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Scientists discover carbonate rocks are unrecognized methane sink

CORVALLIS, Ore. – Since the first undersea methane seep was discovered 30 years ago, scientists have meticulously analyzed and measured how microbes in the seafloor sediments consume the greenhouse gas methane as part of understanding how the Earth works.

The sediment-based microbes form an important methane “sink,” preventing much of the chemical from reaching the atmosphere and contributing to greenhouse gas accumulation. As a byproduct of this process, the microbes create a type of rock known as authigenic carbonate, which while interesting to scientists was not thought to be involved in the processing of methane.

That is no longer the case. A team of scientists has discovered that these authigenic carbonate rocks also contain vast amounts of active microbes that take up methane. The results of their study, which was funded by the National Science Foundation, were reported today in the journal Nature Communications.

“No one had really examined these rocks as living habitats before,” noted Andrew Thurber, an Oregon State University marine ecologist and co-author on the paper. “It was just assumed that they were inactive. In previous studies, we had seen remnants of microbes in the rocks – DNA and lipids – but we thought they were relics of past activity. We didn’t know they were active.

“This goes to show how the global methane process is still rather poorly understood,” Thurber added.

Lead author Jeffrey Marlow of the California Institute of Technology and his colleagues studied samples from authigenic compounds off the coasts of the Pacific Northwest (Hydrate Ridge), northern California (Eel River Basin) and central America (the Costa Rica margin). The rocks range in size and distribution from small pebbles to carbonate “pavement” stretching dozens of square miles.

“Methane-derived carbonates represent a large volume within many seep systems and finding active methane-consuming archaea and bacteria in the interior of these carbonate rocks extends the known habitat for methane-consuming microorganisms beyond the relatively thin layer of sediment that may overlay a carbonate mound,” said Marlow, a geobiology graduate student in the lab of Victoria Orphan of Caltech.

These assemblages are also found in the Gulf of Mexico as well as off Chile, New Zealand, Africa, Europe – “and pretty much every ocean basin in the world,” noted Thurber, an assistant professor (senior research) in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The study is important, scientists say, because the rock-based microbes potentially may consume a huge amount of methane. The microbes were less active than those found in the sediment, but were more abundant – and the areas they inhabit are extensive, making their importance potential enormous. Studies have found that approximately 3-6 percent of the methane in the atmosphere is from marine sources – and this number is so low due to microbes in the ocean sediments consuming some 60-90 percent of the methane that would otherwise escape.

Now those ratios will have to be re-examined to determine how much of the methane sink can be attributed to microbes in rocks versus those in sediments. The distinction is important, the researchers say, because it is an unrecognized sink for a potentially very important greenhouse gas.

“We found that these carbonate rocks located in areas of active methane seeps are themselves more active,” Thurber said. “Rocks located in comparatively inactive regions had little microbial activity. However, they can quickly activate when methane becomes available.

“In some ways, these rocks are like armies waiting in the wings to be called upon when needed to absorb methane.”

The ocean contains vast amounts of methane, which has long been a concern to scientists. Marine reservoirs of methane are estimated to total more than 455 gigatons and may be as much as 10,000 gigatons carbon in methane. A gigaton is approximate 1.1 billion tons.

By contrast, all of the planet’s gas and oil deposits are thought to total about 200-300 gigatons of carbon.

Media Contact: 
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Andrew Thurber, 541-737-4500, athurber@coas.oregonstate.edu

Study finds air temperature models poor at predicting stream temps

CORVALLIS, Ore. – Stream temperatures are expected to rise in the future as a result of climate change, but a new study has found that the correlation between air temperature and stream temperature is surprisingly tenuous.

The findings cast doubt on many statistical models using air temperatures to predict future stream temperatures.

Lead author Ivan Arismendi, a stream ecologist at Oregon State University, examined historic stream temperature data over a period of one to four decades from 25 sites in the western United States to see if increases in air temperature during this period could have predicted – through the use of statistical models – the observed stream temperatures.

He discovered that many streams were cooler than the models predicted, while others were warmer. The difference in temperature between the models and actual measurements, however, was staggering – as much as 12 degrees Celsius different in some rivers.

