Arctic melt season lengthening, ocean rapidly warming

The length of the melt season for Arctic sea ice is growing by several days each decade, and an earlier start to the melt season is allowing the Arctic Ocean to absorb enough additional solar radiation in some places to melt as much as four feet of the Arctic ice cap’s thickness, according to a new study by National Snow and Ice Data Center (NSIDC) and NASA researchers.Arctic sea ice has been in sharp decline during the last four decades. The sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. The seven lowest September sea ice extents in the satellite record have all occurred in the past seven years.”The Arctic is warming and this is causing the melt season to last longer,” said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of the new study, which has been accepted for publication in Geophysical Research Letters. “The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover.”To study the evolution of sea ice melt onset and freeze-up dates from 1979 to the present day, Stroeve’s team used passive microwave data from NASA’s Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried onboard Defense Meteorological Satellite Program spacecraft.When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect. Once the melt season is in full force, the microwave emissivity of the ice and snow stabilizes, and it doesn’t change again until the onset of the freezing season causes another set of spikes. Scientists can measure the changes in the ice’s microwave emissivity using a formula developed by Thorsten Markus, co-author of the paper and chief of the Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md.Results show that although the melt season is lengthening at both ends, with an earlier melt onset in the spring and a later freeze-up in the fall, the predominant phenomenon extending the melting is the later start of the freeze season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up between six and 11 days later per decade. But while melt onset variations are smaller, the timing of the beginning of the melt season has a larger impact on the amount of solar radiation absorbed by the ocean, because its timing coincides with when the sun is higher and brighter in the Arctic sky.Despite large regional variations in the beginning and end of the melt season, the Arctic melt season has lengthened on average by five days per decade from 1979 to 2013.Still, weather makes the timing of the autumn freeze-up vary a lot from year to year.”There is a trend for later freeze-up, but we can’t tell whether a particular year is going to have an earlier or later freeze-up,” Stroeve said. “There remains a lot of variability from year to year as to the exact timing of when the ice will reform, making it difficult for industry to plan when to stop operations in the Arctic.”To measure changes in the amount of solar energy absorbed by the ice and ocean, the researchers looked at the evolution of sea surface temperatures and studied monthly surface albedo data (the amount of solar energy reflected by the ice and the ocean) together with the incoming solar radiation for the months of May through October. The albedo and sea surface temperature data the researchers used comes from the National Oceanic and Atmospheric Administration’s polar-orbiting satellites.They found that the ice pack and ocean waters are absorbing more and more sunlight due both to an earlier opening of the waters and a darkening of the sea ice. …

Read more

Arctic marine mammals are ecosystem sentinels

As the Arctic continues to see dramatic declines in seasonal sea ice, warming temperatures and increased storminess, the responses of marine mammals can provide clues to how the ecosystem is responding to these physical drivers.Seals, walruses and polar bears rely on seasonal sea ice for habitat and must adapt to the sudden loss of ice, while migratory species such as whales appear to be finding new prey, altering migration timing and moving to new habitats.”Marine mammals can act as ecosystem sentinels because they respond to climate change through shifts in distribution, timing of their movements and feeding locations,” said Sue Moore, Ph.D., a NOAA oceanographer, who spoke today at the annual meeting of the American Association for the Advancement of Science in Chicago. “These long-lived mammals also reflect changes to the ecosystem in their shifts in diet, body condition and physical health.”Moore, who was part of a panel of U.S. and Canadian scientists on the health of marine mammals and indigenous people in the Arctic, stressed the importance of integrating marine mammal health research into the overall climate, weather, oceanographic and social science research on changes in the Arctic.”Marine mammals connect people to ecosystem research by making it relevant to those who live in the Arctic and depend on these mammals for diet and cultural heritage and people around the world who look to these animals as symbols of our planet’s health,” Moore said.Story Source:The above story is based on materials provided by National Oceanic and Atmospheric Administration. Note: Materials may be edited for content and length.

