Arctic melting opens sea route to more pollution

Arctic melting opens sea route to more pollution

Increasing loss of Arctic sea ice is likely soon to mean more ships being able to use the polar passage affecting climate, health and air quality.

LONDON, 14 February, 2015 − As Arctic sea ice continues to melt at an alarming rate, maritime traffic is set to increase − and with it the pollution emitted by ships’ engines.

A paper published by the International Council on Clean Transportation (ICCT) says emissions of pollutants from vessels in the US area of the high Arctic could increase by between 150% and 600% by 2025.

Ships typically burn bunker fuel with a high sulphur content. As well as various greenhouse gases (GHGs), the engines also emit soot, or black carbon. And when this covers snow and ice, it reduces their ability to reflect sunlight away from the Earth, and so raises temperatures.

Human health

The ICCT paper says ship-borne pollutants − which include carbon dioxide, nitrous oxide (NOX), oxides of sulphur, particulate matter (PM) and soot − affect local air quality and human health, as well as the global climate.

Without new pollution controls, it is estimated that global soot emissions from shipping may more than quintuple from 2004 to 2050, to a total of more than 744,000 tonnes, because of increased shipping demand.

A growing share of those emissions will occur in the Arctic, because of vessels being diverted to the much shorter Northwest Passage and Northeast Passage to cut the length of voyages.

Earlier studies of increased shipping in the Arctic concentrated on infrastructure needs and estimates of shipping growth, based on potential oil and gas exploration and other development, but did not address air pollution or its effects.

The paper says: “The potential increases in vessel activity associated with oil and gas exploration . . . would increase emissions from vessels beyond those estimated in this paper.”

It also says that a change to higher quality low-sulphur fuel would cut pollution significantly.

“The lack of regional restrictions in the Arctic leaves the area vulnerable to increasing emissions from international traffic . . .”

Mark Jacobson, professor of civil and environmental engineering at Stanford University, US, advised as long ago as 2011 that controlling soot could reduce warming in the Arctic by about 2°C within 15 years.

“That would virtually erase all of the warming that has occurred in the Arctic during the last 100 years,” he said. “No other measure could have such an immediate effect.”

He said soot emissions were second only to carbon dioxide in promoting global warming, accounting for about 17% of the extra heat. But its contribution could be cut by 90% in five to 10 years with aggressive national and international policies.

The International Maritime Organisation (IMO], a UN body, said in the final report of its GHG Study 2014 that, by 2050, emissions of NOX could increase globally by as much as 300%, and PM by 280%.

The IMO has two sets of emission and fuel quality requirements, one for global shipping and the other a more stringent set of rules for ships in Emission Control Areas.

The global requirements include a limit on marine bunker fuel sulphur content, which is currently 3.5%, compared with an actual global average of 2.7%. This limit is due to be cut to 0.5% in 2020, although parts of the shipping industry are urging the IMO to delay the reduction until at least 2025.

International regulations do not directly restrict the emission of soot from vessels, although it is generally understood that improving fuel quality also controls soot.

Increasing impact

The ICCT paper says that, combined with the potential increases in marine emissions, “the current lack of regional environmental requirements for vessels transiting and operating in the US Arctic may lead to an increasing impact on human health for Arctic communities and for the global climate.

“Additional emissions of climate-forcing pollutants such as black carbon and carbon dioxide, combined with emissions of PM and NOX, which can be linked with respiratory health issues, may place additional stress on the Arctic environment and Arctic communities.

“The lack of regional restrictions in the Arctic leaves the area vulnerable to increasing emissions from international traffic that is less tightly regulated than under US law.”

There have also been calls to find alternatives to the many diesel generators currently in use throughout Arctic communities, and which are known to produce large amounts of greenhouse gases and soot. − Climate News Network

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Ancient shells offer evidence of how Ice Age ended

Ancient shells offer evidence of how Ice Age ended

Ocean sediment reveals that release of carbon stored deep in the sea is linked to the rise in atmospheric CO2 that caused the world to warm.

