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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New ocean energy plan could worsen global warming

New ocean energy plan could worsen global warming

An apparently promising way of producing energy from the world’s oceans in fact risks causing catastrophic harm by warming the Earth far more than it can bear, US scientists say.

LONDON, 4 April, 2015 − One of renewable energy’s more outspoken enthusiasts has delivered bad news for the prospects of developing ocean thermal energy. His prediction is that although the technology could work for a while, after about 50 years it could actually exacerbate long-term global warning.

Of all the renewable energy technologies, ocean thermal energy conversion (OTEC) sounded like the perfect choice. This is a plan to exploit the difference between the warm surface and the cold deeps of the seas, and turn that difference into energy.

The agency that did the work would be a network of vertical pipes floating below the surface: it would not spoil the view from the coast, and it would deliver power day or night, whatever the weather. But there was more.

Enthusiasts pointed out that as a bonus, the pipes used in the energy conversion would bring a flow of nutrients from the cold, deep waters to the less-fertile but sunlit surface of the ocean, thus encouraging the growth of marine algae that would soak up more carbon from the atmosphere. And, as a bonus, the same process would accelerate the downward flow of carbon, where it could be sequestered on the sea bed.

Now one of renewable energy’s more vocal supporters has taken a closer look at the long-term consequences of the ocean pipes and come up with some discouraging news: an engineering programme intended to cool the planet would end up making it warmer. It would work for a while, he says, but after about half a century it would reduce the cloud cover and at the same time reduce the sea ice, to accelerate climate change once more.

Warming exacerbated

Ken Caldeira, senior scientist in the Department of Global Ecology at Stanford University’s Carnegie Institution, California, is one of the more energetic voices in climate research: he and his Carnegie colleagues have already warned that the world is feeling the heat from carbon dioxide released from car exhausts and factory chimneys and he has spoken up loudly for nuclear power, and indeed any “clean” energy sources.

He and Stanford colleagues Lester Kwiatkowski and Katharine Ricke report in Environmental Research Letters that when they began to simulate an ocean dotted with vertical pipes that exchanged deeper and shallower waters, they expected to confirm the value of such an approach. They could not.

“Our simulations indicate the likely sign and character of unintended atmospheric consequences of such ocean technologies,” they conclude, in formal science-speak. “Prolonged application of ocean pipe technologies, rather than avoiding global warming, could exacerbate long-term warming of the climate system.”

Research exercises such as this one cost nothing more than laboratory computing power and research time: their value once again is in reminding governments, campaigners and energy investors that the climate is an intricate piece of global machinery, and that there are no easy answers to the problems presented by renewable energy.

Radical change

They are also a reminder that geo-engineering of any kind to damp climate change could have unintended consequences. In this case – in an ideal, global simulation – it would change the thermal structure of the ocean altogether.

The Carnegie calculations work like this: cold air is denser than warm air. Water funnelled up the pipes on a very large scale from the depths would cool the air above the seas, and increase atmospheric pressure, which would reduce cloud formation over the seas. Since most of the planet is ocean, that means fewer clouds overall, which means more sunlight absorbed by the Earth rather than reflected back into space by the clouds.

And the same mixing of sea waters would bring sea ice into contact with warmer waters, which would mean less sea ice to reflect radiation, with the same result: accelerated global warming.

After 60 years, the simulated network of ocean pipes would cause an increase of global temperature by up to 1.2°C. After a few centuries, the same technology would take temperatures up by a catastrophic 8°5C.

“I cannot envisage any scenario in which a large scale global implementation of ocean pipes would be advisable,” said the report’s lead author, Dr Kwiatkowski. “In fact, our study shows it could exacerbate long-term warning and is therefore highly inadvisable at global scales.” – Climate News Network

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Climate-driven loss of habitat endangers marine mammals

Climate-driven loss of habitat endangers marine mammals

Global survey of threatened Arctic species warns that conservation won’t work without regulation of greenhouse gas emissions to halt climate change.

