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Century-old coral reveals Pacific western boundary current strengthened as climate warmed, impacting El Niño

Like rings in a tree, isotopic signatures in coral reveal historical changes in ocean currents



Credit: Xingchen (Tony) Wang
A diver collects a coral sample, illustrative of the process used by researchers in climate studies. One such sample was analyzed to reveal that during the past century, the western boundary current in the southern Pacific Ocean has intensified with global warming, a team of researchers reported recently in Nature Geoscience. The current plays a pivotal role in influencing weather patterns, including phenomena such as El Nino, which, having officially arrived in June 2023, may potentially set a new record for global average temperature.

Newswise — Chestnut Hill, Mass. – The Pacific Ocean’s western boundary current, which forms a critical regulator of sea surface temperature and weather patterns, has significantly strengthened as the planet warms, according to a new study published in the journal Nature Geoscience.

The study provides the first evidence that the western boundary current in the South Pacific has significantly strengthened during the 20th century in response to global warming, contributing to an intensified equatorial undercurrent, according to Boston College Assistant Professor of Earth and Environmental Sciences Xingchen (Tony) Wang, a co-author of the report.

Records drawn from coral samples also showed a pronounced recurring pattern of variable ocean-atmosphere climatic conditions – known as decadal oscillation – indicating that periods of enhanced western boundary current correspond to periods of increased sea surface temperatures in the eastern equatorial Pacific, according to report, prepared by Wang, National Taiwan University’s Haojia Ren and her team, and collaborators from Taiwan’s Academia Sinica, University of California, Berkeley, University of Texas at Austin, and Hawai’i Pacific University.

“This result confirms the significant role of the western boundary current in controlling the heat balance of the equatorial ocean, as predicted by climate models,” Wang said.

The team examined the historical clues embedded in century-old coral, probing the chemical components of tropical coral’s skeleton for data on environmental and climatological conditions in the past, much like examining the rings that mark the year-by-year development of trees. The study, titled “Increased tropical South Pacific western boundary current transport over the past century,” explored how global warming has led to the strengthening of the western boundary current in the South Pacific, which has had a significant effect on the broader global climate.

Wang said that the team set out to better understand how the western boundary current has changed as the climate has warmed. The ocean acts as the largest heat reservoir in the Earth’s climate system, Wang said.

“More than 90 percent of the global warming heat has been absorbed by the ocean,” Wang said. “The circulation of the ocean plays a key role in redistributing the ocean’s energy and in doing so, regulates global and regional climate. This means that the strengthening of the western boundary current has an effect on weather events that take place hundreds if not thousands of miles away.”

He added, “The tropical Western Pacific Ocean is the largest warm pool in the world. It is particularly important for a climate phenomena known as El Niño.”

The El Niño, as NOAA has officially declared its arrival in June, has been closely associated with increased flooding and rain across the Americas and the Pacific.

The western boundary current system in the tropical Pacific Ocean transports water into the equatorial region and regulates its sea surface temperature, influencing El Niño and La Niña activities. However, due to the limited availability of long-term observational data from satellites and instruments, it has been unclear whether the western boundary current is strengthening or weakening in the context of global warming, Wang said.

The researchers collected a century-long coral sample from the Solomon Sea and used a mass spectrometer to analyze the isotopic composition of nitrogen – namely the ratio of nitrogen-15 and nitrogen-14 – preserved in the coral sample, which served as a proxy for western boundary current changes, according to the report.

The coral records also showed a pronounced decadal oscillation, indicating that periods of enhanced western boundary current correspond to periods of increased sea surface temperatures in the eastern equatorial Pacific. 

Wang said the findings indicate that the continued strengthening of the western boundary current will keep playing a significant role in the global climate and the extreme weather events that have become increasingly common in the 21st century.

“We were a bit surprised that the western boundary current has indeed strengthened under global warming,” said Wang. “It implies that the western boundary current will continue to play an important role in regulating tropical and global climate in the future. For example, enhanced western boundary current might make it easier to develop strong El Niño events, such as the one we are currently experiencing.”

Wang said the next steps in this research will continue to use coral samples to study ocean circulation changes and how those changes interact with the climate system, both today and in the past.

Journal Link: Nature Geoscience

Source: Boston College

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Separating out signals recorded at the seafloor



Credit: Clive Jones, Washington University in St. Louis
Roger Bryant studied ocean floor core samples at the Secondary Ion Mass Spectrometry (SIMS) facility at Washington University in St. Louis during his PhD studies. Bryant and David Fike have used this data to prove a discovery that will fundamentally change how scientists use pyrite sulfur isotopes to study oceanic conditions.
« Separating out signals recorded at the seafloor

Newswise — Blame it on plate tectonics. The deep ocean is never preserved, but instead is lost to time as the seafloor is subducted. Geologists are mostly left with shallower rocks from closer to the shoreline to inform their studies of Earth history.