Results of the study have recently been published in the journal Environmental Research Letters. The study involved scientists from Oregon State, the U.S. Forest Service and the U.S. Geological Survey, and was supported by all three organizations, as well as by the National Science Foundation.

“These air-stream temperature models originated as a tool for looking at short-term relationships,” said Arismendi, a researcher in the OSU Department of Fisheries and Wildlife. “The problem is that people are starting to use them for long-term extrapolation. It is unreliable to apply uniform temperature impacts on a regional scale because there are so many micro-climate factors influencing streams on a local basis.”

Sherri Johnson, a U.S. Forest Service research ecologist and co-author on the study, said the findings are important because decisions based on these models may not be accurate. Some states, for example, have projected a major loss of suitable habitat for trout and other species because the models suggest increases in stream temperature commensurate with projected increases in air temperature.

“It just isn’t that simple,” Arismendi said. “Stream temperatures are influenced by riparian shading and in-stream habitat, like side channels. Dams can have an enormous influence, as can groundwater. It is a messy, complex challenge to project stream temperatures into the future.”

What made this study work, the authors say, was evaluating more than two dozen sites that had historic stream temperature data, which can be hard to find. The development about a dozen years ago of data loggers that can be deployed in streams is contributing enormous amounts of new data, but accurate historic records of stream temperatures are sparse.

Researchers at USGS and at sites like the H.J. Andrews Experimental Forest in Oregon, part of the National Science Foundation’s Long-Term Ecological Research program, have compiled stream data for up to 44 years, giving Arismendi and his colleagues enough historical data to conduct the comparative study.

In many of the 25 sites examined in the study, the researchers found that the difference between model-projected stream temperatures and actual stream temperatures was as great as the actual amount of warming projected – 3.0 degrees Celsius, or 5.5 degrees Fahrenheit. And in some cases, the projections were even farther off target.

“The models predictions were poor in summer and winter, and when there are extreme situations,” Arismendi noted. “They were developed to look at Midwest streams and don’t account for the complexity of western streams that are influenced by topography, extensive riparian areas and other factors.”

Increases in air temperatures in the future are still likely to influence stream temperatures, but climate sensitivity of streams “is more complex than what is being realized by using air temperature-based models,” said Mohammad Safeeq, an Oregon State University researcher and co-author on the study.

“The good news is that some of the draconian projections of future stream temperatures may be overstated,” noted Safeeq, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “On the other hand, some may actually be warmer than what air temperature-based models project.”

Not all streams will be affected equally, Johnson said.

“The one constant is that a healthy watershed will be more resilient to climate change than one that isn’t healthy – and that should continue to be the focus of restoration and management efforts,” she noted.

Jason Dunham, an aquatic ecologist with the USGS and co-author on the study, said the study highlights the value of long-term stream temperature records in the Northwest and globally.

“Without a long-term commitment to collecting this kind of data, we won’t have the ability to evaluate existing models as we did in this work,” Dunham said. “Long-term datasets provide vital material for developing better methods for quantifying the effects of climate on our water resources.”

Media Contact: 
Source: 

Ivan Arismendi, 541-750-7443;

Sherri Johnson, 541-758-7771

Anglers, beachcombers asked to watch for transponders from Japan

CORVALLIS, Ore. – Northwest anglers venturing out into the Pacific Ocean in pursuit of salmon and other fish this fall may scoop up something unusual into their nets – instruments released from Japan called “transponders.”

These floating instruments are about the size of a 2-liter soda bottle and were set in the ocean from different ports off Japan in 2011-12 after the massive Tohoku earthquake and tsunami. Researchers from Tattori University for Environmental Studies in Japan have been collaborating with Oregon State University, Oregon Sea Grant, and the NOAA Marine Debris Program on the project.

The researchers’ goal is to track the movement of debris via ocean currents and help determine the path and timing of the debris from the 2011 disaster. An estimated 1.5 million tons of debris was washed out to sea and it is expected to continue drifting ashore along the West Coast of the United States for several years, according to Sam Chan, a watershed health specialist with Oregon State University Extension and Oregon Sea Grant.