LONDON, 2 April, 2015 − Three kinds of whale, six varieties of seal, the walrus and the polar bear all have things in common: they are marine mammals, they depend on the Arctic for survival as species, they are vulnerable, and biologists know surprisingly little about them.

And since the Arctic is warming twice as fast as the rest of the planet, their future could become even more threatened as climate change increases habitat loss.

The stress, so far, is on the word “could”, as the first challenge is to establish the facts.

A global study team led by Kristin Laidre, principal scientist at the University of Washington Polar Science Centre in Seattle, reports in the journal Conservation Biology that marine mammals are “disproportionately threatened and data poor compared with their terrestrial counterparts”.

The narwhal, beluga and bowhead whales, the ringed, bearded, spotted, ribbon, harp and hooded seals, the walrus, and the polar bear are “particularly vulnerable due to their dependence on sea ice”.

Important predators

All these animals make their living on the ice and in waters north of the Arctic Circle, and all are important predators. They are also important to indigenous and settler peoples in the frozen North as many can be legally harvested, and others are iconic tourist attractions. Either way, they help communities survive.

“These species are not only icons of climate change, they are also indicators of ecosystem health, and key resources for humans,” Dr Laidre says. “Accurate scientific data – currently lacking for many species – will be key to making informed and efficient decisions about conservation challenges and trade-offs in the 21st century.”

So the researchers set out on what they believe is the first comprehensive global review of what is known about the populations of these animals, and about the way their local habitats may be changing.

“They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life.”

The study divided the Arctic into 12 regions and began to look at population numbers and trends, and the local pattern of seasonal change in the ice.

They identified 78 distinct populations of the 11 species, and began to assemble estimates of numbers. These range from millions for the ringed seals to a few hundred for the beluga whales of Ungava Bay in the Canadian Arctic.

In many cases, researchers had too little information even to make a guess about whether local populations of any species were stable, declining or increasing. In their table of the trends of the 11 species in the 78 populations, the word “unknown” occurs more than 60 times.

They also charted profound reductions in ice cover. The sea ice naturally advances each winter, and retreats each spring, but because of global warming driven by human emissions of greenhouse gases released by fossil fuel combustion, the pattern of advance and retreat has changed dramatically. By 2040, according to some projections, the Arctic could be more or less ice-free each summer.

Extended summer

But change is visible now. In most regions, the scientists found that the summer period was extended by between five and 10 weeks. In Russia’s Barents Sea, the summer ice period is now 20 weeks longer – five months – than it was 30 years ago.

This presents a threat to the polar bear, and to the seals on which they feed. “These animals require sea ice,” Dr Laidre says. “They need ice to find food, find mates, reproduce, and rear their young. It’s their platform of life. It is very clear those species are going to feel the effects the hardest.”

On the other hand, the whale species might benefit – at least for a while – from reduced ice cover. Open water could offer a wider feeding range and greater marine productivity, and therefore more food.

The scientists provide a set of general recommendations for biologists, local authorities, government agencies and international organisations concerned with conservation of Arctic marine mammals. They also have a message for the entire planet.

As Dr Laidre says: “We may introduce conservation measures or protected species legislation, but none of those things can really address the primary driver of Arctic climate change and habitat loss for these species. The only thing that can do that is regulation of greenhouse gases.” – Climate News Network

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Eyes in the sky see seas rising alarmingly faster

Eyes in the sky see seas rising alarmingly faster

Scientists analysing sophisticated satellite data warn that rises in sea level more rapid than expected are increasing threats to coastal cities and food security.

LONDON, 27 March, 2015 − Satellite observations show that sea level rise may have been underestimated, and that annual rises are increasing.

A collaborative effort between maritime organisations and space agencies in measuring sea level rise has come to the conclusion that it has been increasing by 3.1 millimetres a year since 1993 – higher than previous estimates.

The evidence is growing from a number of recent studies of the ice caps that sea level rise is accelerating, posing a threat to many of the world’s largest and most wealthy cities − most of which are also important ports.