LONDON, 13 February, 2015 − Scientists believe they may have cracked the mystery of the end of the last ice age. The temperatures suddenly soared, and the glaciers went into retreat, because the deep southern ocean released huge quantities of carbon dioxide.

And the convincing answers have been delivered by analysis of the composition of calcium carbonate shells of ancient marine organisms.

The link between human burning of fossil fuels and the steady rise in atmospheric carbon dioxide levels was proposed more than a century ago and firmly established in the last 30 years.

But the ups and downs of planetary temperatures before the emergence of human civilisation are harder to explain. Fossil evidence suggests a link with carbon dioxide levels, but not necessarily a cause.

Bygone climates

Now paleoceanographer Miguel Martínez-Botí, from the University of Southampton, UK, and ocean and climate change researcher Gianluca Marino, from the Australian National University, report in Nature that they found their evidence in sediment cores – in effect, annual records of bygone climates – rich in the shells of tiny foraminifera called Globigerina bulloides.

This is a species that flourishes in conditions of high nutrients, acting as a kind of biological pump, gulping carbon from the atmosphere.

They found that high concentrations of carbon dioxide dissolved in surface waters of the southern Atlantic Ocean and the eastern equatorial Pacific coincided with rises in atmospheric CO2 at the end of the last ice age.

The implication is that these regions were the source of the carbon dioxide to the atmosphere.

“Our findings support the theory that a series of processes in the Southern Ocean changed the amount of carbon in the deep sea”

At their coldest, during the ice ages, carbon dioxide levels fell to 185 parts per million. During the interglacials, when the world warmed and lions and hyenas roamed the plains of Europe, the carbon dioxide levels rose to 280 ppm.

Right now, thanks to human activity, CO2 levels are rising ominously towards 400 ppm.

The oceans are home to about 60 times more carbon than the atmosphere and can, it seems, surrender it rapidly.

“The magnitude and rapidity of the swings in atmospheric CO2 across the ice age cycles suggest that changes in ocean carbon storage are important drivers of natural atmospheric CO2 variations,” Dr Martínez-Botí says.

“Our findings support the theory that a series of processes operating in the southernmost sector of the Atlantic, Pacific and Indian oceans, a region known as the Southern Ocean, changed the amount of carbon in the deep sea.

Into the abyss

“While a reduction in communication between the deep sea and the atmosphere in this region potentially locks carbon away from the atmosphere into the abyss during ice ages, the opposite occurs during warm interglacial periods.”

To arrive at their conclusion, the scientists had to analyse subtle evidence from the isotopic composition of the carbonate shells, and then use mathematical techniques to reconstruct a story of a great, faraway sigh of carbon dioxide from the ocean to the atmosphere.

The finding, based on calculated probabilities, is incomplete as there may have been other forces also at play.

Gavin Foster, associate professor in isotope geochemistry at the University of Southampton, says: “While our results support a primary role for the Southern Ocean processes in these natural cycles, we don’t yet know the full story. Other processes operating in other parts of the ocean, such as the north Pacific, may have an additional role to play.” – Climate News Network

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Growing concern over Iceland’s rising landmass

Growing concern over Iceland’s rising landmass

Satellite data confirms a global warming link between the melting of icecaps and an accelerating increase in the height of Icelandic hills.

LONDON, 10 February, 2015 − Iceland is certainly going up in the world − but that’s not necessarily good news. As the ice melts and glaciers retreat, the mantle below the crust of the Atlantic island has responded, and the ice-capped hills are rising by an average of 30mm a year.

And scientists says that their analysis of precision data from a network of satellite stations indicates that this uplift is accelerating by one or two millimetres a year.

Isostasy is not a new idea. Geologists have known for more than a century that the rigid plates of the Earth’s crust − the lithosphere − ride on a viscous, springy mantle called the asthenosphere.

As crustal mass is lost – the erosion of mountains, for instance, or the retreat of Ice Age glaciers – the asthenosphere responds, and the landmass rises. Similarly, when a volcanic cone is built by a series of rapid eruptions, the asthenosphere below starts to respond to the new burden by sinking.

Heaving and sinking

The principle is well established, and there is geological evidence of this slow heaving and sinking everywhere. But nobody had expected to be able to measure it as it happens.

