It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Friday, April 30, 2021
New Geology articles published online ahead of print in April
Boulder, Colo., USA: Thirty-one new articles were published online ahead of print for Geology in April. Topics include shocked zircon from the Chicxulub impact crater; the Holocene Sonoran Desert; the architecture of the Congo Basin; the southern Death Valley fault; missing water from the Qiangtang Basin; sulfide inclusions in diamonds; how Himalayan collision stems from subduction; ghost dune hollows; and the history of the Larsen C Ice Shelf.
IMAGE: ANCIENT OSTRICH EGGSHELLS FROM YSTERFONTEIN 1, A MIDDLE STONE AGE MIDDEN IN SOUTH AFRICA. SHOWN ARE SELECTED EGGSHELLS FROM THE TOP LAYER OF THE MIDDEN DATED BY URANIUM-THORIUM (U-TH, OR... view more
CREDIT: IMAGE COURTESY OF E. NIESPOLO.
Archeologists have learned a lot about our ancestors by rummaging through their garbage piles, which contain evidence of their diet and population levels as the local flora and fauna changed over time.
One common kitchen scrap in Africa -- shells of ostrich eggs -- is now helping unscramble the mystery of when these changes took place, providing a timeline for some of the earliest Homo sapiens who settled down to utilize marine food resources along the South African coast more than 100,000 years ago.
Geochronologists at the University of California, Berkeley, and the Berkeley Geochronology Center (BGC) have developed a technique that uses these ubiquitous discards to precisely date garbage dumps -- politely called middens -- that are too old to be dated by radiocarbon or carbon-14 techniques, the standard for materials like bone and wood that are younger than about 50,000 years.
In a paper published this month in the journal Proceedings of the National Academy of Sciences, former UC Berkeley doctoral student Elizabeth Niespolo and geochronologist and BGC and associate director Warren Sharp reported using uranium-thorium dating of ostrich eggshells to establish that a midden outside Cape Town, South Africa, was deposited between 119,900 and 113,100 years ago.
That makes the site, called Ysterfontein 1, the oldest known seashell midden in the world, and implies that early humans were fully adapted to coastal living by about 120,000 years ago. This also establishes that three hominid teeth found at the site are among the oldest Homo sapiens fossils recovered in southern Africa.
The technique is precise enough for the researchers to state convincingly that the 12.5-foot-deep pile of mostly marine shells -- mussels, mollusks and limpets -- intermixed with animal bones and eggshells may have been deposited over a period of as little as 2,300 years.
The new ages are already revising some of the assumptions archeologists had made about the early Homo sapiens who deposited their garbage at the site, including how their population and foraging strategies changed with changing climate and sea level.
"The reason why this is exciting is that this site wouldn't have been datable by radiocarbon because it is too old," Niespolo said, noting that there are a lot more such sites around Africa, in particular the coastal areas of South Africa.
"Almost all of this sort of site have ostrich eggshells, so now that we have this technique, there is this potential to go and revisit these sites and use this approach to date them more precisely and more accurately, and more importantly, find out if they are the same age as Ysterfontein or older or younger, and what that tells us about foraging and human behavior in the past," she added.
Because ostrich eggshells are ubiquitous in African middens -- the eggs are a rich source of protein, equivalent to about 20 chicken eggs -- they have been an attractive target for geochronologists. But applying uranium-thorium dating -- also called uranium series -- to ostrich shells has been beset by many uncertainties.
"The previous work to date eggshells with uranium series has been really hit and miss, and mostly miss," Niespolo said.
CAPTION
Eggshell structures exert a primary control on the distribution of secondary U and Th, so spatial characterization of key elements and careful sampling are required to produce accurate ages by 230Th/U dating. Scale bars are 1 mm. A. Thin section photomicrograph of a modern ostrich eggshell in cross section, and corresponding eggshell structures denoted by V (vertical layer), P (palisade or prismatic layer), and C (cone layer). Pores serving as oxygen pathways for incubating chicks are visible as open holes penetrating through the eggshell. B. Epoxy-mounted fragment of an ancient eggshell from Ysterfontein 1 in cross section, showing the same eggshell structures are well preserved in deep time. Analyses from laser ablation are evident along pitted lines and track concentrations of U and Th. A pore is apparent in the center of the mounted fragment. 230Th/U burial ages of eggshells from this layer are ~118 thousand years old.