“We have only a good record of the deep ocean for the last ~180 million years,” said David Fike, the Glassberg/Greensfelder Distinguished University Professor of Earth, Environmental, and Planetary Sciences in Arts & Sciences at Washington University in St. Louis. “Everything else is just shallow-water deposits. So it’s really important to understand the bias that might be present when we look at shallow-water deposits.”

One of the ways that scientists like Fike use deposits from the seafloor is to reconstruct timelines of past ecological and environmental change. Researchers are keenly interested in how and when oxygen began to build up in the oceans and atmosphere, making Earth more hospitable to life as we know it.

For decades they have relied on pyrite, the iron-sulfide mineral known as “fool’s gold,” as a sensitive recorder of conditions in the marine environment where it is formed. By measuring the bulk isotopic composition of sulfur in pyrite samples — the relative abundance of sulfur atoms with slightly different mass — scientists have tried to better understand ancient microbial activity and interpret global chemical cycles.

But the outlook for pyrite is not so shiny anymore. In a pair of companion papers published Nov. 24 in the journal Science, Fike and his collaborators show that variations in pyrite sulfur isotopes may not represent the global processes that have made them such popular targets of analysis.

Instead, Fike’s research demonstrates that pyritte responds predominantly to local processes that should not be taken as representative of the whole ocean. A new microanalysis approach developed at Washington University helped the researchers to separate out signals in pyrite that reveal the relative influence of microbes and that of local climate.

For the first study, Fike worked with Roger Bryant, who completed his graduate studies at Washington University, to examine the grain-level distribution of pyrite sulfur isotope compositions in a sample of recent glacial-interglacial sediments. They developed and used a cutting-edge analytical technique with the secondary-ion mass spectrometer (SIMS) in Fike’s laboratory.

“We analyzed every individual pyrite crystal that we could find and got isotopic values for each one,” Fike said. By considering the distribution of results from individual grains, rather than the average (or bulk) results, the scientists showed that it is possible to tease apart the role of the physical properties of the depositional environment, like the sedimentation rate and the porosity of the sediments, from the microbial activity in the seabed.

“We found that even when bulk pyrite sulfur isotopes changed a lot between glacials and interglacials, the minima of our single grain pyrite distributions remained broadly constant,” Bryant said. “This told us that microbial activity did not drive the changes in bulk pyrite sulfur isotopes and refuted one of our major hypotheses.”

“Using this framework, we’re able to go in and look at the separate roles of microbes and sediments in driving the signals,” Fike said. “That to me represents a huge step forward in being able to interpret what is recorded in these signals.”

In the second paper, led by Itay Halevy of the Weizmann Institute of Science and co-authored by Fike and Bryant, the scientists developed and explored a computer model of marine sediments, complete with mathematical representations of the microorganisms that degrade organic matter and turn sulfate into sulfide and the processes that trap that sulfide in pyrite.

“We found that variations in the isotopic composition of pyrite are mostly a function of the depositional environment in which the pyrite formed,” Halevy said. The new model shows that a range of parameters of the sedimentary environment affect the balance between sulfate and sulfide consumption and resupply, and that this balance is the major determinant of the sulfur isotope composition of pyrite.

“The rate of sediment deposition on the seafloor, the proportion of organic matter in that sediment, the proportion of reactive iron particles, the density of packing of the sediment as it settles to the seafloor — all of these properties affect the isotopic composition of pyrite in ways that we can now understand,” he said.

Importantly, none of these properties of the sedimentary environment are strongly linked to the global sulfur cycle, to the oxidation state of the global ocean, or essentially any other property that researchers have traditionally used pyrite sulfur isotopes to reconstruct, the scientists said.

“The really exciting aspect of this new work is that it gives us a predictive model for how we think other pyrite records should behave,” Fike said. “For example, if we can interpret other records — and better understand that they are driven by things like local changes in sedimentation, rather than global parameters about ocean oxygen state or microbial activity — then we can try to use this data to refine our understanding of sea level change in the past.”

Source: Washington University in St. Louis

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Plastic-eating bacteria turn waste into useful starting materials for other products



Newswise — Mountains of used plastic bottles get thrown away every day, but microbes could potentially tackle this problem. Now, researchers in ACS Central Science report that they’ve developed a plastic-eating E. coli that can efficiently turn polyethylene terephthalate (PET) waste into adipic acid, which is used to make nylon materials, drugs and fragrances.

