Monday, August 16, 2021

 

Nearby star-forming region yields clues to the formation of our solar system

The Ophiuchus star-forming complex offers an analog for the formation of the solar system, including the sources of elements found in primitive meteorites

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - SANTA CRUZ

Ophiuchus star-forming region 

IMAGE: MULTI-WAVELENGTH OBSERVATIONS OF THE OPHIUCHUS STAR-FORMING REGION REVEAL INTERACTIONS BETWEEN CLOUDS OF STAR-FORMING GAS AND RADIONUCLIDES PRODUCED IN A NEARBY CLUSTER OF YOUNG STARS. THE TOP IMAGE (A) SHOWS THE DISTRIBUTION OF ALUMINUM-26 IN RED, TRACED BY GAMMA-RAY EMISSIONS. THE CENTRAL BOX REPRESENTS THE AREA COVERED IN THE BOTTOM LEFT IMAGE (B), WHICH SHOWS THE DISTRIBUTION OF PROTOSTARS IN THE OPHIUCHUS CLOUDS AS RED DOTS. THE AREA IN THE BOX IS SHOWN IN THE BOTTOM RIGHT IMAGE (C), A DEEP NEAR-INFRARED COLOR COMPOSITE IMAGE OF THE L1688 CLOUD, CONTAINING MANY WELL KNOWN PRESTELLAR DENSE-GAS CORES WITH DISKS AND PROTOSTARS. view more 

CREDIT: FORBES ET AL., NATURE ASTRONOMY 2021

A region of active star formation in the constellation Ophiuchus is giving astronomers new insights into the conditions in which our own solar system was born. In particular, a new study of the Ophiuchus star-forming complex shows how our solar system may have become enriched with short-lived radioactive elements.

Evidence of this enrichment process has been around since the 1970s, when scientists studying certain mineral inclusions in meteorites concluded that they were pristine remnants of the infant solar system and contained the decay products of short-lived radionuclides. These radioactive elements could have been blown onto the nascent solar system by a nearby exploding star (a supernova) or by the strong stellar winds from a type of massive star known as a Wolf-Rayet star.

The authors of the new study, published August 16 in Nature Astronomy, used multi-wavelength observations of the Ophiuchus star-forming region, including spectacular new infrared data, to reveal interactions between the clouds of star-forming gas and radionuclides produced in a nearby cluster of young stars. Their findings indicate that supernovas in the star cluster are the most likely source of short-lived radionuclides in the star-forming clouds.

“Our solar system was most likely formed in a giant molecular cloud together with a young stellar cluster, and one or more supernova events from some massive stars in this cluster contaminated the gas which turned into the sun and its planetary system,” said coauthor Douglas N. C. Lin, professor emeritus of astronomy and astrophysics at UC Santa Cruz. “Although this scenario has been suggested in the past, the strength of this paper is to use multi-wavelength observations and a sophisticated statistical analysis to deduce a quantitative measurement of the model’s likelihood.”

First author John Forbes at the Flatiron Institute’s Center for Computational Astrophysics said data from space-based gamma-ray telescopes enable the detection of gamma rays emitted by the short-lived radionuclide aluminum-26. “These are challenging observations. We can only convincingly detect it in two star-forming regions, and the best data are from the Ophiuchus complex,” he said.

The Ophiuchus cloud complex contains many dense protostellar cores in various stages of star formation and protoplanetary disk development, representing the earliest stages in the formation of a planetary system. By combining imaging data in wavelengths ranging from millimeters to gamma rays, the researchers were able to visualize a flow of aluminum-26 from the nearby star cluster toward the Ophiuchus star-forming region.

“The enrichment process we’re seeing in Ophiuchus is consistent with what happened during the formation of the solar system 5 billion years ago,” Forbes said. “Once we saw this nice example of how the process might happen, we set about trying to model the nearby star cluster that produced the radionuclides we see today in gamma rays.”

Forbes developed a model that accounts for every massive star that could have existed in this region, including its mass, age, and probability of exploding as a supernova, and incorporates the potential yields of aluminum-26 from stellar winds and supernovas. The model enabled him to determine the probabilities of different scenarios for the production of the aluminum-26 observed today.

“We now have enough information to say that there is a 59 percent chance it is due to supernovas and a 68 percent chance that it’s from multiple sources and not just one supernova,” Forbes said.

This type of statistical analysis assigns probabilities to scenarios that astronomers have been debating for the past 50 years, Lin noted. “This is the new direction for astronomy, to quantify the likelihood,” he said.

The new findings also show that the amount of short-lived radionuclides incorporated into newly forming star systems can vary widely. “Many new star systems will be born with aluminum-26 abundances in line with our solar system, but the variation is huge—several orders of magnitude,” Forbes said. “This matters for the early evolution of planetary systems, since aluminum-26 is the main early heating source. More aluminum-26 probably means drier planets.”

The infrared data, which enabled the team to peer through dusty clouds into the heart of the star-forming complex, was obtained by coauthor João Alves at the University of Vienna as part of the European Southern Observatory’s VISION survey of nearby stellar nurseries using the VISTA telescope in Chile.