Read more

Cat parasite found in western Arctic Beluga deemed infectious

University of British Columbia scientists have found for the first time an infectious form of the cat parasite Toxoplasma gondii in western Arctic Beluga, prompting a health advisory to the Inuit people who eat whale meat.The same team also discovered a new strain of the parasite, previously sequestered in the icy north, that is responsible for killing 406 grey seals in the north Atlantic in 2012.Presenting their findings today at the 2014 Annual Meeting of the American Association for the Advancement of Science (AAAS), Michael Grigg and Stephen Raverty from UBC’s Marine Mammal Research Unit say that the “big thaw” occurring in the Arctic is allowing never-before-seen movement of pathogens between the Arctic and the lower latitudes.”Ice is a major eco-barrier for pathogens,” says Michael Grigg, a molecular parasitologist with the U.S. National Institutes of Health and an adjunct professor at UBC. “What we’re seeing with the big thaw is the liberation of pathogens gaining access to vulnerable new hosts and wreaking havoc.”Toxoplasmosis, also known as kitty litter disease, is the leading cause of infectious blindness in humans and can be fatal to fetuses and to people and animals with compromised immune systems.”Belugas are not only an integral part of Inuit culture and folklore, but also a major staple of the traditional diet. Hunters and community members are very concerned about food safety and security,” says Raverty, a veterinary pathologist with the B.C. Ministry of Agriculture and Lands’ Animal Health Centre and an adjunct professor at UBC. Raverty has led the systematic sampling and screening of hunter-harvested Beluga for 14 years.Grigg has also identified the culprit of the 2012 grey seal die-off as a new strain of Sarcocystis. While not harmful to humans, the Arctic parasite, which was named Sarcocystis pinnipedi at the AAAS meeting today, has now killed an endangered Steller sea lion, seals, Hawaiian monk seals, walruses, polar and grizzly bears in Alaska and as far south as British Columbia.Story Source:The above story is based on materials provided by University of British Columbia. Note: Materials may be edited for content and length.

Read more

Arctic biodiversity under serious threat from climate change

Unique and irreplaceable Arctic wildlife and landscapes are crucially at risk due to global warming caused by human activities according to the Arctic Biodiversity Assessment (ABA), a new report prepared by 253 scientists from 15 countries under the auspices of the Conservation of Arctic Flora and Fauna (CAFF), the biodiversity working group of the Arctic Council.”An entire bio-climatic zone, the high Arctic, may disappear. Polar bears and the other highly adapted organisms cannot move further north, so they may go extinct. We risk losing several species forever,” says Hans Meltofte of Aarhus University, chief scientist of the report.From the iconic polar bear and elusive narwhal to the tiny Arctic flowers and lichens that paint the tundra in the summer months, the Arctic is home to a diversity of highly adapted animal, plant, fungal and microbial species. All told, there are more than 21,000 species.Maintaining biodiversity in the Arctic is important for many reasons. For Arctic peoples, biodiversity is a vital part of their material and spiritual existence. Arctic fisheries and tourism have global importance and represent immense economic value. Millions of Arctic birds and mammals that migrate and connect the Arctic to virtually all parts of the globe are also at risk from climate change in the Arctic as well as from development and hunting in temperate and tropical areas. Marine and terrestrial ecosystems such as vast areas of lowland tundra, wetlands, mountains, extensive shallow ocean shelves, millennia-old ice shelves and huge seabird cliffs are characteristic to the Arctic. These are now at stake, according to the report.”Climate change is by far the worst threat to Arctic biodiversity. Temperatures are expected to increase more in the Arctic compared to the global average, resulting in severe disruptions to Arctic biodiversity some of which are already visible,” warns Meltofte.A planetary increase of 2 C, the worldwide agreed upon acceptable limit of warming, is projected to result in vastly more heating in the Arctic with anticipated temperature increases of 2.8-7.8 C this century. …