CREDIT
Images courtesy of E. Niespolo.
Precision dating pushed back to 500,000 years ago
Other methods applicable to sites older than 50,000 years, such as luminescence dating, are less precise -- often by a factor of 3 or more -- and cannot be performed on archival materials available in museums, Sharp said.
The researchers believe that uranium-thorium dating can provide ages for ostrich eggshells as old as 500,000 years, extending precise dating of middens and other archeological sites approximately 10 times further into the past.
"This is the first published body of data that shows that we can get really coherent results for things well out of radiocarbon range, around 120,000 years ago in this case," said Sharp, who specializes in using uranium-thorium dating to solve problems in paleoclimate and tectonics as well as archeology. "It is showing that these eggshells maintain their intact uranium-series systems and give reliable ages farther back in time than had been demonstrated before."
"The new dates on ostrich eggshell and excellent faunal preservation make Ysterfontein 1 the as-yet best dated multi-stratified Middle Stone Age shell midden on the South African west coast," said co-author Graham Avery, an archeozoologist and retired researcher with the Iziko South African Museum. "Further application of the novel dating method, where ostrich eggshell fragments are available, will strengthen chronological control in nearby Middle Stone Age sites, such as Hoedjiespunt and Sea Harvest, which have similar faunal and lithic assemblages, and others on the southern Cape coast."
The first human settlements?
Ysterfontein 1 is one of about a dozen shell middens scattered along the western and eastern coasts of Western Cape Province, near Cape Town. Excavated in the early 2000s, it is considered a Middle Stone Age site established around the time that Homo sapiens were developing complex behaviors such as territoriality and intergroup competition, as well as cooperation among non-kin groups. These changes may be due to the fact that these groups were transitioning from hunter-gatherers to settled populations, thanks to stable sources of high-quality protein -- shellfish and marine mammals -- from the sea.
Until now, the ages of Middle Stone Age sites like Ysterfontein 1 have been uncertain by about 10%, making comparison among Middle Stone Age sites and with Later Stone Age sites difficult. The new dates, with a precision of about 2% to 3%, place the site in the context of well-documented changes in global climate: it was occupied immediately after the last interglacial period, when sea level was at a high, perhaps 8 meters (26 feet) higher than today. Sea level dropped rapidly during the occupation of the site -- the shoreline retreated up to 2 miles during this period -- but the accumulation of shells continued steadily, implying that the inhabitants found ways to accommodate the changing distribution of marine food resources to maintain their preferred diet.
The study also shows that the Ysterfontein 1 shell midden accumulated rapidly -- perhaps about 1 meter (3 feet) every 1,000 years --- implying that Middle Stone Age people along the southern African coast made extensive use of marine resources, much like people did during the Later Stone Age, and suggesting that effective marine foraging strategies developed early.
For dating, eggshells are better
Ages can be attached to some archeological sites older than 50,000 years through argon-argon (40Ar/39Ar) dating of volcanic ash. But ash isn't always present. In Africa, however -- and before the Holocene, throughout the Middle East and Asia -- ostrich eggshells are common. Some sites even contain ostrich eggshell ornaments made by early Homo sapiens.
Over the last four years, Sharp and Niespolo conducted a thorough study of ostrich eggshells, including analysis of modern eggshells obtained from an ostrich farm in Solvang, California, and developed a systematic way to avoid the uncertainties of earlier analyses. One key observation was that animals, including ostriches, do not take up and store uranium, even though it is common at parts-per-billion levels in most water. They demonstrated that newly laid ostrich shells contain no uranium, but that it is absorbed after burial in the ground.
The same is true of seashells, but their calcium carbonate structure -- a mineral called aragonite -- is not as stable when buried in soil as the calcite form of calcium carbonate found in eggshell. Because of this, eggshells retain better the uranium taken up during the first hundred years or so that that they are buried. Bone, consisting mostly of calcium phosphate, has a mineral structure that also does not remain stable in most soil environments nor reliably retains absorbed uranium.
Uranium is ideal for dating because it decays at a constant rate over time to an isotope of thorium that can be measured in minute amounts by mass spectrometry. The ratio of this thorium isotope to the uranium still present tells geochronologists how long the uranium has been sitting in the eggshell.
