Hummingbirds may struggle to go any further uphill

Peer-Reviewed Publication

THE COMPANY OF BIOLOGISTS

Any animal ascending a mountain experiences a double whammy of impediments: the air gets thinner as it also becomes colder, which is particularly problematic for creatures struggling to keep warm when less oxygen is available. For tiny animals with the highest-octane lifestyles, such as hovering hummingbirds, the challenges of relocating to higher levels to evade climate change may be too much, but no one knew whether these extraordinary aviators may have more gas in the tank to keep them aloft at higher altitudes.

As Anna’s hummingbirds (Calypte anna) are comfortable up to elevations of ~2800 m, Austin Spence from the University of Connecticut, USA, and Morgan Tingley from the University of California, Los Angeles, USA, were curious to find out how hummingbirds that originated from close to sea level and those that live at the loftier end of the range would cope when transported well above their natural habitat to an altitude of 3800m. They publish their discovery in Journal of Experimental Biology (https://journals.biologists.com/jeb) that the birds struggle to hover and suffer a 37% drop in their metabolic rate at that height – in addition to becoming torpid for most of the night to conserve energy – making it unlikely that they can relocate to higher altitudes.

To find out how the agile aeronauts fared at high altitude, Spence lured the animals into net traps, from sites 10m above sea level (Sacramento, CA) up to 2400m (Mammoth Lakes, CA), then he and Hannah LeWinter (Humboldt State University, USA) transported them to an aviary in western California at 1215m. Once the birds had spent a few days in their new home, the scientists set up a tiny funnel into which the birds could insert their heads as they hovered while sipping tasty syrup, and measured the birds’ O2 consumption (metabolic rate). Spence and LeWinter also measured the hummingbird’s CO2 production (another measure of metabolic rate) overnight, as the tiny creatures allowed their metabolism to tumble when they became torpid – a form of mini hibernation – to conserve energy while they slept. Then, the duo relocated the birds to a nearby research station near the peak of Mount Barcroft , CA (3800m) where the air is thinner (~39% less oxygen) and colder (~5°C), and after ~4days at the new altitude, Spence and LeWinter remeasured the birds’ metabolic rates as they hovered and how often and deeply the birds went into torpor as they slumbered.

Even though the hovering hummingbirds should have been working harder to remain aloft in the thin air 1000m above their natural range, the birds actually experienced a 37% drop in their metabolic rate. And when the team compared the energy used by birds that originated close to sea level and from the higher end of their range, they all struggled equally on the mountain top. ‘Overall, these results suggest low air pressure and oxygen availability may reduce hovering performance in hummingbirds when exposed to the acute challenge of high-elevation conditions’, says Spence.

In addition to struggling to hover, the birds resorted to dropping their metabolic rate and became torpid for lengthier periods at night, spending more than 87.5% of the chilly high-altitude night in torpor. ‘It means that even if they’re from a warm or cool spot, they use torpor when its super-cold, which is cool’, says Spence. And when the team checked the size of the animals’ lungs, to find out whether the birds that originated from higher altitudes had larger lungs to compensate for their meagre oxygen supply, they did not. But the birds did have larger hearts to circulate oxygen around the body.

What does this mean for the hummingbird’s future as climate change forces them to find more comfortable conditions? ‘Our results suggest lower oxygen availability and low air pressure may be difficult challenges to overcome for hummingbirds’, says Spence, meaning that the birds will likely have to shift north in search of cooler climes.

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IF REPORTING THIS STORY, PLEASE MENTION JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: https://journals.biologists.com/jeb/article-lookup/doi/10.1242/jeb.243294

REFERENCE: Spence, A. R., LeWinter, H. and Tingley, M. W. (2022). Anna’s hummingbird (Calypte anna) physiological response to novel thermal and hypoxic conditions at high elevations. J. Exp. Biol. 225, jeb243294. doi:10.1242/jeb.243294.

DOI:10.1242/jeb.244313

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. The story posted here is COPYRIGHTED. Advance permission is required before any and every reproduction of this article in full from permissions@biologists.com.

