Tag Archives: Arctic

Data adds to confusion over polar sea ice

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

By Tim Radford

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

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

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

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

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

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

Spliced together

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

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

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

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

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

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

Missing heat

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

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

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

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

Svalbard’s reindeer thrive as climate warms

Warm welcome: Svalbard's distinctive reindeer are increasing in numbers. Image: courtesy of Dr Jonathan Codd, University of Manchester
Warm welcome: Svalbard’s distinctive reindeer are increasing in numbers
Image: courtesy of Dr Jonathan Codd, University of Manchester

By Alex Kirby

The rising temperatures that have many negative impacts in the Arctic region are not a problem for a Norwegian subspecies of reindeer whose population increased by a remarkable 30% last year.

LONDON, 21 July, 2014 − There will be winners as well as losers as climate change intensifies, and scientists say they have just found one species that is prospering already.

Far from threatening the reindeer on the Norwegian high Arctic archipelago of Svalbard, rising temperatures appear to be driving a remarkable increase in the animals’ numbers.

Scientists from the University of Manchester, UK, and the Arctic University of Norway in Tromsø have found that the numbers of Svalbard reindeer, continuing a trend that has been observed over the last 36 years, increased by 30% in the last year.

Physically counted

The scientists established the population spurt by counting the reindeer in the valley of Adventdalen, in central Spitsbergen. They say their research is one of only very few studies on animal populations and climate change that involves animals being physically counted annually, rather than estimated.

The total number of animals − including all births and all deaths − in Adventdalen has been recorded annually since 1979 by a team led by Dr Nicholas Tyler, of the Arctic University of Norway.

Svalbard’s reindeer population had increased in close parallel with winter warming in the last 35 years, growing from an average of around 600 animals in the early 1980s to around 1,000 today.

Dr Tyler said: “Winter warming is widely held to be a major threat to reindeer across the Arctic, but, in Svalbard, global warming has had the opposite effect. Our data provides remarkable confirmation of this counter-intuitive observation.”

This summer, a team from Manchester, led by Jonathan Codd and Nathan Thavarajah, helped with the annual census of reindeer in Adventdalen.

Dr Codd, the programme director for zoology at the university, said: “The results revealed a remarkably successful year for Svalbard reindeer. Despite very high numbers in 2013, the population increased by almost 30% and reached a new record of just over 1,300 animals − more than three times the population size in 1979, when the present series of counts began.”

The team found very little winter mortality and very high calving. There were over 300 calves in the valley, the second highest number recorded.

Streets awash

“The substantial increase in the numbers of reindeer is linked with frequent and pronounced periods of warm weather last winter,” said Dr Codd. “In February, the temperature rose above freezing for six days, reaching a maximum of +4.2°C, and the streets of the Norwegian settlement at Longyearbyen were reported awash with melt water.”

Dr Codd told the Climate News Network: “We count the reindeer by walking the same set routes every day, and there is no possibility of any double counting.

“There are signs that Svalbard’s predators are in good shape. I think most of the polar bear populations are at least stable, and the Arctic foxes are doing pretty well too.

“But neither seems to be bothering the reindeer. The foxes will eat dead deer, but don’t attack live ones. And the main prey of the bears is seals.

“And the reindeer can move fast if they need to. I’ve heard reports that they have been known to reach a speed of 50 miles an hour (80 kph).” − Climate News Network

Hi-tech quest for Arctic sea ice answers

Walrus surfacing through sea ice off the Alaska coast Image: Joel Garlich Miller/USFWS via Wikimedia Commons
Breakthrough: walrus surfacing in sea ice off the coast of Alaska
Image: Joel Garlich Miller/USFWS via Wikimedia Commons

By Tim Radford

A sophisticated array of automatic sensors will allow scientists to conduct the longest ever monitoring programme to determine the precise physics of summer sea ice melt in the Arctic.

LONDON, 20 July, 2014 − An international team of scientists plan to spend months watching ice melt. But although it will take longer and cost a lot more than watching paint dry, it will be much more interesting and rewarding.