Uranium-series dating relies on uranium-238, the dominant uranium isotope in nature, which decays to thorium-230. In the protocol developed by Sharp and Niespolo, they used a laser to aerosolize small patches along a cross-section of the shell, and ran the aerosol through a mass spectrometer to determine its composition. They looked for spots high in uranium and not contaminated by a second isotope of thorium, thorium-232, which also invades eggshells after burial, though not as deeply. They collected more material from those areas, dissolved it in acid, and then analyzed it more precisely for uranium-238 and thorium-230 with "solution" mass spectrometry.
These procedures avoid some of the previous limitations of the technique, giving about the same precision as carbon-14, but over a time range that is 10 times larger.
"The key to this dating technique that we have developed that differs from previous attempts to date ostrich egg shells is the fact that we are explicitly accounting for the fact that ostrich eggshells have no primary uranium in them, so the uranium that we are using to date the eggshells actually comes from the soil pore water and the uranium is being taken up by the eggshells upon deposition," Niespolo said.
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Working with UC Berkeley professor of integrative biology Todd Dawson, Niespolo also analyzed other isotopes in eggshells -- stable isotopes of carbon, nitrogen and oxygen -- to establish that the climate rapidly became drier and cooler over the period of occupation, consistent with known climate changes at that time.
Niespolo, now a postdoctoral fellow at the California Institute of Technology but soon to be an assistant professor at Princeton University, is working with Sharp to date middens at other sites near Ysterfontein. She also is developing the uranium-series technique to use with other types of eggs, such as those of emus in Australia and rheas in South America, as well as the eggs of now extinct flightless birds, such as the two-meter (6.6-foot) tall Genyornis, which died out some 50,000 years ago in Australia.
The work was supported by the Leakey Foundation, Ann and Gordon Getty Foundation and National Science Foundation (BCS-1727085).
An OU-led study sheds new insight on forest loss and degradation in Brazilian Amazon
IMAGE: INTERANNUAL CHANGES OF FOREST AREA, ABOVEGROUND BIOMASS (AGB), ACTIVE FIRE AREA, BURNED AREA, AND ATMOSPHERIC CO2 CONCENTRATION IN THE BRAZILIAN AMAZON view more
CREDIT: XIANGMING XIAO
An international team led by Xiangming Xiao, George Lynn Cross Research Professor in the Department of Microbiology and Plant Biology, University of Oklahoma College of Arts and Sciences, published a paper in the April issue of the journal Nature Climate Change that has major implications on forest policies, conservation and management practices in the Brazilian Amazon. Xiao also is director of OU's Center for Earth Observation and Modeling. Yuanwei Qin, a research scientist at the Center for Earth Observation and Modeling, is the lead author of the study.
For the study described in the paper, "Carbon loss from forest degradation exceeds that from deforestation in the Brazilian Amazon," Xiao, Qin and a team of research scientists and faculty from institutes and universities in the United States, France, the United Kingdom, Denmark and China used satellite data to track spatial-temporal changes of forest area and aboveground biomass in the Brazilian Amazon from 2010 to 2019. They discovered that carbon loss from forest degradation was greater than that resulting from deforestation in the region, which indicates forest degradation should become a high priority in policies, conservation and management.
Tropical forests in the Amazon account, Qin notes, for approximately 50% of the rainforests in the world and are important for global biodiversity, hydrology, climate and the carbon cycle. Accurate and timely data on vegetation aboveground biomass and forest area in the region at various spatial and temporal scales are also essential for data-based policies and decision making. This international team harnessed diverse data for monitoring, reporting and verification of tropical forests. The paper published in Nature Climate Change is a follow-up of a previous study published in Nature Sustainability in 2019, which reported improved estimates of forest areas in the Brazilian Amazon.
IMAGE: THIS ILLUSTRATION OF THE NEWLY FORMING EXOPLANET PDS 70B SHOWS HOW MATERIAL MAY BE FALLING ONTO THE GIANT WORLD AS IT BUILDS UP MASS. BY EMPLOYING HUBBLE'S ULTRAVIOLET LIGHT (UV)... view more
CREDIT: CREDITS: NASA, ESA, STSCI, JOSEPH OLMSTED (STSCI)
NASA's Hubble Space Telescope is giving astronomers a rare look at a Jupiter-sized, still-forming planet that is feeding off material surrounding a young star.
