Nature

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

Published

1 year ago

August 14, 2023

Daily News Staff

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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The Earth

La Niña Weather Pattern to Disrupt Arizona Winter: What to Expect for 2024-2025

Arizona is expected to have a warmer, drier winter due to a developing La Niña, though uncertainty remains about precipitation levels, highlighting the complexity of weather patterns.

Published

3 weeks ago

November 2, 2024

Rod Washington, Daily News Staff

La Niña

As we prepare for the winter months, the National Oceanic and Atmospheric Administration (NOAA) has released its forecast for the 2024-2025 winter season, and it looks like Arizona might be in for a significant change. According to meteorologists, the state is likely to experience a warmer and drier winter than usual due to the influence of a developing La Niña weather pattern.

@stmblog
Arizona may face a warmer, drier winter due to a developing La Niña, but there’s still a chance for wetter conditions. Stay informed! #LaNiña ♬ original sound – STMDailyNews

Understanding La Niña

La Niña is a climate phenomenon that occurs in the Eastern Pacific Ocean. Typically, trade winds push warm surface waters toward Asia, but when these winds are stronger than normal, they lead to cooler ocean waters in the Eastern Pacific. This shift in ocean temperatures can have widespread effects on weather patterns across the United States.

In Arizona, La Niña usually correlates with above-normal temperatures and below-normal precipitation. This year, however, NOAA indicates that the La Niña phenomenon may be on the weaker side. While moderate to strong La Niña events are more likely to cause significant dry spells, the current weak La Niña means that the impacts may not be as pronounced.

Is Drier Always Drier?

It’s important to note that not every La Niña leads to a dry winter. According to the National Weather Service, there remains a 10% to 30% chance of experiencing wetter than normal conditions this winter. This uncertainty highlights the complexity of weather patterns and the need for ongoing monitoring and analysis.

Factors Influencing the Forecast

The official winter outlook takes into account various factors beyond La Niña, including the latest climate models and the broader context of climate change. These elements play a crucial role in shaping the weather we can expect in the coming months.

As we move closer to winter, it will be essential for residents and visitors in Arizona to stay informed about potential weather changes and be prepared for a season that might not follow the traditional patterns.

Preparing for the Winter

For those living in Arizona, it might be worth considering how a warmer, drier winter could affect your plans, from water conservation efforts to outdoor activities. Staying updated with NOAA and local weather forecasts will be crucial as we approach the winter months.

As winter approaches, it’s clear that La Niña will play a key role in shaping the weather across Arizona. While there is still some uncertainty regarding precipitation levels, one thing is for sure: it’s going to be an interesting season ahead.

Resources

Stay warm and stay informed this winter!

The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/

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Rod: A creative force, blending words, images, and flavors. Blogger, writer, filmmaker, and photographer. Cooking enthusiast with a sci-fi vision. Passionate about his upcoming series and dedicated to TNC Network. Partnered with Rebecca Washington for a shared journey of love and art. View all posts
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Science

Separating out signals recorded at the seafloor

Roger Bryant and David Fike’s research reveals that pyrite sulfur isotopes mainly reflect local conditions, shifting fundamental understanding of oceanic environmental studies.

Published

3 weeks ago

November 1, 2024

Daily News Staff

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.

Signals from the Sea

“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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Nature

Sharks and rays leap out of the water for many reasons, including feeding, courtship and communication

Research by A. Peter Klimley on sharks and rays breaching reveals it functions mainly to remove parasites, attract mates, or hunt prey.

Published

2 months ago

October 4, 2024

The Conversation

A. Peter Klimley, University of California, Davis

Many sharks and rays are known to breach, leaping fully or partly out of the water. In a recent study, colleagues and I reviewed research on breaching and ranked the most commonly hypothesized functions for it.

We found that removal of external parasites was the most frequently proposed explanation, followed by predators chasing their prey; predators concentrating or stunning their prey; males chasing females during courtship; and animals fleeing predators, such as a ray escaping from a hammerhead shark in shallow water.

We found that the highest percentage of breaches, measured by the number of studies that described it, occurred in manta rays and devil rays, followed by basking sharks and then by eagle rays and cownose rays. However, many other species of sharks, as well as sawfishes and stingrays, also perform this behavior. https://www.youtube.com/embed/wXkMqk8mwjs?wmode=transparent&start=0 A breaching white shark surprises researchers off Cape Cod, Massachusetts.

Why it matters

It takes a lot of energy for a shark or ray to leap out of the water – especially a massive creature like a basking shark, which can grow up to 40 feet (12 meters) and weigh up to 5 tons (4.5 tonnes). Since the animal could use that energy for feeding or mating, breaching must serve some useful purpose.

Sharks that have been observed breaching include fast-swimming predatory species such as blacktip sharks and blue sharks. White sharks have been seen breaching while capturing seals in waters off South Africa and around the Farallon Islands off central California.

However, basking sharks – enormous, slow-swimming sharks that feed by filtering tiny plankton from seawater – also breach. So do many ray species, such as manta rays, which also are primarily filter feeders. This suggests that breaching likely serves different functions among different types of sharks and rays.

The most commonly proposed explanation for breaching in planktivores, like basking sharks and most rays, is that it helps dislodge parasites attached to their bodies. Basking sharks are known to host parasites, including common remoras and sea lampreys. The presence of fresh wounds on basking sharks that match the shape and size of a lamprey’s mouth suggests that breaching has torn the lampreys off the sharks’ bodies. https://www.youtube.com/embed/zsC61g36EqM?wmode=transparent&start=0 Basking sharks are filter feeders that live on plankton. They may breach to rid their bodies of parasites.

Other species may breach to communicate. For example, white sharks propelling themselves out of the water near the Farallon Islands may do so to deter other sharks from feeding upon the carcass of a seal.

Researchers have seen large groups of mantas and devil rays jumping together among dense schools of plankton – presumably to concentrate or stun the plankton so the rays can more easily scoop them up. Scientists have also suggested that planktivorous sharks and rays may breach to clear the prey-filtering structures in their gills.

Understanding more clearly when and how different types of sharks and rays breach can provide insights into these animals’ life habits, and into their interactions with their own species and competitors.

How we did our work

I worked with marine scientists Tobey Curtis, Emmett Johnston, Alison Kock and Guy Stevens. Across our various projects, we have seen breaching in bull sharks in Florida, basking sharks in Ireland, white sharks in South Africa and central California, and manta rays in the Maldives. Each of us has proposed different explanations for why the animals did it.

We reviewed scientific studies and video footage to see what species had been observed to breach, under what conditions, and the functions that other researchers had proposed for them doing so. This included information gathered from data logging tags attached to sharks and rays, digital photography, and imagery from underwater and aerial drones.

Our review proposes further studies that could provide more information about breaching in different species. For example, attaching data loggers to individual animals would help scientists measure how quickly a shark or ray accelerates as it propels itself out of the water.

Experiments in aquarium tanks could provide more insight into why the animals breach. For example, scientists could add remoras to a tank containing bull sharks, which can live in an aquarium environment, and observe how the sharks respond when remoras attach themselves to the sharks’ bodies.

In the field, researchers could play audio recordings of splashes from breaches to elicit withdrawal or attraction responses from sharks tagged with ultrasonic transmitters. There remains much to learn about why these animals spend precious energy jumping out of the water.

The Research Brief is a short take on interesting academic work.

A. Peter Klimley, Adjunct Associate Professor of Wildlife, Fish, & Conservation Biology, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.