Kathleen Compton,  of the University of Arizona’s Department of Geosciences, and colleagues report in Geophysical Research Letters that they used a network of 62 global positioning satellite stations to measure ground movements with exquisite accuracy.

They chose a set of stable icecaps away from the more active volcanic zones, to eliminate the heaving and sighing of the bedrock that is connected with eruption. Enough data was available from early installations of GPS stations to confirm that uplift from the end of the last ice age about 9,000 years ago was more or less at an end.

“What we’re observing is climatically-induced change in the Earth’s surface”

A glacier year that began in October and ended in September was chosen, so that measurements would not be confused by spring melting or early snowfall.

In the last 30 years, the world has warmed and the high latitudes of the northern hemisphere have warmed the fastest. The Arctic melting season has been advancing at the rate of about 17 days a decade.

The researchers’ measurements show that uplift began about 30 years ago, with some sites in Iceland now rising at 35mm a year. And this rate is increasing.

“Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ice caps,” said Compton, a doctoral student.

“Iceland is the first place we can say accelerated uplift means accelerated ice loss,” said her co-author, associate professor Richard Bennett. “What we’re observing is climatically-induced change in the Earth’s surface.”

Volcanic activity

There is a tantalising possibility that they may also be observing a change in volcanic activity. Geological evidence suggests that, as the glaciers began to retreat 12,000 years ago, Iceland’s eruptions increased thirty-fold.

Other researchers have raised the possibility that warming-induced ice loss could increase the frequency of eruptions now.

But the Arizona team simply wanted to establish a connection between the rate of melting and the rate of uplift, and used mathematical models to confirm the coupling.

Dr Bennett says: “There’s no way to explain that accelerated uplift unless the glacier is disappearing at an accelerating rate.” – Climate News Network

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Greenland’s hidden meltwater lakes store up trouble

Greenland’s hidden meltwater lakes store up trouble

Scientists find evidence of vast “storage tanks” of water deep below the melting Greenland ice sheet that could have a major effect on sea level rise.

LONDON, 5 February, 2015 − One small mystery that surrounds Greenland’s melting ice is a little closer to being solved as scientists in the US confirm that surface meltwater can drain all the way down to fill concealed lakes under the ice.

This means that atmospheric warming can reach thousands of metres below the ice sheet − warming the glacial base and potentially increasing its rate of flow.

One group, led by geologist Michael Willis, of Cornell University, and another team led by glaciologist Ian Howat, of Ohio State University, report in two different journals on separate but related studies of Greenland’s plumbing system: what happens to meltwater.

The ice sheet of Greenland adds up to about four-fifths of the mass of the vast frozen island, and there is evidence that, as a consequence of global warming, the rate of melting has begun to accelerate.

Measurable difference

This has already begun to make a measureable difference to global sea levels, and were the entire island to shed its burden of ice – a process that would take a considerable time − then sea levels would rise by seven metres or more.

So what exactly happens to the water that forms on the surface and collects in lakes each summer, and how much of it gets into the sea, has become an important but perplexing problem. Surface lakes are now appearing much further inland, and at higher altitudes, than recorded in the past.

Dr Howat and his colleagues report in The Cryosphere that they measured a two kilometre-wide depression 70 metres deep in the icecap of southwest Greenland, which they then identified as “the first direct evidence for concentrated long-term storage and sudden release of meltwater at the bed”.

The slumped crater suggested a holding capacity of more than 30 million cubic metres of water, which had suddenly drained away.

“If we are going to do something to mitigate sea level rise, we need to do it earlier rather than later”

“The fact that our lake appears to have been stable for at least several decades, and then drained in a matter of weeks – or less – after a few very hot summers, may signal a fundamental change happening to the ice sheet,” Dr Howat said.

The Cornell team worked in northeast Greenland, and in 2011 found a collapsed basin 70 metres deep. Dr Willis and colleagues report in Nature journal that between 2011 and 2014 they watched as summer meltwater made its way down fissures in the depression and refilled a lake basin at the base of the icecap. When this in turn emptied, the researchers calculated that the flow from the subglacial lake was at a rate of 215 cubic metres per second.