They plan to discover just how the Arctic ice retreats, the rate at which it melts, and the oceanographic processes at work.

The Arctic ice cap is a vital part of the climate machine, and the basis of an important ecosystem. But although the polar ice once stretched far further south, it has been both thinning and shrinking for more than three decades. This melting shows signs of accelerating, with consequences for nations far to the south, but researchers still don’t know much about the physics of the process.

Suite of technologies

So the US Naval Research Laboratory, oceanographers from France and the US, the British Antarctic Survey, the Korean Polar Research Institute, the Scottish Association for Marine Science, and the Universities of Cambridge in the UK and Yale in the US have co-ordinated a suite of technologies to monitor every detail of this summer’s ice retreat from the Alaskan shoreline, northwards.

They will use an array of floats, buoys, sensors, thermometers, tethers, GPS receivers and automated weather stations to measure every detail, such as the flow of warmer water, growth and pattern of waves, the wind speed and direction, air pressure, and humidity.

There will be buoys fixed in the ice to record both the melting and – later in the year – its refreezing, and an array of ice-tethered profilers to monitor the changes in the upper ocean. Autonomous sea gliders, too, will be released to explore below the ice shelf and report back every time they surface.

The Arctic summer ice is an example of positive feedback. Ice reflects sunlight, so it is its own insulator, and keeps itself cold. But as it melts and retreats, the exposed darker ocean waters can absorb more radiation, and bring more warmth to the edges of the retreating ice, thus accelerating the process.

It freezes again, but – on average – each year the ice cap becomes thinner, and the total area frozen continues to shrink. Researchers think they understand the big picture, but now they want the confirmatory fine detail.

Melt season

“This has never been done at this level, over such a large area and for such a long period of time,” said Craig Lee, of the University of Washington, who leads the Marginal Ice Zone Programme project. “We’re really trying to resolve the physics over the course of an entire melt season.”

The project began in March, when researchers planted an array of sensors along a line 200 miles to the north of Alaska. In August, a Korean icebreaker will install more equipment, and a team from Miami is studying high resolution satellite pictures of ice floes in the region. Biologists will also want to understand the effect of temperature changes on marine micro-organisms.

“The field programme will provide unique insight into the processes driving the summer melt of Arctic ice,” Dr Lee said. “It’s the automation and unprecedented collaboration that allows us to be out there for the entire season. You couldn’t afford to be out there at this intensity, for this length of time, any other way.” − Climate News Network

Atlases reveal climate and weather impacts

NASA says Arctic sea ice thickness in some areas has halved since 1980 Image: Hannes Grobe 20:05 via Wikimedia Commons

NASA says Arctic sea ice thickness in some areas has halved since 1980
Image: Hannes Grobe 20:05 via Wikimedia Commons

By Alex Kirby

Two new atlases provide clear visual evidence of the effect climate change and extreme weather can have on people and property.

LONDON, 12 July 2014 – For people who find it hard to believe the Earth really is warming, new visual evidence will soon be available – two atlases, one showing graphically the retreat of Arctic ice, the other the human and economic price exacted by extreme weather.

The 10th edition of the National Geographic Atlas of the World is to be published on 30 September. The publication’s geographer, Juan José Valdés, says the reduction in multi-year ice – ice that has survived for two summers – is so noticeable compared with previous editions that it is the biggest visible change since the breakup of the USSR.

“You hear reports all the time in the media about this,” he said. “Until you have a hard-copy map in your hand, the message doesn’t really hit home.” He believes atlases “open people’s eyes to what’s happening in the world.”

The Arctic sea ice has been retreating in the last 30 years or so by 12% each decade, NASA says. (On land the change is even more marked. Spring and autumn on the Greenland icecap have warmed by more than 3°C, although summer temperatures have not changed)

According to NASA’s Operation IceBridge the sea ice is now as much as 50% thinner than in previous decades, falling from an average thickness of 3.8 metres (12.5 feet) in 1980 to 1.9 m (6.2 ft) in recent years. May 2014 represented the third lowest extent of sea ice for that month in the satellite record, the US National Snow and Ice Data Center (NSIDC) says.