“These transponders only have a battery life of about 30 months and then they no longer communicate their location,” Chan said. “So the only way to find out where they end up is to physically find them and report their location. That’s why we need the help of fishermen, beachcombers and other coastal visitors.

“These bottles contain transmitters and they are not a hazardous device,” Chan added. “If you find something that looks like an orange soda bottle with a short antenna, we’d certainly like your help in turning it in.”

Persons who find a transponder are asked to photograph it if possible, and report the location of their find to Chan at Samuel.Chan@oregonstate.edu; or to the NOAA Marine Debris Program regional coordinator in their area at http://marinedebris.noaa.gov/contact-us. They will provide shipping instructions to persons who find the transponders so that the instruments can be returned to the research team.

One of the first transponders discovered in the Northwest washed ashore near Arch Cape, Oregon, in March 2013, about 19 months after it was set adrift. The persons who found it reported it to Chan, who began collaborating with researchers in Japan.

Another transponder was found near the Haida Heritage Site, formerly the Queen Charlotte Islands – the same location where a Harley-Davidson motorcycle floated up on a beach in a shipping container long after being swept out to sea in Japan by the tsunami.

“These transponders have recorded a lot of important data that will help us better understand the movement of tsunami and marine debris throughout the Pacific Ocean,” Chan said. “Everyone’s help in recovering these instruments is greatly appreciated.”

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Sam Chan, 541-737-4828; samuel.chan@oregonstate.edu

Concern grows over pet pills and products, as well as those of owners

CORVALLIS, Ore. – Scientists have long been aware of the potential environment impacts that stem from the use and disposal of the array of products people use to keep themselves healthy, clean and smelling nice.

Now a new concern is emerging – improper disposal of pet care products and pills.

Dog shampoos, heartworm medicine, flea and tick sprays, and a plethora of prescription and over-the-counter medicines increasingly are finding their way into landfills and waterways, where they can threaten the health of local watersheds. An estimated 68 percent of American households have at least one pet, illustrating the potential scope of the problem.

How bad is that problem? No one really knows, according to Sam Chan, a watershed health expert with the Oregon Sea Grant program at Oregon State University.

But Chan and his colleagues aim to find out. They are launching a national survey (online at: http://tinyurl.com/PetWellbeingandEnvironment)  of both pet owners and veterinary care professionals to determine how aware that educated pet owners are of the issue, what is being communicated, and how they dispose of  “pharmaceutical and personal care products” (PPCPs) for both themselves and their pets. Pet owners are encouraged to participate in the survey.

“You can count on one hand the number of studies that have been done on what people actively do with the disposal of these products,” Chan said. “PPCPs are used by almost everyone and most wastewater treatment plants are not able to completely deactivate many of the compounds they include.”

Increasingly, Chan said, a suite of PPCPs used by pets and people are being detected at low levels in surface water and groundwater. Examples include anti-inflammatory medicines such as ibuprofen, antidepressants, antibiotics, estrogens, the insect repellent DEET, and ultraviolet (UV) sunblock compounds.

Some of the impacts from exposure to these products are becoming apparent. Fish exposed to levels of antidepressants at concentrations lower than sewage effluence, for example, have been shown to become more active and bold – making them more susceptible to predation, noted Chan, an OSU Extension Sea Grant specialist.

“Triclosan is another concern; it is a common anti-microbial ingredient in soaps, toothpaste, cosmetics, clothing, cookware, furniture and toys to prevent or reduce bacterial contamination for humans and pets,” Chan said. “It is being linked to antibiotic resistance in riparian zones, as well as to alterations in mammal hormone regulation – endocrine disruptor – and impacts on immune systems.”

Another common endocrine disruptor, the researchers say, is coal tar, a common ingredient in dandruff shampoo for humans, and pet medicines for skin treatment.

Jennifer Lam conducted a preliminary survey of veterinary practitioners as part of her master’s thesis at Oregon State University and found awareness by veterinary professionals of the environmental issues caused by improper disposal of PPCPs was high. Yet many did not share that information with their clients.

In fact, veterinarians only discussed best practices for disposal with their clients 18 percent of the time, her survey found.