“There is nothing special about Ophiuchus as a star formation region,” Alves said. “It is just a typical configuration of gas and young massive stars, so our results should be representative of the enrichment of short-lived radioactive elements in star and planet formation across the Milky Way.”

The team also used data from the European Space Agency’s (ESA) Herschel Space Observatory, the ESA’s Planck satellite, and NASA’s Compton Gamma Ray Observatory.

CAPTION

Deep near-infrared color composite image of the L1688 cloud in the Ophiuchus star-forming complex from the VISIONS European Southern Observatory public survey, where blue, green and red are mapped to the NIR bands J (1.2 μm), H (1.6 μm) and KS (2.2 μm), respectively.

CREDIT

João Alves/ESO VISIONS

Disclaimer: AAAS an

 TECHNOCRACY ENERGY CREDITS

Pandemic and digitalization set stage for revival of a cast-off idea: personal carbon allowances

Peer-Reviewed Publication

KTH, ROYAL INSTITUTE OF TECHNOLOGY

Carbon allowances and sustainable development 

IMAGE: PERSONAL CARBON ALLOWANCES PROVIDE INDIVIDUALS WITH MEANINGFUL CHOICES THAT LINK THEIR ACTIONS WITH GLOBAL CARBON GOALS. view more 

CREDIT: FRANCESCO FUSO NERINI

In a recent study, researchers from Sweden, UK and Israel say the time may be right for many industrialized nations to resurrect an idea once thought to be unfeasible: personal carbon allowances (PCAs). The concept, they report, has stronger possibilities due to a worsening climate crisis, changes in personal behavior due to the COVID-19 crisis and advances in artificial intelligence and ICT.

Led by KTH Royal Institute of Technology in Stockholm, the research team from University of Oxford, Israel’s Interdisciplinary Center (IDC), Herzliya, and University College London (UCL), published design principles to ensure PCAs would benefit all nations in terms of economic growth, job creation, better education and protection of human rights, among other areas, in accordance with the United Nation’s Sustainable Development Goals.

Publishing in Nature Sustainability on the heels of the IPCC’s sobering recent report, the researchers found that changes in behavior due to the COVID-19 crisis, combined with increased digitalization and advancements in ICT and artificial intelligence, offer a perfect storm of opportunity to reconsider an idea that had once been rejected as being “ahead of its time”, as the UK government put it.

Current climate policy mostly address emissions targeting large-scale carbon emitters, such as power plants and industrial activities. But the new research targets the gap between public policy and individual behavior.

“People are watching helplessly while wildfires, floods and the pandemic wreak havoc on society, yet they are not empowered to shift the course of events,” says lead author Francesco Fuso Nerini, Associate Professor at KTH and director of the university’s Climate Action Centre. “Personal climate allowances would apply a market-based approach, providing personal incentives and options that link their actions with global carbon reduction goals.”

Co-author Yael Parag, energy policy professor at the IDC in Israel, says the scientist’ underlying purpose with the paper is to help enable shared responsibility, at all levels of society, since the threat of global warming is universal. “It is not about shifting the mitigation responsibility from governments and big industries to individuals. It is about adding individuals to the effort,” Parag says.

And PCAs provide individuals with clear framework for contributing effectively, says co-author Paul Ekins, resources and environment policy professor at UCL. “People are desperate to do something … but too often they get trivial advice, such as pre-rinsing dishes before putting them in the dishwasher,” Ekins says. “A personal carbon allowance system would tell them what they could do to make a real difference, in a context where they knew other people would also be making their contribution.

“Look no further for a radical, effective suggestion for how individuals can make their lifestyles more climate-friendly.”

Co-author Tina Fawcett, Acting Leader of the Energy Programme, Environmental Change Institute, University of Oxford, says the PCAs embody fairness and transparency, offering people meaningful choices. “It doesn't take away the need for some difficult decisions, but it does ensure these add up to effective society-wide action to reduce our climate risk,” she says.

Once assumed to be too costly and unworkable, PCAs could now be implemented with less difficulty, thanks to advances in ICT and AI. However, the researchers state that PCAs must be designed in a way that will not negatively impact poor and vulnerable populations, and should consider how its components align with the UN Sustainable Development Goals to eliminate poverty and reduce inequality, among others.

Fuso Nerini says that implementing PCAs would require courageous ´first mover´ countries. “There are clear political risks in advocating challenging or radical policies, particularly if they have never been implemented elsewhere and there is no previous policy experience to learn from,” he says.

“At the same time, those ´first movers´ may experience benefits that go well-beyond reducing emissions and achieving net-zero targets.”

Among these benefits could be to help enable a sustainable recovery from the COVID-19 crisis. PCAs would favor the adoption of low-carbon lifestyles, and thus benefit low-carbon infrastructure and innovation.

This direction would open up room for new businesses and technologies to support decreasing personal emissions, Fuso Nerini says. For instance, new tech companies could capitalize on carbon credit trading between individuals, connecting those with more carbon allowances than they need with those in need of allowances.

