Author: Neville

Melt Ponds Cause Artic Sea Ice to Melt More Rapidly

Jan. 18, 2013 — The Arctic sea ice has not only declined over the past decade but has also become distinctly thinner and younger. Researchers are now observing mainly thin, first-year ice floes which are extensively covered with melt ponds in the summer months where once metre-thick, multi-year ice used to float. Sea ice physicists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), have now measured the light transmission through the Arctic sea ice for the first time on a large scale, enabling them to quantify consequences of this change.

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They come to the conclusion that in places where melt water collects on the ice, far more sunlight and therefore energy is able to penetrate the ice than is the case for white ice without ponds. The consequence is that the ice is absorbing more solar heat, is melting faster, and more light is available for the ecosystems in and below the ice. The researchers have now published these new findings in the scientific journal Geophysical Research Letters.

Melt ponds count among the favourite motifs for ice and landscape photographers in the Arctic. They are captured glistening in a seductive Caribbean sea blue or dark as a stormy sea on the ice floe. “Their colour depends entirely on how thick the remaining ice below the melt pond is and the extent to which the dark ocean beneath can be seen through this ice. Melt ponds on thicker ice tend to be turquoise and those on thin ice dark blue to black,” explains Dr. Marcel Nicolaus, sea ice physicist and melt pond expert at the Alfred Wegener Institute.

In recent years he and his team have observed a strikingly large number of melt ponds during summer expeditions to the central Arctic. Virtually half of the one-year ice was covered with melt ponds. Scientists attribute this observation to climate change. “The ice cover of the Arctic Ocean has been undergoing fundamental change for some years. Thick, multi-year ice is virtually nowhere to be found any more. Instead, more than 50 per cent of the ice cover now consists of thin one-year ice on which the melt water is particularly widespread. The decisive aspect here is the smoother surface of this young ice, permitting the melt water to spread over large areas and form a network of many individual melt ponds,” explains Marcel Nicolaus. By contrast, the older ice has a rougher surface which has been formed over the years by the constant motion of the floe and innumerable collisions. Far fewer and smaller ponds formed on this uneven surface which were, however, considerably deeper than the flat ponds on the younger ice.

The growing number of “windows to the ocean,” as melt ponds are also referred to, gave rise to a fundamental research question for Marcel Nicolaus: to what extent do the melt ponds and the thinning ice alter the amount of light beneath the sea ice? After all, the light in the sea — as on the land — constitutes the main energy source for photosynthesis. Without sunlight neither algae nor plants grow. Marcel Nicolaus: “We knew that an ice floe with a thick and fresh layer of snow reflects between 85 and 90 per cent of sunlight and permits only little light through to the ocean. In contrast, we could assume that in summer, when the snow on the ice has melted and the sea ice is covered with melt ponds, considerably more light penetrates through the ice.”

To find out the extent to which Arctic sea ice permits the penetration of the sun’s rays and how large the influence of the melt ponds is on this permeability, the AWI sea ice physicists equipped a remotely operated underwater vehicle (ROV “Alfred”) with radiation sensors and cameras. In the summer of 2011 during an Arctic expedition of the research ice breaker POLARSTERN, they sent this robot to several stations directly under the ice. During its underwater deployments, the device recorded how much solar energy penetrated the ice at a total of 6000 individual points all with different ice properties!

A unique data set was obtained in this way, the results of which are of great interest. Marcel Nicolaus explains: “The young thin ice with the many melt ponds does not just permit three times as much light to pass through than older ice. It also absorbs 50 per cent more solar radiation. This conversely means that this thin ice covered by melt ponds reflects considerably fewer sun rays than the thick ice. Its reflection rate is just 37 per cent. The young ice also absorbs more solar energy, which causes more melt. The ice melts from inside out to a certain extent,” says Marcel Nicolaus.

What might happen in the future considering these new findings? Marcel Nicolaus: “We assume that in future climate change will permit more sunlight to reach the Arctic Ocean — and particularly also that part of the ocean which is still covered by sea ice in summer. The reason: the greater the share of one-year ice in the sea ice cover, the more melt ponds will form and the larger they will be. This will also lead to a decreasing surface albedo (reflectivity) and transmission into the ice and ocean will increase. The sea ice will become more porous, more sunlight will penetrate the ice floes, and more heat will be absorbed by the ice. This is a development which will further accelerate the melting of the entire sea ice area.” However, at the same time the organisms in and beneath the ice will have more light available to them in future. Whether and how they will cope with the new brightness is currently being investigated in cooperation with biologists.