“We’re seeing surface meltwater make its way to the base of the ice where it can get trapped and stored at the boundary between the bedrock beneath the ice sheet and the ice itself,” they say.

“As the lake beneath the ice fills with surface meltwater, the heat released by this trapped meltwater can soften surrounding ice, which may eventually cause an increase in ice flow.”

Glacial flow

The researchers do not yet know whether the draining water is increasing glacial flow, and nor can they be sure how many such depressions in the Greenland ice mask buried meltwater storage tanks.

But melting of glacial ice is likely to accelerate anyway, according to new research in the journal Climate Dynamics.

Earth scientist Patrick Applegate, of Penn State University, reports that computer models confirm that the more temperatures increase, the faster the ice will melt.

Were all Greenland’s ice to melt, sea levels would rise catastrophically. At least one billion people live on coasts and estuaries vulnerable to a mere one metre rise.

The Arctic is already the fastest warming place in the northern hemisphere, and the Penn State scientists wanted to see how present warming could play back into future warming. Engineers call this positive feedback.

“If we are going to do something to mitigate sea level rise, we need to do it earlier rather than later,” Dr Applegate said. “The longer we wait, the more rapidly the changes will take place and the more difficult it will be to change.” − Climate News Network

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Arctic glacier’s galloping melt baffles scientists

Arctic glacier’s galloping melt baffles scientists

New satellite data analysis has produced evidence that rapid melting in the last three years has caused dramatic shrinkage of an Arctic ice cap.

LONDON, 31 January, 2015 – An ice cap in the high Arctic has lost what British scientists say is a significant amount of ice in an unusually short time.

It has thinned by more than 50 metres since 2012 – about one sixth of its original thickness – and the ice flow is now 25 times faster, accelerating to speeds of several kilometres per year.

Over the last two decades, thinning of the Austfonna ice cap in the Svalbard archipelago − , roughly half way between Norway and the North Pole − has spread more than 50km inland, to within 10km of the summit. .

A team led by the scientists from the UK Centre for Polar Observation and Modelling (CPOM) at the University of Leeds combined observations from eight satellite missions, including Sentinel-1A and CryoSat, with results from regional climate models, to understand what was happening.

Sea level rise

The study’s lead author, geophysicist Dr Mal McMillan, a member of the CPOM team, said: “These results provide a clear example of just how quickly ice caps can evolve, and highlight the challenges associated with making projections of their future contribution to sea level rise.”

The study, published in Geophysical Research Letters, is the first to make use of measurements from the European Space Agency’s latest Earth observation satellite, Sentinel-1A.

Dr McMillan said: “New satellites, such as the Sentinel-1A and CryoSat missions, are essential for enabling us to systematically monitor ice caps and ice sheets, and to better understand these remote polar environments.”

“Whether or not the warmer ocean water
and ice cap behaviour are directly linked
remains an unanswered question”

Melting ice caps and glaciers account for about a third of recent global sea level rise. Although scientists predict that they will continue to lose ice in the future, determining the exact amount is difficult, because of a lack of observations and the complex nature of how they interact with the climate around them.

The 20 years of satellite data that the scientists have amassed show some fairly small changes at the start of the study period, but these have since increased.

“Glacier surges, similar to what we have observed, are a well-known phenomenon”, said Professor Andrew Shepherd, the director of CPOM. “What we see here is unusual because it has developed over such a long period of time, and appears to have started when ice began to thin and accelerate at the coast.”

There is evidence that the surrounding ocean temperature has increased in recent years, which may have been the original trigger for the ice cap thinning.

Flow models

Prof Shepherd said: “Whether or not the warmer ocean water and ice cap behaviour are directly linked remains an unanswered question. Feeding the results into existing ice flow models may help us to shed light on the cause, and also improve predictions of global ice loss and sea level rise in the future.”

The team says long-term observations by satellites are the key to monitoring such climate-related phenomena.

Dr McMillan told Climate News Network he did not think what was happening in Austfonna suggested any sort of tipping point in the Arctic, which scientists say is warming more than twice as fast as anywhere else on Earth.

