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Methane Releases From Arctic Shelf

Thawing by climate change of subsea layer of permafrost may release stores of underlying, seabed methane

A section of the Arctic Ocean seafloor that holds vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas, according to the findings of an international research team led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov.

The research results, published in the March 5 edition of the journal Science, show that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.

“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans,” said Shakhova, a researcher at UAF’s International Arctic Research Center. “Subsea permafrost is losing its ability to be an impermeable cap.”

Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. It is released from previously frozen soils in two ways. When the organic material (which contains carbon) stored in permafrost thaws, it begins to decompose and, under anaerobic conditions, gradually releases methane. Methane can also be stored in the seabed as methane gas or methane hydrates and then released as subsea permafrost thaws. These releases can be larger and more abrupt than those that result from decomposition.

The East Siberian Arctic Shelf is a methane-rich area that encompasses more than 2 million square kilometers of seafloor in the Arctic Ocean. It is more than three times as large as the nearby Siberian wetlands, which have been considered the primary Northern Hemisphere source of atmospheric methane. Shakhova’s research results show that the East Siberian Arctic Shelf is already a significant methane source, releasing 7 teragrams of methane yearly, which is as much as is emitted from the rest of the ocean. A teragram is equal to about 1.1 million tons.

“Our concern is that the subsea permafrost has been showing signs of destabilization already,” she said. “If it further destabilizes, the methane emissions may not be teragrams, it would be significantly larger.”

Shakhova notes that the Earth’s geological record indicates that atmospheric methane concentrations have varied between about .3 to .4 parts per million during cold periods to .6 to .7 parts per million during warm periods. Current average methane concentrations in the Arctic average about 1.85 parts per million, the highest in 400,000 years, she said. Concentrations above the East Siberian Arctic Shelf are even higher.

The East Siberian Arctic Shelf is a relative frontier in methane studies. The shelf is shallow, 50 meters (164 feet) or less in depth, which means it has been alternately submerged or terrestrial, depending on sea levels throughout Earth’s history. During the Earth’s coldest periods, it is a frozen arctic coastal plain, and does not release methane. As the Earth warms and sea level rises, it is inundated with seawater, which is 12-15 degrees warmer than the average air temperature.

“It was thought that seawater kept the East Siberian Arctic Shelf permafrost frozen,” Shakhova said. “Nobody considered this huge area.”

“This study is a testament to sustained, careful observations and to international cooperation in research,” said Henrietta Edmonds of the National Science Foundation, which partially funded the study. “The Arctic is a difficult place to get to and to work in, but it is important that we do so in order to understand its role in global climate and its response and contribution to ongoing environmental change. It is important to understand the size of the reservoir–the amount of trapped methane that potentially could be released–as well as the processes that have kept it “trapped” and those that control the release. Work like this helps us to understand and document these processes.”

Earlier studies in Siberia focused on methane escaping from thawing terrestrial permafrost. Semiletov’s work during the 1990s showed, among other things, that the amount of methane being emitted from terrestrial sources decreased at higher latitudes. But those studies stopped at the coast. Starting in the fall of 2003, Shakhova, Semiletov and the rest of their team took the studies offshore. From 2003 through 2008, they took annual research cruises throughout the shelf and sampled seawater at various depths and the air 10 meters above the ocean. In September 2006, they flew a helicopter over the same area, taking air samples at up to 2,000 meters (6,562 feet) in the atmosphere. In April 2007, they conducted a winter expedition on the sea ice.

They found that more than 80 percent of the deep water and more than 50 percent of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached more than 250 times that of background levels in the summer and 1,400 times higher in the winter. They found corresponding results in the air directly above the ocean surface. Methane levels were elevated overall and the seascape was dotted with more than 100 hotspots. This, combined with winter expedition results that found methane gas trapped under and in the sea ice, showed the team that the methane was not only being dissolved in the water, it was bubbling out into the atmosphere.

These findings were further confirmed when Shakhova and her colleagues sampled methane levels at higher elevations. Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline. When they flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated Arctic levels.