THIS ARTICLE IS EMBARGOED UNTIL THURSDAY, 26 MAY 2022, 18:00 HRS EDT (23:00 HRS BST)

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JOURNAL

Journal of Experimental Biology

DOI

10.1242/jeb.244313 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Anna’s hummingbird (Calypte anna) physiological response to novel thermal and hypoxic conditions at high elevations.

ARTICLE PUBLICATION DATE

26-May-2022

FIRST BATS & BIRDS NOW THIS

Offshore wind farms could disturb marine mammal behavior #ASA182

As the number and size of offshore turbines increase, so does the possible disruption to aquatic life.

Reports and Proceedings

ACOUSTICAL SOCIETY OF AMERICA

DENVER, May 26, 2022 – When an offshore wind farm pops up, there is a period of noisy but well-studied and in most cases regulated construction. Once the turbines are operational, they provide a valuable source of renewable energy while emitting a constant lower level of sound.

Frank Thomsen, of DHI, will discuss how this constant noise may impact wildlife in his presentation, "Operational underwater sound from future offshore wind turbines can affect the behavior of marine mammals." The session will take place May 26 at 4:25 p.m. Eastern U.S. as part of the 182nd Meeting of the Acoustical Society of America at the Sheraton Denver Downtown Hotel.

Thomsen and colleagues reviewed published sound levels from operational wind farms to identify trends with turbine size. In general, the larger the turbine, the higher the noise emissions.

However, newer wind farms using quieter driving technology can to a certain extent cancel out the impact of larger turbines. Older gear box technology reaches disruptive levels for marine mammals up to 6.3 kilometers away. In contrast, newer direct drive turbines are expected to only impact animal behavior within a 1.4-kilometer radius.

"It is very unlikely that operational noise will lead to any injury or even hearing impairment, but behavioral changes could be a concern, as our study shows," Thomsen said. "It's possible that impact zones of individual turbines overlap, but that still does not mean that the wind farm is a no-go area for marine life. We see harbor porpoises frequently swimming in the vicinity of turbines."

The long-term consequences of this noise on wildlife are still largely unknown. The impact could depend on the number of turbines and their overlapping affected areas.

In theory, the sound can lead to behavior changes in marine mammals and mask calls from whales, but harbor porpoises are frequently seen swimming in the vicinity of wind farms in Europe, so it may not be as simple as it seems.

"Since offshore wind farms have a relatively long lifespan, and there will be many of them, the potential impacts should not be overlooked," said Thomsen. "The point of our work is to raise awareness."

----------------------- MORE MEETING INFORMATION -----------------------

USEFUL LINKS

Main meeting website: https://acousticalsociety.org/asa-meetings/

Technical program: https://eventpilotadmin.com/web/planner.php?id=ASASPRING22

Press Room: https://acoustics.org/world-wide-press-room/

 

WORLDWIDE PRESS ROOM

In the coming weeks, ASA's Worldwide Press Room will be updated with additional tips on dozens of newsworthy stories and with lay language papers, which are 300 to 500 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio and video. You can visit the site during the meeting at http://acoustics.org/world-wide-press-room/.

 

PRESS REGISTRATION

We will grant free registration to credentialed journalists and professional freelance journalists. If you are a reporter and would like to attend, contact AIP Media Services at media@aip.org.  For urgent requests, staff at media@aip.org can also help with setting up interviews and obtaining images, sound clips, or background information.

 

ABOUT THE ACOUSTICAL SOCIETY OF AMERICA

The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards.

Race, ethnicity, and poverty linked to worse outcomes in children treated for high-risk neuroblastoma

Cancer of immature nerve cells arising from the adrenal gland, nerve ganglia or the neck. This causes abdominal pain, diarrhea or constipation, lumps of tissue under the skin, wheezing and weight loss.

Urgent medical attention is usually recommended by healthcare providers

Can be dangerous or life threatening if untreated

Very rare (Fewer than 1,000 cases per year in Canada)

Treatable by a medical professional

Requires lab test or imaging

Can last several years or be lifelong

Reports and Proceedings

DANA-FARBER CANCER INSTITUTE

BOSTON - Children with high-risk neuroblastoma had worse outcomes if they were from certain racial/ethnic groups or were on public rather than private insurance, despite being treated in clinical trials with standardized protocols, according to a study led by investigators from Dana-Farber/Boston Children’s Cancer and Blood Disorders Center.