Self-supporting

The ice loss is accelerated by what scientists call a positive feedback: the warming in effect fuels itself. Thin ice reflects light less effectively than thick ice, allowing more sunlight to be absorbed by the ocean, which further weakens the ice and warms the ocean even more.

The melting ice also triggers another feedback. Thinner ice is flatter and scientists say this allows melt ponds to accumulate on the surface, reducing the ice’s reflectiveness and absorbing more heat.

In National Geographic’s atlas the multi-year ice, which is older, is shown as a large white mass, with the maximum extent of sea ice – the pack ice that melts and refreezes each season – shown by a simple line. This edition shows the area of multi-year ice is strikingly smaller than previously.

Some scientists say the atlas should show the total ice area at the end of the Arctic summer, including the remaining ice newly formed in the previous winter. This total minimum cover is measured in September, while total maximum cover is measured in March, at the end of winter.

Omitting the minimum cover means ice one year old or less is not being shown, the critics say. But the mapmakers say they do not show the minimum extent because there is only so much information they can include without confusing users.

There is also criticism of the atlas’s reliance on a single year (the new edition uses 2012 data, an extremely low year for ice cover). The critics say this probably over-emphasises long-term trends. But if 2013, a year with more ice, is shown, the mapmakers counter, it could under-emphasise the trend towards rising temperatures.

Steep underestimate

The second publication, the Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes 1970-2012, is the work of the World Meteorological Organization (WMO) and the Centre for Research on the Epidemiology of Disasters (CRED) of the Catholic University of Louvain (UCL) in Belgium.

Disasters caused by such extremes, it says, are increasing globally, killing people and slowing economic and social development by years or decades. The period covered, the authors say, saw 8,835 disasters, 1.94 million deaths and US$2.4 trillion of economic losses resulting from droughts, extreme temperatures, floods, tropical cyclones and related health epidemics.

Preparations start in Geneva, Switzerland, on 14 July for the third World Conference on Disaster Risk Reduction, to be held in Japan in March 2015 by the United Nations.

Jochen Luther of WMO told the Climate News Network: “It’s not necessarily the number of extreme events that is increasing, but the increasing exposure and vulnerability that turns them into disasters, as well as better reporting of them than in the past.”

The UN’s Global Assessment Report on Disaster Risk Reduction 2013 said direct and indirect losses from natural hazards of all kinds had been underestimated by at least half because of problems with data collection. – Climate News Network

Arctic warming upsets birds’ breeding calendar

 

A chick of the Arctic migrant bird, the red-necked phalarope Image: US Fish and Wildlife Service via Wikimedia Commons
Early bird: a chick of the Arctic migrant, the red-necked phalarope
Image: US Fish and Wildlife Service via Wikimedia Commons

By Tim Radford

As global warming increasingly causes Arctic snow to melt earlier, researchers warn that it could have a long-term adverse effect on the breeding success of migrant birds.

LONDON, 8 July, 2014 − Arctic migrants are nesting up to seven days earlier as the world warms. The sandpiper makes a beeline for the Alaskan shores, to join the phalarope on the beach and the songbirds in the woods − and all because the winter snows are melting earlier.

Conservation scientists Joe Liebezeit and Steve Zack – both then of the Wildlife Conservation Society (WCS) – and colleagues report in the journal Polar Biology that they looked into nearly 2,500 nests of four shorebird species in Alaska – two sandpipers, two phalaropes − and a songbird called the Lapland songspur over a nine-year period.

Nest timing

They recorded when the first eggs were laid. And they also assessed snow melt in nesting plots at different times in the early spring, and took note of predator abundance and the seasonal flush of vegetation − both of which can affect nest timing − to see what mattered most in terms of breeding.

“It seems clear that the timing of the snow melt in Arctic Alaska is the most important mechanism driving the earlier and earlier breeding dates we observed in the Arctic,” said Liebezeit, now of the Audubon Society of Portland, Oregon.

“The rates of advancement in earlier breeding are higher in Arctic birds than in other temperate bird species, and this accords with the fact that the Arctic climate is changing at twice the rate.”