Many of these in the developing world have little or no protection against rising sea levels. Some in Europe – such as London and Rotterdam − already have flood barriers to protect areas below high tide or storm surge level, but  these will need to be replaced and raised in the next 30 years.

Delta areas in Egypt, Vietnam, Bangladesh and China – vital to each of the nation’s food supply – are already losing land to the sea.

Difficult to measure

One of the problems scientists have had in getting accurate worldwide data is that the sea does not rise evenly around the globe. This, added to the fact that in some places the land is sinking and in other places is rising, makes exact information difficult to measure from tide gauges.

Since 1991, it has been possible to measure the surface of the oceans across the entire globe by using satellite altimetry, whereby the satellite emits a signal towards the ocean’s surface and receives the reflected echo. The sea level is calculated from the round-trip time between the satellite and the sea surface and the position of the satellite along its trajectory.

While the data from tide gauges provides information about local changes relative to the land, the use of altimeter satellites enables the recording of data on a global basis.

Luciana Fenoglio-Marc, a scientist specialising in physical and satellite geodesy at the Technical University of Darmstadt, Germany, uses these and other satellite geodetic observation data in her research.

She is working with the European Space Agency and the European Organisation for the Exploitation of Meteorological Satellites, and in close consultation with the German Federal Institute of Hydrology and the Federal Maritime and Hydrographic Agency of Germany.

This lends credibility to the report that European coastal cities are not sufficiently prepared for the threats that climate change poses

The increase of around 3.1mm per year since 1993 indicates a marked rise in the average sea level when compared to previously recorded values, which show a sea level rise of between 1mm and 2mm per year in the 20th century.

In its fifth Assessment Report (AR5, 2013), the Intergovernmental Panel on Climate Change (IPCC) predicted a further increase in the global sea level of 30cm to 70cm by the end of the 21st century, based on a scenario involving a medium rate of global warming.

The report predicted that increases will not be even, but will have a greater impact on some regions than on others. The result could be coastal flooding and rising groundwater levels – an outlook that makes it essential to have a reliable data basis for dealing with the dangers this poses.

Protecting coasts from the rising seas will require considerable adaptations, particularly in such low-lying coastal regions as the North Sea coast of Germany and the many low-lying islands in the tropics.

Another aspect of the work with satellites is measuring ocean density to see how much water expansion − because of warming − is leading to sea level rise. A direct estimation of mass changes in the Mediterranean Sea show expansion to be the cause of an average sea level rise of about 2.1mm per year since 1993.

According to the IPCC, about 35% of the sea level increase between 1993 and 2010 was the result of thermal expansion, and the rest was due to melting ice and increasing run-off from land. But the latest observation shows this may not be true of the Mediterranean.

Too cautious

There is wide debate about whether the IPCC estimates of sea level rise have been too cautious, suggesting that the sea level will rise more than a metre this century – and some have even suggested that the rise could be two metres.

This is mainly because there has been uncertainty about how much of the huge icecap in Greenland, and most of all in Antarctica, would contribute to sea level rise by 2100 – if at all.

Research published since the IPCC estimates were made show that both icecaps will be large net contributors to sea level rise, and possibly much quicker than previously thought.

This lends credibility to the report last week that European coastal cities are not sufficiently prepared for the threats that climate change poses. The report − titled Underfunded, Unprepared, Underwater? Cities at Risk – is by the E3G non-governmental organisation, and it says governments across the European Union are leaving their major cities exposed to danger from climate change, including floods, heat waves and sea level rise.

Since it takes an average of 30 years from planning to complete construction of a major flood barrier to protect a city, the report warns that the problem needs to be given urgent consideration and funding. – Climate News Network

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Deep concerns as climate impacts on Gulf Stream flow

Deep concerns as climate impacts on Gulf Stream flow

Ocean scientists find evidence of an increasing slowdown in the Atlantic’s “invisible river” that could seriously affect weather and sea levels in the US and Europe.

LONDON, 25 March, 2015 − Climate scientists have once again confirmed an alarming slowdown in the circulation of the Atlantic Ocean − the process that drives the current that warms Europe, and powers the planetary climate.