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Unrestricted Access to the Details of Deadly Volcanic Eruptions

Jan. 18, 2013 — Details of around 2,000 major volcanic eruptions which occurred over the last 1.8 million years have been made available in a new open access database, complied by scientists at the University of Bristol with colleagues from the UK, US, Colombia and Japan.

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Volcanic eruptions have the potential to cause loss of life, disrupt air traffic, impact climate, and significantly alter the surrounding landscape. Knowledge of the past behaviours of volcanoes is key to producing risk assessments of the hazards of modern explosive events.

The open access database of Large Magnitude Explosive Eruptions (LaMEVE) will provide this crucial information to researchers, civil authorities and the general public alike.

Compiled by an international team headed by Dr Sian Crosweller from the Bristol’s School of Earth Sciences with support from the British Geological Survey, the LaMEVE database provides — for the first time — rapid, searchable access to the breadth of information available for large volcanic events of magnitude 4 or greater with a quantitative data quality score.

Dr Crosweller said: “Magnitude 4 or greater eruptions — such as Vesuvius in 79AD, Krakatoa in 1883 and Mount St Helens in 1980 — are typically responsible for the most loss of life in the historical period. The database’s restriction to eruptions of this size puts the emphasis on events whose low frequency and large hazard footprint mean preparation and response are often poor.”

Currently, data fields include: magnitude, Volcanic Explosivity Index (VEI), deposit volumes, eruption dates, and rock type; such parameters constituting the mainstay for description of eruptive activity.

Planned expansion of LaMEVE will include the principal volcanic hazards (such as pyroclastic flows, tephra fall, lahars, debris avalanches, ballistics), and vulnerability (for example, population figures, building type) — details of value to those involved in research and decisions relating to risk.

LaMEVE is the first component of the Volcanic Global Risk Identification and Analysis Project (VOGRIPA) database for volcanic hazards developed as part of the Global Volcano Model (GVM).

Principal Investigator and co-author, Professor Stephen Sparks of Bristol’s School of Earth Sciences said: “The long-term goal of this project is to have a global source of freely available information on volcanic hazards that can be used to develop protocols in the event of volcanic eruptions.

“Importantly, the scientific community are invited to actively participate with the database by sending new data and modifications to the database manager and, after being given clearance as a GVM user, entering data thereby maintaining the resource’s dynamism and relevance.”

LaMEVE is freely available online.

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New Insights On Drought Predictions in East Africa

Jan. 18, 2013 — With more than 40 million people living under exceptional drought conditions in East Africa, the ability to make accurate predictions of drought has never been more important. In the aftermath of widespread famine and a humanitarian crisis caused by the 2010-2011 drought in the Horn of Africa — possibly the worst drought in 60 years — researchers are striving to determine whether drying trends will continue.

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While it is clear that El Niño can affect precipitation in this region of East Africa, very little is known about the drivers of long-term shifts in rainfall. However, new research described in the journal Nature helps explain the mechanisms at work behind historical patterns of aridity in Eastern Africa over many decades, and the findings may help improve future predictions of drought and food security in the region.

“The problem is, instrumental records of temperature and rainfall, especially in East Africa, don’t go far enough in time to study climate variability over decades or more, since they are generally limited to the 20th century,” explains first author Jessica Tierney, a geologist at the Woods Hole Oceanographic Institution (WHOI). Tierney and her colleagues at WHOI and the Lamont-Doherty Earth Observatory of Columbia University used what is known as the paleoclimate record, which provides information on climate in the geologic past, to study East African climate change over a span of 700 years.

The paleoclimate record in East Africa consists of indicators of moisture balance — including pollen, water isotopes, charcoal, and evidence for run-off events — measured in lake sediment cores. Tierney and her colleagues synthesized these data, revealing a clear pattern wherein the easternmost sector of East Africa was relatively dry in medieval times (from 1300 to 1400 a.d.), wet during the “Little Ice Age” from approximately 1600 to 1800 a.d., and then drier again toward the present time.

Climate model simulations analyzed as part of the study revealed that the relationship between sea surface temperatures and atmospheric convection in the Indian Ocean changes rainfall in East Africa. Specifically, wet conditions in coastal East Africa are associated with cool sea surface temperatures in the eastern Indian Ocean and warm sea surface temperatures in the western Indian Ocean, which cause ascending atmospheric circulation over East Africa and enhanced rainfall. The opposite situation — cold sea surface temperatures in the western Indian Ocean and warmer in the East — causes drought. Such variations in sea-surface temperatures likely caused the historical fluctuations in rainfall seen in the paleorecord.

The central role of the Indian Ocean in long-term climate change in the region was a surprise. “While the Indian Ocean has long been thought of as a ‘little brother’ to the Pacific, it is clear that it is in charge when it comes to these decades-long changes in precipitation in East Africa,” says Tierney.