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Pollinators: First global risk index for species declines and effects on humanity


Peer-Reviewed Publication

UNIVERSITY OF CAMBRIDGE

Disappearing habitats and use of pesticides are driving the loss of pollinator species around the world, posing a threat to “ecosystem services” that provide food and wellbeing to many millions – particularly in the Global South – as well as billions of dollars in crop productivity.

This is according to an international panel of experts, led by the University of Cambridge, who used available evidence to create the first planetary risk index of the causes and effects of dramatic pollinator declines in six global regions.  

The bees, butterflies, wasps, beetles, bats, flies and hummingbirds that distribute pollen, vital for the reproduction of over 75% of food crops and flowering plants – including coffee, rapeseed and most fruits –  are visibly diminishing the world over, yet little is known of the consequences for human populations.

“What happens to pollinators could have huge knock-on effects for humanity,” said Dr Lynn Dicks from Cambridge’s Department of Zoology. “These small creatures play central roles in the world’s ecosystems, including many that humans and other animals rely on for nutrition. If they go, we may be in serious trouble.”

Dicks assembled a 20-strong team of scientists and indigenous representatives to attempt an initial evaluation of the drivers and risks for pollinator declines worldwide. The research is published today in Nature Ecology & Evolution.  

The top three global causes of pollinator loss are habitat destruction, followed by land management – primarily the grazing, fertilizers and crop monoculture of farming – and then widespread pesticide use, according to the study. The effect of climate change comes in at number four, although data are limited.

Perhaps the biggest direct risk to humans across all regions is “crop pollination deficit”: falls in quantity and quality of food and biofuel crops. Experts ranked the risk of crop yield “instability” as serious or high across two-thirds of the planet – from Africa to Latin America – where many rely directly on pollinated crops through small-holder farming.   

“Crops dependent on pollinators fluctuate more in yield than, for example, cereals,” said Dicks. “Increasingly unusual climatic phenomena, such as extreme rainfall and temperature, are already affecting crops. Pollinator loss adds further instability – it’s the last thing people need.”   

A major 2016 report to which Lynn Dicks contributed suggested there has been up to a 300% increase in pollinator-dependent food production over the past half century, with an annual market value that may be as much as US$577 billion.   

Reduced species diversity was seen as a high-ranking global risk to humans, which not only risks food security but a loss of “aesthetic and cultural value”. These species have been emblems of nature for millennia, argue the experts, and too little consideration is given to how their declines affect human wellbeing.

“Pollinators have been sources of inspiration for art, music, literature and technology since the dawn of human history,” said Dicks. “All the major world religions have sacred passages about bees. When tragedy struck Manchester in 2017, people reached for bees as a symbol of community strength.”

“Pollinators are often the most immediate representatives of the natural world in our daily lives. These are the creatures that captivate us early in life. We notice and feel their loss. Where are the clouds of butterflies in the late summer garden, or the myriad moths fluttering in through open windows at night?” 

“We are in the midst of a species extinction crisis, but for many people that is intangible. Perhaps pollinators are the bellwether of mass extinction,” said Dicks.

Loss of access to “managed pollinators” such as industrial beehives was ranked as a high risk to North American society, where they boost crops including apples and almonds, and have suffered serious declines from disease and ‘colony collapse disorder’.

The impact of pollinator decline on wild plants and fruits was viewed a serious risk in Africa, Asia-Pacific and Latin America – regions with many low-income countries where rural populations rely on wild-growing foods.

In fact, Latin America was viewed as the region with most to lose. Insect-pollinated crops such as cashew, soybean, coffee and cocoa are essential to regional food supply and international trade right across the continent. It is also home to large indigenous populations reliant on pollinated plants, with pollinator species such as hummingbirds embedded in oral culture and history.

Asia Pacific was another global region where pollinator decline was perceived to pose serious risks to human well-being. China and India are increasingly reliant on fruit and vegetable crops that need pollinators, some of which now require people to pollinate by hand.

The researchers caution that not enough is known about the state of pollinator populations in the Global South, as evidence of decline is still primarily from wealthy regions such as Europe (where at least 37% of bee and 31% of butterfly species are in decline). Pollination deficits and biodiversity loss were seen as the biggest risks to Europeans, with potential to affect crops ranging from strawberries to oilseed rape.

Dr Tom Breeze, co-author and Ecological Economics Research Fellow at the University of Reading, said: "This study highlights just how much we still don’t know about pollinator decline and the impacts this has on human societies, particularly in parts of the developing world.

“While we have data on how pollinators are doing in regions like Europe, there are significant knowledge gaps in many others. More research is needed on a global level so we can really understand the problems we face, and how we might address them."