"We just don't know very much about how giant planets grow," said Brendan Bowler of the University of Texas at Austin. "This planetary system gives us the first opportunity to witness material falling onto a planet. Our results open up a new area for this research."
Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. And the planets are so far away and small, they are simply dots in the best photos. The team's fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet's formative years.
This huge exoplanet, designated PDS 70b, orbits the orange dwarf star PDS 70, which is already known to have two actively forming planets inside a huge disk of dust and gas encircling the star. The system is located 370 light-years from Earth in the constellation Centaurus.
"This system is so exciting because we can witness the formation of a planet," said Yifan Zhou, also of the University of Texas at Austin. "This is the youngest bona fide planet Hubble has ever directly imaged." At a youthful five million years, the planet is still gathering material and building up mass.
Hubble's ultraviolet light (UV) sensitivity offers a unique look at radiation from extremely hot gas falling onto the planet. "Hubble's observations allowed us to estimate how fast the planet is gaining mass," added Zhou.
The UV observations, which add to the body of research about this planet, allowed the team to directly measure the planet's mass growth rate for the first time. The remote world has already bulked up to five times the mass of Jupiter over a period of about five million years. The present measured accretion rate has dwindled to the point where, if the rate remained steady for another million years, the planet would only increase by approximately an additional 1/100th of a Jupiter-mass.
Zhou and Bowler emphasize that these observations are a single snapshot in time - more data are required to determine if the rate at which the planet is adding mass is increasing or decreasing. "Our measurements suggest that the planet is in the tail end of its formation process."
The youthful PDS 70 system is filled with a primordial gas-and-dust disk that provides fuel to feed the growth of planets throughout the entire system. The planet PDS 70b is encircled by its own gas-and-dust disk that's siphoning material from the vastly larger circumstellar disk. The researchers hypothesize that magnetic field lines extend from its circumplanetary disk down to the exoplanet's atmosphere and are funneling material onto the planet's surface.
"If this material follows columns from the disk onto the planet, it would cause local hot spots," Zhou explained. "These hot spots could be at least 10 times hotter than the temperature of the planet." These hot patches were found to glow fiercely in UV light.
These observations offer insights into how gas giant planets formed around our Sun 4.6 billion years ago. Jupiter may have bulked up on a surrounding disk of infalling material. Its major moons would have also formed from leftovers in that disk.
A challenge to the team was overcoming the glare of the parent star. PDS 70b orbits at approximately the same distance as Uranus does from the Sun, but its star is more than 3,000 times brighter than the planet at UV wavelengths. As Zhou processed the images, he very carefully removed the star's glare to leave behind only light emitted by the planet. In doing so, he improved the limit of how close a planet can be to its star in Hubble observations by a factor of five.
"Thirty-one years after launch, we're still finding new ways to use Hubble," Bowler added. "Yifan's observing strategy and post-processing technique will open new windows into studying similar systems, or even the same system, repeatedly with Hubble. With future observations, we could potentially discover when the majority of the gas and dust falls onto their planets and if it does so at a constant rate."
The researchers' results were published in April 2021 in The Astronomical Journal.
CAPTION
The European Southern Observatory's Very Large Telescope caught the first clear image of a forming planet, PDS 70b, around a dwarf star in 2018. The planet stands out as a bright point to the right of the center of the image, which is blacked out by the coronagraph mask used to block the light of the central star.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C
CAPTION
Hubble observations pinpoint planet PDS 70b. A coronagraph on Hubble's camera blocks out the glare of the central star for the planet to be directly observed. Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. The team's fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet's formative years.
CREDIT
Credits: Joseph DePasquale (STScI)
Combining solar panels and lamb grazing increases land productivity, study finds
IMAGE: SHEEP GRAZING UNDERNEATH SOLAR PANELS AT OREGON STATE UNIVERSITY. view more
CREDIT: SEAN NEALON, OREGON STATE UNIVERSITY
CORVALLIS, Ore. - Land productivity could be greatly increased by combining sheep grazing and solar energy production on the same land, according to new research by Oregon State University scientists.
This is believed to be the first study to investigate livestock production under agrivoltaic systems, where solar energy production is combined with agricultural production, such as planting agricultural crops or grazing animals.
The researchers compared lamb growth and pasture production in pastures with solar panels and traditional open pastures. They found less overall but higher quality forage in the solar pastures and that lambs raised in each pasture type gained similar amounts of weight. The solar panels, of course, provide value in terms of energy production, which increases the overall productivity of the land.
