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Saving our soil (part 2) | NPR
Monday, December 4, 2017
NPR talks with experts -- including UW Earth and space sciences professor David Montgomery -- about improving the nation's soil. [This is Part 2 of the program] Read More
Saving our soil (part 1) | NPR
Monday, December 4, 2017
NPR talks with experts -- including UW Earth and space sciences professor David Montgomery -- about improving the nation's soil. [This is Part 1 of the program] Read More
Groundwater on Mars? Salty Antarctic pond could reveal clues | Space.com
Monday, December 4, 2017
A shallow, briny pond located in the most Mars-like region on Earth is probably being fed by groundwater seeping up, rather than moisture seeping down from the atmosphere, providing clues as to what stores of liquid water, if they exist, might look like on Mars. Jonathan Toner, a geochemist at the UW, is quoted. Read More
Shipping routes have more lightning | KOMO Radio
Thursday, November 30, 2017
A new University of Washington study shows ship exhaust along popular shipping routes actually increases lightning strikes. Robert Holzworth, UW professor of Earth and space sciences, and Joel Thornton, UW professor of atmospheric sciences, are interviewed. Read More
Less life: Limited phosphorus recycling suppressed early Earth's biosphere
Tuesday, November 28, 2017
The amount of biomass - life - in Earth’s ancient oceans may have been limited due to low recycling of the key nutrient phosphorus, according to new research by the University of Washington and the University of St. Andrews in Scotland.
The research, published online Nov. 22 in the journal Science Advances, also comments on the role of volcanism in supporting Earth’s early biosphere -- and may even apply to the search for life on other worlds.
The paper’s lead author is Michael Kipp, a UW doctoral student in Earth and space sciences; coauthor is Eva St?eken, a research fellow at the University of St. Andrews and former UW postdoctoral researcher. Roger Buick, UW professor of Earth and space sciences, advised the researchers.
Their aim, Kipp said, was to use theoretical modeling to study how ocean phosphorus levels have changed throughout Earth’s history.
“We were interested in phosphorus because it is thought to be the nutrient that limits the amount of life there is in the ocean, along with carbon and nitrogen,” said Kipp. “You change the relative amount of those and you change, basically, the amount of biological productivity.”
Kipp said their model shows the ability of phosphorus to be recycled in the ancient ocean “was much lower than today, maybe on the order of 10 times less.”
All life needs abundant food to thrive, and the chemical element phosphorus - which washes into the ocean from rivers as phosphate -- is a key nutrient. Once in the ocean, phosphorus gets recycled several times as organisms such as plankton or eukaryotic algae that “eat” it are in turn consumed by other organisms.
“As these organisms use the phosphorus, they in turn get grazed upon, or they die and other bacteria decompose their organic matter,” said Kipp, “and they release some of that phosphorus back into the ocean. It actually cycles through several times," allowing the liberated phosphorus to build up in the ocean. The amount of recycling is a key control on the amount of total phosphorus in the ocean, which in turn supports life.
Buick explained: "Every gardener knows that their plants grow only small and scraggly without phosphate fertilizer. The same applies for photosynthetic life in the oceans, where the phosphate 'fertilizer' comes largely from phosphorus liberated by the degradation of dead plankton."
But all of this requires oxygen. In today's oxygen-rich oceans, nearly all phosphorus gets recycled in this way and little falls to the ocean floor.
Several billion years ago, in the Precambrian era, however, there was little or no oxygen in the environment.
"There are some alternatives to oxygen that certain bacteria could use, said co-author St?eken. "Some bacteria can digest food using sulfate. Others use iron oxides." Sulfate, she said, was the most important control on phosphorus recycling in the Precambrian era.
"Our analysis shows that these alternative pathways were the dominant route of phosphorus recycling in the Precambrian, when oxygen was very low," St?eken said. "However, they are much less effective than digestion with oxygen, meaning that only a smaller amount of biomass could be digested. As a consequence, much less phosphorus would have been recycled, and therefore total biological productivity would have been suppressed relative to today."
Kipp likened early Earth's low-oxygen ocean to a kind of "canned" environment, with oxygen sealed out: "It's a closed system. If you go back to the early Precambrian oceans, there's not very much going on in terms of biological activity."
St?eken noted that volcanoes were the biggest source of sulfate in the Precambrian, unlike now, and so they were necessary for sustaining a significant biosphere by enabling phosphorus recycling.
In fact, minus such volcanic sulfate, St?eken said, Earth’s biosphere would have been very small, and may not have survived over billions of years. The findings, then, illustrate “how strongly life is tied to fundamental geological processes such as volcanism on the early Earth,” she said.
Kipp and St?eken’s modeling may have implications as well for the search for life beyond Earth.
Astronomers will use upcoming ground- and space-based telescopes such as the James Webb Space Telescope, set for launch in 2019, to look for the impact of a marine biosphere, as Earth has, on a planet’s atmosphere. But low phosphorus, the researchers say, could cause an inhabited world to appear uninhabited -- making a sort of “false negative.”