During the nine years in which the scientists conducted their study, they found that nesting advanced by between four and seven days.

“Migratory birds are nesting earlier in the changing Arctic, presumably to track the earlier springs and abundance of insect pray,” said Steve Zack, who is the WCS co-ordinator of bird conservation.

“Many of these birds winter in the tropics and may be compromising their complicated calendar of movements to accommodate this change. We’re concerned that there will be a threshold where they will no longer be able to track the emergence of these earlier springs, which may impact breeding success or even population viability.”

Ecology changing

The calendar of Arctic life is shaped by ice, and the ecology of the region is beginning to change as the area of sea covered by ice shrinks with successive summers.

But Ingrid Onarheim, of the University of Bergen’s Geophysical Institute, and colleagues warn in the journal Tellus − published by the International Meteorological Institute at Stockholm University − that the Arctic ocean is losing ice even in winter, at least north of the island of Svalbard, Norway.

A study of satellite records shows that this region is losing winter ice at the rate of almost 10% per decade, and the north Atlantic water that enters the Arctic ocean at this point has been warming at 0.3°C per decade. At the same time, the surface air temperature has been warming at 2°C per decade, and researchers have recorded an average rise in winter temperatures of 6.9°C in the last 34 years.

They believe that winds have not caused the long-term warming or loss of ice, so it must be warmer ocean temperatures pushing into the region west of Svalbard. The ice, furthermore, has thinned with the decades, making it more likely to melt and retreat with each succeeding winter. – Climate News Network

Whalers tale sheds new light on Arctic ice

Oil painting by John Wood (1798-49) of British whalers circa 1840 Image: Lee and Juliet Fulger Fund via Wikimedia Commons
Oil painting by John Wood (1798-1849) of British whalers circa 1840
Image: Lee and Juliet Fulger Fund via Wikimedia Commons

By Tim Radford

Vital data on the Arctic ice sheet before extensive fossil fuel use began to impact on climate has been gleaned from a new study analysing the log books of British whaling ships’ journeys more than 200 years ago.

LONDON, 5 July, 2014 − British whaling ships from Tyneside in the north-east of England made 458 trips to the edge of the Arctic ice between 1750 and 1850. Their log books contained detailed records of perilous journeys, whales caught, and the tons of blubber and barrels of oil they brought home.

For Matthew Ayre, a PhD student at the University of Sunderland, UK, and Dennis Wheeler, the university’s Emeritus Professor of Climatology, these log books and other records by merchant ships and Arctic explorers such as Sir John Franklin − who tried in 1845 to navigate the icy North-West Passage between the Atlantic and the Pacific − represent an extraordinary resource.

They give an account of the southern edge of the ice sheet, the prevailing weather, the spring and summer extremes, the storms, and the condition of the Arctic ice shelf.

Planetary climate

And the log books offer a snapshot of conditions in the century before the first systematic use of fossil fuels began subtly to alter the planetary climate.

The catch, of course, is that the log books were composed in the technical language used by the masters of sailing ships more than 200 years ago, augmented by the jargon appropriate to a trade abandoned by the British more than a century ago.

For Ayre, the first great challenge was to compile a systematic sea ice dictionary and translate it into the language used by scientists today. He then validated his data with five weeks on the US Coastguard ice breaker and research vessel, USCGC Healy, exploring the edge of the polar ice at first hand. His study, which is part of the collaborative ARCdoc project, concentrates on the Davis Straits between north America and Greenland, and the north-west Atlantic.

The evidence confirms satellite observations made in the last three decades that the extent of the polar ice was once far greater, and that the Arctic ice is in historic retreat.

“Significantly, this is the first time we have ever had direct observational information on the ice fronts in the north Atlantic and the Davis Straits area before 1900,” Dr Wheeler said. “Until the introduction of satellite information from the 1970s, we didn’t know what the ice was doing.

“These log books contain absolutely vital
climatological information”

“Well, now we know it was more advanced − therefore, the retreat of the ice in the last 30 years is part of a more recent and new pattern of climate change. So these log books contain absolutely vital climatological information.”