The study shows that young patients from historically marginalized populations or from lower-income backgrounds had poorer five-year survival rates even when they were assigned to receive uniform initial treatment after diagnosis with high-risk neuroblastoma.

“These findings recapitulate what we have known for decades at the population level—children from historically marginalized groups are less likely to survive their cancer,” said Puja J. Umaretiya, MD, a clinical fellow in pediatric hematology/oncology at Dana-Farber/Boston Children’s. “They add an essential next layer to our understanding of racial and ethnic disparities in childhood cancer, and that is that enrollment on clinical trials is not enough to achieve racial and ethnic equity in survival.” Umaretiya is presenting the study results at the American Society of Clinical Oncology (ASCO) Annual meeting, being held June 3-7, 2022, and the study is included in the ASCO press program.

“Clinical trials represent highly standardized care – yet even when receiving care on clinical trials, children with high-risk neuroblastoma do not experience the same outcomes based on their race, ethnicity, and whether they live in poverty,” said Umaretiya, lead author of the study. “This is key, because thus far attention has been paid to getting historically marginalized groups to trials with the assumption that this will reduce survival disparities, but our data suggest that in pediatrics, trial-enrollment is a first step, but clearly not a sufficient one.”

Senior author is Kira Bona, MD, MPH, a pediatric oncologist at Dana-Farber/Boston Children’s with research focused on identifying poverty-associated outcome disparities in childhood cancer and developing interventions to mitigate those disparities.

Bona notes, “That stark racial/ethnic disparities in survival persist despite clinical trial participation makes it crystal clear that pediatric oncology trials must incorporate health equity interventions. If a new gene mutation were found to increase risk for trial-enrolled patients, pediatric oncology would not hesitate to begin intervening. That same urgency must apply to these data. It is imperative that pediatric oncologists begin to test healthcare delivery and supportive care interventions in our trials just like we do new drugs.”

The study looked at outcomes in 696 children enrolled in three Children’s Oncology Group (COG) clinical trials of treatment for high-risk neuroblastoma. Neuroblastoma is a type of cancer that forms in nerve tissue. It frequently begins in one of the adrenal glands but can also originate in the neck, chest, abdomen, or spine. High-risk disease is defined by age, how widely the disease has spread, and biologic characteristics of the cancer cells. The prognosis for long-term survival remains challenging. Treatment is usually an intensive combination of chemotherapy, surgery, stem cell transplantation, radiation, and immunotherapy.

Of the 696 patients in the COG trials, 11% were Hispanic, 16% were Black non-Hispanic, 4% were other non-Hispanic, and 69% were white non-Hispanic. One-third of the children were household poverty-exposed (covered by public insurance); 26% were exposed to neighborhood level poverty (living in a high-poverty ZIP code defined by 20% or more of the population living below the federal poverty line).

The five-year overall survival rate varied by race/ethnicity (47% for Hispanic children; 50% for other non-Hispanic children; 61% for white non-Hispanic children; and 63% for Black non-Hispanic children.) After adjusting for disease-associated factors, Hispanic children were 1.8 times more likely to die and other non-Hispanic patients were 1.5 times more likely to die than white non-Hispanic children.

Patients who had only public insurance (a proxy for household poverty) had a 53% five-year survival rate compared to 63% for others.  The survival rate was also lower – 54% -- in children living in neighborhood level poverty compared with 62% for others.

 “A huge strength of the way that this dataset was created is that we have the ability to look at potential mechanisms that may explain these survival disparities,” said Umaretiya. “For the first time, we will be able to ask whether certain groups experienced delays in therapy or were more likely to stop participating in trials perhaps because of competing family needs secondary to poverty. Most importantly, we will be able to start to look at what happens after relapse – a time when we know treatment becomes less standardized, which may increase the chance that racial, ethnic, or socioeconomic privilege helps some families access life-extending therapy for their children while others are less able to. Understanding what happens after relapse will be essential to guiding interventions to improve survival disparities and we are excited to take this on next.”