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The Arctic Ocean’s deep past provides clues to its imminent future


Nitrogen isotopes reveal that stratification of Arctic waters will prevent surface plankton from receiving enough nutrients to grow abundantly

Peer-Reviewed Publication

PRINCETON UNIVERSITY

Arctic Sea Ice 2020 

IMAGE: GLOBAL CLIMATE CHANGE IS WARMING THE ARCTIC OCEAN AND SHRINKING SEA ICE. HERE, THE BLUE-WHITE ICE CAP SHOWS THE COVERAGE OF SEA ICE AT ITS SMALLEST EXTENT IN SUMMER 2020, AND THE YELLOW LINE SHOWS THE TYPICAL ARCTIC SEA ICE MINIMUM EXTENT BETWEEN 1981 AND 2010. SOME HAVE PROPOSED THAT THE NEWLY EXPOSED SEA SURFACE WILL LEAD TO A PLANKTON POPULATION BOOM AND A BURGEONING ECOSYSTEM IN THE OPEN ARCTIC OCEAN, BUT A TEAM OF PRINCETON AND MAX PLANCK INSTITUTE FOR CHEMISTRY SCIENTISTS SAY THAT’S NOT LIKELY. THEY HAVE EXAMINED THE HISTORY AND SUPPLY RATE OF NITROGEN, A KEY NUTRIENT. THEIR RECENT WORK FINDS THAT STRATIFICATION OF THE OPEN ARCTIC WATERS, ESPECIALLY IN THE AREAS FED BY THE PACIFIC OCEAN VIA THE BERING STRAIT, WILL PREVENT SURFACE PLANKTON FROM RECEIVING ENOUGH NITROGEN TO GROW ABUNDANTLY. view more 

CREDIT: CREATED BY JESSE FARMER, PRINCETON UNIVERSITY; MODIFIED FROM REBECCA LINDSEY AND MICHON SCOTT, “CLIMATE CHANGE: ARCTIC SEA ICE,” NOAA CLIMATE.GOV

As the North Pole, the Arctic Ocean, and the surrounding Arctic land warm rapidly, scientists are racing to understand the warming’s effects on Arctic ecosystems. With shrinking sea ice, more light reaches the surface of the Arctic Ocean. Some have predicted that this will lead to more plankton, which in turn would support fish and other animals.

Not so fast, says a team of scientists led by Princeton University and the Max Planck Institute for Chemistry.

They point to nitrogen, a vital nutrient. The researchers used fossilized plankton to study the history of sources and supply rates of nitrogen to the western and central open Arctic Ocean. Their work, detailed in a paper in the current issue of the journal Nature Geoscience, suggests that under a global warming regime, these open Arctic waters will experience more intense nitrogen limitation, likely preventing a rise in productivity.

“Looking at the Arctic Ocean from space, it’s difficult to see water at all, as much of the Arctic Ocean is covered by a layer of sea ice,” said lead author Jesse Farmer, a postdoctoral research associate in the Department of Geosciences at Princeton University who is also a visiting postdoctoral fellow at the Max Planck Institute for Chemistry in Mainz, Germany. This sea ice naturally expands during winters and contracts during summers. In recent decades, however, global warming has caused a rapid decline in summer sea ice coverage, with summer ice cover now roughly half that of 1979.

As sea ice melts, photosynthesizing plankton that form the base of Arctic food webs should benefit from the greater light availability. “But there’s a catch,” said contributing author Julie Granger, an associate professor of marine sciences at the University of Connecticut. “These plankton also need nutrients to grow, and nutrients are only abundant deeper in the Arctic Ocean, just beyond the reach of the plankton.” Whether plankton can acquire these nutrients depends on how strictly the upper ocean is “stratified,” or separated into layers. The upper 200 meters (660 feet) of the ocean consists of distinct layers of water with different densities, determined by their temperature and saltiness.

“When the upper ocean is strongly stratified, with very light water floating on top of dense deep water, the supply of nutrients to the sunlit surface is slow,” said Farmer.

New research led by scientists from Princeton University shows how the supply of nitrogen to the Arctic has changed since the last ice age, which reveals the history of Arctic Ocean stratification. Using sediment cores from the western and central Arctic Ocean, the researchers measured the isotopic composition of organic nitrogen trapped in the limestone fossils of foraminifera (plankton that grew in surface waters, then died and sank to the sea floor). Their measurements reveal how the proportions of Atlantic- and Pacific-derived nitrogen changed over time, while also tracking changes in the degree of nitrogen limitation of plankton at the surface. Ona Underwood of the Class of 2021 was a key member of the research team, analyzing western Arctic Ocean sediment cores for her junior project.


CAPTION

As the Arctic Ocean warms and sea ice shrinks, will the newly exposed sea surface see a plankton population boom and a burgeoning ecosystem in the open Arctic Ocean? Not likely, say a team of Princeton scientists who have examined the history and supply rate of nitrogen, a key nutrient. Stratification of the open Arctic waters, especially in the areas fed by the Pacific Ocean via the Bering Strait, will prevent surface plankton from receiving enough nitrogen to grow abundantly. Ona Underwood of Princeton University's Class of 2021 was a key member of the research team, analyzing western Arctic Ocean sediment cores for her junior project. Here, she performs nitrogen analyses on Arctic Ocean forams in the Sigman laboratory. She and the other members of the research team measured the nitrogen isotope ratios of the trace organic matter trapped in the walls of these fossils. Their measurements reveal how the proportions of Atlantic- and Pacific-derived nitrogen changed over time, while also tracking changes in the degree of nitrogen limitation of plankton at the surface.