All systematic weather records are relatively recent. The oldest continuous temperature series dates from England in 1659, but records from most of the world, until the last century, were random or simply sparse.

So climate researchers go for what they call proxy data – such as ice cores, lake sediments and tree rings – that provides overall clues to changing patterns of climate during the millennia.

There are other secondary sources – such as monastery and historic estate archives recording farm yields − that offer clues to bygone summers.

Life or death

But the richest resource is probably the log books of the naval ships and merchantmen, the whalers and adventurers who took to the seas in the great age of exploration that began in the 16th century. For such men, the state of the ice and the weather at its edge was a matter of life or death.

The challenge was to match what 18th-century observers recorded with the scientific observations to be made now.

Ayre got his chance aboard the US research vessel, using as a guide an epic account of the Arctic regions, written in 1820 by the Whitby whaler and pioneer scientist, William Scoresby.

“I was making observations every four hours aboard Healy, using Scoresby’s definitions and the Healy researchers’ own daily records, testing how accurate our data is to validate what is in the sea ice dictionary,” Ayre said.

“Apart from modern day research vessels, these are the only books in history from ships that seek out the ice edge in great detail and follow it.” – Climate News Network

Underworld threat to melting icecap

 

Concealed beneath the Petermann glacier are towering blocks of ice Image: Michael Studinger/NASA via Wikimedia Commons
Concealed beneath the Petermann glacier are towering blocks of ice
Image: Michael Studinger/NASA via Wikimedia Commons

By Tim Radford

Radar images of Greenland’s glaciers have revealed a spectacular underground landscape of “skyscraper” ice blocks created by a melt-and-freeze cycle that is accelerating the reduction of the icecap

LONDON, 16 June − Researchers in the US have identified a new reason for the acceleration in the melting of Greenland’s icecap − the ice underneath, as it melts and then refreezes, appears to speed up glacial flow.

The melt-and-freeze-again cycle is not itself new, as a similar process has been diagnosed under the ice cap of Antarctica. Nor is the process itself necessarily connected with global warming. Such things must always have happened.

But Robin Bell, a geophysicist at Columbia University’s Lamont Doherty Earth Observatory, reports with colleagues in Nature Geoscience that they used ice-penetrating radar to identify ragged blocks of ice as tall as skyscrapers and as wide as the island of Manhattan at the very bottom of the ice sheet. These structures cover about a tenth of the island and seem to form as melted water below the ice freezes again. They then warp the ice around and above them.

Easier to flow

“We see more of these features where the ice sheet starts to go fast,” Professor Bell said. “We think the refreezing process uplifts, distorts and warms the ice above, making it softer and easier to flow.”

Bell and her colleagues looked at the Petermann Glacier in Greenland’s north, which in 2010 pushed a huge chunk of ice into the sea. Observations suggest that the glacier is moving twice as fast as the surrounding ice, and the hypothesis is that the melt-and-freeze-again process is contributing to this acceleration.

Researchers have been troubled for a decade or more by the apparent increase in ice loss from Greenland. Were the whole island to melt, sea levels worldwide would rise by more than seven metres, so the concern is practical.

Recently, researchers have found that the bedrock beneath many glaciers is actually below sea level, making the glaciers vulnerable from ocean inflow. They have identified a process called “dynamic thinning”, triggered by warmer air temperatures, and they know anyway that natural geothermal heat flow mis likely to melt the base of the ice and lubricate any acceleration.

They have measured a fourfold increase since 1997 in summer flow speeds in the island’s Jakobshavn glacier. And they have indicated that the Greenland icecap each summer becomes more vulnerable to melting because the snows themselves are becoming darker, as more dust blows in from areas that are increasingly ice free.

Ice slide

So the discovery of a process that will make the ice slide to the sea more efficiently is not of itself more sinister. The meltwater could come from a number of sources. The friction created by a glacier as it moves must contribute. So could natural heat flow from the bedrock. Surface ice could melt in the summer sun and drain through crevasses to the base.

However, what the discovery helps to offer, literally and metaphorically, is a deeper understanding of the processes at work below the ice.