He said: “What I take from this work is that we don’t understand well enough what’s caused this sort of behaviour − natural variability, ocean temperatures or atmospheric temperatures. It reinforces the complexities and the challenges of the future.” – Climate News Network

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Increased carbon spill from glaciers sets new puzzle

Increased carbon spill from glaciers sets new puzzle

Samples taken from five continents indicate that a big rise in organic carbon released by melting glaciers could have serious implications for ecosystems.

LONDON, 28 January, 2015 − Researchers in the US have calculated that, thanks to climate change, melting glaciers will have spilled an extra 15 million tonnes of organic carbon into the seas by 2050.

The consequences for the ecosystems that depend on glacial meltwater are uncertain, but this burden of biological soot and sediment has potential implications for the global carbon cycle as well.

The researchers estimate that the dissolved organic carbon released by melting glaciers will be an increase of half as much again on the current flow − the equivalent of about half the annual flow of dissolved carbon down the mighty Amazon River. And their calculations have identified another puzzle for climate scientists trying to understand the carbon cycle.

The planet’s glaciers and ice sheets cover about 11% of the planet’s surface and hold about 70% of the world’s fresh water. Spread thinly through this frozen water is a significant amount of biological carbon, with the Antarctic ice sheet alone hosting 6 billion tonnes of it.

Increased meltwater

It is safe for the time being, but mountain glaciers almost everywhere in the world are in retreat, and meltwater flow from the glaciers that drain the Greenland icecap is on the increase.

Eran Hood, professor of environmental science at the University of Alaska Southeast in Juneau, and colleagues report in Nature Geoscience that they developed a database of dissolved organic carbon found in 300 samples collected from glaciers on five continents.

Some of it was clearly preserved from living things on the ice itself, some of was scraped up as the glaciers moved over old soils, and some of it was soot from fossil fuel combustion or distant forest fires.

There was a wide spread of carbon concentrations in the samples, but it was enough to estimate a global average.

“We know we are losing glaciers, but what does that mean for marine life, fisheries, things downstream
that we care about?”

They also knew that Greenland and Antarctic icebergs delivered 4,250 billion tonnes of water to the oceans each year, and that the run-off from retreating mountain glaciers was somewhere between 369-905 billion tonnes.

So they could begin to make an estimate of the rate at which dissolved organic carbon is re-entering the planetary system, and perhaps augmenting the carbon cycle.

The carbon cycle underwrites all life: plants and microbes withdraw carbon from the atmosphere and some of it gets stored in the soilspreserved as peat, or locked away as rock, or frozen as ice to be returned to the planetary system in all sorts of ways,

New questions

Research like this is basic: it adds another detail or two to an understanding of how the planet works. It starts to answer existing questions − but it also raises new ones.

“This research makes it clear that glaciers represent a substantial reservoir of organic carbon,” said Dr Hood. “As a result, the loss of glacier mass worldwide, along with the corresponding release of carbon, will affect high latitude marine ecosystems, particularly those surrounding the major ice sheets that now receive fairly limited land-to-ocean fluxes of carbon.”

His co-author Robert Spencer, assistant professor of oceanography at Florida State University, said: “The thing people have to think about is what this means for the Earth. We know we are losing glaciers, but what does that mean for marine life, fisheries, things downstream that we care about?” – Climate News Network

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Scientists say rise in sea levels is faster than feared

Scientists say rise in sea levels is faster than feared

Harvard researchers find that there has been an almost threefold annual increase in global sea levels over the last quarter of a century.

LONDON, 22 January, 2015 − Sea level rise for most of the 20th century may have been over-estimated by as much as 30%. But the less welcome news is that, if that’s the case, then sea levels since 1990 have started to accelerate more sharply than anyone had ever expected.

Scientists at Harvard University, in the US, report in the journal Nature that they came to the conclusions after deciding that old data needed fresh analysis − using sophisticated mathematical filtering techniques for handling the uncertainties and gaps in such data.