Solar panels also benefit the welfare of the lambs by providing shade, which allows the animals to preserve energy. Also lamb grazing alleviates the need to manage plant growth under the solar panels through herbicides or regular mowing, which require extra labor and costs.
"The results from the study support the benefits of agrivoltaics as a sustainable agricultural system," said Alyssa Andrew, a master's student at Oregon State who is the lead author of the paper published in Frontier in Sustainable Food Systems.
Solar photovoltaic installation in the U.S. has increased by an average of 48% per year over the past decade, and current capacity is expected to double again over the next five years, the researchers say.
Past research has found that grasslands and croplands in temperate regions are the best places to install solar panels for maximum energy production. However, energy production in photovoltaic systems requires large areas of land, potentially causing a competition between agricultural uses.
Agrivoltaics looks to diffuse that competition by measuring the economic value of energy production and agricultural use of the same land. Past research has focused on crops and solar panels and found that some crops, particularly types that like shade, can be more productive in combination with solar panels.
Another recent Oregon State study found that shade provided by solar panels increased the abundance of flowers under the panels and delayed the timing of their bloom, both findings that could aid the agricultural community.
The just-published study with lambs and solar panels was carried out in 2019 and 2020 at Oregon State's campus in Corvallis. Findings included:
The lambs gained almost the same amount of weight in the two pasture types in both years.
The daily water consumption of the lambs in the two pasture types in spring 2019 were similar during early spring, but lambs in open pastures consumed more water than those grazed under solar panels in the late spring period. There was no difference observed in water intake of the lambs in spring 2020.
Over the two years, solar pastures produced 38% less forage than open pastures.
Overall, the return from grazing was $1,046 per hectare (one hectare equals 2.47 acres) per year in open pastures and $1,029 per hectare per year in pastures with solar panels.
"The overall return is about the same, and that doesn't take into account the energy the solar
Lightning and subvisible discharges produce molecules that clean the atmosphere
IMAGE: NITROGEN, OXYGEN AND WATER VAPOR MOLECULES ARE BROKEN APART BY LIGHTNING AND ASSOCIATED WEAKER ELECTRICAL DISCHARGES, GENERATING THE REACTIVE GASES NO, O3, HO2, AND THE ATMOSPHERE'S CLEANSER, OH. view more
CREDIT: JENA JENKINS, PENN STATE
Lightning bolts break apart nitrogen and oxygen molecules in the atmosphere and create reactive chemicals that affect greenhouse gases. Now, a team of atmospheric chemists and lightning scientists have found that lightning bolts and, surprisingly, subvisible discharges that cannot be seen by cameras or the naked eye produce extreme amounts of the hydroxyl radical -- OH -- and hydroperoxyl radical -- HO2.
The hydroxyl radical is important in the atmosphere because it initiates chemical reactions and breaks down molecules like the greenhouse gas methane. OH is the main driver of many compositional changes in the atmosphere.
"Initially, we looked at these huge OH and HO2 signals found in the clouds and asked, what is wrong with our instrument?" said William H. Brune, distinguished professor of meteorology at Penn State. "We assumed there was noise in the instrument, so we removed the huge signals from the dataset and shelved them for later study."
The data was from an instrument on a plane flown above Colorado and Oklahoma in 2012 looking at the chemical changes that thunderstorms and lightning make to the atmosphere.
But a few years ago, Brune took the data off the shelf, saw that the signals were really hydroxyl and hydroperoxyl, and then worked with a graduate student and research associate to see if these signals could be produced by sparks and subvisible discharges in the laboratory. Then they did a reanalysis of the thunderstrom and lightning dataset.
"With the help of a great undergraduate intern," said Brune, "we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground."
The researchers report their results online today (April 29) in Science First Release and the Journal of Geophysical Research -- Atmospheres.
Brune notes that airplanes avoid flying through the rapidly rising cores of thunderstorms because it is dangerous, but can sample the anvil, the top portion of the cloud that spreads outward in the direction of the wind. Visible lightning happens in the part of the anvil near the thunderstorm core.
"Through history, people were only interested in lightning bolts because of what they could do on the ground," said Brune. "Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts."