What is not clear is whether the melt-and-freeze cycle will influence the rate at which ice is lost in future. Nor does anyone yet know what triggers the cycle.

“The conditions under which such switches occur should be investigated, as they directly affect the ability of an ice sheet to slide over its bed,” advises Joseph A. McGregor, of the University of Texas at Austin, writing in the same issue of Nature Geoscience. − Climate News Network

Dark shadow falls on melting icecap

 

Signs of melting as darkness falls on the Greenland icecap Image: Matthew Hoffmann/NASA ICE via Wikimedia Commons
Signs of melting can be seen as darkness descends on the Greenland icecap
Image: Matthew Hoffmann/NASA ICE via Wikimedia Commons

By Tim Radford

Dust blowing in from warming areas of the Arctic is causing the Greenland icecap to melt faster by reducing the whiteness that reflects light and keeps it cool 

LONDON, 13 June − French scientists have identified a new mechanism that could cause the Greenland icecap to melt even faster – because dust is making its surface darker.

Marie Dumont, of the French national meteorological service, Météo-France, reports with colleagues in Nature Geoscience that, since 2009, the snows of the Arctic region’s biggest single permanent white space have been steadily darkened by “light-absorbing impurities” − known to the rest of the world simply as dust.

The Arctic has always been cold and white, simply because it is not just cold but is also white. The phenomenon is called albedo. Regions with a high albedo reflect light and stay cooler, so ice is a form of self-insulation.

Conversely, things that absorb light become warmer − and satellite data analysed by Dr Dumont and her fellow researchers shows that the Greenland ice is getting darker in the springtime.

They think the dust is blowing in from areas of the Arctic that are losing snow cover much earlier in the season as the climate warms. And, they calculate, this steady darkening alone has led to “significant” melting of the icecap.

This finding is ominous. What the researchers have identified is yet another case of what engineers call positive feedback. In the last 30 years, the Arctic sea ice has been in retreat, and researchers expect that, later in the century, the Arctic ocean will be entirely free of ice most summers.

Insulating layers

That means that there will be more atmospheric dust each spring, landing on the snows of Greenland and lowering its albedo even more, so the insulating layers of ice on the huge island will continue to retreat.

Researchers have twice in the last few months had to revise their predictions for the melting of the Greenland glaciers. The continued melting of the ice sheet is expected to raise global sea levels by 20cm by 2100, and since the whole ice sheet – which would take much longer to melt − holds enough frozen water to raise sea levels by more than seven metres, what happens in Greenland matters very much to maritime cities as far apart as Miami and Mumbai.

The French researchers have backed up their observations with a computer model of potential surface melt in Greenland. If a perfect reflecting surface would have a value of one, then meteorologists allot a value of 0.9 to the albedo of fresh snow. They calculate that a decrease in the albedo of even a very small ratio, such as 0.01, could lead to the melting of 27 billion tons of ice every year.

They are not saying that this is already happening, but they do argue that “future trends in light-absorbing impurities should therefore be considered in projections of Greenland’s mass loss”.

Accelerating warming

This is not the only newly-identified potential mechanism for positive feedback. A report by Laetitia Pichevin, of the University of Edinburgh’s School of GeoSciences, Scotland, and fellow researchers, was published in the same issue of Nature Geoscience. It says that rising global temperatures could decrease the amount of carbon dioxide naturally taken up by the world’s oceans, thus also accelerating global warming. This, too, is another process that could go on accelerating.

The researchers analysed sediments laid down 26,000 years ago in the Gulf of California and measured the abundance of silicon and iron in tiny marine fossils. They found that those periods when silicon was least abundant in ocean waters coincide with relatively warmer climates, low levels of atmospheric iron, and reduced carbon dioxide uptake by the plankton in the oceans.