About Dana-Farber/Boston Children's Cancer and Blood Disorders Center

Dana-Farber/Boston Children's Cancer and Blood Disorders Center – one of the nation's top pediatric cancer centers, according to U.S. News & World Report – brings together two internationally known research and teaching institutions that have provided comprehensive care for pediatric oncology and hematology patients since 1947. The Harvard Medical School affiliates share a clinical staff that delivers inpatient care at Boston Children's Hospital and most outpatient care at Dana-Farber Cancer Institute. Follow the center on Twitter at @DFBC_PedCare.

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METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

UK’s first and only research Centre dedicated to placing empathy at the heart of healthcare

The incoming director of a major new research and teaching Centre has described the urgent need to place empathy at the heart of healthcare.

Business Announcement

UNIVERSITY OF LEICESTER

 

IMAGE: PROFESSOR JEREMY HOWICK, INCOMING DIRECTOR OF THE STONEYGATE CENTRE FOR EXCELLENCE IN EMPATHIC HEALTHCARE, BASED AT THE UNIVERSITY OF LEICESTER. view more 

CREDIT: UNIVERSITY OF LEICESTER

The incoming director of a major new research and teaching Centre has described the urgent need to place empathy at the heart of healthcare.

Professor Jeremy Howick will join the University of Leicester as the first director of the Stoneygate Centre for Excellence in Empathic Healthcare this June. His research shows that empathic care reduces patient pain while improving their satisfaction with care and quality of life.

Also, whereas the side effects of many medical interventions can be harmful, the side effects of empathy are that it reduces anxiety and improves a practitioner’s own sense of self-satisfaction with their careers. Professor Howick said:

“People go into the medical profession because they care about people, yet a lot of the time their motivation is forgotten amidst the need to memorise facts for exams and, after they qualify, filling out forms.”

With over 100 peer-reviewed publications, three books, and regular media appearances, Professor Howick has an established track record of research and teaching in evidence-based medicine, placebo effects, and empathy. He joins Leicester having directed the Oxford University Empathy Programme. He added:

“Medical Schools have long-recognised the importance of communication skills, but this Centre will be pivotal in breaking down the perceived separation between good communication and the ‘objective’ knowledge of human bodies and what to prescribe them.”

The unique £10m Stoneygate Centre for Excellence in Empathic Healthcare, co-funded by the University and The Stoneygate Trust, will provide the resources required to embed empathy into the core of the Medical School curriculum, and then expand it across the UK and beyond. The Centre will officially launch in autumn later this year.

It will build on the empathy curriculum delivered to Leicester Medical School’s Foundation Year students, also supported by the Stoneygate Trust. The training is planned to include inviting students to experience healthcare first-hand – for example, through spending the night as a patient – to extending and enhancing the use of expert patients and scenario-based learning with actors.

The Stoneygate Trust is a charity established in 2007 by Sir Will and Lady Nadine Adderley, with a particular focus on medical research and helping to support equal educational opportunities for economically disadvantaged children and students.

AI learns coral reef 'song'

Peer-Reviewed Publication

UNIVERSITY OF EXETER

 

IMAGE: A HEALTHY CORAL REEF IN SULAWESI, INDONESIA view more 

CREDIT: TIM LAMONT

Artificial Intelligence (AI) can track the health of coral reefs by learning the "song of the reef", new research shows.

Coral reefs have a complex soundscape – and even experts have to conduct painstaking analysis to measure reef health based on sound recordings.

In the new study, University of Exeter scientists trained a computer algorithm using multiple recordings of healthy and degraded reefs, allowing the machine to learn the difference.

The computer then analysed a host of new recordings, and successfully identified reef health 92% of the time.

The team used this to track the progress of reef restoration projects.

"Coral reefs are facing multiple threats including climate change, so monitoring their health and the success of conservation projects is vital," said lead author Ben Williams.

"One major difficulty is that visual and acoustic surveys of reefs usually rely on labour-intensive methods.

"Visual surveys are also limited by the fact that many reef creatures conceal themselves, or are active at night, while the complexity of reef sounds has made it difficult to identify reef health using individual recordings.