Read more

Greenland’s fastest glacier reaches record speeds

Jakobshavn Isbr (Jakobshavn Glacier) is moving ice from the Greenland ice sheet into the ocean at a speed that appears to be the fastest ever recorded. Researchers from the University of Washington and the German Space Agency (DLR) measured the dramatic speeds of the fast-flowing glacier in 2012 and 2013.The results are published today in The Cryosphere, an open access journal of the European Geosciences Union (EGU).”We are now seeing summer speeds more than 4 times what they were in the 1990s on a glacier which at that time was believed to be one of the fastest, if not the fastest, glacier in Greenland,” says Ian Joughin, a researcher at the Polar Science Center, University of Washington and lead-author of the study.In the summer of 2012 the glacier reached a record speed of more than 17 kilometres per year, or over 46 metres per day. These flow rates are unprecedented: they appear to be the fastest ever recorded for any glacier or ice stream in Greenland or Antarctica, the researchers say.They note that summer speeds are temporary, with the glacier flowing more slowly over the winter months. But they add that even the annually averaged speedup over the past couple of years is nearly 3 times what it was in the 1990s.This speedup of Jakobshavn Isbr means that the glacier is adding more and more ice to the ocean, contributing to sea-level rise. “We know that from 2000 to 2010 this glacier alone increased sea level by about 1 mm. With the additional speed it likely will contribute a bit more than this over the next decade,” explains Joughin.Jakobshavn Isbr, which is widely believed to be the glacier that produced the large iceberg that sank the Titanic in 1912, drains the Greenland ice sheet into a deep ocean fjord on the coast of the island. At its calving front, where the glacier effectively ends as it breaks off into icebergs, some of the ice melts while the rest is pushed out, floating into the ocean. Both of these processes contribute about the same amount to sea-level rise from Greenland.As the Arctic region warms, Greenland glaciers such as Jakobshavn Isbr have been thinning and calving icebergs further and further inland. This means that, even though the glacier is flowing towards the coast and carrying more ice into the ocean, its calving front is actually retreating. In 2012 and 2013, the front retreated more than a kilometre further inland than in previous summers, the scientists write in the new The Cryosphere study.In the case of Jakobshavn Isbr, the thinning and retreat coincides with an increase in speed. …

Read more

Carbon cycle models underestimate indirect role of animals

Oct. 16, 2013 — Animal populations can have a far more significant impact on carbon storage and exchange in regional ecosystems than is typically recognized by global carbon models, according to a new paper authored by researchers at the Yale School of Forestry & Environmental Studies (F&ES).In fact, in some regions the magnitude of carbon uptake or release due to the effects of specific animal species or groups of animals — such as the pine beetles devouring forests in western North America — can rival the impact of fossil fuel emissions for the same region, according to the paper published in the journal Ecosystems.While models typically take into account how plants and microbes affect the carbon cycle, they often underestimate how much animals can indirectly alter the absorption, release, or transport of carbon within an ecosystem, says Oswald Schmitz, the Oastler Professor of Population and Community Ecology at F&ES and lead author of the paper. Historically, the role of animals has been largely underplayed since animal species are not distributed globally and because the total biomass of animals is vastly lower than the plants that they rely upon, and therefore contribute little carbon in the way of respiration.”What these sorts of analyses have not paid attention to is what we call the indirect multiplier effects,” Schmitz says. “And these indirect effects can be quite huge — and disproportionate to the biomass of the species that are instigating the change.”In the paper, “Animating the Carbon Cycle,” a team of 15 authors from 12 universities, research organizations and government agencies cites numerous cases where animals have triggered profound impacts on the carbon cycle at local and regional levels.In one case, an unprecedented loss of trees triggered by the pine beetle outbreak in western North America has decreased the net carbon balance on a scale comparable to British Columbia’s current fossil fuel emissions.And in East Africa, scientists found that a decline in wildebeest populations in the Serengeti-Mara grassland-savanna system decades ago allowed organic matter to accumulate, which eventually led to about 80 percent of the ecosystem to burn annually, releasing carbon from the plants and the soil, before populations recovered in recent years.”These are examples where the animals’ largest effects are not direct ones,” Schmitz says. “But because of their presence they mitigate or mediate ecosystem processes that then can have these ramifying effects.””We hope this article will inspire scientists and managers to include animals when thinking of local and regional carbon budgets,” said Peter Raymond, a professor of ecosystem ecology at the Yale School of Forestry & Environmental Studies.According to the authors, a more proper assessment of such phenomena could provide insights into management schemes that could help mitigate the threat of climate change.For example, in the Arctic, where about 500 gigatons of carbon is stored in permafrost, large grazing mammals like caribou and muskoxen can help maintain the grasslands that have a high albedo and thus reflect more solar energy. In addition, by trampling the ground these herds can actually help reduce the rate of permafrost thaw, researchers say.”It’s almost an argument for rewilding places to make sure that the natural balance of predators and prey are there,” Schmitz says. “We’re not saying that managing animals will offset these carbon emissions. What we’re trying to say is the numbers are of a scale where it is worthwhile to start thinking about how animals could be managed to accomplish that.”