The East Siberian Arctic Shelf, in addition to holding large stores of frozen methane, is more of a concern because it is so shallow. In deep water, methane gas oxidizes into carbon dioxide before it reaches the surface. In the shallows of the East Siberian Arctic Shelf, methane simply doesn’t have enough time to oxidize, which means more of it escapes into the atmosphere. That, combined with the sheer amount of methane in the region, could add a previously uncalculated variable to climate models.

“The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to 3 to 4 times,” Shakhova said. “The climatic consequences of this are hard to predict.”

Shakhova, Semiletov and collaborators from 12 institutions in five countries plan to continue their studies in the region, tracking the source of the methane emissions and drilling into the seafloor in an effort to estimate how much methane is stored there.

###

Shakhova and Semiletov hold joint appointments with the Pacific Oceanological Institute, part of the Far Eastern Branch of the Russian Academy of Sciences. Their collaborators on this paper include Anatoly Salyuk, Vladimir Joussupov and Denis Kosmach, all of the Pacific Oceanological Institute, and Orjan Gustafsson of Stockholm University.

-NSF-

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Significant Red Tide In 2010

Seed Population on Seafloor Points to a large ‘Red Tide’; Impacts will Depend on Ocean Conditions and Weather

Scientists from the NOAA-funded Gulf of Maine Toxicity project issued an outlook for a significant regional bloom of a toxic alga that causes ‘red tides’ in the spring and summer of this year, potentially threatening the New England shellfish industry.

The outlook is based on a seafloor survey of the seed-like cysts of Alexandrium fundyense, an organism that causes harmful algal blooms, sometimes referred to as ‘red tides’. Cysts deposited in the fall hatch the following spring; last fall the abundance of cysts in the sediment was 60 percent higher than observed prior to the historic bloom of 2005, indicating that a large bloom is likely in the spring of 2010.

The cyst bed also appears to have expanded to the south, so the 2010 bloom may affect areas such as Massachusetts Bay and Georges Bank sooner than has been the case in past years.

Although the algae in the water pose no direct threat to human beings, toxins produced by Alexandrium can accumulate in filter-feeding organisms such as mussels and clams, which can cause paralytic shellfish poisoning in humans who consume them. In order to protect public health, shellfish beds are monitored by state agencies and closed when toxin concentrations rise above a quarantine level. There have been no illnesses from legally harvested shellfish in recent years despite some severe blooms.

Scientists are reluctant to make a “forecast” of precisely where and when the bloom will make landfall because bloom transport depends on weather events that cannot be predicted months in advance.

“Our research has shown that cyst abundance in the fall is an indicator of the magnitude of the bloom in the following year,” said Dennis McGillicuddy, a senior scientist with Woods Hole Oceanographic Institution and member of the Gulf of Maine Toxicity project, or GOMTOX. “Even if there is a large bloom offshore, certain wind patterns and ocean currents in the late spring and summer are needed to transport it onshore where it can affect coastal shellfish.”

This year’s bloom could be similar to the major blooms of 2005 and 2008, according to Don Anderson, a biologist with Woods Hole Oceanographic Institution and principal investigator of the GOMTOX study. The 2005 bloom shut down shellfish beds from Maine to Martha’s Vineyard for several months and caused an estimated $20 million in losses to the Massachusetts shellfish industry alone.

Government agencies and researchers believe that the regional-scale, seasonal outlook can be useful in preparing for contingencies. “NOAA’s goal is to provide tools to prevent, control, or mitigate the occurrence of harmful algal blooms and their impacts,” said David M. Kennedy, acting assistant administrator for NOAA’s National Ocean Service. “This advanced warning, along with updates during the season, can help state agencies prepare for monitoring harmful algal blooms and assessing public health risks.”

Early warnings can give shellfish farmers and fishermen the opportunity to shift the timing of their harvest or postpone plans for expansion of aquaculture beds. Area restaurants may also benefit from advance warnings by making contingency plans for supplies of seafood during the summer.

GOMTOX researchers regularly share their field observations and models with more than 80 coastal resource and fisheries managers in six states as well as federal entities like NOAA, the Environmental Protection Agency and the Food and Drug Administration.