Most lightning never strikes the ground, and the lightning that stays in the clouds is particularly important for affecting ozone, and important greenhouse gas, in the upper atmosphere. It was known that lightning can split water to form hydroxyl and hydroperoxyl, but this process had never been observed before in thunderstorms.
What confused Brune's team initially was that their instrument recorded high levels of hydroxyl and hydroperoxyl in areas of the cloud where there was no lightning visible from the aircraft or the ground. Experiments in the lab showed that weak electrical current, much less energetic than that of visible lightning, could produce these same components.
While the researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, they found little evidence of ozone and no evidence of nitric oxide, which requires visible lightning to form. If subvisible lightning occurs routinely, then the hydroxyl and hydroperoxyl these electrical events create need to be included in atmospheric models. Currently, they are not.
According to the researchers, "Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation."
"These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe," said Brune. "We only flew over Colorado and Oklahoma. Most thunderstorms are in the tropics. The whole structure of high plains storms is different than those in the tropics. Clearly we need more aircraft measurements to reduce this uncertainty."
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Other researchers at Penn State include Patrick J. McFarland, undergraduate; David O. Miller, doctoral recipient; and Jena M. Jenkins, doctoral candidate, all in meteorology and atmospheric science.
Also working on the project were Eric Bruning, associate professor of atmospheric science, Texas Tech University; Sean Waugh, research meteorologist, and Donald MacGorman, senior research scientist, both at NOAA National Severe Storm Laboratory; Xinrong Ren, physical scientist, NOAA Air Resources Laboratory; Jingqiu Mao, assistant professor of atmospheric chemistry, Univeristy of Alaska; and Jeff Peischl, senior professional research assistant, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder.
The National Science Foundation, NASA, and the National Oceanic and Atmospheric Administration supported this work.
IMAGE: THE KOREAN ICEBREAKER ARAON, WHICH UNEXPECTEDLY FOUND ITSELF IN AN ARCTIC CYCLONE IN 2016, UNLOCKED THE KEY TO HOW THESE STORMS WREAK HAVOC ON SEA ICE IN THE ARCTIC OCEAN. view more
CREDIT: PHOTO BY JOO-HONG KIM, KOREA POLAR RESEARCH INSTITUTE
In August 2016 a massive storm on par with a Category 2 hurricane churned in the Arctic Ocean. The cyclone led to the third-lowest sea ice extent ever recorded. But what made the Great Arctic Cyclone of 2016 particularly appealing to scientists was the proximity of the Korean icebreaker Araon.
For the and their international colleagues recently published a new study showing that sea ice declined 5.7 times faster than normal during the storm. They werefirst t me ever, scientists were able to see exactly what happens to the ocean and sea ice when a cyclone hits. University of Alaska Fairbanks researchers also ab and their international colleagues recently published a new study showing that sea ice declined 5.7 times faster than normal during the storm. They were e to prove that the rapid decline was driven by cyclone-triggered processes within the ocean.
"Generally, when storms come in, they decrease sea ice, but scientists didn't understand what really caused it," said lead author Xiangdong Zhang from the UAF International Arctic Research Center.
There was general speculation that sea ice declined solely from atmospheric processes melting ice from above. Zhang and his team proved this theory incomplete using "in-situ" observations from directly inside the cyclone. The measurements reflected things like air and ocean temperature, radiation, wind and ocean currents.
It was a stroke of good luck for science, and perhaps a bit nerve-racking for those onboard, that the icebreaker was in position to capture data from the cyclone. Usually ships try to avoid such storms, but Araon had just sailed into the middle of an ice-covered zone and was locked in an ice floe.
Thanks to the ship's position so close to the storm, Xiangdong and his team were able to explain that cyclone-related sea ice loss is primarily due to two physical ocean processes.
First, strong spinning winds force the surface water to move away from the cyclone. This draws deeper warm water to the surface. Despite this warm water upwelling, a small layer of cool water remains directly beneath the sea ice.
That's where a second process comes into play. The strong cyclone winds act like a blender, mixing the surface water.
Together, the warm water upwelling and the surface turbulence warm the entire upper ocean water column and melt the sea ice from below.
Although the August storm raged for only 10 days, there were lasting effects.
"It's not just the storm itself," explained Zhang. "It has lingering effects because of the enhanced ice-albedo feedback."