And this time, they are prepared to say that the changes are recent − and may be linked to global warming.

The Atlantic Conveyor is a great invisible river that flows in two directions at the same time. The equatorial surface waters − warm, and therefore less dense − flow towards the north in the form of the Gulf Stream. Around Greenland, the denser and colder Arctic waters sink to the ocean bottom and begin their progress towards the south.

It is the difference in temperatures that maintains the turnover and keeps the climate engine going.

As a consequence, the two-way traffic of warm and cold water redistributes heat around the planet and keeps Britain and maritime Europe in relatively mild conditions.

But as global average temperatures rise, and the Greenland ice sheet melts, ocean scientists have warned that the speed of the ocean turnover could be put at risk.

Greater weakening

Stefan Rahmstorf, an ocean physicist at the Potsdam Institute for Climate Impact Research in Germany, is lead author of a report in Nature Climate Change that says they now have evidence of a slowdown during the 20th century, and greater weakening since the first alarms 40 years ago about the possible effects of greenhouse emissions.

“It is conspicuous that one specific area in the North Atlantic has been cooling in the past hundred years, while the rest of the world heats up,” Professor Rahmstorf says. “Now we have detected strong evidence that the global conveyor has indeed been weakening in the past hundred years, particularly since 1970.”

The paradox of the Atlantic current is that, in a warmer world, it could slow down or halt, which would deliver uncomfortable consequences for maritime Europe.

Fears of such an effect provided the scenario for the 2004 climate disaster movie, The Day After Tomorrow, which predicated a frozen Britain and a glaciated US.

“Now we have detected strong evidence that the global conveyor has indeed been weakening in the past hundred years, particularly since 1970”

No such extreme outcome was ever likely, but the Gulf Stream certainly makes a big difference to Britain. A former UK chief scientist once calculated that it delivered 27,000 times the warmth that Britain’s power stations could supply and, as a consequence, the UK is on average 5°C warmer than it might be, given its latitude.

Strength of current

At a number of points in the last two decades, researchers have wondered about the strength of the Atlantic current, but since systematic oceanographic record-keeping began only relatively recently, they had no way of distinguishing between a natural oceanic cycle and real change.

So the Potsdam team used all available data, and “proxy temperatures” derived from ice-cores, tree-rings, coral, and ocean and lake sediments, to reconstruct the story of the Atlantic current − and, in particular, the phenomenon called the Atlantic meridional overturning circulation (AMOC) − for the last 1,000 years.

The changes happening now have no precedent since 900 AD, they say. And the increasingly rapid melting of the Greenland icecap – bringing an increased flow of water that is less saline and also less dense, and therefore less likely to sink − could disturb the circulation.

The consequences of all this could, they say, “contribute to further weakening of the AMOC” in the coming decades.

Atlantic Conveyor: a graph of the Atlantic Meridional Overturning Circulation (AMOC). Image: Stefan Rahmstorf/PIK

Atlantic Conveyor: a graph of the Atlantic Meridional Overturning Circulation (AMOC).
Image: Stefan Rahmstorf/PIK

This is not the first such alarm. The same weakening was identified last year, but at the time researchers could not be sure they were not looking at a natural fluctuation.

Now they are sure, and they suspect that the cooling of the north Atlantic that they now observe is even stronger than most computer simulations have so far predicted.

“Common climate models are underestimating the change we’re facing, either because the Atlantic overturning is too stable in the models or because they don’t properly account for the Greenland ice sheet melt, or both,” says one of the co-authors, Michael Mann, professor of meteorology at Pennsylvania State University in the US.

Climate predictions

“That is another example where observations suggest that climate model predictions are in some respects still overly-conservative when it comes to the pace at which certain aspects of climate change are proceeding.”

Another of the authors, Jason Box, professor of glaciology at the Geological Survey of Denmark and Greenland, adds that “the human-caused mass loss of the Greenland ice sheet appears to be slowing down the Atlantic overturning − and this effect might increase if temperatures are allowed to rise further”.