“’Red tide’ is a chronic problem in the Gulf of Maine and states have limited resources to handle it,” said Darcie Couture, director of Biotoxin Monitoring for the Maine Department of Marine Resources. “When we get this information about the potential severity of a bloom season and the dynamics of the bloom once the season has started, then it gives us an advantage in staging our resources during an otherwise overwhelming environmental and economic crisis.”

Ruoying He, associate professor at North Carolina State University and GOMTOX member, will present data and models on the projected bloom at the 2010 Ocean Sciences Meeting today in Portland, Ore.

The GOMTOX project, funded by NOAA’s ECOHAB Program, is a collaboration of investigators from NOAA, Woods Hole Oceanographic Institution, North Carolina State University, University of Maine, University of Massachusetts Dartmouth, Rutgers University, the Food and Drug Administration, the Canadian Department of Fisheries and Oceans, Maine Department of Marine Resources, Massachusetts Division of Marine Fisheries and the New Hampshire Department of Environmental Services. Other support for Alexandrium studies in the Gulf of Maine is provided by the National Institutes of Health and the National Science Foundation (through the Woods Hole Center for Oceans and Human Health).

NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.

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Latest Earthquakes Shake The World

Magnitude 8.8 – OFFSHORE MAULE, CHILE
Magnitude 8.8
Date-Time Saturday, February 27, 2010 at 06:34:14 UTC
Saturday, February 27, 2010 at 03:34:14 AM at epicenter
Time of Earthquake in other Time Zones

Location 35.846°S, 72.719°W
Depth 35 km (21.7 miles) set by location program
Region OFFSHORE MAULE, CHILE
Distances 100 km (60 miles) NNW of Chillan, Chile

Summary: This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 80 mm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate.

Coastal Chile has a history of very large earthquakes. Since 1973, there have been 13 events of magnitude 7.0 or greater. The February 27 shock originated about 230 km north of the source region of the magnitude 9.5 earthquake of May, 1960 – the largest earthquake worldwide in the last 200 years or more. This giant earthquake spawned a tsunami that engulfed the Pacific Ocean. An estimated 1600 lives were lost to the 1960 earthquake and tsunami in Chile, and the 1960 tsunami took another 200 lives among Japan, Hawaii, and the Philippines. Approximately 870 km to the north of the February 27 earthquake is the source region of the magnitude 8.5 earthquake of November, 1922. This great quake significantly impacted central Chile, killing several hundred people and causing severe property damage. The 1922 quake generated a 9-meter local tsunami that inundated the Chile coast near the town of Coquimbo; the tsunami also crossed the Pacific, washing away boats in Hilo harbor, Hawaii. The magnitude 8.8 earthquake of February 27, 2010 ruptured the portion of the South American subduction zone separating these two massive historical earthquakes.

A large vigorous aftershock sequence can be expected from this earthquake.

Magnitude 7.0 – RYUKYU ISLANDS, JAPAN
Magnitude 7.0
Date-Time Friday, February 26, 2010 at 20:31:27 UTC
Saturday, February 27, 2010 at 05:31:27 AM at epicenter
Time of Earthquake in other Time Zones

Location 25.902°N, 128.417°E
Depth 22 km (13.7 miles) set by location program
Region RYUKYU ISLANDS, JAPAN
Distances 80 km (50 miles) ESE of Naha, Okinawa, Japan

Summary: The Ryukyu Islands earthquake of February 26, 2010, occurred near the boundary that accommodates most of the relative motion between the Philippine Sea and Eurasia tectonic plates. In the region of the earthquake, the Philippine Sea plate moves WNW with respect to the interior of the Eurasia plate, with a relative velocity of approximately 60 mm/yr. The Philippine Sea plate subducts beneath the Eurasia plate at the Ryukyu Trench and is seismically active to depths of about 250 km. The initial estimates of the earthquake’s epicenter, focal-depth, and focal-mechanism imply that the shock occurred as an intraplate event either within the subducting Philippine Sea Plate, or within the overlying Eurasia plate, rather than on the thrust-fault plate interface that separates the two, but preliminarily data do not clearly discriminate between these two possibilities.

The largest, instrumentally recorded, shallow-focus, earthquakes from the region of the central Ryukyu trench have had magnitudes in the 7.1 – 7.4 range.

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