Read more

Plant community plays key role in controlling greenhouse gas emissions from carbon rich moorlands

Sep. 18, 2013 — Different moorland plants, particularly heather and cotton grass, can strongly influence climate warming effects on greenhouse gas emissions, researchers from Lancaster University, The University of Manchester and the Centre for Ecology & Hydrology have discovered.The findings, published this week in the journal Ecology Letters, show valuable carbon stores, which lie deep below peaty moorlands, are at risk from changes in climate and from land management techniques that alter plant diversity.But the study found that the make-up of the plant community could also play a key role in controlling greenhouse gas emissions from these carbon rich ecosystems, as not all vegetation types respond in the same way to warming.The research, supported by a Natural Environment Research Council (NERC) grant, took place at Moor House National Nature Reserve, high up in the North Pennines, a long-term, ecological monitoring site for the UK Environmental Change Network.The newly set up experimental site manipulated both temperature and the composition and diversity of vegetation at the same time, allowing the team to study the combined effects of these global change phenomena for the first time.Temperatures were increased by around 1°C using open-topped, passive warming chambers, specially built on site, which mimicked the predicted effects of global warming.The researchers found that when heather was present, warming increased the amount of CO2 taken up from the atmosphere, making the ecosystem a greater sink for this greenhouse gas. However, when cotton grass was present, the CO2 sink strength of system decreased with warming, and the amount of methane released increased.Professor Richard Bardgett, who led the research team, and has recently moved to The University of Manchester, said: “What surprised us was that changes in vegetation, which can result from land management or climate change itself, also had such a strong impact on greenhouse gas emissions and even changed the way that warming affected them.”In other words, the diversity and make-up of the vegetation, which can be altered by the way the land is farmed, can completely change the sink strength of the ecosystem for carbon dioxide. This means that the way we manage peat land vegetation will strongly influence the way that peat land carbon sink strength responds to future climate change.”Dr Sue Ward, the Senior Research Associate for the project at Lancaster Environment Centre, said: “Setting up this experiment allowed us to test how greenhouse gas emissions are affected by a combination of changes in climate and changes in plant communities.”By taking gas samples every month of the year, we were able to show that the types of plants growing in these ecosystems can modify the effects of increase in temperature.”Dr Ward said the study would be of interest and relevance to ecological and climate change scientists and policy makers.”Changes in vegetation as well as physical changes in climate should be taken into account when looking at how global change affects carbon cycling,” she added. “Otherwise a vital part is missing — the biology is a key ingredient.”Professor Nick Ostle, from the Centre for Ecology & Hydrology, a joint partner in the research, said: “This ‘real-world’ study of the response of peat lands to climate change is unique, making these findings even more important.”It seems that the identity of the plants present in these landscapes will exert a strong influence on the effect of climate warming on soil CO2 emissions back to the atmosphere. If this is true then we can expect similar responses in other carbon rich systems in the Arctic and Boreal regions.”