Estimating and accounting for global mean sea level (GMSL) rise is critical to characterising current and future human-induced changes. The catch is that sea level measurement hasn’t been going on for very long, so not all measurement techniques have been the same. In addition, reliable, systematic and sustained sets of data are relatively sparse.

Rise and fall

The term “sea level” sounds pretty basic, but the oceans are hardly ever level. Tides swell and ebb, regions of sea rise and fall according to temperature and salinity, and the shorelines at which researchers take measurements can also go up because of tectonic movement or sink because of the abstraction of groundwater.

Measurements along some of the world’s great estuary systems can be skewed because of human interference over the decades with the flow downstream, and great tracts of ocean cannot be measured directly at all.

The challenge, then, is to arrive at an average sea level rise for the whole planet.

“We know that sea level is changing for a variety of reasons,” said Dr Carling Hay, post-doctoral fellow in Harvard’s Department of Earth and Planetary Sciences (EPS).

“There are ongoing effects due to the last ice age, heating and expansion of the ocean due to global warming, changes in ocean circulation, and present day melting of land-ice − all of which result in unique patterns of sea level change. These processes combine to produce the observed global mean sea level rise.”

So the Harvard scientists, working with colleagues from Rutgers University in New Jersey, made estimates for the meltwater from glaciers and dwindling ice caps, from ocean thermal expansion and factors. They then “smoothed” the data, using a mathematical modelling algorithm.

Earlier estimates put mean sea level rise in the 20th century at between 1.5 and 1.8 millimetres a year. Dr Hay and her colleagues now think that, between 1901 and 1990, the true figure was probably closer to 1.2mm a year.

But since 1990, global sea level has risen by 3mm a year on average. So, in fact, the acceleration since then has been faster than anybody expected – and this in turn could affect future projections.

Question of accuracy

“Another concern with this is that many efforts to project sea level change into the future use estimates of sea level rise over the time period from 1900 to 1990,” said co-author Eric Morrow, a recent Ph.D graduate of Harvard’s EPS

“If we’ve been over-estimating the sea level change during that period, it means that these models are not calibrated appropriately, and that calls into question the accuracy of projections out to the end of the century.”

Dr Hay added: “We expected that we would estimate the individual contributions, and that their sum would get us back to the 1.5 to 1.8mm a year that other people had predicted. But the math doesn’t work out that way.

“Unfortunately, our new lower rate of sea level rise prior to 1990 means that sea level acceleration that resulted in higher rates over the last 20 years is really much larger than anyone thought.” – Climate News Network

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Science gains from clearer sight of Greenland’s ice melt

Science gains from clearer sight of Greenland's ice melt

Research into how Greenland’s ice melts should lead to more accurate predictions of sea level rise and global warming.

LONDON, 18 January, 2015 − Scientists in the US have used on-the-ice measurements and military-grade satellite imagery to take a much closer look at just how Greenland’s icesheet melts.

They already knew that huge icebergs fall from the glaciers into the ocean, and that surface lakes drain suddenly in the summer warmth. But now they know considerably more about what happens to the network of streams, rivers and ponds that collect in the summer sunshine, and then flow across the top of the icesheet into moulins, or sinkholes.

They report in the Proceedings of the National Academy of Sciences that they used the data collected to chart 523 streams in a catchment area of about 6,800 square kilometres during the freak thaw of 2012, when almost the whole of the Greenland icecap was covered in slush. They measured the run-off at between 1,550 and 1,700 cubic metres per second − twice the average flow of the Colorado River.

Thereafter, all this water drained into moulins, and began to filter towards the base of the icesheet. What happened to it then is not yet certain, but the guess is that a percentage was soaked up within the iceshelf, while a proportion reached the sea.

Only the start

The study placed 11 researchers on the ice for six days in July 2012, during a massive and unusual melt. Only on one other occasion in the last 700 years, in 1889, did Greenland’s ice melt on such a scale.

The scientists were moved around by helicopter and equipped with a specially-designed automaton boat, buoys fitted with GPS technology, and sophisticated satellite imagery.