Many questions remain, though. “We still don’t understand exactly what causes the changes in sea surface temperatures in the Indian Ocean and the relationship between those changes and global changes in climate, like the cooling that occurred during the Little Ice Age or the global warming that is occurring now,” says Tierney. “We’ll need to do some more experiments with climate models to understand that better.”

In the past decade, the easternmost region of Africa has gotten drier, yet general circulation climate models predict that the region will become wetter in response to global warming. “Given the geopolitical significance of the region, it is very important to understand whether drying trends will continue, in which case the models will need to be revised, or if the models will eventually prove correct in their projections of increased precipitation in East Africa,” says co-author Jason Smerdon, of the Lamont-Doherty Earth Observatory.

While it’s currently unclear which theory is correct, the discovery of the importance of the Indian Ocean may help solve the mystery. “In terms of forecasting long-term patterns in drought and food security, we would recommend that researchers make use of patterns of sea surface temperature changes in the Indian Ocean rather than just looking at the shorter term El Niño events or the Pacific Ocean,” says Tierney.

In addition, Tierney and her colleagues lack paleoclimate data from the region that is most directly affected by the Indian Ocean — the Horn of Africa. The paleoclimate data featured in this study are limited to more equatorial and interior regions of East Africa. With support from National Science Foundation, Tierney and her colleagues are now developing a new record of both aridity and sea surface temperatures from the Gulf of Aden, at a site close to the Horn.

“This will give us the best picture of what’s happened to climate in the Horn, and in fact, it will be the first record of paleoclimate in the Horn that covers the last few millennia in detail. We’re working on those analyses now and should have results in the next year or so,” says Tierney.

This research was based on work supported by the National Science Foundation and the National Oceanic and Atmospheric Administration (NOAA).

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Beijing is not the only Asian city with lethal air pollution

The Chinese capital is just one of hundreds of cities where poisonous air is the fastest growing cause of death
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A view of the Oriental Pearl TV tower and downtown Shanghai. A report in the Lancet says that worldwide, a record 3.2 million people died from air pollution in 2010, compared with 800,000 in 2000. Photograph: Carlos Barria/Reuters

Air pollution in Beijing has been described as “apocalyptic” this week with people choking their way through murky streets, short of breath and their eyes stinging from toxic air. But Beijing is just one of hundreds of cities, largely in Asia, where poisonous air is now the fastest growing cause of death in urban populations.

In the past few months there have been acute air pollution incidents reported in Bangladesh, Iran, Afghanistan, Nepal, and Pakistan. In Tehran, the desperate authorities had to close all public offices, schools, universities and banks twice in the last two months; In Nepal the army has had to give up its cars and in Kabul it has been reported that there are now more deaths as a result of air and water pollution than from conflict.

Statistics are unreliable, with few cities able to monitor accurately either the source or the level of the cocktail of pollutants emitted by traffic, ships, industry, brick kilns and domestic heating. But go to the hospitals and doctors will tell you that up to 80% of people admitted come with respiratory or other chronic diseases linked to air pollution. In Tehran, more than 4,500 people were said to have died last year because of air pollution – but because cancers can take years to develop the true figure may be far higher.

Perhaps because there are no drugs available to counter air pollution, it has never been taken as seriously by governments as other diseases like HIV/Aids or malaria, even though the World Health Organisation estimates more than 2 million people worldwide die every year from bad air and that it is now among the top 10 killers in the world. But governments may have to act as new research shows it to be rapidly worsening.

The biggest study done so far, published one month ago in the Lancet suggested that, worldwide, a record 3.2 million people died from air pollution in 2010, compared with 800,000 in 2000. The annual Global Burden of Disease (GBD) report ranked air pollution for the first time in the world’s top 10 list of killer diseases, with 1.2 million deaths a year in east Asia and China, and 712,000 in south Asia, including India.

But while Beijing got the headlines this week, there is mounting evidence that air pollution in India is as bad, if not worse, than in China. A study conducted by satellite imagery by Tel Aviv University last year reported that Indian megacities were seeing double digit increases in air pollution. From 2002 to 2010, said the paper, Bangalore saw the second highest increase in air-pollution levels in the world at 34%,with Pune, Mumbai, Nagpur and Ahmedabad not far behind. Improvements in car and fuel technology have been made since 2000 but these are nullified by the sheer increase in car numbers. Nearly 18m cars are expected to be sold this year alone in India.

