantic species − among them cod and herring − could reach the Pacific, while 44 species could get into the Atlantic.

They warn: “This exchange of fish species may trigger changes in the North Atlantic and the North Pacific, with ecological and economic consequences to ecosystems that at present contribute 39% to global marine fish landings.”

Changes to marine chemistry also threaten the balance of power in the oceans

The Danish-led team was essentially modelling temperature, currents and spawning strategies to see which species were most likely to find new grounds. But changes to marine chemistry also threaten the balance of power in the oceans.

The seas are predicted to become more acidic as more carbon dioxide gets into the atmosphere, and this change in water chemistry is likely to affect not just fish and shellfish but also entire communities of creatures.

Scientists have tested the fauna that foul ships’ hulls. These are the tiny barnacles and squirts that attach themselves to hard surfaces wherever they can in the oceans.

Lloyd Peck, a biologist with the British Antarctic Survey, and colleagues report in Global Change Biology that they tested creatures from a lagoon off the Algarve in Portugal, in aquarium tanks.

One set of tanks was filled with normal sea water; in the other set, the sea water was set at levels of acidity predicted to be normal within the next 50 years. Within 100 days, in the more acid tanks, the make-up of the community that colonised the hard surfaces had begun to change.

Worms with hard shells in the more acidic tanks were reduced to a fifth of their normal levels, but sponges and sea squirts multiplied twofold and even fourfold.

“Our experiment shows the response of one biofouling community to a very rapid change in acidity,” said Professor Peck. “What’s interesting is that the increased acidity at the levels we studied destroys not only the building blocks in the outer shell of the worms itself, but the binding that holds it together.

“Many individuals perish, but we also showed their larvae and juveniles are also unable to establish and create their hard exoskeletons.”

Altered behaviour

Climate change could also alter the behaviour of the green sea turtle, Chelonia mydas, according to an international team led by Professor Kyle Van Houtan, of the Nicholas School of the Environment and Earth Sciences at Duke University, US.

The researchers studied six years of turtle observations off Oahu, Hawaii, and 24 years of satellite data for sea surface temperatures in regions that are home to 11 populations of the turtle.

They report in Biology Letters that they know why the turtles crawl up onto the beach to bask. Not all populations bask, but the ones that do tend to sprawl in the sand do so to regulate body temperatures, and were least likely to bask when local winter sea temperatures stayed above 23°C. When the seas stayed warm, the turtles stayed in the water.

Given the predicted ocean temperature rises over the next century, the scientists calculate that green turtles may stop basking altogether by 2100. – Climate News Network

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