“The awareness is there, but so are barriers,” Lam said. “Communicating about these issues in addition to care instructions takes time. There may be a lack of educational resources – or a lack of awareness on their availability. And some may not think of it during the consultation process.”

The National Sea Grant program recently partnered with the American Veterinary Medicine Association to promote the reduction of improper PPCP disposal. The national survey is a first step in that process.

“Most people tend to throw extra pills or personal care products into the garbage and in fewer instances, flush them down the drain,” Chan said. “It seems like the right thing to do, but is not the most environmentally friendly method for disposing unused or expired PPCPs. Waste in landfills produce leachates and these contaminates may not be fully deactivated by current wastewater treatments. They can get into groundwater and streams, where they can cause a variety of environmental problems and create a health risk as well.”

When disposing of expired or unneeded medications, the researchers say, don’t flush them. Instead, take to them to a drug take-back event or depository. New rules to be implemented by the U.S. Drug Enforcement Agency (DEA) later this fall will make drug take-back options more available.

Chan and Lam suggest that in areas where take-back options are not available, people should mix unused or unwanted drugs with coffee grounds or kitty litter – something that will be unpalatable to pets. Then put the mixture in a sealed container and deposit it in the trash.

Results from the national survey led by Oregon Sea Grant will provide much-needed information to guide education, watershed monitoring and improvements on ways to reduce PPCP contamination and their environmental impacts.

The survey will continue until Nov. 1.

Media Contact: 
Source: 

Sam Chan, 503-679-4828, sam.chan@oregonstate.edu;

Jennifer Lam, lamj@onid.oregonstate.edu

OSU part of major grant to study Southern Ocean carbon cycle

CORVALLIS, Ore. – A new six-year, $21 million initiative funded by the National Science Foundation will explore the role of carbon and heat exchanges in the vast Southern Ocean – and their potential impacts on climate change.

The Southern Ocean Carbon and Climate Observations and Modeling program will be headquartered at Princeton University, and include researchers at several institutions, including Oregon State University. It is funded by NSF’s Division of Polar Programs, with additional support from the National Oceanic and Atmospheric Administration and NASA.

The Southern Ocean acts as a carbon “sink” by absorbing as much as half of the human-derived carbon in the atmosphere and much of the planet’s excess heat. Yet little is known of this huge body of water that accounts for 30 percent of the world’s ocean area.

Under this new program known by the acronym SOCCOM, Princeton and 10 partner institutions will create a physical and biogeochemical portrait of the ocean using hundreds of robotic floats deployed around Antarctica. The floats, which will be deployed over the next five years, will collect seawater profiles using sophisticated sensors to measure pH, oxygen and nitrate levels, temperature and salinity – from the ocean surface to a depth of 1,000 meters, according to Laurie Juranek, an Oregon State University oceanographer and project scientist.

“This will be the first combined large-scale observational and modeling program of the entire Southern Ocean,” said Juranek, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “It is a very important region, but difficult to access – hence the use of robotic floats to collect data. However, not everything that we need to know can be measured by sensors, so we’ll need to get creative.”

Juranek's role in this project is to develop relationships between the measured variables and those that can't be measured directly by a sensor but are needed for understanding Southern Ocean carbon dioxide exchanges. These relationships can be applied to the float data as well as to high-resolution models. To do this work she is partnering with colleagues at NOAA's Pacific Marine Environmental Laboratory.

In addition to its role in absorbing carbon and heat, the Southern Ocean delivers nutrients to lower-latitude surface waters that are critical to ocean ecosystems around the world, said program director Jorge Sarmiento, Princeton's George J. Magee Professor of Geoscience and Geological Engineering and director of the Program in Atmospheric and Oceanic Sciences. And as levels of carbon dioxide increase in the atmosphere, models suggest that the impacts of ocean acidification are projected to be most severe in the Southern Ocean, he added.

"The scarcity of observations in the Southern Ocean and inadequacy of earlier models, combined with its importance to the Earth's carbon and climate systems, means there is tremendous potential for groundbreaking research in this region," Sarmiento said.