“We were surprised by the many ways in which iron affects the CO2 given off by the oceans,” Dr Pichevin said. “If warming climates lower iron levels at the sea surface, as occurred in the past, this is bad news for the environment.” – Climate News Network

Threat from new gases found in air

 FOR IMMEDIATE RELEASE

rays of the setting sun stream through clouds over Antarctica Image: Dave Mobley/Jet Propulsion Laboratory via Wikimedia Commons

The setting sun streams through clouds in Antarctica, where the ozone hole was discovered in 1985
Image: Dave Mobley/NOAA Jet Propulsion Laboratory via Wikimedia Commons

 

By Alex Kirby

Comparison of air samples spread over more than 30 years has revealed three new CFC gases with the potential to add to global warming – and the evidence suggests they are man-made

LONDON, 4 June − Twenty-five years after the world first moved to protect the ozone layer, British scientists have found three new potentially damaging gases in the atmosphere. While they do not expect the gases to do much damage to the ozone layer, think they may add to global warming.

The scientists, at the University of East Anglia (UEA), in the UK, have found two new chlorofluorocarbons (CFCs) and one new hydrochlorofluorocarbon (HCFC). Their research, published in the journal Atmosphere, appears shortly after the same team found four other man-made gases in March this year.

They made the discovery by comparing samples of today’s air with samples collected between 1978 and 2012 in the unpolluted air of Tasmania, and samples taken during aircraft flights. Their measurements show that two of the new gases have reached the atmosphere in recent years.

Harmful effects

Ozone protects living things against the harmful effects of ultra-violet radiation from the sun, which can cause cancer and blindness in humans, as well as harming crops and wildlife on land and at sea.

Scientists discovered in 1985 that CFCs − the man-made gases used mainly in refrigerants and aerosols − were damaging the Earth’s protective layer of ozone over the Antarctic, thinning it and causing what has become known as “the ozone hole”. A similar, but less marked, weakening occurs over the Arctic as well.

That led to the world’s governments agreeing the Montreal Protocol in 1987. The production of all CFCs was banned in 2010, and the prediction was that, if countries observed the Protocol strictly, the damage to the ozone layer would be repaired by mid-century.

“Two of the gases that we found earlier
in the year were particularly worrying”

Dr Johannes Laube, from UEA’s school of environmental sciences, said: “Two of the gases that we found earlier in the year were particularly worrying because they were still accumulating significantly up until 2012.

“Emission increases of this scale have not been seen for any other CFCs since controls were introduced during the 1990s, but they are nowhere near peak CFC emissions of the 1980s.”

He said the three gases that had now been identified were in much lower concentrations than the ones found in March, so they were unlikely to threaten the ozone layer. But the findings strengthened the team’s argument that there are many more gases in the atmosphere that still await identification, and which together might well have an impact.

Corinna Kloss, who undertook the research while at UEA and is now at the Jülich Research Centre in Germany, said: “All seven gases were only around in the atmosphere in very small amounts before the 1980s, with four not present at all before the 1960s, which suggests they are man-made.

Possible sources

“Where these new gases are coming from should be investigated. Possible sources include industrial solvents, feedstock chemicals, and refrigerants.”

But there is a further concern over the chemicals that destroy the ozone layer, and that is their ability also to intensify global warming.

Dr Laube told the Climate News Network that the concentrations of all three newly-discovered gases were about one-tenth of those found in March. None seemed to have drastically increased in concentration in recent years, so he thought they were unlikely to be a problem to the ozone layer in the foreseeable future.

On global warming, however, one gas (HCFC-225ca) had been estimated as being 127 times stronger than CO2 on a per kg basis. This, Dr Laube estimated, meant an impact equivalent to about 50,000 tonnes of CO2 for 2012.

“For the two CFCs, global warming potentials are currently unknown,” he said. “If we look at other similar CFCs, they are likely to be 5,000 to 10,000 times more effective than CO2.”

This meant a best estimate for 2012 of emissions by one gas equivalent to 50,000 to 100,000 tonnes, and of 40,000 to 80,000 tonnes of carbon dioxide by the other gas.

For comparison, global CO2 emissions in 2011 were estimated by the Netherlands Environmental Assessment Agency at 34 billion tonnes. − Climate News Network

How nature affects the carbon cycle

FOR IMMEDIATE RELEASE

By Tim Radford

In Australia and the Arctic, scientists say, they have found unexpected ways in which natural processes are helping to compensate for global warming.