Read more

Unprecedented rate and scale of ocean acidification found in the Arctic

Sep. 12, 2013 — Acidification of the Arctic Ocean is occurring faster than projected, according to new findings published in the journal PLoS ONE. The increase in rate is being blamed on rapidly melting sea ice, a process that may have important consequences for health of the Arctic ecosystem.Ocean acidification is the process by which pH levels of seawater decrease due to greater amounts of carbon dioxide being absorbed by the oceans from the atmosphere. Currently oceans absorb about one-fourth of the greenhouse gas. Lower pH levels make water more acidic and lab studies have shown that more acidic water decrease calcification rates in many calcifying organisms, reducing their ability to build shells or skeletons. These changes, in species ranging from corals to shrimp, have the potential to impact species up and down the food web.The team of federal and university researchers found that the decline of sea ice in the Arctic summer has important consequences for the surface layer of the Arctic Ocean. As sea ice cover recedes to record lows, as it did late in the summer of 2012, the seawater beneath is exposed to carbon dioxide, which is the main driver of ocean acidification.In addition, the freshwater melted from sea ice dilutes the seawater, lowering pH levels and reducing the concentrations of calcium and carbonate, which are the constituents, or building blocks, of the mineral aragonite. Aragonite and other carbonate minerals make up the hard part of many marine micro-organisms’ skeletons and shells. The lowering of calcium and carbonate concentrations may impact the growth of organisms that many species rely on for food.The new research shows that acidification in surface waters of the Arctic Ocean is rapidly expanding into areas that were previously isolated from contact with the atmosphere due to the former widespread ice cover.”A remarkable 20 percent of the Canadian Basin has become more corrosive to carbonate minerals in an unprecedented short period of time. Nowhere on Earth have we documented such large scale, rapid ocean acidification” according to lead researcher and ocean acidification project chief, U.S. …

Read more

Sea ice decline spurs the greening of the Arctic

Aug. 23, 2013 — Sea ice decline and warming trends are changing the vegetation in nearby arctic coastal areas, according to two University of Alaska Fairbanks scientists.Uma Bhatt, an associate professor with UAF’s Geophysical Institute, and Skip Walker, a professor at UAF’s Institute of Arctic Biology, contributed to a recent review of research on the response of plants, marine life and animals to declining sea ice in the Arctic.”Our thought was to see if sea ice decline contributed to greening of the tundra along the coastal areas,” Bhatt said. “It’s a relatively new idea.”The review appeared in a recent issue of Science magazine. It is a close, comprehensive look at how the losses of northern sea ice affect surrounding areas. Bhatt and Walker were two of ten authors.The review team analyzed 10 years worth of data and research on the subject. The findings show that sea ice loss is changing marine and terrestrial food chains. Sea-ice disappearance means a loss of sea-ice algae, the underpinning of the marine food web. Larger plankton is thriving, replacing smaller, but more nutrient dense plankton. What that means exactly is not yet understood.Above water, loss of sea ice has destroyed old pathways of animal migration across sea ice while opening new pathways for marine animals in others. Some animals and plants will become more isolated. …

Read more

Polar ecosystems acutely vulnerable to sunlight-driven tipping points

July 31, 2013 — Slight changes in the timing of the annual loss of sea-ice in polar regions could have dire consequences for polar ecosystems, by allowing a lot more sunlight to reach the sea floor.The research by scientists at UNSW and the Australian Antarctic Division predicts that biodiversity on some areas of the polar seabed could be reduced by as much as one third within decades, as the poles warm.The study, Light-driven tipping points in polar ecosystems, will be published in the journal Global Change Biology.Dr Graeme Clark, of the UNSW School of Biological, Earth and Environmental Sciences, says the team’s research shows that polar ecosystems may be even more sensitive to climate change than previously thought.”Even a slight shift in the date of the annual sea-ice departure could cause a tipping point, leading to widespread ecosystem shifts. On the Antarctic coast this may cause unique, invertebrate-dominated communities that are adapted to the dark conditions to be replaced by algal beds, which thrive on light, significantly reducing biodiversity,” Dr Clark says.The invertebrates lost could include sponges, moss animals, sea squirts and worms. These animals perform important functions such as filtering of water and recycling of nutrients and provide a food source for fish and other creatures.”This is a prime example of the large-scale ecological impacts that humans can impose through global warming — even in places as remote as Antarctica,” says UNSW team member, Associate Professor Emma Johnston.”Our modelling shows that recent changes in ice and snow cover at the poles have already transformed the amount of light reaching large areas of the Arctic and Antarctic annually.”For the study, the team deployed light meters on the sea floor at seven sites near Casey Station in Antarctica, at depths of up to 10 metres. They used cameras to photograph the coast at midday every day for two and a half years, to determine sea-ice cover.They determined the growth rates of Antarctic algae in the lab in different light conditions, and conducted experiments in Antarctic waters to test the sensitivity of algae to available light. They also surveyed species living on sub-tidal boulders, to see how communities varied with ice cover.Tipping points are events where small changes in environmental conditions cause rapid and extensive ecological change.The amount of sunlight reaching the poles is highly dependent on the seasons because Earth’s tilt causes the sun to be above the horizon for considerably longer during summer than winter, and the lower solar angle during winter increases reflectance from the water surface.”Early melt that brings the date of sea-ice loss closer to midsummer will cause an exponential increase in the amount of sunlight reaching some areas per year,” says Dr Clark.

