Faster in the past: New seafloor images – the highest resolution of any taken off the West Antarctic Ice Sheet – upend understanding of Thwaites Glacier retreat

At times in its past, retreat of the massive Thwaites Glacier was even quicker than it is today, heightening concerns for its future

Peer-Reviewed Publication

UNIVERSITY OF SOUTH FLORIDA

 

IMAGE: THE R/V NATHANIEL B. PALMER PHOTOGRAPHED FROM A DRONE AT THWAITES GLACIER ICE FRONT IN FEBRUARY 2019. view more 

CREDIT: ALEXANDRA MAZUR/UNIVERSITY OF GOTHENBURG

TAMPA, Fla. (Sept. 2, 2022) – The Thwaites Glacier in West Antarctica – about the size of Florida – has been an elephant in the room for scientists trying to make global sea level rise predictions.

This massive ice stream is already in a phase of fast retreat (a “collapse” when viewed on geological timescales) leading to widespread concern about exactly how much, or how fast, it may give up its ice to the ocean.

The potential impact of Thwaites’ retreat is spine-chilling: a total loss of the glacier and surrounding icy basins could raise sea level from three to 10 feet.

A new study in Nature Geoscience led by marine geophysicist Alastair Graham at the University of South Florida’s College of Marine Science adds cause for concern. For the first time, scientists mapped in high-resolution a critical area of the seafloor in front of the glacier that gives them a window into how fast Thwaites retreated and moved in the past.

The stunning imagery shows geologic features that are new to science, and also provides a kind of crystal ball to see into Thwaites’ future. In people and ice sheets alike, past behavior is key to understanding future behavior.

The team documented more than 160 parallel ridges that were created, like a footprint, as the glacier’s leading edge retreated and bobbed up and down with the daily tides.

“It’s as if you are looking at a tide gauge on the seafloor,” Graham said. “It really blows my mind how beautiful the data are.”

Beauty aside, what’s alarming is that the rate of Thwaites’ retreat that scientists have documented more recently are small compared to the fastest rates of change in its past, said Graham.

To understand Thwaites’ past retreat, the team analyzed the rib-like formations submerged 700 meters (just under half a mile) beneath the polar ocean and factored in the tidal cycle for the region, as predicted by computer models, to show that one rib must have been formed every single day.

At some point in the last 200 years, over a duration of less than six months, the front of the glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometers per year (1.3 miles per year) – twice the rate documented using satellites between 2011 and 2019.

“Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th Century,” Graham said.

“Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future–even from one year to the next–once the glacier retreats beyond a shallow ridge in its bed,” said marine geophysicist and study co-author Robert Larter from the British Antarctic Survey.

To collect the imagery and supporting geophysical data, the team, which included scientists from the United States, the United Kingdom and Sweden, launched a state-of-the-art orange robotic vehicle loaded with imaging sensors called ‘Rán’from the R/V Nathaniel B. Palmer during an expedition in 2019.

Rán, operated by scientists at the University of Gothenburg in Sweden, embarked on a 20-hour mission that was as risky as it was serendipitous, Graham said. It mapped an area of the seabed in front of the glacier about the size of Houston – and did so in extreme conditions during an unusual summer notable for its lack of sea ice.

This allowed scientists to access the glacier front for the first time in history.

“This was a pioneering study of the ocean floor, made possible by recent technological advancements in autonomous ocean mapping and a bold decision by the Wallenberg foundation to invest into this research infrastructure,” said Anna Wåhlin, a physical oceanographer from the University of Gothenburg who deployed Rán at Thwaites. “The images Ran collected give us vital insights into the processes happening at the critical junction between the glacier and the ocean today.”

“It was truly a once in a lifetime mission,” said Graham, who said the team would like to sample the seabed sediments directly so they can more accurately date the ridge-like features.

“But the ice closed in on us pretty quickly and we had to leave before we could do that on this expedition,” he said.

While many questions remain, one thing’s for sure: It used to be that scientists thought of the Antarctic ice sheets as sluggish and slow to respond, but that’s simply not true, said Graham.

“Just a small kick to Thwaites could lead to a big response,” he said.

According to the United Nations, roughly 40 percent of the human population lives within 60 miles of the coast.

“This study is part of a cross-disciplinary collective effort to understand the Thwaites Glacier system better,” said Tom Frazer, dean of the USF College of Marine Science, “and just because it’s out of sight, we can’t have Thwaites out of mind. This study is an important step forward in providing essential information to inform global planning efforts.”