“It was a real preview of just how quickly that ice sheet can melt and the meltwater can escape”, said lead author Laurence Smith, Professor of Earth, Planetary, and Space Sciences at University of California Los Angeles. “The question was whether the ice sheet acts like a sponge or like Swiss cheese.”

The provisional answer is: both. Some meltwater stays, and some certainly escapes altogether. But it will take more than just one visit to arrive at more precise calculations.

“Greenland is really the big player for sea level rise in the future, so improving climate models is extremely crucial”

The scientists also took measurements of Greenland’s Isortoq river − just one of about 100 large terrestrial rivers delivering Greenland meltwater to the oceans.

They found that the Isortoq carries water from the ice sheet to the ocean at between 650 and 1,300 cubic metres per second, which is less than models have projected.

Such direct measurements are important because they make predictions of melt rate and sea level rise more accurate − and more credible.

“If we can get better estimates, then we can have better projections for the extent and impact of global warming”, said another of the report’s authors, Marco Tedesco, founder and director of the City College of New York’s Cryospheric Processes Laboratory. “Greenland is really the big player for sea level rise in the future, so improving climate models is extremely crucial.” – Climate News Network

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Ocean warming speeds up cycle of climate change

Ocean warming speeds up cycle of climate change

British and German scientists have identified another consequence of global warming that is likely to accelerate climate change still further.

LONDON, 9 January, 2015 − The warming oceans could start to return more carbon dioxide to the atmosphere as the planet warms, according to new research.

And since 70% of the planet is covered by clear blue water, anything that reduces the oceans’ capacity to soak up and sequester carbon could only make climate change more certain and more swift.

It is a process that engineers call “positive feedback”. And under such a cycle of feedback, the world will continue to get even warmer, accelerating the process yet again.

Many such studies are, in essence, computer simulations. But Chris Marsay − a marine biochemist at the UK’s National Oceanography Centre in Southampton − and colleagues based their results on experiments at sea.

Sediment traps

They report in the Proceedings of the National Academy of Sciences that they examined sediment traps in the North Atlantic to work out what happens to organic carbon – the tissue of the living things that exploit photosynthesis, directly or indirectly, to convert carbon dioxide – as it sinks to the depths.

Sooner or later, much of this stuff gets released into the sea water as carbon dioxide. This is sometimes called the ocean’s biological carbon pump. In deep, cold waters, the process is slow. In warmer, shallower waters, it accelerates.

And as there is evidence that the ocean is responding to atmospheric changes in temperature, both at the surface and at depth, the study suggests that “predicted future increases in ocean temperatures will result in reduced CO2 storage by the oceans”.

The research was conducted on a small scale, in a limited stretch of ocean, so the conclusion is still provisional − and, like all good science, will be confirmed by replication. But it is yet another instance of the self-sustaining momentum of global warming.

Such positive feedbacks are already at work in high latitudes. Ice reflects sunlight, and therefore the sun’s heat. So as the Arctic ice sheet steadily diminishes over the decades, more and more blue water is available to absorb heat − and accelerate warming.

“The world is at a crossroads in terms of climate health and climate change”

The same gradual warming has started to release another greenhouse gas trapped at the ocean’s edge. Natural “marsh gas”, or methane, is stored in huge masses, “frozen” as methane hydrate in cold continental shelves.

Methane exists in much smaller quantities than carbon dioxide, and has a shorter life in the atmosphere, but is far more potent, volume for volume, as a greenhouse gas.

Researchers at the Arctic University of Norway in Tromso reported last month in Geophysical Research Letters that once-frozen methane gas was leaking from thawing ocean floor off Siberia. Some of this thaw is natural, and perhaps inevitable. But some is connected with human influence and could accelerate.

Alexei Portnov, a geophysicists at the university’s Centre for Arctic Gas Hydrate, Climate and Environment  says: “If the temperature of the oceans increases by two degrees, as suggested by some reports, it will accelerate the thawing to the extreme. A warming climate could lead to an explosive gas release from the shallow areas.”

Biological origin

Arctic methane, like ocean organic carbon, has a biological origin. It is released by decaying vegetation under marshy conditions and tends to form as a kind of ice at low temperatures and high pressures, much of it along continental shelves that, at the height of the Ice Ages, were above sea level.

