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Tag: University of Alaska Fairbanks

  • Arctic beavers boost methane emissions

    Arctic beavers boost methane emissions

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    Newswise — The climate-driven advance of beavers into the Arctic tundra is causing the release of more methane — a greenhouse gas — into the atmosphere.

    Beavers, as everyone knows, like to make dams. Those dams cause flooding, which inundates vegetation and turns Arctic streams and creeks into a series of ponds. Those beaver ponds and surrounding inundated vegetation can be devoid of oxygen and rich with organic sediment, which releases methane as the material decays.

    Methane is also released when organics-rich permafrost thaws as the result of heat carried by the spreading water.

    A study linking Arctic beavers to an increase in the release of methane was published in July in Environmental Research Letters. 

    The lead author is Jason Clark, a former postdoctoral fellow at the University of Alaska Fairbanks Geophysical Institute. Research Professor Ken Tape, also of the Geophysical Institute, was Clark’s adviser and is a co-author. Other co-authors include Benjamin Jones, a research assistant professor at the UAF Institute of Northern Engineering; and researchers from the National Park Service and NASA’s Jet Propulsion Laboratory.

    Tape has done extensive research about the northward migration of beavers and their resultant impact on the Arctic environment.

    “What we found is that there are lots of methane hotspots right next to ponds and they start to diminish as you go away from the pond,” he said.

    The new study is the first to link large numbers of new beaver ponds to methane emissions at the landscape scale. It suggests that beaver engineering in the Arctic will at least initially increase methane release. 

    “We say ‘initially’ because that’s the data we have,” Tape said. “What the longer-term implications are, we don’t know.” 

    As a greenhouse gas, methane is 25 times more potent than carbon dioxide at trapping heat in Earth’s atmosphere.

    It accounts for about 20 percent of global greenhouse gas emissions, according to the U.S. Environmental Protection Agency. The agency says human activities have more than doubled atmospheric methane concentrations in the past two centuries.

    The new research focused on 166 square miles of the lower Noatak River basin in Northwest Alaska. Data was obtained by airborne hyperspectral imaging through NASA’s Arctic-Boreal Vulnerability Experiment program. That program and the National Science Foundation funded the research.

    Hyperspectral cameras image an area in hundreds of wavelengths across the electromagnetic spectrum, including many not visible to the human eye. That differs from other cameras, which typically only image in the primary colors of red, green and blue.

    The researchers compared the location of methane hot spots to the locations of 118 beaver ponds and to a number of nearby unaffected stream reaches and lakes. They analyzed the area up to approximately 200 feet from the perimeter of each water body and found a “significantly greater” number of methane hot spots around beaver ponds.

    “We have these datasets that largely overlap, in space and mostly in time,” Tape said. “It’s kind of a simple design relying on a new tool.”

    Additional research about the relationship between beaver migration and Arctic methane release will occur next year.

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    University of Alaska Fairbanks

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  • Alaska scientists’ novel aid for earthquake magnitude

    Alaska scientists’ novel aid for earthquake magnitude

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    Newswise — Sensors that detect changes in atmospheric pressure due to ground shaking can also obtain data about large earthquakes and explosions that exceed the upper limit of many seismometers, according to new research.

    The sensors, which detect inaudible infrasounds carried through the air, could improve tsunami warnings and other emergency responses while also lowering costs.

    Research by University of Alaska Fairbanks Geophysical Institute scientists shows that infrasound sensors can improve magnitude determinations. An initial tsunami warning is based solely on estimated magnitude and location.

    Infrasound sensors cost less than seismometers, are reliable and exist in large numbers in Alaska for other uses.

    “What we’ve done is use infrasound for a purpose it wasn’t really intended for,” said Ken Macpherson at the Geophysical Institute’s Wilson Alaska Technical Center.“We’ve found that it works well for providing complete data about strong earthquakes.”

    These pressure-sensing infrasound instruments are generally used for non-seismic purposes such as the detection of mining explosions or nuclear detonations. They also record landslides, erupting volcanoes or meteors entering Earth’s atmosphere.

    Macpherson details the use of infrasound sensors for seismology in a research paper published April 21 in the Bulletin of the Seismological Society of America. 

    Macpherson is a seismo-acoustic research and operations scientist. Others from the Wilson Alaska Technical Center involved in the research include Director David Fee, data specialist  Juliann Coffey and machine-learning specialist Alex Witsil, now working in the private sector.

    Infrasound sensors record changes in air pressure caused by infrasound waves, which are at a frequency below what humans can hear. 

    Infrasound sensors can register the full range of an earthquake’s ground motion by detecting air pressure changes caused by the ground’s up and down movement during an earthquake. 

    Upward movement of the ground compresses the air, increasing air pressure much like a piston does. Downward movement reduces the pressure. 

    Pressure changes from even the largest earthquakes are far below infrasound sensors’ upper limit. 

    In contrast, seismometers, which record the actual movement of the ground, have an upper limit, meaning top-end data can be absent for large earthquakes. They can also miss data of smaller earthquakes if those occur too close to a seismometer.

    Seismologists call that data loss “clipping.”

    “If you crank up your stereo too high, you get a horrible sound,” Macpherson said. “That means you’ve exceeded the dynamic range of the speaker. That can happen to a seismometer.”