LONDON, 1 June – The great drylands of the planet – and they cover almost half of the terrestrial surface – may be bigger players in the carbon cycle than anyone had suspected. The world’s semi-arid regions may absorb huge volumes of carbon dioxide from the atmosphere whenever it rains enough.

A greening semi-arid ecosystem in Australia's Northern Territory, a key factor the record 2011 global land carbon sink following prolonged La Niña rainfall and long-term vegetation changes  
Image: Eva van Gorsel (CSIRO)

A greening semi-arid ecosystem in Australia’s Northern Territory, a key factor in the record 2011 global land carbon sink following prolonged La Niña rainfall and long-term vegetation changes

Image: Eva van Gorsel (CSIRO)

Benjamin Poulter of Montana State University and colleagues report in Nature that they used a mix of computer-driven accounting methods to work out where the carbon goes after fossil fuel burning emits extra carbon dioxide into the atmosphere. Decades of meticulous measurement confirm that, overall, carbon dioxide levels are increasing inexorably, and the world is warming accordingly.

But inside this big picture is a lot of seasonal and inter-annual variation. So climate scientists, when they try to work out what all this means for future climates, need to understand the carbon cycle better.

The assumption has always been that the most important terrestrial consumers of carbon dioxide were the tropical rainforests. But the match of terrestrial biogeochemical and atmospheric carbon dioxide and global carbon budget accounting models by 13 scientists from the US, Europe and Australia has revealed a different story.

In 2011 more than half of the terrestrial world’s carbon uptake was in the southern hemisphere – which is unexpected because most of the planet’s land surface is in the northern hemisphere – and 60% of this was in Australia.

Natural brake

That is, after a procession of unusually rainy years, and catastrophic flooding, the vegetation burst forth and the normally empty arid centre of Australia bloomed. Vegetation cover expanded by 6%.

Human activity now puts 10 billion tonnes of carbon into the atmosphere annually, and vegetation in 2011 mopped up 4.1 billion tonnes of that, mostly in Australia.

There remains a great deal of uncertainty about the carbon cycle and how the soils and the trees manage the extra carbon. Nobody knows what will happen to this extra carbon now in the hot dry landscapes of Australia: will it be tucked away in the soil? Will it be returned to the atmosphere by subsequent bushfires? As scientists are fond of saying, more research is necessary.

But this is an example of negative feedback: as carbon dioxide levels and temperatures rise, the green things respond, and slow the acceleration of both. This is quite different from the positive feedback that follows when Arctic ice – which reflects sunlight – melts and gives way to blue water which absorbs solar energy, thus accelerating the melting.

But even the slow disaster of the polar regions could be accompanied by an ameliorating process. British researchers report in Nature Communications that the ice sheet meltwaters may be rich in iron. A boost of iron would stimulate phytoplankton growth, which means more carbon dioxide could accordingly be absorbed from the atmosphere.

Feeding the oceans

The scientists collected meltwater from a Greenland glacier in the summer of 2012, and then tested it to discover significant quantities of what geochemists call “bio-available” iron.

So, in another example of those cycles of the elements that make the world go round, ice that scrapes over rock also delivers vital nutrients to the sea, for marine plants to take up yet more carbon dioxide and flourish more vigorously in the oceans and keep the planet a little cooler.

The Greenland research gives scientists a chance to estimate more accurately the delivery of this dietary supplement to the oceans: they reckon somewhere between 400,000 and 2.5 million tonnes a year in Greenland and somewhere between 60,000 and 100,000 tonnes in Antarctica. Or, to put it more graphically, it would be like dropping 3,000 fully-laden Boeing 747s into the ocean each year.

“The Greenland and Antarctic ice sheets cover around 10% of the global land surface,” said Jon Hawkings, of the University of Bristol, UK. “Our finding that there is also significant iron discharged in runoff from large ice sheet catchments is new. This means that relatively high concentrations are released from the ice sheet all summer, providing a continuous source of iron to the coastal ocean.” – Climate News Network