Media Contact: 
Source: 

Laurie Juranek, 541-737-2368; ljuranek@coas.oregonstate.edu

Study resolves discrepancy in Greenland temperatures during end of last ice age

CORVALLIS, Ore. – A new study of three ice cores from Greenland documents the warming of the large ice sheet at the end of the last ice age – resolving a long-standing paradox over when that warming occurred.

Large ice sheets covered North America and northern Europe some 20,000 years ago during the coldest part of the ice age, when global average temperatures were about four degrees Celsius (or seven degrees Fahrenheit) colder than during pre-industrial times. And then changes in the Earth’s orbit around the sun increased the solar energy reaching Greenland. Beginning some 18,000 years ago, release of carbon from the deep ocean led to a graduate rise in atmospheric carbon dioxide (CO2).

Yet past analysis of ice cores from Greenland did not show any warming response as would be expected from an increase in CO2 and solar energy flux, the researchers note.

In this new study, funded by the National Science Foundation and published this week in the journal Science, scientists reconstructed air temperatures by examining ratios of nitrogen isotopes in air trapped within the ice instead of isotopes in the ice itself, which had been used in past studies.

Not only did the new analysis detect significant warming in response to increasing atmospheric CO2, it documents a warming trend at a rate closely matching what climate change models predict should have happened as the Earth shifted out of its ice age, according to lead author Christo Buizert, a postdoctoral researcher at Oregon State University and lead author on the Science article.

“The Greenland isotope records from the ice itself suggest that temperatures 12,000 years ago during the so-called Younger Dryas period near the end of the ice age were virtually the same in Greenland as they were 18,000 years ago when much of the northern hemisphere was still covered in ice,” Buizert said. “That never made much sense because between 18,000 and 12,000 years ago atmospheric CO2 levels rose quite a bit.”

“But when you reconstruct the temperature history using nitrogen isotope ratios as a proxy for temperature, you get a much different picture,” Buizert pointed out. “The nitrogen-based temperature record shows that by 12,000 years ago, Greenland temperatures had already warmed by about five degrees (Celsius), very close to what climate models predict should have happened, given the conditions.”

Reconstructing temperatures by using water isotopes provides useful information about when temperatures shift but can be difficult to calibrate because of changes in the water cycle, according to Edward Brook, an Oregon State paleoclimatologist and co-author on the Science study.

“The water isotopes are delivered in Greenland through snowfall and during an ice age, snowfall patterns change,” Brook noted. “It may be that the presence of the giant ice sheet made snow more likely to fall in the summer instead of winter, which can account for the warmer-than-expected temperatures because the snow records the temperature at the time it fell.”

In addition to the gradual warming of five degrees (C) over a 6,000-year period beginning 18,000 years ago the study investigated two periods of abrupt warming and one period of abrupt cooling documented in the new ice cores. The researchers say their leading hypothesis is that all three episodes are tied to changes in the Atlantic meridional overturning circulation (AMOC), which brings warm water from the tropics into the high northern latitudes.

The first episode caused a jump in Greenland’s air temperatures of 10-15 degrees (C) in just a few decades beginning about 14,700 years ago. An apparent shutdown of the AMOC about 12,800 years ago caused an abrupt cooling of some 5-9 degrees (C), also over a matter of decades.

When the AMOC was reinvigorated again about 11,600 years ago, it caused a jump in temperatures of 8-, 11 degrees (C), which heralded the end of the ice age and the beginning of the climatically warm and stable Holocene period, which allowed human civilization to develop.

“For these extremely abrupt transitions, our data show a clear fingerprint of AMOC variations, which had not yet been established in the ice core studies,” noted Buizert, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences.  “Other evidence for AMOC changes exists in the marine sediment record and our work confirms those findings.”

In their study, the scientists examined three ice cores from Greenland and looked at the gases trapped inside the ice for changes in the isotopic ration of nitrogen, which is very sensitive to temperature change. They found that temperatures in northwest Greenland did not change nearly as much as those in southeastern Greenland – closest to the North Atlantic – clearly suggesting the influence of the AMOC.

“The last deglaciation is a natural example of global warming and climate change,” Buizert said. “It is very important to study this period because it can help us better understand the climate system and how sensitive the surface temperature is to atmospheric CO2.”