Read more

Santa’s workshop not flooded — but lots of melting in the Arctic

July 30, 2013 — Santa’s workshop at the North Pole is not under water, despite recent reports. A dramatic image captured by a University of Washington monitoring buoy reportedly shows a lake at the North Pole. But Santa doesn’t yet need to buy a snorkel.”Every summer when the sun melts the surface the water has to go someplace, so it accumulates in these ponds,” said Jamie Morison, a polar scientist at the UW Applied Physics Laboratory and principal investigator since 2000 of the North Pole Environmental Observatory. “This doesn’t look particularly extreme.”After media coverage in CBS News, The Atlantic and the U.K.’s Daily Mail, Morison returned from overseas travel late last week to a pile of media inquiries. Over the weekend the team posted an explanatory page on the project website.One of the issues in interpreting the image, researchers said, is that the camera uses a fisheye lens.”The picture is slightly distorted,” said Axel Schweiger, who heads the Applied Physics Laboratory’s Polar Science Center. “In the background you see what looks like mountains, and that’s where the scale problem comes in — those are actually ridges where the ice was pushed together.”Researchers estimate the melt pond in the picture was just over 2 feet deep and a few hundred feet wide, which is not unusual to find on an Arctic ice floe in late July.In the midst of all the concern, the pool drained late July 27. This is the normal cycle for a meltwater pond that forms from snow and ice — it eventually drains through cracks or holes in the ice it has pooled on.The now-infamous buoy was first plunked into floating ice in April, at the beginning of the melt season, about 25 miles from the North Pole. Morison drilled a hole about three football fields away for a second camera, which is pointing in a different direction and shows a more typical scene. Since then the ice floe holding both cameras has drifted about 375 miles south.North Pole Environmental Observatory Watch an April interview with Jamie Morison when he was deploying the buoy The U.S. National Science Foundation has funded an observatory since 2000 that makes yearly observations at fixed locations and installs 10 to 15 drifting buoys.The buoys record weather, ice, and ocean data, and the webcams transmit images via satellite every 6 hours. …

Read more

Ice-free Arctic winters could explain amplified warming during Pliocene

July 29, 2013 — Year-round ice-free conditions across the surface of the Arctic Ocean could explain why Earth was substantially warmer during the Pliocene Epoch than it is today, despite similar concentrations of carbon dioxide in the atmosphere, according to new research carried out at the University of Colorado Boulder.In early May, instruments at the Mauna Loa Observatory in Hawaii marked a new record: The concentration of carbon dioxide climbed to 400 parts per million for the first time in modern history.The last time researchers believe the carbon dioxide concentration in the atmosphere reached 400 ppm — between 3 and 5 million years ago during the Pliocene — Earth was about 3.5 to 9 degrees Fahrenheit warmer (2 to 5 degrees Celsius) than it is today. During that time period, trees overtook the tundra, sprouting right to the edges of the Arctic Ocean, and the seas swelled, pushing ocean levels 65 to 80 feet higher.Scientists’ understanding of the climate during the Pliocene has largely been pieced together from fossil records preserved in sediments deposited beneath lakes and on the ocean floor.”When we put 400 ppm carbon dioxide into a model, we don’t get as warm a planet as we see when we look at paleorecords from the Pliocene,” said Jim White, director of CU-Boulder’s Institute of Arctic and Alpine Research and co-author of the new study published online in the journal Palaeogeography, Paleoclimatology, Palaeoecology. “That tells us that there may be something missing in the climate models.”Scientists have proposed several hypotheses in the past to explain the warmer Pliocene climate. One idea, for example, was that the formation of the Isthmus of Panama, the narrow strip of land linking North and South America, could have altered ocean circulations during the Pliocene, forcing warmer waters toward the Arctic. But many of those hypotheses, including the Panama possibility, have not proved viable.For the new study, led by Ashley Ballantyne, a former CU-Boulder doctoral student who is now an assistant professor of bioclimatology at the University of Montana, the research team decided to see what would happen if they forced the model to assume that the Arctic was free of ice in the winter as well as the summer during the Pliocene. Without these additional parameters, climate models set to emulate atmospheric conditions during the Pliocene show ice-free summers followed by a layer of ice reforming during the sunless winters.”We tried a simple experiment in which we said, ‘We don’t know why sea ice might be gone all year round, but let’s just make it go away,’ ” said White, who also is a professor of geological sciences. “And what we found was that we got the right kind of temperature change and we got a dampened seasonal cycle, both of which are things we think we see in the Pliocene.”In the model simulation, year-round ice-free conditions caused warmer conditions in the Arctic because the open water surface allowed for evaporation. Evaporation requires energy, and the water vapor then stored that energy as heat in the atmosphere. The water vapor also created clouds, which trapped heat near the planet’s surface.”Basically, when you take away the sea ice, the Arctic Ocean responds by creating a blanket of water vapor and clouds that keeps the Arctic warmer,” White said.White and his colleagues are now trying to understand what types of conditions could bridge the standard model simulations with the simulations in which ice-free conditions in the Arctic are imposed. If they’re successful, computer models would be able to model the transition between a time when ice reformed in the winter to a time when the ocean remained devoid of ice throughout the year.Such a model also would offer insight into what could happen in our future. …