"Our approach to that problem was to use machine learning – to see whether a computer could learn the song of the reef.

"Our findings show that a computer can pick up patterns that are undetectable to the human ear. It can tell us faster, and more accurately, how the reef is doing."

The fish and other creatures living on coral reefs make a vast range of sounds.

The meaning of many of these calls remains unknown, but the new AI method can distinguish between the overall sounds of healthy and unhealthy reefs.

The recordings used in the study were taken at the Mars Coral Reef Restoration Project, which is restoring heavily damaged reefs in Indonesia.

Co-author Dr Tim Lamont, from Lancaster University, said the AI method creates major opportunities to improve coral reef monitoring.

"This is a really exciting development. Sound recorders and AI could be used around the world to monitor the health of reefs, and discover whether attempts to protect and restore them are working," Dr Lamont said.

"In many cases it's easier and cheaper to deploy an underwater hydrophone on a reef and leave it there than to have expert divers visiting the reef repeatedly to survey it – especially in remote locations."

The study was funded by the Natural Environment Research Council and the Swiss National Science Foundation.

The paper, published in the journal Ecological Indicators, is entitled: "Enhancing automated analysis of marine soundscapes using machine learning to combine ecoacoustic indices."

CAPTION

A damaged coral reef in Sulawesi, Indonesia

CREDIT

The Ocean Agency

CAPTION

Coral attached to a Reef Star on a newly restored reef

CREDIT

Tim Lamont

JOURNAL

Ecological Indicators

DOI

10.1016/j.ecolind.2022.108986 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Enhancing automated analysis of marine soundscapes using ecoacoustic indices and machine learning

Putin masking invasion policies with 1990s humanitarian propaganda, finds extensive analysis

A Russia-NATO expert analyses foreign policy statements from the USSR collapse, until the current day, to provide new insight

Peer-Reviewed Publication

TAYLOR & FRANCIS GROUP

Russia is reinventing decades-old propaganda based on supposed humanitarian principles to justify its invasion of Ukraine, according to research published in the peer-reviewed journal, The International Spectator.

Carried out by an expert on Russia-NATO relations, this extensive analysis of Russia’s official foreign policy statements since the USSR’s collapse provides new insights into Vladimir Putin’s tactics regarding separatism.

The research identifies attempts by officials to mask a policy change from intervention to invasion towards former Soviet republics. This shift is apparent from 2008 – when Russian forces went into Georgia – according to the study which covers the years after the Soviet Union’s collapse until present day.

The study has been conducted by Dr Vasile Rotaru, from the Department of International Relations and European Integration, at the National University of Political Studies and Public Administration, Bucharest, in Romania.

His findings demonstrate that the Kremlin has used narratives from the 1990s to claim Russian minorities need protecting with military support. A former research fellow at the NATO Defence College, Dr Rotaru also states that his analysis highlights how Russia has embellished rhetoric used in the years after the USSR’s dissolution to legitimise a new more aggressive approach towards secessionist conflicts.

“The narratives post-2008 seek to present themselves as consistent with the past,” says Dr Rotaru, who specialises in Russian foreign policy, the former Soviet region, the Eastern Partnership, and the Eurasian Economic Union.

“The aim is inducing the perception that Russia’s strategy towards the secessionist conflicts…has remained the same. That is, supporting the separatist regions militarily with the proclaimed aim of protecting the Russian minority living in those regions.

“By using the arguments emerged already in the 1990s, the Kremlin suggests the continuity of its strategy towards separatist conflicts.

“However, empirical evidence has shown that since 2008 Moscow has not simply intervened in secessionist territories to put pressure on central governments of other post-Soviet states. It has also not abstained from direct invasion to control the foreign policy of the countries in its neighbourhood.”

Russia’s invasion of Ukraine has triggered international condemnation and fears of a Third World War.

This military action is the latest carried out by Russia in post-Soviet republics – known as ‘the near abroad’ – since the dissolution of the USSR in 1991.

The study findings are based on a review of written documents, and audio and video records by Russian foreign policy-makers.