The blame is variously levelled on the geography of cities, the inversion of temperatures especially in cold months which trap pollutants, the vastly increasing number of cars, power plants, forest fires and the boom in building construction. However, the Lancet study found that it was specifically the type of air pollution caused by car and truck exhaust that was doing the most health damage.

There is increasing evidence too that the air pollution now plaguing cities is because the fuel being burned by millions of cars and motorbikes is heavily contaminated by dealers who mix petrol and diesel with kerosene, waste industrial solvents and other additives to produce cheaper fuel. The result is a cocktail of poisonous emissions, many of which are not picked up by government monitoring stations and which are not filtered out by catalytic converters.

The scale of illegal fuel adulteration is unknown, but academic studies suggest it is rampant in poor countries like Nepal, Pakistan and Afghanistan, all of which depend on importing fuel from outside. One study in Nepal found that at least half the motorbikes in use had engines damaged by contaminated fuel.

But rich countries should not think their air is clean. A report by the European environment agency found that almost one third of Europe’s city dwellers are exposed to PM10 particulate concentrations above EU legal limits and 90-95% to concentrations of smaller and even more deadly PM2.5 particulates. If nothing is done to improve it, the EU expects to see 200,000 premature deaths a year in Europe by 2020 due to particle emissions alone.

EU environment commissioner Janez Potočnik spelled out the financial costs on the European economy in September: “Clean air is an investment. We cannot afford not to act. In monetary terms … the associated costs [will] amount to between €189-609bn per year in 2020. Our current analysis shows that if we do nothing, we will see 200,000 premature deaths in the EU by 2020 due to particle emissions alone – but with concerted action, this number can be pushed down to 130,000. To invest in clean air means to invest in our future.”

Amazon showing signs of degradation due to climate change, Nasa warns

Rainforest area twice the size of California experiencing drought rate that is unprecedented in a century, study shows
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Jonathan Watts, Latin America correspondent

guardian.co.uk, Friday 18 January 2013 16.33 GMT

The megadrought in the Amazon rainforest during the summer of 2005 caused widespread damage and die-offs to trees, as depicted in this photo taken in western Amazonia in Brazil. Photograph: JPL-Caltech/Nasa

The US space agency Nasa warned this week that the Amazon rainforest may be showing the first signs of large-scale degradation due to climate change.

A team of scientists led by the agency found that an area twice the size of California continues to suffer from a mega-drought that began eight years ago.

The new study shows the severe dry spell in 2005 caused far wider damage than previously estimated and its impact persisted longer than expected until an even harsher drought in 2010.

With little time for the trees to recover between what the authors describe as a “double whammy”, 70m hectares of forest have been severely affected, the analysis of 10 years of satellite microwave radar data revealed.

The data showed a widespread change in the canopy due to the dieback of branches, especially among the older, larger trees that are most vulnerable because they provide the shelter for other vegetation.

“We had expected the forest canopy to bounce back after a year with a new flush of leaf growth, but the damage appeared to persist right up to the subsequent drought in 2010,” said study co-author Yadvinder Malhi of Oxford University.

The Amazon is experiencing a drought rate that is unprecedented in a century, said the agency. Even before 2005, water availability had been shrinking steadily for more than 10 years, which made the trees more vulnerable. Between 2005 and 2010, localised dry spells added to the problem.

The leader of the research team, Sassan Saatchi of Nasa’s Jet Propulsion Laboratory, said forests will find it increasingly difficult to recover if climate change makes droughts more frequent and severe.

“This may alter the structure and function of Amazonian rainforest ecosystems,” he warned.

Nasa has been monitoring the Amazon for more than 40 years. Images it released last year showed the dramatic impacts of man-made deforestation over that period.

Although the speed of forest clearance has slowed, the Amazon continues to shrink in area. The latest study suggests the quality as well as the quantity of forest is declining due to extreme climate conditions.
At left, the extent of the 2005 megadrought in the western Amazon rainforests during the summer months of June, July and August as measured by Nasa satellites. The most impacted areas are shown in shades of red and yellow. The circled area in the right panel shows the extent of the forests that experienced slow recovery from the 2005 drought, with areas in red and yellow shades experiencing the slowest recovery. Photograph: GSFC/JPL-Caltech/Nasa

Rainforest area twice the size of California experiencing drought rate that is unprecedented in a century, study shows
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Jonathan Watts, Latin America correspondent

guardian.co.uk, Friday 18 January 2013 16.33 GMT

The megadrought in the Amazon rainforest during the summer of 2005 caused widespread damage and die-offs to trees, as depicted in this photo taken in western Amazonia in Brazil. Photograph: JPL-Caltech/Nasa

The US space agency Nasa warned this week that the Amazon rainforest may be showing the first signs of large-scale degradation due to climate change.