The enlarged patches of open water from the storm absorb more heat, which melts more sea ice, causing even more open water. From Aug. 13-22, the amount of sea ice in the entire Arctic Ocean declined by 230,000 square miles, an area more than twice the size of the state of Arizona.
Xiangdong is now working with a new computer model for the Department of Energy to evaluate whether climate change will lead to more Arctic cyclones. Previous research shows that over the past half-century, the number and intensity of cyclones in the Arctic have increased. Some of those storms, like the biggest Arctic cyclone on record in 2012, also led to record low sea ice extent.
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Additional co-authors for this paper include two University of Alaska Fairbanks graduate students, Liran Peng and Han Tang, along with Korean researchers Joo-Hong Kim, Kyoung-Ho Cho and Baek-Min Kim, and Zhaomin Wang from China.
Northern forest fires could accelerate climate change
BU researchers used NASA satellite imaging data to analyze 30 years of Earth's northern forests and found that fires are increasingly hampering forests' ability to capture and store atmospheric carbon
IMAGE: THE STUDY FOCUSED ON WOODED PEATLAND AND FORESTS LIKE THE LANDSCAPE PICTURED HERE NEAR THE TOWN OF WRIGLEY IN CANADA'S NORTHWEST TERRITORIES. THIS DRONE IMAGERY WAS TAKEN BY THEN-BU PHD... view more
CREDIT: COURTESY OF JONATHAN WANG
New research indicates that the computer-based models currently used to simulate how Earth's climate will change in the future underestimate the impact that forest fires and drying climate are having on the world's northernmost forests, which make up the largest forest biome on the planet. It's an important understanding because these northern forests absorb a significant amount of Earth's carbon dioxide.
The finding, reached by studying 30 years of the world's forests using NASA satellite imaging data, suggests that forests won't be able to sequester as much carbon as previously expected, making efforts to reduce carbon emissions all the more urgent.
"Fires are intensifying, and when forests burn, carbon is released into the atmosphere," says Boston University environmental earth scientist Mark Friedl, senior author on the study published in Nature Climate Change. "But we're also seeing longer growing seasons, warmer temperatures, which draws carbon out of the atmosphere [and into plants]. More CO2 in the atmosphere acts as a fertilizer, increasing growth of trees and plants—so, scientifically, there's been this big question out there: What is happening on a global scale to Earth's forests? Will they continue to absorb as much carbon as they do now?"
Today's forests capture about 30 percent of all human-related CO2 emissions, which Friedl calls a "huge buffer on anthropogenic climate change." The new study, however, reveals that scientists have so far been underestimating the impact that fires and other disturbances—like timber harvests—are having on Earth's northern forests and, at the same time, have been overestimating the growth-enhancing effect of climate warming and rising atmospheric CO2 levels.
"Current Earth systems models appear to be misrepresenting a big chunk of the global biosphere. These models simulate the atmosphere, oceans, and biosphere, and our results suggest [the model-based simulation of northern forests] has been way off," says Friedl, a BU College of Arts & Sciences professor of earth and environment and interim director of BU's Center for Remote Sensing. He is an expert in utilizing satellite imaging data to monitor Earth's ecosystems on a global scale.
"It is not enough for a forest to absorb and store carbon in its wood and soils. For that to be a real benefit, the forest has to remain intact—an increasing challenge in a warming, more fire-prone climate," says Jonathan Wang, the paper's lead author. "The far north is home to vast, dense stores of carbon that are very sensitive to climate change, and it will take a lot of monitoring and effort to make sure these forests and their carbon stores remain intact."
Working on his PhD in Friedl's lab, Wang researched new ways to leverage the record of data collected from the long-standing Landsat program, a joint NASA/US Geological Survey mission that has been extensively imaging Earth's surface from satellites for decades, to understand how Earth's forests are changing. Wang says new computational and machine learning techniques for combining large remote sensing datasets have become much more advanced, "enabling the monitoring of even the most remote ecosystems with unprecedented detail."
He developed a method to gain richer information from 30 years of Landsat data by comparing it with more recent measurements from NASA's ICESat mission, a satellite carrying laser-based imaging technology, called LiDAR, that can detect the height of vegetation within a forest. Landsat, on the other hand, primarily detects forest cover but not how tall the trees are.