“The warming that we observed in Greenland at the end of the ice age had already been predicted correctly by climate models several years ago,” Buizert added. “This gives us more confidence that these models also predict future temperatures correctly.”

Media Contact: 
Source: 

Christo Buizert, 541-737-1209

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Study: Pacific Northwest shows warming trend over past century-plus

CORVALLIS, Ore. – The annual mean temperature in the Pacific Northwest has warmed by about 1.3 degrees Fahrenheit since the early 20th century – a gradual warming trend that has been accelerating over the past 3-4 decades and is attributed to anthropogenic, or human, causes.

The study is one of the first to isolate the role of greenhouse gases associated with regional warming, the authors say. It was published in a recent issue of the Journal of Climate, a publication of the American Meteorological Society.

“The amount of warming may not sound like a lot to the casual observer, but we already are starting to see some of the impacts and what is particularly significant is that the rate of warming is increasing,” said Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State University and a co-author on the study.

“Just a 1.3-degree increase has lengthened the ‘freeze-free’ season by 2-3 weeks and is equivalent to moving the snowline 600 feet up the mountain,” Mote added. “At the rate the temperature is increasing, the next 1.3-degree bump will happen much more quickly.”

In their study, the researchers looked at temperatures and precipitation from 1901 to 2012 in the Northwest, which includes Washington, Oregon, Idaho, western Montana, and the northwestern tip of Wyoming. They examined four different factors to determine the influence of human activities, including greenhouse gases and aerosols; solar cycles; volcanic eruptions; and naturally occurring phenomena including El Niño events and the Pacific Decadal Oscillation.

Using what is called a “multilinear regression” approach, they were able to tease out the influences of the different factors. Volcanic activity, for example, led to cooler temperatures in 1961, 1982 and 1991. Likewise, El Niño events led to warming in numerous years.

“Natural variation can explain much of the change from year to year, but it cannot account for this long-term warming trend,” noted David Rupp, a research associate with the Oregon Climate Change Research Institute and co-author on the report. “Anthropogenic forcing was the most significant predictor of, and leading contributor to, the warming.”

Among the study’s findings:

  • The Northwest experienced relatively cool periods from 1910-25 and from 1945-60, and a warm period around 1940 and from the mid-1980s until the present.
  • The warmest 10-year period has been from 1998 to 2007, and very few years since 1980 have had below average annual mean temperatures.
  • The most apparent warming trend is in the coldest night of the year, which has warmed significantly in recent decades.
  • The only cooling trend the study documented was for spring temperatures the last three decades and is tied to climate variability and increasing precipitation during those spring months.

“The spring has been robustly wetter,” Mote said, “and that has brought some cooler temperatures for a couple of months. But it has been drier in the fall and winter, and the warming in fall and winter has been steepest since the 1970s.”

Lead author John Abatzoglou of the University of Idaho said that the study ties the warming trend to human activities.

“Climate is a bit like a symphony where different factors like El Niño, solar variability, volcanic eruptions and manmade greenhouse emissions all represent different instruments,” Abatzoglou said. “At regional scales like in the Northwest, years or decades can be dominated by natural climate variability, thereby muffling or compounding the tones of human-induced warming.

“Once you silence the influence of natural factors,” he said, “the signal of warming due to human causes is clear – and it is only getting louder.”

The researchers also explored but were unable to find any link between warming in the Northwest over the past century and solar variability.

A major concern, the authors say, is that the warming seems to be increasing.

“Climate is complex and you can get significant variations from year to year,” Mote said. “You have to step back and look at the big picture of what is happening over time. Clearly the Northwest, like much of the world, is experiencing a warming pattern that isn’t likely to change and, in fact, is accelerating.

“At this rate, the chance of the temperature only going up 1.3 degrees in the next century is close to zero.”

The study was funded by the U.S. Department of Agriculture and the National Oceanic and Atmospheric Administration.