CREDIT

Photo by Jesse Farmer, Princeton University

Where the oceans meet: Pacific waters float above saltier, denser Atlantic waters

The Arctic Ocean is the meeting place of two great oceans: the Pacific and the Atlantic. In the western Arctic, Pacific Ocean waters flow northward across the shallow Bering Strait that separates Alaska from Siberia. Arriving in the Arctic Ocean, the relatively fresh Pacific water flows over saltier water from the Atlantic. As a result, the upper water column of the western Arctic is dominated by Pacific-sourced nitrogen and is strongly stratified.

However, this was not always the case. “During the last ice age, when the growth of ice sheets lowered global sea level, the Bering Strait didn’t exist,” said Daniel Sigman, Princeton’s Dusenbury Professor of Geological and Geophysical Sciences and one of Farmer’s research mentors. At that time, the Bering Strait was replaced by the Bering Land Bridge, a land connection between Asia and North America that allowed for the migration of humans into the Americas. Without the Bering Strait, the Arctic would only have Atlantic water, and the nitrogen data confirm this.

When the ice age ended 11,500 years ago, as ice sheets melted and sea level rose, the data show the sudden appearance of Pacific nitrogen in the open western Arctic basin, dramatic evidence of the opening of the Bering Strait.



Arctic sea ice, as seen from the USCG Healy (IMAGE)

PRINCETON UNIVERSITY

CAPTION

As the Arctic Ocean warms and sea ice shrinks, will the newly exposed sea surface see a plankton population boom and a burgeoning ecosystem in the open Arctic Ocean? Not likely, say a team of Princeton, University of Connecticut, and Max Planck Institute for Chemistry scientists who have examined the history and supply rate of nitrogen, a key nutrient. Stratification of the open Arctic waters, especially in the areas fed by the Pacific Ocean via the Bering Strait, will prevent surface plankton from receiving enough nitrogen to grow abundantly.

CREDIT

Photo by Julie Granger, University of Connecticut

“We had expected to see this signal in the data, but not so clearly!” Sigman said.

This was just the first of the surprises. Analyzing the data, Farmer also realized that, prior to the opening of the Bering Strait, the Arctic had not been strongly stratified as it is today. Only with opening the Bering Strait did the western Arctic become strongly stratified, as reflected by the onset of nitrogen limitation of plankton in the surface waters.

Heading eastward away from the Bering Strait, the Pacific-sourced water is diluted away, so that the modern central and eastern Arctic are dominated by Atlantic water and relatively weak stratification. Here, the researchers found that nitrogen limitation and density stratification varied with climate. As in the western Arctic, stratification was weak during the last ice age, when climate was colder. After the ice age, central Arctic stratification strengthened, reaching a peak between about 10,000 and 6,000 years ago, a period of naturally warmer Arctic summer temperatures called the “Holocene Thermal Maximum.” Since that time, central Arctic stratification has weakened, allowing enough deep nitrogen to reach surface waters to exceed the requirements of plankton.

Global warming is quickly returning the Arctic to the climate of the Holocene Thermal Maximum. As this warming continues, some scientists have predicted that reduced ice cover would enhance the productivity of Arctic plankton by increasing the amount of sunlight reaching the ocean. The new historical information acquired by Farmer and his colleagues suggests that such a change is unlikely for the open basin waters of the western and central Arctic. The western Arctic will remain strongly stratified due to persistent inflow of Pacific water through the Bering Strait, while the warming will strengthen stratification in the central Arctic. In both of these open ocean regions, slow nitrogen supply is likely to limit plankton productivity, the researchers concluded.

“A rise in the productivity of the open Arctic basin would likely have been seen as a benefit, for example, increasing fisheries,” said Farmer. “But given our data, a rise in open Arctic productivity seems unlikely. The best hope for a future rise in Arctic productivity is probably in the Arctic’s coastal waters.”

CAPTION

As the Arctic Ocean warms and sea ice shrinks, will the newly exposed sea surface see a plankton population boom and a burgeoning ecosystem in the open Arctic Ocean? Not likely, say a team of Princeton scientists who have examined the history and supply rate of nitrogen, a key nutrient. Stratification of the open Arctic waters, especially in the areas fed by the Pacific Ocean via the Bering Strait, will prevent surface plankton from receiving enough nitrogen to grow abundantly. These white lumps are fossilized foraminifera from an Arctic Ocean sediment core, magnified 30 times. The researchers used organic material inside these “forams” — plankton that grew in surface waters, then died and sank to the sea floor — to measure the isotopic composition of nitrogen.

CREDIT

Photo by Jesse Farmer, Princeton University

“Arctic Ocean stratification set by sea level and freshwater inputs since the last ice age,” by Jesse R. Farmer, Daniel M. Sigman, Julie Granger, Ona M. Underwood, François Fripiat, Thomas M. Cronin, Alfredo Martínez-García and Gerald H. Haug, appears in the current issue of Nature Geoscience (DOI: 10.1038/s41561-021-00789-y). The research was supported by the Max Planck Society, the Tuttle Fund of the Department of Geosciences of Princeton University, the Grand Challenges Program of the Princeton Environmental Institute, ExxonMobil through the Andlinger Center for Energy and the Environment of Princeton University, the U.S. National Science Foundation (OCE-1535002) and the USGS Land Change Program.