    Seismologists can overcome clipping by deploying strong-motion detectors, which are different from infrasound sensors. These motion sensors won’t go off scale during intense shaking but are costly and aren’t accurate for smaller quakes. About 130 are located around Alaska, mostly in urban areas and near known faults.

    As one example, Macpherson and his colleagues compared infrasound data of the magnitude 7.1 Anchorage earthquake of Nov. 30, 2018, to data from a seismometer. Both instruments were in the same location 18.6 miles from the epicenter.

    “The seismometer recording of that earthquake went right to the dynamic range of the instrument and stopped,” Macpherson said. “So there’s a loss of amplitude information.”

    The seismometer was one of several in the Southcentral Alaska region missing top-end data from that earthquake. Data from the infrasound sensor was not clipped.

    To check the accuracy of the infrasound monitor’s top-end data, Macpherson matched it against the data from a strong-motion seismometer at the same location. They matched.

    Infrasound sensors can also provide data just as timely as seismometers. That’s especially important if a tsunami is possible. The National Tsunami Warning Center has just four minutes to issue a warning from the time of a quake’s occurrence.

    “If all of the close seismometers clip, and the Tsunami Warning Center is trying to get an accurate magnitude for warning of a tsunami, they could quickly compute magnitudes from a nearby infrasound station that’s colocated with a seismometer,” Coffey said.

    Alaska has about 150 infrasound sensors alongside seismic monitors throughout the state. 

    Some of these were part of the EarthScope Transportable Array, a project funded by the National Science Foundation to map Earth’s crust and upper mantle. The temporary array moved gradually across the nation, reaching Alaska in 2014. Ninety-six of these stations are now part of the Alaska Earthquake Center’s permanent monitoring network. 

    “We have this unique resource in Alaska, and we’re pushing the science to get the most out of it that we can,” Macpherson said. “We’re looking to utilize it in novel ways.”

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  • New method of monitoring shore ice could improve public safety

    New method of monitoring shore ice could improve public safety

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    Newswise — Specialized portable radar could serve as an early warning system to reduce risk for humans working on shorefast sea ice, according to a recently published study.

    The researchers suggest that use of portable interferometric radar can quickly reveal small changes that could indicate imminent movement or detachment of the ice, which is important as climate change affects ice behavior. The capability could also be useful for near-coastal navigation.

    “If you want to learn about what makes the shorefast ice go unstable and detach from the coast, we need to be able to detect some early warning signals,” said research assistant professor Andy Mahoney of the University of Alaska Fairbanks Geophysical Institute.

    Shorefast ice—also known as landfast ice—is ice that’s attached to the shore.

    “Satellites give you snapshots that are separated by hours if not days,” he said. “This portable ground-based system can be looking continuously for signs of instability.”

    The research was published in January in the journal Cold Regions Science and Technology. Former UAF graduate student Dyre Oliver Dammann is the lead author. UAF oceanography professor Mark Johnson, Mahoney and Geophysical Institute colleagues Emily Fedders, a graduate student researcher, and research professor Mark Fahnestock are among the seven co-authors.

    Imagery from a portable ground-based radar interferometer can reveal sea ice changes down to the centimeter and millimeter levels. The devices can monitor areas continuously.

    Interferometric radar differs from regular radar in that it compares two different images of an object to identify small changes in the distance to it. By collecting a near-continuous time series of data from a single location, the coast-based interferometric radar can measure the compression or stretching of sea ice before it fails. It also can detect small cracks that might go unnoticed by observers on the ice. 

    Researchers from the UAF Geophysical Institute, the UAF College of Fisheries and Ocean Sciences and institutions in Oregon, New Hampshire, Norway and Japan collected and analyzed several series of measurements in Utqiaġvik, Alaska.

    They used the portable interferometric radar to look for evidence of strain on the ice from wind and sea level change. The radar could detect displacement of as little as 1 centimeter.

    Landfast ice in shallow water depths such as that near Utqiaġvik consists of pans of smooth, floating ice anchored by ridges of deformed ice resting on the seafloor. Winds and currents alone  typically do not dislodge ice grounded in this way. Storm surges or high tides, coupled with onshore winds, can lift the grounded ice and make it more likely to detach. 

    The researchers concluded that processing radar data in near real time can reduce risk to humans on the ice by serving as an early warning system for fracturing, destabilization and break-out events. It could also serve as a warning to vessels navigating near the coast. 

    They also state that seasonal monitoring could aid in long-term strategic decision-making in response to large-scale environmental change. 

    The research is the latest in a continuing effort to better understand the behavior of coastal ice. 

    The aim is to gather interferometric images of a variety of ice interactions: landfast ice interacting with the drifting ice, landfast ice affected by wind and landfast ice during a period of higher sea level due to onshore wind, for example.

    “Through these observations, we can learn a little bit more about how landfast ice responds in these different scenarios,” Fedders said. “The eventual goal would be to incorporate that into a better prediction of land-fast ice stability.”

    Researchers were back in the area last year.

    “We saw some interesting tidal motions during a period when there wasn’t pack ice up against the landfast ice, where a lead was open,” Fedders said. “That was something we hadn’t captured with the radar before.”

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    University of Alaska Fairbanks

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