The author analysed statements regarding the country’s position towards secessionist conflicts. These include in South Ossetia, Crimea, Donbas, and preliminary evidence on the Russia-Ukraine war.

The study author investigated both similarities and differences between official Russian narratives. These related to conflicts in the 1990s when the USSR was breaking up, and post 2008. 

They reveal that the humanitarian narratives from the 1990s and post 2008 share common patterns. Both relate to sovereignty and territorial integrity; the right to self-determination; and the illegitimacy of central authority.

Examples include references to Ukrainian authorities as ‘Neo-Nazis and Banderovtsy’ in the context of the recognition of the independence of the Lugansk and Donetsk regions and the invasion of Ukraine.

However, the study highlights that foreign policy statements post 2008 also cite historical injustices, and invoke the Kosovo precedent (the country’s independence from Serbia) which President Putin has used to justify Russia’s annexation of the Crimea.

In addition, the legality of Russia’s actions is presented as a humanitarian feature of foreign policy with the Ukraine invasion deemed in accordance with international law.

Overall, the authors conclude post-2008 narratives are more coherent. They attribute this to power being regained by former members of the Soviet leadership – those trained during the Cold War – without much opposition and with Putin’s backing.

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JOURNAL

The International Spectator

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Change or Continuity in Russia’s Strategy towards Secessionist Regions in the ‘Near Abroad’?

ARTICLE PUBLICATION DATE

27-May-2022

Scientists shine new light on role of Earth's orbit in the fate of ancient ice sheets

by Cardiff University

Credit: Pixabay/CC0 Public Domain

In a new study published today in the journal Science, the team from Cardiff University has been able to pinpoint exactly how the tilting and wobbling of the Earth as it orbits around the Sun has influenced the melting of ice sheets in the Northern Hemisphere over the past 2 million years or so.

Scientists have long been aware that the waxing and waning of massive Northern Hemisphere ice sheets results from changes in the geometry of Earth's orbit around the Sun.

There are two aspects of the Earth's geometry that can influence the melting of ice sheets: obliquity and precession.

Obliquity is the angle of the Earth's tilt as it travels around the Sun and is the reason why we have different seasons.

Precession is how the Earth wobbles as it rotates, much like a slightly off-center spinning top. The angle of this wobble means that sometimes the Northern Hemisphere is closest to the Sun and other times the Southern Hemisphere is closest, meaning that roughly every 10,000 years one hemisphere will have warmer summers compared to the other, before it switches.

Scientists have determined that over the past million years or so, the combined effects of obliquity and precession on the waxing and waning of Northern Hemisphere ice sheets has resulted, through complicated interactions within the climate system, in ice age cycles lasting approximately 100 thousand years.

However, before 1 million years ago, in a period known as the early Pleistocene, the duration of ice age cycles was controlled only by obliquity and these ice age cycles were almost exactly 41,000 years long.

For decades, scientists have been puzzled as to why precession did not play a more important part in driving ice age cycles during this period.

In their new study, the Cardiff University team reveal new evidence suggesting that precession did actually play a role during the early Pleistocene.

Their results show that more intense summers, driven by precession, have always caused Northern Hemisphere ice sheets to melt, but before 1 million years ago, these events were less devastating and did not lead to the complete collapse of ice sheets.

Lead author of the study Professor Stephen Barker, from Cardiff University's School of Earth and Environmental Sciences, says that "early Pleistocene ice sheets in the northern hemisphere were smaller than their more recent counterparts, and limited to higher latitudes where the effects of obliquity dominate over precession. This probably explains why it has taken so long for us to find evidence of precession forcing during early Pleistocene."

"These findings are the culmination of a major effort, involving more than 12 years of painstaking work in the laboratory to process nearly 10,000 samples and the development of a range of new analytical approaches. Thanks to this we can finally put to rest a long-standing problem in paleoclimatology and ultimately contribute to a better understanding of Earth's climate system."