The stakes are high. If the Atlantic conveyor system continues to weaken, ocean ecosystems will change, fishing communities will be affected, and some coastal cities – such as New York and Boston in the US − could be hit by additional regional sea level rises.

The 2004 Hollywood version – promoted with a huge poster of New York’s Statue of Liberty all but covered by ice – is not likely to happen. But if the ocean circulation weakens too much, there could be a relatively rapid and difficult-to-reverse change in the world’s climate system.

The Intergovernmental Panel on Climate Change estimates that there is a one-in-10 chance of this “tipping point” happening within the 21st century.

But the evidence from the Potsdam team is now likely to prompt other climate scientists to go back to their calculations and re-evaluate the risk. – 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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Two oceans may explain global warming pause

Two oceans may explain global warming pause

Temperatures may be rising more slowly than expected because of two natural oceanic cycles − the latest refutation of the global warming “pause”.

LONDON, 1 March, 2015 − US scientists have suggested yet another explanation for the so-called pause in global warming. They think it might all be down to the juxtaposition of two independent natural climate cycles – each with periods of half a century or more – one of which is blowing cold, and the other not very hot.

Between them, the phenomena known to meteorologists as the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation could account for the seeming slowdown in predicted temperature rises.

Any pause or hiatus in global warming is only apparent: in fact, 14 of the warmest years on record have happened in the last 15 years and 2014 was scored separately, by the World Meteorological Organisation, the US National Oceanic and Atmospheric Administration, and the US space agency Nasa,  as the warmest on record.

But overall, the palpable increases in average temperatures per decade recorded in the last 30 years of the 20th century have not been maintained, and climate scientists and meteorologists have been trying to work out why.

The latest proposal is from Byron Steinman, a geologist at the University of Minnesota Duluth, and Michael Mann and Sonya Miller of Pennsylvania State University.

Multiple theories

Professor Mann is the scientist who, much to the fury of people who deny climate change, first formulated the famous “hockey-stick graph” which highlights the magnitude of change that threatens to overtake global climate as greenhouse gas levels rise because of human activity.

They report in Science that the northern hemisphere is warming more slowly, not because of the Atlantic oscillation, which has been relatively flat, but because of a second, different but still natural downward trend in the Pacific cycle.

This is not the only explanation on the table. In the past two years Climate News Network has reported that climate scientists certainly expected a slowdown, but just not right now; or that planetary measurements might be incomplete or misleading; or that even though average levels were down, this masked a series of hotter extremes.

The oceans have certainly been under suspicion. One group has already identified the cooling Pacific as a damper on global warming. Another has suggested that in fact the “missing heat” is collecting in the Atlantic depths.

Yet another has questioned the role of the trade winds, while still another has pointed to an upswing in volcanic activity that could have delivered a fine smear of sunblock aerosols to the atmosphere.

“The North Atlantic and North Pacific Oceans appear to be drivers of substantial natural… climate variability on timescales of decades”

Any or all of these could have some role in the big picture. The climate would vary anyway, and the question in every case is: how much would any or all natural variation affect the overall path of change because of increasing carbon dioxide levels in the atmosphere?

The latest study is based on sophisticated climate models that match the predicted impact of the great ocean-atmosphere cycles with the pattern of climate shifts recorded in the past.

“We know that it is important to distinguish between human-caused and natural climate variability so we can assess the impact of human-caused climate change, including drought and weather extremes,” Professor Mann said.

“The North Atlantic and North Pacific Oceans appear to be drivers of substantial natural, internal climate variability on timescales of decades.” – Climate News Network

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Acid attack on algae damages ocean ecosystem

Acid attack on algae damages ocean ecosystem

Increasing acidity in the Southern Ocean is having a serious effect on the growth of a small but hugely important food source for marine life.

LONDON, 27 February, 2015 − As the planet’s oceans become more acidic, the diatoms − a major group of alga − in the Southern Ocean could grow more slowly.

Nobody expected this. And since tiny, single-celled algae are a primary food source for an entire ocean ecosystem, the discovery seems ominous.