Kipp said, “If there is less life -- basically, less photosynthetic output -- it’s harder to accumulate atmospheric oxygen than if you had modern phosphorus levels and production rates. This could mean that some planets might appear to be uninhabited due to their lack of oxygen, but in reality they have biospheres that are limited in extent due to low phosphorus availability.
"These ‘false negatives’ are one of the biggest challenges facing us in the search for life elsewhere," said Victoria Meadows, UW astronomy professor and principal investigator for the NASA Astrobiology Institute’s Virtual Planetary Laboratory, based at the UW.
“But research on early Earth’s environments increases our chance of success by revealing processes and planetary properties that guide our search for life on nearby exoplanets."
The work was funded by grants from NASA and the National Science Foundation.
NASA Exobiology grant NNX16AI37G to Prof. Buick.Read More
UW researchers use unmanned subs | KOMO 4
Monday, November 27, 2017
The UW is going to send robots into ice caves to collect data. Knut Christianson, assistant professor of Earth and space sciences at the UW, is interviewed. Read More
A Bolt from the Brown: Why Pollution May Increase Lightning Strikes
Thursday, November 16, 2017
Scientific American reports on a University of Washington paper using World Wide Lightning Location Network data to show that pollution from ship exhaust in the Indian Ocean and South China Sea enhances the probability of lightning by a factor of two. This pollution problem and consequent increase in lightning was shown to occur every year over the last decade or more. Read More
Salt pond in Antarctica, among the saltiest waters on Earth, is fed from beneath
Wednesday, November 15, 2017
At the base of the Transantarctic Mountains lies a geological oddity. Don Juan Pond is one of the saltiest bodies of water on the planet, filled with a dense, syrupy brine rich in calcium chloride that can remain liquid to minus 50 degrees Celsius, far below the freezing point of water. But the source of water and salt to this unusual pond remains a mystery -- even as hints emerge that water in a similar form could exist on Mars.
A new University of Washington study uses the pond’s bizarre chemistry to pinpoint the water’s source. The recent paper, published Sept. 15 in Earth and Planetary Science Letters, reports that it is fed by a regional deep groundwater system and not, as previously suggested, from moisture seeping down from local valley slopes.
“Don Juan Pond is probably one of the most interesting ponds on Earth,” said lead author Jonathan Toner, a UW research assistant professor in Earth and space sciences. “After 60 years of extensive study, we still don't really know exactly where it’s coming from, what drives the fact that it’s visible on the surface, and how it’s changing.”
The perennial pond measures about 100 by 300 meters, the size of a few football fields, and is about 10 centimeters (4 inches) deep on average. It was first visited in 1961 and named after the expedition’s helicopter pilots, Donald Roe and John Hickey, earning it the name Don Juan Pond. The unique salts in the pond lower the freezing point, which is why this saline pond can exist in a place where the temperature ranges from minus 50 to plus 10 degrees Celsius (-58 to +50 F).
The pond was long believed to be fed by deep groundwater. But then a high-profile 2013 paper suggested that near-surface moisture seeps, similar to recurring slope lineae features recently observed on Mars, were transporting salts downhill to create the salt pond.
Toner is a geochemist specializing in the formation and properties of water in extreme environments on Earth, Mars and beyond. For the new study, Toner created a model to compute how salty water changes during evaporation, freezing, and with different water and salt inputs and outputs. In Antarctica’s appropriately named McMurdo Dry Valleys, water evaporation concentrates salts in the pond, which forces some salts to crystallize. These processes, along with inputs and outputs, cause the pond’s water to change over time.
Toner ran his model for two situations: one where the water was gurgling up from beneath, and another where it was trickling down from near-surface seeps. Results show that the observed chemical makeup could only be produced from underneath.
“You couldn't get Don Juan Pond from these shallow groundwaters,” Toner said. “It's definitely coming from the deep groundwater.”
His calculations also show that upwelling groundwater cycles through the pond every six months, meaning the water must exit the pond via some unseen underground outflow.
The pond’s hydrology is important to geologists because nowhere on Earth is more similar to Mars. The Red Planet is extremely cold and dry, and the McMurdo Dry Valleys are one of the coldest and driest locations on Earth.
“If there is water on Mars, it’s probably going to look a lot like this pond,” Toner said. “Understanding how it formed has large implications for where would you expect to find similar environments on Mars.”
Recent studies hint that liquid water might exist on the surface of Mars, potentially harboring life or even eventually supporting long-term human settlements. The darker lines on steep slopes, which look like moisture streaks observed above Don Juan Pond, could be caused by a similar groundwater system.
Toner will be part of a team exploring Don Juan Pond and surrounding areas this December, sponsored by NASA and the National Science Foundation. Researchers will spend six weeks camping near the pond and taking repeated chemical measurements of its liquid. They will also explore the nearby slopes to measure the chemistry of the moisture seeps, and try to find further evidence for the source of salts to Don Juan Pond.
“If we accept that the deep groundwater theory is true, then what we’re seeing could be part of a bigger process that involves quite an extensive aquifer,” Toner said. “When thinking about the implications for a similar environment on Mars, that’s much more exciting than just a localized surface phenomenon.”
For more information, contact Toner at email@example.com.