 

Robotic floats provide new look at ocean health and global carbon cycle


Peer-Reviewed Publication

MONTEREY BAY AQUARIUM RESEARCH INSTITUTE

Biogeochemical-Argo float 

IMAGE: MBARI RESEARCHERS DEMONSTRATED THAT A FLEET OF ROBOTIC FLOATS COULD PROVIDE IMPORTANT INSIGHT INTO OCEAN PRIMARY PRODUCTIVITY ON A GLOBAL SCALE. DATA FROM THESE FLOATS CAN BE USED TO IMPROVE COMPUTER MODELING OF EARTH’S CARBON CYCLE, CLIMATE CHANGE PREDICTIONS, AND OCEAN HEALTH. IMAGE: NATALIE FREEMAN © 2019 SOCCOM view more 

CREDIT: NATALIE FREEMAN © 2019 SOCCOM

MOSS LANDING, California—Microscopic marine life plays a fundamental role in the health of the ocean and, ultimately, the planet. Just like plants on land, tiny phytoplankton use photosynthesis to consume carbon dioxide and convert it into organic matter and oxygen. This biological transformation is known as marine primary productivity.

In a new study in Nature Geoscience today, MBARI Senior Scientist Ken Johnson and former MBARI postdoctoral fellow Mariana Bif demonstrated how a fleet of robotic floats could revolutionize our understanding of primary productivity in the ocean on a global scale.

Data collected by these floats will allow scientists to more accurately estimate how carbon flows from the atmosphere to the ocean and shed new light on the global carbon cycle. Changes in phytoplankton productivity can have profound consequences, like affecting the ocean’s ability to store carbon and altering ocean food webs. In the face of a changing climate, understanding the ocean’s role in taking carbon out of the atmosphere and storing it for long periods of time is imperative.

“Based on imperfect computer models, we’ve predicted primary production by marine phytoplankton will decrease in a warmer ocean, but we didn’t have a way to make global-scale measurements to verify models. Now we do,” said MBARI Senior Scientist Ken Johnson.

By converting carbon dioxide into organic matter, phytoplankton not only support oceanic food webs, they are the first step in the ocean’s biological carbon pump.

Phytoplankton consume carbon dioxide from the atmosphere and use it to build their bodies. Marine organisms eat those phytoplankton, die, and then sink to the deep seafloor. This organic carbon is gradually respired by bacteria into carbon dioxide. Since a lot of this happens at great depths, carbon is kept away from the atmosphere for long periods of time. This process sequesters carbon in deep-sea water masses and sediments and is a crucial component in modeling Earth’s climate now and in the future.

Marine primary productivity ebbs and flows in response to changes in our climate system. “We might expect global primary productivity to change with a warming climate,” explained Johnson. “It might go up in some places, down in others, but we don’t have a good grip on how those will balance.” Monitoring primary productivity is crucial to understanding our changing climate, but observing the response on a global scale has been a significant problem. 

Directly measuring productivity in the ocean requires collecting and analyzing samples. Limitations in resources and human effort make direct observations at a global scale with seasonal to annual resolution challenging and cost prohibitive. Instead, remote sensing by satellites or computer-generated circulation models offer the spatial and temporal resolution required. “Satellites can be used to make global maps of primary productivity, but the values are based on models and aren’t direct measurements,” cautioned Johnson.

“Scientists estimate about half of Earth's primary productivity happens in the ocean, but the sparsity of measurements couldn’t give us a reliable global estimate for the ocean yet,” added Mariana Bif, a biogeochemical oceanographer and a former postdoctoral fellow at MBARI. Now, scientists have a new alternative for studying ocean productivity—thousands of autonomous robots drifting throughout the ocean. 

These robots are giving scientists a glimpse at marine primary productivity across area, depth, and time. They are dramatically transforming our ability to estimate how much carbon the global ocean accumulates each year. For example, the Indian Ocean and the middle of the South Pacific Ocean are regions where scientists have very little information about primary productivity. But this changed with the deployment of Biogeochemical-Argo (BGC-Argo) floats across the globe.

“This work represents a significant milestone in ocean data acquisition,” emphasized Bif. “It demonstrates how much data we can collect from the ocean without actually going there.”

The BGC-Argo profiling floats measure temperature, salinity, oxygen, pH, chlorophyll, and nutrients. When scientists first deploy a BGC-Argo float, it sinks to 1,000 meters (3,300 feet) deep and drifts at this depth. Then, its autonomous programming gets to work profiling the water column. The float descends to 2,000 meters (6,600 feet), then ascends to the surface. Once at the surface, the float communicates with a satellite to send its data to scientists on shore. This cycle is then repeated every 10 days.