Bioscientist Clara Hoppe and colleagues from the Alfred Wegener Institute [http://www.awi.de/en/home/]at the Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, report in the journal New Phytologist that they tested the growth of the Antarctic diatom Chaetoceros debilis under laboratory conditions.

They used two levels of pH – which is an indicator of acidity – and they exposed their tiny volunteers to constant light and to changing light, providing both standard laboratory conditions and lighting levels that approximated to the real world.

Plant growth

In the unblinking glare of light, the diatoms responded well. Their growth levels were consistent with an assumption that more dissolved carbon dioxide – which makes the waters more acidic – would in effect fertilise plant growth.

Under conditions of changing light, however, it was a different story. The algae grew more slowly, which suggests that the oceans could become less efficient at removing carbon from the atmosphere, and perhaps less valuable as a primary food source for the creatures that teem in the Antarctic waters.

“Diatoms fulfil an important role in the Earth’s climate system,” Dr Hoppe says. “They can absorb large quantities of carbon dioxide, which they bind before ultimately transporting part of it to the depths of the ocean.

“Once there, the greenhouse gas remains naturally sequestered for centuries.”

Previous research into the steady acidification of the oceans has tended to concentrate on the consequences for coral reefs,  fisheries, and tourism, but not on the impact on plant life in the seas.

Since carbon dioxide acts as a fertiliser, higher levels dissolved in the water might stimulate more growth.

“We now know that when the light intensity constantly changes, the effect of ocean acidification reverses”

But growth depends not just on more carbon dioxide, but also on reliable sunlight. In the stormy southern seas, this is not steadily supplied.

Dr Hoppe says: “Several times a day, winds and currents transport diatoms in the Southern Ocean from the uppermost water layer to the layers below, and then back to the surface – which means that, in the course of a day, the diatoms experience alternating phases with more and with less light.”

Her co-author, marine biogeochemist Björn Rost, from the Alfred Wegener Institute, says: “Our findings show for the first time that our old assumptions most likely fall short of the mark. We now know that when the light intensity constantly changes, the effect of ocean acidification reverses.

“All of a sudden, lower pH values don’t increase growth, like studies using constant light show. Instead, they have the opposite effect.”

The implication is that, at certain intensities, the photosynthesis chain breaks down. The point at which light becomes too much light is more quickly reached in waters that are more acidic.

Like all such research, the finding has limitations. It applies to one species of single-celled creature in the waters of one ocean, and the tests were in a laboratory on a small scale, and not in a turbulent ocean rich in life. The Alfred Wegener team will continue their studies.

But in the real world, coastal communities in 15 US states could be at long-term economic risk, as ocean acidification starts to take its toll on the commercial oyster fisheries.

Julia Ekstrom, then of the Natural Resources Defense Council and now director of the Climate Adaptation Programme at the University of California, Davis, and George Waldbusser, assistant professor of ocean ecology and biogeochemistry at Oregon State University report with colleagues, in Nature Climate Change, on an unholy mix in the oceans.

Fisheries at risk

They say that a combination of rising greenhouse gas levels, more acid waters, polluted rivers, and upwelling currents put at risk mollusc fisheries from the Pacific Northwest, New England, the Mid-Atlantic states and the Gulf of Mexico – affecting the shellfish industry that is worth at least $1bn to the US.

Oyster larvae are sensitive to changes in ocean water, and more likely to die as pH levels shift towards the acidic.

But acidification is not the only source of stress, as nitrogen-rich nutrients and chemical pollutants cascade from the land into the rivers, and wash through estuaries and fish hatcheries on the coast.

Things can be done. Scientists have been looking at ways in which the industry might be able to adapt to change. But how well the oyster stock can adapt in the long term remains problematic.

“Ocean acidification has already cost the oyster industry in the Pacific Northwest nearly $110 million and has jeopardised about 3,200 jobs,” Dr Ekstrom says.

And Dr Waldbusser adds: “Without curbing carbon emissions, we will eventually run out of tools to address the short term, and we will be stuck with a much longer-term problem.” – 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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