Read more

You are what (and where) you eat: Mercury pollution threatens Arctic foxes

May 6, 2013 — New scientific results show that arctic foxes accumulate dangerous levels of mercury if they live in coastal habitats and feed on prey which lives in the ocean. Researchers from the Leibniz Institute for Zoo and Wildlife Research, Moscow State University and the University of Iceland just published their discovery in the science online journal PLOS ONE.

Mercury is usually transferred across the food chain, so the researchers checked which items were the main source of food and measured mercury levels in the main prey of Arctic foxes.

The scientists compared three fox populations in different environments. Foxes on the small Russian Commander Island of Mednyi fed almost exclusively on sea birds, with some foxes eating seal carcasses. In Iceland, foxes living on the coast ate sea birds whereas those living inland ate non-marine birds and rodents.

In all three environments different levels of mercury were present in their hair. Foxes living in coastal habitats such as Iceland and Mednyi Island exhibited high levels of mercury.

What does this mean for the foxes? Using museum skin samples from the Commander Islands, the researchers could show that the foxes suffered exposure to mercury for a long time. The researchers confirmed that the source of contamination was their food, as they measured high mercury levels in the prey of foxes such as seals and sea birds.

However, the inland Arctic fox populations of Iceland had low mercury levels. Thus, living inland and eating non-marine birds and rodents instead of eating prey that feeds from the sea protected the inland foxes from mercury exposure. This may have health and conservation implications. The Mednyi Island foxes are almost an opposite example to the inland Icelandic fox population. They live on a small island with no rodents or alternative food source to seals or sea birds. They suffered a tremendous population crash and while the population is currently stable, it is very small and juvenile foxes in particular show high mortality rates. Foxes of all ages exhibit low body weight and have poor coat condition.

“When going into this project we thought that an introduced pathogen would explain the poor condition of the foxes and their high mortality but after extensive screening, we did not find anything,” says Alex Greenwood, principal investigator of the study. Instead, the researchers began to suspect that something else was at play. “If pathogens were not the cause, we thought perhaps pollutants could be involved. We thought of mercury because it has been reported in high concentration in other Arctic vertebrates also in remote areas and mercury intoxication is known to increase mortality in mammals. As mercury can have negative effects on overall health, particularly in young individuals, and as we knew that Mednyi foxes were exclusively feeding on potentially contaminated sources, we wanted to see whether contamination with mercury depended on feeding ecology and hence might have been the crucial factor for the population decline on Mednyi Island,” comments Gabriele Treu, one of the lead authors of the study. As it turned out, the observed high mercury demonstrated a tight association with feeding ecology and geographical distribution of the foxes.

In terms of conservation and long term population health for the entire arctic food chain of carnivores, mercury pollution must be stopped.