Credit: Adapted from ACS Central Science 2023, DOI: 10.1021/acscentsci.3c00414
These beads contain engineered E. coli that efficiently transform PET waste into a high-value compound.
« Plastic-eating bacteria turn waste into useful starting materials for other products

Previously, a team of researchers including Stephen Wallace engineered a strain of E. coli to transform the main component in old PET bottles, terephthalic acid, into something tastier and more valuable: the vanilla flavor compound vanillin. At the same time, other researchers engineered microbes to metabolize terephthalic acid into a variety of small molecules, including short acids. So, Wallace and a new team from the University of Edinburgh wanted to expand E. coli’s biosynthetic pathways to include the metabolism of terephthalic acid into adipic acid, a feedstock for many everyday products that’s typically generated from fossil fuels using energy-intensive processes.

The team developed a new E. coli strain that produced enzymes that could transform terephthalic acid into compounds such as muconic acid and adipic acid. Then, to transform the muconic acid into adipic acid, they used a second type of E. coli, which produced hydrogen gas, and a palladium catalyst. In experiments, the team found that attaching the engineered microbial cells to alginate hydrogel beads improved their efficiency, and up to 79% of the terephthalic acid was converted into adipic acid. Using real-world samples of terephthalic acid from a discarded bottle and a coating taken from waste packaging labels, the engineered E. coli system efficiently produced adipic acid. In the future, the researchers say they will look for pathways to biosynthesize additional higher-value products.

The authors acknowledge funding from the Carnegie Trust for the Universities of Scotland; the Industrial Biotechnology Innovation Centre; a Future Leaders Fellowship from UK Research and Innovation; and an Engineering and Physical Sciences Research Council Sustainable Manufacturing grant.

The paper’s abstract will be available on Nov. 1 at 8 a.m. Eastern time here: http://pubs.acs.org/doi/abs/10.1021/acscentsci.3c00414  

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

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Source: American Chemical Society (ACS)

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State of Emergency in Iceland: Impending Volcanic Eruption Triggers Evacuation

Iceland declares state of emergency as volcanic eruption looms, thousands ordered to evacuate Grindavík. Tremors raise concerns at Fagradalsfjall volcano.



Fagradalsfjall. (2023, November 11). In Wikipedia. https://en.wikipedia.org/wiki/Fagradalsfjall

Iceland, known for its extraordinary landscapes and natural wonders, is currently facing a state of emergency as the Department of Civil Protection has ordered the mandatory evacuation of the city of Grindavík and the Svartsengi Power Station. The imminent threat of a volcanic eruption at Fagradalsfjall volcano has prompted this decisive action. With over 1,000 earthquakes reported in the past 24 hours and concerns about the underground movement of magma, authorities are taking swift measures to ensure the safety of the affected population.

A Troubled Region:
The recent surge in seismic activity has been primarily concentrated in Iceland’s Reykjanes Peninsula, an area that had remained dormant for 800 years until the eruption of Fagradalsfjall in 2021. The recurrence of tremors in this region has raised significant concerns among experts and prompted close monitoring by the Icelandic Met Office. The situation is further compounded by the possibility of substantial amounts of magma rising to the surface, intensifying the need for precautionary measures.

Fagradalsfjall volcano in Iceland. Image via Wikipedia.

Evacuation Orders:
In response to the escalating threat, authorities have issued mandatory evacuation orders for the southwestern town of Grindavík, situated in proximity to the potential eruption site. The evacuation aims to relocate thousands of residents to safer areas, away from the imminent danger. Such measures are crucial to safeguard lives and minimize the potential impact of the volcanic activity on human settlements.

The Role of the Icelandic Met Office:
The Icelandic Met Office, responsible for monitoring natural phenomena in the region, plays a vital role in providing up-to-date information about seismic events, volcanic activity, and potential hazards. They have been closely observing the seismic patterns and underground movements to assess the likelihood and scale of an eruption. By issuing timely warnings and recommendations, they contribute to the coordinated response efforts of the authorities and assist in mitigating the risks associated with volcanic activity.

The Impact on Svartsengi Power Station:
The evacuation order also extends to the Svartsengi Power Station, a significant geothermal power plant located near Grindavík. This power station harnesses the volcanic energy of the area to generate electricity and provide district heating. However, the proximity to the potential eruption site poses an immediate risk to the facility and its personnel. The evacuation ensures the safety of the power station’s staff and prevents potential damage that could disrupt the region’s power supply.

Iceland’s declaration of a state of emergency and the subsequent evacuation orders in Grindavík and the Svartsengi Power Station reflect the country’s proactive approach to protecting its citizens in the face of natural disasters. The persistent seismic activity and the possibility of a volcanic eruption at Fagradalsfjall volcano have compelled authorities to take swift action. While the situation remains uncertain, the coordination between the Department of Civil Protection and the Icelandic Met Office provides hope in effectively managing the potential risks. As the affected residents seek shelter and support, the resilience and unity of the Icelandic community will undoubtedly play a crucial role in navigating this challenging period and recovering from its aftermath.

For more information, please refer to the story on EarthSky. https://earthsky.org/earth/iceland-braces-for-volcanic-eruption/


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