The International Union for Conservation of Nature also reminded the world last month that the ocean plays a vital role in climate, and that plankton, fish and crustaceans could be considered as “mobile carbon units”.

In this sense, the fish in the sea are not just suppers waiting to be caught, but are important parts of the planetary climate system. The healthier the oceans, and the richer they are in living things, the more effective they become at soaking up atmospheric carbon.

“The world is at a crossroads in terms of climate health and climate change,” said Dan Laffoley, vice-chairman of the IUCN World Commission on Protected Areas, introducing a new report on the marine role in the carbon cycle.

“Neglect the ocean and wonder why our actions are not effective, or manage and restore the ocean to boost food security and reduce the impact of climate change. The choice should be an easy one.” – Climate News Network

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Satellite provides sharper picture of shrinking ice sheet

Satellite provides sharper picture of shrinking ice sheet

The most detailed study yet of the Greenland ice sheet illustrates the complex process that is causing billions of tonnes to melt ever year.

LONDON, 27 December, 2014 − Greenland’s ice sheet shrank by an average of 243 billion tonnes a year between 2003 and 2009 – a rate of melting that is enough to raise the world’s sea levels by 0.68 mm per year.

In what is claimed as the first detailed study, geologist Beata Csatho, of the University of Buffalo in the US, and colleagues report in the Proceedings of the National Academy of Sciences that they used satellite and aerial data to reconstruct changes in the ice sheet at 100,000 places, and to confirm that the process of losing 277 cubic kilometres of ice a year is more complex than anyone had predicted.

The Greenland ice sheet is the second biggest body of ice on Earth − second only to Antarctica − and its role in the machinery of the northern hemisphere climate is profound.

Careful measurements

It has been closely studied for decades, but such are the conditions in the high Arctic that researchers have tended to make careful measurements of ice melt and glacier calving in fixed locations – in particular, at four glaciers − and then try to estimate what that might mean for the island as a whole.

“The great importance of our data is that, for the first time, we have a comprehensive picture of how all of Greenland’s glaciers have changed over the past decade,” Dr Csatho said.

The study looked at readings from NASA’s ice, cloud and land elevation satellite ICESat, and from aerial surveys of 242 glaciers wider than 1.5 km at their outlets, to get a more complete picture of melting, loss and – in some cases – thickening of the ice sheet as a whole.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures”

Previous studies have focused on the four glaciers. One of them, Jakobshavn, has doubled its speed of flow since 2003, and closer studies have begun to reveal more about the dynamics of individual flows.

But the real strength of the study is that it establishes the pattern of ice melt in more detail, and suggests that climate models may not give a clear enough picture of the future of the ice cap. To put it crudely, Greenland could lose ice faster in the future than any of today’s predictions suggest.

Meanwhile, a team from the UK has been trying to work out what is happening on the surface of the ice sheet. Each summer, of course, some of the ice melts. Some of this gets to the sea, but some freezes again in the natural seasonal order of things.

But glaciology researcher Amber Leeson, of the University of Leeds, and colleagues report in Nature Climate Change that the “supraglacial” lakes that form each summer could also affect ice flow.

Their computer simulations suggest that these lakes will migrate further inland as the century wears on and the world continues to warm. Ice reflects heat, water absorbs it. So the process could trigger further melting. Some of this extra meltwater could slide or drain to the base of the glacier, lubricating its flow and accelerating the process yet again.

Thin pancake

“Our research shows that, by 2060, the area of Greenland covered by them will double,” Dr Leeson said. “When you pour pancake batter into a pan, if it rushes quickly to the edge of the pan, you end up with a thin pancake. It’s similar to what happens with ice sheets. The faster it flows, the thinner it will be.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would be if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”

In the last 40 years, the band in which such supraglacial lakes can form has crept 56 km inland. By 2060, the simulations now suggest, it could reach 110km inland, doubling the area of coverage and delivering yet more meltwater to fuel further warming.

Once again, the research suggests that current models underestimate the rate of ice loss. – Climate News Network

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