Read more

Research into carbon storage in Arctic tundra reveals unexpected insight into ecosystem resiliency

May 16, 2013 — When UC Santa Barbara doctoral student Seeta Sistla and her adviser, environmental studies professor Josh Schimel, went north not long ago to study how long-term warming in the Arctic affects carbon storage, they had made certain assumptions.

“We expected that because of the long-term warming, we would have lost carbon stored in the soil to the atmosphere,” said Schimel. The gradual warming, he explained, would accelerate decomposition on the upper layers of what would have previously been frozen or near-frozen earth, releasing the greenhouse gas into the air. Because high latitudes contain nearly half of all global soil carbon in their ancient permafrost — permanently frozen soil — even a few degrees’ rise in temperature could be enough to release massive quantities, turning a carbon repository into a carbon emitter.

“The Arctic is the most rapidly warming biome on Earth, so understanding how permafrost soils are reacting to this change is of major concern globally,” Sistla said.

To test their hypothesis, the researchers visited the longest-running climate warming study in the tundra, the U.S. Arctic Long-Term Ecological Research site at Toolik Lake in northern Alaska. This ecosystem-warming greenhouse experiment was started in 1989 to observe the effects of sustained warming on the Arctic environment.

What they initially found was typical of Arctic warming: low-lying, shallow-rooted vegetation giving way to taller plants with deeper roots; greater wood shrub dominance; and increased thaw depth. What they weren’t expecting was that two decades of slow and steady warming had not changed the amounts of carbon in the soil, despite changes in vegetation and even the soil food web.

The answer to that mystery, according to Sistla, might be found in the finer workings of the ecosystem: Increased plant growth appears to have facilitated stabilizing feedbacks to soil carbon loss. Their research is published in the recent edition of the journal Nature.

“We hypothesize that net soil carbon hasn’t changed after 20 years because warming-accelerated decomposition has been offset by increased carbon inputs to the soil due to a combination of increased plant growth and changing soil conditions,” Sistla said.

The increased plant productivity, caused by the warmer temperatures — on average 2 degrees Celsius in the air and 1 degree in the soil to the permafrost — has increased plant litter inputs to the soil. Unexpectedly, the soils in the greenhouse experiment developed higher winter temperatures, while the summer warming effect declined.

“These changes reflect a complicated feedback,” Sistla said. “Shrubs trap more snow than the lower-lying vegetation, creating warmer winter soil temperatures that further stimulate both decomposers and plant growth. Shrubs also increase summer shading, which appears to have reduced decomposer activity in the surface soil by reducing the greenhouse effect during the summer.”

The increased plant growth and deeper thaw, meanwhile, also may have enabled increased carbon availability in the deeper mineral layer that overlies the permafrost. In fact, the researchers found the strongest biological effects of warming at depth, a “biotic awakening,” with mineral soil decomposers showing more activity, along with the increased carbon stock at that level. “It’s a surprising counterbalance,” said Schimel. “It may be that those soil systems are not quite as vulnerable to warming as initially expected.”

However, whether or not this phenomenon — no net loss of soil carbon despite long-term warming — is a transient phase that will eventually give way to increased decomposition activity and more carbon release, is not yet known. Future studies will include investigation into the mineral soil to determine the age of the carbon, which may in turn yield clues into how the carbon cycle is changing at depth, where the majority of tundra soil carbon is stored.

Funding for this study came from the National Science Foundation Long Term Ecological Research (LTER) Program, DOE Global Change Education Program Graduate Fellowship, a Leal Anne Kerry Mertes scholarship, and Explorer’s Club.

According to Sistla and Schimel, this research paradigm validates the NSF LTER program’s commitment to supporting long-term experiments, because it creates opportunities for younger scientists to observe effects and condition decades after experiments are established — results that could not have been foreseen when the experiments were started.

Researchers participating in this study include John C. Moore and Rodney T. Simpson from Colorado State University, Fort Collins; Laura Gough from the University of Texas at Arlington; and Gaius R. Shaver from the Marine Biological Laboratory at Woods Hole, Mass.

Read more

Utilizzando il sito, accetti l'utilizzo dei cookie da parte nostra. maggiori informazioni

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close