For the past decade, an increasing fleet of BGC-Argo floats has been taking measurements across the global ocean. The floats capture thousands of profiles every year. This trove of data provided Johnson and Bif with scattered measurements of oxygen over time.

Knowing the pattern of oxygen production allowed Johnson and Bif to compute net primary productivity at the global scale.

During photosynthesis, phytoplankton consume carbon dioxide and release oxygen at a certain ratio. By measuring how much oxygen phytoplankton release over time, researchers can estimate how much carbon phytoplankton produce and how much carbon dioxide they consume. “Oxygen goes up in the day due to photosynthesis, down at night due to respiration—if you can get the daily cycle of oxygen, you have a measurement of primary productivity,” explained Johnson. Although this is a well-known pattern, this work represents the first time that it has been quantitatively measured by instruments at the global scale rather than estimated through modeling and other tools.

But profiling floats only sample once every 10 days, and Johnson and Bif needed multiple measurements in one day to get a daily cycle. A novel approach to analyzing the float data allowed Johnson and Bif to calculate ocean primary productivity. With each profiling float coming up at a different time of day, combining data from 300 floats and samples from various times of day allowed Johnson and Bif to recreate the daily cycle of oxygen going up and down and then calculate primary productivity.

To confirm the accuracy of the primary productivity estimates computed from the BGC-Argo floats, Johnson and Bif compared their float data to ship-based sampling data in two regions—the Hawaii Ocean Time-series (HOT) Station and the Bermuda Atlantic Time-series Station (BATS). The data acquired from the profiling floats near those regions gave similar results as monthly sampling from ships at these two sites over many years.

Johnson and Bif found that phytoplankton produced about 53 petagrams of carbon per year. This measurement was close to the 52 petagrams of carbon per year estimated by the most recent computer models. (One petagram is 1,000,000,000,000 kilograms, or one gigaton, and roughly the equivalent of the weight of 200 million elephants.) This study validated recent biogeochemical models and highlighted how robust these models have become.

High-resolution data from the BGC-Argo floats can help scientists better calibrate computer models to simulate productivity and ensure they represent real-world ocean conditions. These new data will allow scientists to better predict how marine primary productivity will respond to changes in the ocean by simulating different scenarios such as warming temperatures, shifts in phytoplankton growth, ocean acidification, and changes in nutrients. As more floats are deployed, Johnson and Bif expect the results of their study can be updated, decreasing uncertainties.

“We can’t yet say if there is change in ocean primary productivity because our time series is too short,” cautioned Bif. “But it establishes a current baseline from which we might detect future change. We hope that our estimates will be incorporated into models, including those used for satellites, to improve their performance.”

But already, the wealth of data from these floats has proved invaluable in bettering our understanding of marine primary productivity and how Earth’s climate is linked to the ocean.

The BGC-Argo floats have been instrumental to the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM), an NSF-sponsored program focused on unlocking the mysteries of the Southern Ocean and determining its influence on climate. And last year marked the debut of the Global Ocean Biogeochemistry Array (GO-BGC Array) project, which will allow scientists to pursue fundamental questions about ocean ecosystems, observe ecosystem health and productivity, and monitor the elemental cycles of carbon, oxygen, and nitrogen in the ocean through all seasons of the year. 

The information gathered by these collaborative global initiatives provides data essential to improving computer models of ocean fisheries and climate and monitoring and forecasting the effects of ocean warming and ocean acidification on marine life.

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This work was supported by the Global Ocean Biogeochemical Array project (NSF OCE-1946578), the Southern Ocean Carbon and Climate Observations and Modeling project (NSF PLR-1425989 and OPP-1936222), and the David and Lucile Packard Foundation. Profiling floats in the Equatorial Pacific were supported by NOAA under grant NA16OAR4310161 to the University of Washington.

About MBARI
MBARI (Monterey Bay Aquarium Research Institute) is a private non-profit oceanographic research center, founded by David Packard in 1987 focused on developing innovative technologies for exploring and understanding the ocean. The mission of MBARI is to advance marine science and technology to understand a changing ocean.

For additional information or images relating to this release, please email pressroom@mbari.org.

 

Inflatable robotic hand gives amputees real-time tactile control

Prosthetic enables a wide range of daily activities, such as zipping a suitcase, shaking hands, and petting a cat.

Peer-Reviewed Publication

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

Neuroprosthetic hand 

IMAGE: AN MIT-DEVELOPED INFLATABLE ROBOTIC HAND GIVES AMPUTEES REAL-TIME TACTILE CONTROL. THE SMART HAND IS SOFT AND ELASTIC, WEIGHS ABOUT HALF A POUND, AND COSTS A FRACTION OF COMPARABLE PROSTHETICS. view more 

CREDIT: COURTESY OF XUANHE ZHAO, SHAOTING LIN, ET AL

For the more than 5 million people in the world who have undergone an upper-limb amputation, prosthetics have come a long way. Beyond traditional mannequin-like appendages, there is a growing number of commercial neuroprosthetics — highly articulated bionic limbs, engineered to sense a user’s residual muscle signals and robotically mimic their intended motions.