Media Contact: 
Source: 

Phil Mote, 541-913-2274, philip.mote@coas.oregonstate.edu

David Rupp, 541-737-5222, David.Rupp@oregonstate.edu

John Abatzoglou, jabatzoglous@uidaho.edu, 208-885-6239

Study provides new look at ancient coastline, pathway for early Americans

CORVALLIS, Ore. – The first humans who ventured into North America crossed a land bridge from Asia that is now submerged beneath the Bering Sea, and then may have traveled down the West Coast to occupy sites in Oregon and elsewhere as long as 14,000 to 15,000 years ago.

Now a new study has found that the West Coast of North America may have looked vastly different than scientists previously thought, which has implications for understanding how these early Americans made this trek.

The key to this new look at the West Coast landscape is a fresh approach to the region’s sea level history over the last several thousand years. Following the peak of the last ice age about 21,000 years ago, the large continental ice sheets began to retreat, causing sea levels to rise by an average of about 430 feet. When the ice was prominent and sea levels were lower, large expanses of the continental shelf that today are submerged were then exposed.

As the melting progressed and sea levels rose, likely archaeological sites along the coast were submerged.

Most past models have assumed that as the massive North American ice sheets melted, global sea levels rose in concert – a phenomenon known as “the bathtub model.” But the authors of this new study, which was just published in the Journal of Archaeological Science, say sea level rise does not happen uniformly.

“During the last deglaciation, sea level rise was significantly influenced by the weight of the large ice sheets, which depressed the land under and near the ice sheets,” said Jorie Clark, a courtesy professor at Oregon State University and lead author on the study. “As the ice sheets melted, this land began to rise. At the same time, the weight of the water melting from the ice sheets and returning to the oceans also depressed the ocean basins.

“This exchange of mass between ice sheets and oceans led to significant differences in sea level at any given location from the assumption of a uniform change,” she added.

The implications of this new approach are significant. The researchers ran models of what the sea level may have looked like over the last 20,000 years – based on knowledge of ice sheet dimensions and the topography of the ocean floor – and concluded that parts of the West Coast looked radically different than previous reconstructions based on a model of uniform sea level rise.

The central Oregon shelf, for example, was thought to be characterized by a series of small islands some 14,000 years ago. However, the models run by Clark and her colleagues suggest that much of the continental shelf was exposed as a solid land mass, creating an extensive coastline. In some areas, the change in estimated sea level may have been as much as 100 feet.

 “There has been new evidence that the peopling of the Americas happened earlier than was long thought to be the case, which has put a lot of focus on coastal paleogeography,” said Clark, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “This new look at sea level changes helps explain how that earlier introduction into the Americas could be possible.”

 “It is also important for predicting where coastal villages that are now submerged on the continental shelf may be located.”

 Other authors on the study were Jerry Mitrovica of Harvard University, and Jay Alder of the U.S. Geological Survey.

Media Contact: 
Source: 

Jorie Clark, 541-737-1575; clarkjc@geo.oregonstate.edu

Science study: Sunlight, not microbes, key to CO2 in Arctic

CORVALLIS, Ore. – The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.

However, a new study – funded by the National Science Foundation and published this week in the journal Science – concludes that sunlight and not bacteria is the key to triggering the production of CO2 from material released by Arctic soils.

The finding is particularly important, scientists say, because climate change could affect when and how permafrost is thawed, which begins the process of converting the organic carbon into CO2.

“Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth – and equals an amount twice of that in the atmosphere,” said Byron Crump, an Oregon State University microbial ecologist and co-author on the Science study. “This represents a major change in thinking about how the carbon cycle works in the Arctic.”

Converting soil carbon to carbon dioxide is a two-step process, notes Rose Cory, an assistant professor of earth and environmental sciences at the University of Michigan, and lead author on the study. First, the permafrost soil has to thaw and then bacteria must turn the carbon into greenhouse gases – carbon dioxide or methane. While much of this conversion process takes place in the soil, a large amount of carbon is washed out of the soils and into rivers and lakes, she said.

“It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2,” Cory said. “This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling.

“In other words, if we only consider what the bacteria are doing, we’ll get the wrong answer about how much CO2 may eventually be released from Arctic soils,” Cory added.