A team of scientists led by the agency found that an area twice the size of California continues to suffer from a mega-drought that began eight years ago.

The new study shows the severe dry spell in 2005 caused far wider damage than previously estimated and its impact persisted longer than expected until an even harsher drought in 2010.

With little time for the trees to recover between what the authors describe as a “double whammy”, 70m hectares of forest have been severely affected, the analysis of 10 years of satellite microwave radar data revealed.

The data showed a widespread change in the canopy due to the dieback of branches, especially among the older, larger trees that are most vulnerable because they provide the shelter for other vegetation.

“We had expected the forest canopy to bounce back after a year with a new flush of leaf growth, but the damage appeared to persist right up to the subsequent drought in 2010,” said study co-author Yadvinder Malhi of Oxford University.

The Amazon is experiencing a drought rate that is unprecedented in a century, said the agency. Even before 2005, water availability had been shrinking steadily for more than 10 years, which made the trees more vulnerable. Between 2005 and 2010, localised dry spells added to the problem.

The leader of the research team, Sassan Saatchi of Nasa’s Jet Propulsion Laboratory, said forests will find it increasingly difficult to recover if climate change makes droughts more frequent and severe.

“This may alter the structure and function of Amazonian rainforest ecosystems,” he warned.

Nasa has been monitoring the Amazon for more than 40 years. Images it released last year showed the dramatic impacts of man-made deforestation over that period.

Although the speed of forest clearance has slowed, the Amazon continues to shrink in area. The latest study suggests the quality as well as the quantity of forest is declining due to extreme climate conditions.
At left, the extent of the 2005 megadrought in the western Amazon rainforests during the summer months of June, July and August as measured by Nasa satellites. The most impacted areas are shown in shades of red and yellow. The circled area in the right panel shows the extent of the forests that experienced slow recovery from the 2005 drought, with areas in red and yellow shades experiencing the slowest recovery. Photograph: GSFC/JPL-Caltech/Nasa

Great Oxidation Event: More Oxygen Through Multicellularity

Jan. 17, 2013 — The appearance of free oxygen in Earth’s atmosphere led to the Great Oxidation Event. This was triggered by cyanobacteria producing oxygen that was used by multicellular forms as early as 2.3 billion years ago. As evolutionary biologists from the Universities of Zurich and Gothenburg have shown, this multicellularity was linked to the rise in oxygen and thus played a significant role for life on Earth as it is today.

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Cyanobacteria belong to Earth’s oldest organisms. They are still present today in oceans and waters and even in hot springs. By producing oxygen and evolving into multicellular forms, they played a key role in the emergence of organisms that breathe oxygen. This has, now, been demonstrated by a team of scientists under the supervision and instruction of evolutionary biologists from the University of Zurich. According to their studies, cyanobacteria developed multicellularity around one billion years earlier than eukaryotes — cells with one true nucleus. At almost the same time as multicellular cyanobacteria appeared, a process of oxygenation began in the oceans and in Earth’s atmosphere.

Multicellularity as early as 2.3 billion years ago

The scientists analyzed the phylogenies of living cyanobacteria and combined their findings with data from fossil records for cyanobacteria. According to the results recorded by Bettina Schirrmeister and her colleagues, multicellular cyanobacteria emerged much earlier than previously assumed. “Multicellularity developed relatively early in the history of cyanobacteria, more than 2.3 billion years ago,” Schirrmeister explains in her doctoral thesis, written at the University of Zurich.

Link between multicellularity and the Great Oxidation Event

According to the scientists, multicellularity developed shortly before the rise in levels of free oxygen in the oceans and in the atmosphere. This accumulation of free oxygen is referred to as the Great Oxidation Event, and is seen as the most significant climate event in Earth’s history. Based on their data, Schirrmeister and her doctoral supervisor Homayoun Bagheri believe that there is a link between the emergence of multicellularity and the event. According to Bagheri, multicellular life forms often have a more efficient metabolism than unicellular forms. The researchers are thus proposing the theory that the newly developed multicellularity of the cyanobacteria played a role in triggering the Great Oxidation Event.

Cyanobacteria occupied free niches

The increased production of oxygen set Earth’s original atmosphere off balance. Because oxygen was poisonous for large numbers of anaerobic organisms, many anaerobic types of bacteria were eliminated, opening up ecological ‘niches’. The researchers have determined the existence of many new types of multicellular cyanobacteria subsequent to the fundamental climatic event, and are deducing that these occupied the newly developed habitats. “Morphological changes in microorganisms such as bacteria were able to impact the environment fundamentally and to an extent scarcely imaginable,” concludes Schirrmeister.

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