But this high-tech dexterity comes at a price. Neuroprosthetics can cost tens of thousands of dollars and are built around metal skeletons, with electrical motors that can be heavy and rigid.

Now engineers at MIT and Shanghai Jiao Tong University have designed a soft, lightweight, and potentially low-cost neuroprosthetic hand. Amputees who tested the artificial limb performed daily activities, such as zipping a suitcase, pouring a carton of juice, and petting a cat, just as well as — and in some cases better than —those with more rigid neuroprosthetics.

The researchers found the prosthetic, designed with a system for tactile feedback, restored some primitive sensation in a volunteer’s residual limb. The new design is also surprisingly durable, quickly recovering after being struck with a hammer or run over with a car.

The smart hand is soft and elastic, and weighs about half a pound. Its components total around $500 — a fraction of the weight and material cost associated with more rigid smart limbs.

“This is not a product yet, but the performance is already similar or superior to existing neuroprosthetics, which we’re excited about,” says Xuanhe Zhao, professor of mechanical engineering and of civil and environmental engineering at MIT. “There’s huge potential to make this soft prosthetic very low cost, for low-income families who have suffered from amputation.”

Zhao and his colleagues have published their work today in Nature Biomedical Engineering. Co-authors include MIT postdoc Shaoting Lin, along with Guoying Gu, Xiangyang Zhu, and collaborators at Shanghai Jiao Tong University in China.

Big Hero hand

The team’s pliable new design bears an uncanny resemblance to a certain inflatable robot in the animated film “Big Hero 6.” Like the squishy android, the team’s artificial hand is made from soft, stretchy material — in this case, the commercial elastomer EcoFlex. The prosthetic comprises five balloon-like fingers, each embedded with segments of fiber, similar to articulated bones in actual fingers. The bendy digits are connected to a 3-D-printed “palm,” shaped like a human hand.

Rather than controlling each finger using mounted electrical motors, as most neuroprosthetics do, the researchers used a simple pneumatic system to precisely inflate fingers and bend them in specific positions. This system, including a small pump and valves, can be worn at the waist, significantly reducing the prosthetic’s weight.

Lin developed a computer model to relate a finger’s desired position to the corresponding pressure a pump would have to apply to achieve that position. Using this model, the team developed a controller that directs the pneumatic system to inflate the fingers, in positions that mimic five common grasps, including pinching two and three fingers together, making a balled-up fist, and cupping the palm.

The pneumatic system receives signals from EMG sensors — electromyography sensors that measure electrical signals generated by motor neurons to control muscles. The sensors are fitted at the prosthetic’s opening, where it attaches to a user’s limb. In this arrangement, the sensors can pick up signals from a residual limb, such as when an amputee imagines making a fist.

The team then used an existing algorithm that “decodes” muscle signals and relates them to common grasp types. They used this algorithm to program the controller for their pneumatic system. When an amputee imagines, for instance, holding a wine glass, the sensors pick up the residual muscle signals, which the controller then translates into corresponding pressures. The pump then applies those pressures to inflate each finger and produce the amputee’s intended grasp.

Going a step further in their design, the researchers looked to enable tactile feedback — a feature that is not incorporated in most commercial neuroprosthetics. To do this, they stitched to each fingertip a pressure sensor, which when touched or squeezed produces an electrical signal proportional to the sensed pressure. Each sensor is wired to a specific location on an amputee’s residual limb, so the user can “feel” when the prosthetic’s thumb is pressed, for example, versus the forefinger.

Good grip

To test the inflatable hand, the researchers enlisted two volunteers, each with upper-limb amputations. Once outfitted with the neuroprosthetic, the volunteers learned to use it by repeatedly contracting the muscles in their arm while imagining making five common grasps.

After completing this 15-minute training, the volunteers were asked to perform a number of standardized tests to demonstrate manual strength and dexterity. These tasks included stacking checkers, turning pages, writing with a pen, lifting heavy balls, and picking up fragile objects like strawberries and bread. They repeated the same tests using a more rigid, commercially available bionic hand and found that the inflatable prosthetic was as good, or even better, at most tasks, compared to its rigid counterpart.

One volunteer was also able to intuitively use the soft prosthetic in daily activities, for instance to eat food like crackers, cake, and apples, and to handle objects and tools, such as laptops, bottles, hammers, and pliers. This volunteer could also safely manipulate the squishy prosthetic, for instance to shake someone’s hand, touch a flower, and pet a cat.

In a particularly exciting exercise, the researchers blindfolded the volunteer and found he could discern which prosthetic finger they poked and brushed. He was also able to “feel” bottles of different sizes that were placed in the prosthetic hand, and lifted them in response. The team sees these experiments as a promising sign that amputees can regain a form of sensation and real-time control with the inflatable hand.

The team has filed a patent on the design, through MIT, and is working to improve its sensing and range of motion.

“We now have four grasp types. There can be more,” Zhao says. “This design can be improved, with better decoding technology, higher-density myoelectric arrays, and a more compact pump that could be worn on the wrist. We also want to customize the design for mass production, so we can translate soft robotic technology to benefit society.”

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Written by Jennifer Chu, MIT News Office