The research team measured the speed at which both bacteria and sunlight converted dissolved organic carbon into carbon dioxide in all types of rivers and lakes in the Alaskan Arctic, from glacial-fed rivers draining the Brooks Range to tannin-stained lakes on the coastal plain. Measuring these processes is important, the scientists noted, because bacteria types and activities are variable and the amount of sunlight that reaches the carbon sources can differ by body of water.

In virtually all of the freshwater systems they measured, however, sunlight was always faster than bacteria at converting the organic carbon into CO2.

“This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river – and most lakes – so that no dissolved organic carbon is kept in the dark,” said Crump, an associate professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “Also, there is little shading of rivers and lakes in the Arctic because there are no trees.”

Another factor limiting the microbial contribution is that bacteria grow more slowly in these cold, nutrient-rich waters.

“Light, therefore, can have a tremendous effect on organic matter,” University of Michigan’s Cory pointed out.

The source of all of this organic carbon is primarily tundra plants – and it has been building up for hundreds of thousands of years, but doesn’t completely break down immediately because of the Arctic’s cold temperatures. Once the plant material gets deep enough into the soil, the degradation stops and it becomes preserved, much like peat.

“The level of thawing only gets to be a foot deep or so, even in the summer,” Crump said. “Right now, the thaw begins not long before the summer solstice. If the seasons begin to shift with climate change – and the thaw begins earlier, exposing the organic carbon from permafrost to more sunlight – it could potentially trigger the release of more CO2.”

The science community has not yet been able to accurately calculate how much organic carbon from the permafrost is being converted into CO2, and thus it will be difficult to monitor potential changes because of climate change, they acknowledge.

“We have to assume that as more material thaws and enters Arctic lakes and rivers, more will be converted to CO2,” Crump said. “The challenge is how to quantify that.”

Some of the data for the study was made available through the National Science Foundation’s Arctic Long-Term Ecological Research project, which has operated in the Arctic for nearly 30 years.

Other authors on the study are Collin Ward and George Kling of the University of Michigan.

Media Contact: 
Source: 

Byron Crump, 541-737-4369; bcrump@coas.oregonstate.edu;

Rose Cory, 734-615-3199, rmcory@umich.edu

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Three OSU faculty members named fellows of American Geophysical Union

CORVALLIS, Ore. – Three Oregon State University faculty members have been named 2014 fellows of the American Geophysical Union. They are the only three fellows in this class from the state of Oregon.

The three selected as fellows were Edward Brook and Gary Egbert from the College of Earth, Ocean, and Atmospheric Sciences; and Beverly Law from the College of Forestry.

Brook is a paleoclimatologist who studies the Earth’s ancient climates through examination of ice cores, specializing in the history of greenhouse gases. His studies have helped explain the processes that led to large-scale climate shifts throughout Earth’s history. In 2011, he was part of a team that completed the excavation of a 10,928-foot ice core – the longest core ever drilled by United States scientists – with ice more than 67,000 years old.

Egbert is a geophysicist and oceanographer whose studies range from ocean tides to electromagnetic imaging of the solid Earth. In one pioneering study, he and his colleagues used satellite altimetry data to show that ocean tides lose significant energy over rough topography in the open ocean. These results imply that the tides may provide an important source of mechanical energy for vertical ocean mixing, and large-scale heat transport in the ocean – processes which are critical to Earth’s climate.

Law is a professor of global change biology and terrestrial systems science who examines the role of forests in the global carbon cycle, and the impacts of climate change on those forests. She was science chair of the AmeriFlux network of more than 100 research sites for 11 years, and in 2014 was listed as a “most highly cited” researcher, in the top 1 percent for the period of 2002-12. She is a principal investigator on a five-year, $4 million project studying the impacts of drought, insects and fires on western forests.

The American Geophysical Union established the AGU Fellows program in 1962, and restricts annual recognition to less than 0.1 percent of its overall membership. This year, 62 fellows were named for their scientific eminence, a major breakthrough, a major discovery, paradigm shifts and/or sustained scientific impact. They will be recognized on Dec. 17 at the annual AGU conference in San Francisco.

Media Contact: 
Source: 

Joan Buhrman, 1+ 202 777-7509, jbuhrman@agu.org