"Improving our understanding of Earth's climate dynamics, even in the remote past, is crucial if we hope to predict changes over the next century and beyond. Ongoing changes may be manmade, but there's only one climate system and we need to understand Earth's orbit affects millennial climate variability

More information: Stephen Barker et al, Persistent influence of precession on northern ice sheet variability since the early Pleistocene, Science (2022). DOI: 10.1126/science.abm4033. www.science.org/doi/10.1126/science.abm4033

Journal information: Science 

Provided by Cardiff University 

Arc volcanoes are wetter than previously thought, with scientific and economic implications

by Woods Hole Oceanographic Institution

Credit: Pixabay/CC0 Public Domain

The percentage of water in arc volcanoes, which form above subduction zones, may be far more than many previous studies have calculated.

This increased amount of water has broad implications for understanding how Earth's lower crust forms, how magma erupts through the crust, and how economically important mineral ore deposits form, according to a new paper published in Nature Geoscience.

The estimated water concentrations in primitive arc magmas from this study are more variable and significantly higher than the average of about four weight percent of water found in other studies, according to the paper. The results show that primitive arc magmas may contain ~0.6–10wt% H2O and may reach H2O saturation of ~20wt% H2O after extensive crystal fractionation in the lower arc crust, the paper adds.

"The big picture here is that water is essentially the lubricant of plate tectonics. The water content is going to affect all sorts of different parameters involved in how tectonic plates move," says lead author Benjamin Urann, who was a doctoral student in the Massachusetts Institute of Technology (MIT)—WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering at the time of the study.

"Being able to get some idea of what the actual water content of the arc magmas is, which is what we did in this study, can help refine estimates of how much water is being subducted deep into the mantle globally; quantify different water reservoirs on Earth, including surface and deep water reservoirs; and better understand the transport between these different reservoirs," says Urann, who is currently a National Science Foundation Ocean Sciences Postdoctoral Research Fellow at the University of Wyoming. Urann added that the paper also discusses the implications of water content for forming economically important ore deposits, such as porphyry copper deposits. These deposits make up about 60% of the world's source of copper, according to the U.S. Geological Survey.

Many earlier studies have relied on techniques such as measuring melt inclusions—which are tiny droplets of magma that have been trapped by a crystals that grows around them—and measuring lava and other volcanic deposits that have erupted to the Earth's surface. "However, these methods have inherent limitations that obfuscate the full range of H2O in arc magmas," the paper states.

Urann and his Ph.D. supervisor, Véronique Le Roux, who is a co-author of the paper, developed methods with the Secondary Ion Mass Spectrometry instrument located at WHOI to measure water content in minerals, with their work building on other efforts that suggested that arc magmas should contain significantly more H2O than inferred from melt-inclusion measurements.

The researchers determined that instead of examining lava samples that have erupted to the Earth's surface, it would be fruitful to examine deep crustal magmas that have not lost too much of their water content.

"Although you can't retrieve the liquid magma at these depths, what you may be able to sample is a cumulate: it is magma that has solidified at depth in the crust. We're lucky enough that sometimes with plate tectonics, some of those really deep crusts are exhumed at the surface," says Le Roux, associate scientist in the Geology and Geophysics department at WHOI, and Faculty member of the MIT-WHOI Joint Program. The researchers used cumulates that the paper's co-authors had collected from the Kohistan paleo-arc terrane in the Himalaya Mountain range in northwestern Pakistan.

Instead of examining surface rocks that travel far up through the crust as magma, and lose much of their water content in the process, the researchers examined magma—lower crustal cumulates—that had crystallized deep down in the crust at a high enough pressure to retain their original water content signature.

Le Roux says that "analyzing water in cumulate minerals is a new promising approach to access the deep levels of the crust in subduction zones."

The researchers calculated that the magma they analyzed contained between 10-20 weight percent of water depending on the magma's composition. "While this weight percent of water had been predicted experimentally as being possible, it had never been shown on natural samples," Le Roux said.

"The bottom line is that arc magmas can be wetter than we thought," said Urann.Advanced computer simulations reveal intriguing insights on magma deep below Earth's surface

More information: Benjamin Urann, High water content of arc magmas recorded in cumulates from subduction zone lower crust, Nature Geoscience (2022). DOI: 10.1038/s41561-022-00947-w. www.nature.com/articles/s41561-022-00947-w

Journal information: Nature Geoscience 

Provided by Woods Hole Oceanographic Institution