NASA grant: NNX15AP19GRead More
Ships Cause their own Stormy Seas
Thursday, November 9, 2017
Physics Today (Search and Discovery) of the November 2017 edition reports on research using WWLLN lightning network data: 'Increased lightning frequency over maritime trade routes links pollution to the development of thunderclouds.' Underlying paper by Thornton (Atmos. Sci), Virts (NASA Huntsville), Holzworth (ESS) and Mitchell (JISAO) recently published in Geophysical Research Letters). Read More
50 simulations of the 'Really Big One' show how a 9.0 Cascadia earthquake could play out
Monday, October 23, 2017
One of the worst nightmares for many Pacific Northwest residents is a huge earthquake along the offshore Cascadia Subduction Zone, which would unleash damaging and likely deadly shaking in coastal Washington, Oregon, British Columbia and northern California.
The last time this happened was in 1700, before seismic instruments were around to record the event. So what will happen when it ruptures next is largely unknown.
A University of Washington research project, to be presented Oct. 24 at the Geological Society of America’s annual meeting in Seattle, simulates 50 different ways that a magnitude-9.0 earthquake on the Cascadia subduction zone could unfold.
“There had been just a handful of detailed simulations of a magnitude-9 Cascadia earthquake, and it was hard to know if they were showing the full range,” said Erin Wirth, who led the project as a UW postdoctoral researcher in Earth and space sciences. “With just a few simulations you didn’t know if you were seeing a best-case, a worst-case or an average scenario. This project has really allowed us to be more confident in saying that we’re seeing the full range of possibilities.”
Off the Oregon and Washington coast, the Juan de Fuca oceanic plate is slowly moving under the North American plate. Geological clues show that it last jolted and unleashed a major earthquake in 1700, and that it does so roughly once every 500 years. It could happen any day.
Wirth’s project ran simulations using different combinations for three key factors: the epicenter of the earthquake; how far inland the earthquake will rupture; and which sections of the fault will generate the strongest shaking.
Results show that the intensity of shaking can be less for Seattle if the epicenter is fairly close to beneath the city. From that starting point, seismic waves will radiate away from Seattle, sending the biggest shakes in the direction of travel of the rupture.
“Surprisingly, Seattle experiences less severe shaking if the epicenter is located just beneath the tip of northwest Washington,” Wirth said. “The reason is because the rupture is propagating away from Seattle, so it’s most affecting sites offshore. But when the epicenter is located pretty far offshore, the rupture travels inland and all of that strong ground shaking piles up on its way to Seattle, to make the shaking in Seattle much stronger.”
The research effort began by establishing which factors most influence the pattern of ground shaking during a Cascadia earthquake. One, of course, is the epicenter, or more specifically the “hypocenter,” which locates the earthquake's starting point in three-dimensional space.
Another factor they found to be important is how far inland the fault slips. A magnitude-9.0 earthquake would likely give way along the whole north-south extent of the subduction zone, but it’s not well known how far east the shake-producing area would extend, approaching the area beneath major cities such as Seattle and Portland.
The third factor is a new idea relating to a subduction zone’s stickiness. Earthquake researchers have become aware of the importance of “sticky points,” or areas between the plates that can catch and generate more shaking. This is still an area of current research, but comparisons of different seismic stations during the 2010 Chile earthquake and the 2011 Tohoku earthquake show that some parts of the fault released more strong shaking than others.
Wirth simulated a magnitude-9.0 earthquake, about the middle of the range of estimates for the magnitude of the 1700 earthquake. Her 50 simulations used variables spanning realistic values for the depth of the slip, and had randomly placed hypocenters and sticky points. The high-resolution simulations were run on supercomputers at the Pacific Northwest National Laboratory and the University of Texas, Austin.
Overall, the results confirm that coastal areas would be hardest hit, and locations in sediment-filled basins like downtown Seattle would shake more than hard, rocky mountaintops. But within that general framework, the picture can vary a lot; depending on the scenario, the intensity of shaking can vary by a factor of 10. But none of the pictures is rosy.
“We are finding large amplification of ground shaking by the Seattle basin,” said collaborator Art Frankel, a U.S. Geological Survey seismologist and affiliate faculty member at the UW. “The average duration of strong shaking in Seattle is about 100 seconds, about four times as long as from the 2001 Nisqually earthquake.”
The research was done as part of the M9 Project, a National Science Foundation-funded effort to figure out what a magnitude-9 earthquake might look like in the Pacific Northwest and how people can prepare. Two publications are being reviewed by the USGS, and engineers are already using the simulation results to assess how tall buildings in Seattle might respond to the predicted pattern of shaking.
As a new employee of the USGS, Wirth will now use geological clues to narrow down the possible earthquake scenarios.
“We’ve identified what parameters we think are important,” Wirth said. “I think there’s a future in using geologic evidence to constrain these parameters, and maybe improve our estimate of seismic hazard in the Pacific Northwest.”
Other co-authors are Nasser Marafi, a UW doctoral student in civil and environmental engineering; John Vidale, a former UW professor now at the University of Southern California; and Bill Stephenson with the USGS.
For more information, contact Wirth at firstname.lastname@example.org.
Videos and images for two of the simulations are available here.Read More