Comparing the newer LiDAR measurements with imaging data gathered from Landsat during the same time period, the team then worked backwards to calculate how tall and dense the vegetation was over the last three decades. They could then determine how the biomass in Earth's northern forests has changed over time—revealing that the forests have been losing more biomass than expected due to increasingly frequent and extensive forest fires.
Specifically, Friedl says, the forests are losing conifers, trees that are emblematic of Earth's northern forests, and for good reason. "Fires come in and burn, and then the most opportunistic types of species grow back first—like hardwoods—which then get replaced by conifers such as black spruce," he says. "But over the last 30 years, which isn't a long time frame in the context of climate change, we see fires taking out more forests, and we see hardwoods sticking around longer rather than being replaced by conifers."
Conifers are better adapted to cold climates than hardwoods, which could potentially be contributing to the dwindling overall biomass of the forests.
"An often-stated argument against climate action is the supposed benefits that far northern ecosystems and communities will enjoy from increased warmth," Wang says. He hopes the study's discovery will help people understand that the global climate crisis has serious issues for the far north, as well. "It may be greening, in some sense," he says, "but in reality the climate-driven increase in wildfires is undoing much of the potential benefits of a warming, greening north."
Wang and Friedl's findings shed light on a question that would have been difficult to answer without the help of NASA's "eyes in the sky."
"Fire regimens are changing because of climate, and many areas of the world's forests are in uninhabited areas where the effects of intense fires may not be easily noticed," Friedl says. "When big chunks of real estate in places like California go up in flames, that gets our attention. But northern forests, which hold some of the largest stocks of carbon in the world, are being impacted by fires more than we realized until now."
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Additional authors on the study include James Randerson, faculty member of UC Irvine Earth System Science; BU alum Mary Farina, now a PhD candidate at Montana State University; and Alessandro Baccini, research professor in BU's Center for Remote Sensing.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news rele
Could the makeup of medical teams help explain why Black patients are more likely than white patients to die after heart surgery in the same hospitals?
IMAGE: COULD THE MAKEUP OF MEDICAL TEAMS HELP EXPLAIN WHY BLACK PATIENTS ARE MORE LIKELY THAN WHITE PATIENTS TO DIE AFTER HEART BYPASS SURGERY IN THE SAME HOSPITALS? view more
CREDIT: JACOB DWYER/ MICHIGAN MEDICINE
A new study finds Black patients are more likely to die after their heart bypass surgery if they're at a hospital where some care teams see mostly white patients and others see mostly Black patients. On the other hand, mortality rates are comparable between Black and white patients after heart bypass surgery when the teams of health care providers at their hospitals all care for patients of all races.
Some level of care team segregation within hospitals was very common, and the findings bring up another angle to better understand racial inequities in surgical outcomes, says co-first author John Hollingsworth, M.D., M.Sc., a professor of urology at Michigan Medicine and of health management and policy at the University of Michigan School of Public Health.
Previous studies have already shown that mortality after heart bypass surgery is higher overall in Black patients than white patients, but known factors such as access to care and use of lower resourced hospitals don't fully explain the disparities.
Hollingsworth and colleagues' new paper reviewed Medicare claims from more than 12,000 heart bypass procedures between 2008 and 2014. The data included claims from 72 hospitals across the country where at least 10 Black patients and at least 10 white patients underwent heart bypass surgery over the study interval.
Researchers used social network analysis to see where provider overlap happened--or didn't happen--between Black and white heart bypass patients and create a provider care team segregation score for each hospital.
"In the Medicare population, there is a lack of overlap in the composition of the provider care teams that treat Black and white patients undergoing heart bypass surgery in the same hospital," Hollingsworth says. "Such provider care team segregation is associated with higher operative mortality for this procedure among Black patients."
Researchers say the reasons for this segregation may include patient preference, in which people prefer to have a care provider who looks like them; admission priority, in which Black patients are more likely to come from the emergency room for their heart bypass than schedule it in advance as an elective surgery; and effects of structural racism on the process of assigning patients to provider care teams, which includes a variety of decisions that don't always get shared or explained.
Co-senior author Brahmajee Nallamothu, M.D., M.P.H., a professor of internal medicine and an interventional cardiologist at the Michigan Medicine Frankel Cardiovascular Center, says the findings point to the need for in-depth study of provider care team segregation as part of the effort to reduce health care inequities.
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Hollingsworth and Nallamothu are both members of U-M's Institute for Healthcare Policy & Innovation.