The study was supported by the National Science Foundation and the UK Natural Environment Research Council through the International Thwaites Glacier Collaboration.

The 2019 expedition was the first in a five-year project dubbed THOR, which stands for Thwaites Offshore Research, and also included team members from a sister project called the Thwaites-Amundsen Regional Survey and Network Integrating Atmosphere-Ice-Ocean Processes, or TARSAN.

For more information, read this companion story authored by Graham and the team.

About the University of South Florida

The University of South Florida, a high-impact global research university dedicated to student success, generates an annual economic impact of more than $6 billion. Over the past 10 years, no other public university in the country has risen faster in U.S. News and World Report’s national university rankings than USF. Serving more than 50,000 students on campuses in Tampa, St. Petersburg and Sarasota-Manatee, USF is designated as a Preeminent State Research University by the Florida Board of Governors, placing it in the most elite category among the state’s 12 public universities. USF has earned widespread national recognition for its success graduating under-represented minority and limited-income students at rates equal to or higher than white and higher income students. USF is a member of the American Athletic Conference. Learn more at www.usf.edu

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JOURNAL

Nature

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Rapid retreat of Thwaites Glacier in the pre-satellite era

ARTICLE PUBLICATION DATE

5-Sep-2022

A 3D-rendered view of the multibeam bathymetry (seafloor shape) colored by depth, collected by Rán across a seabed ridge, just in front of Thwaites Ice Shelf.

CREDIT

Alastair Graham/University of South Florida

Rán, a Kongsberg HUGIN autonomous underwater vehicle, amongst sea ice in front of Thwaites Glacier, after a 20-hour mission mapping the seafloor.

CREDIT

Anna Wåhlin/University of Gothenburg

THOR scientists Alastair Graham (right) and Robert Larter (left) look on in awe at the crumbling ice face of the Thwaites Glacier margin, from the bridge deck of the R/V Nathaniel B. Palmer.

CREDIT

Frank Nitsche

SEE LA REVUE GAUCHE - Left Comment: Search results for THWAITES 

COVID rekindled an appreciation of nature for many

An opportunity to rediscover why the great outdoors are so great in the first place

Peer-Reviewed Publication

UNIVERSITY OF CONNECTICUT

The pandemic has impacted our lives in a multitude of ways, many of which will no doubt be felt for years to come. While many of those effects are clearly negative, UConn researchers have identified at least one positive impact – our perception of natural spaces changed. The findings are published in Nature Scientific Reports.

As people flocked to outdoor spaces for recreation in the spring of 2020, Sohyun Park, assistant professor in UConn’s College of Agriculture, Health and Natural Resources Department of Plant Science and Landscape Architecture, noticed some interesting trends: more people were on the trails, and many of those people had traveled from far away to enjoy nature.

Park was also part of the team for the Connecticut Trail Census and co-wrote a paper about the trends.

Sohyun Park of the Department of Plant Science and Landscape Architecture in her office in the W.B. Young Building. Mar. 8, 2022. (Jason Sheldon/UConn Photo)

“What’s interesting was rural trail use increased compared to urban trails,” Park says. “I wanted to try to find out how people were changing their mindset or their attitudes or perceptions.”

To do this, Park and co-authors Seungman Kim and Jaehoon Lee of Texas Tech University, and Biyoung Heo of James Corner Field Operations, looked to social media data and machine learning techniques to help make sense of the vast quantities of information on Twitter and try to find a pattern among those data, says Park. They utilized Twitter’s Application Programming Interface (API), which allows researchers to obtain aggregated data from Twitter posts.

“We wanted to know from the people who have been in greenspaces, what were they doing and what they were writing about on Twitter. We utilized very innovative and advanced levels of machine learning methods,” says Park. “The machine categorized the keywords and classified them into several human-recognizable groups. One group was nature related. The second group is all traditional park-related activities and the third one is obviously the COVID-related one, so mask wearing and social distancing, and things like that.”

A newfound appreciation for nature

Though what people were doing in the parks did not change significantly, the researchers noticed some significant changes in keyword usage between pre-pandemic and pandemic Twitter, with people frequently referencing nature, and their experiences within it.

“Users began to put the word ‘nature’ and nature-related activities or nature-related pictures on their Twitter,” Park says. “It was very interesting because, in the past, there were not many keywords like that, but people used keywords like ‘playing’, ‘walking the dog’, ‘baseball’, and other traditional, active park activities that they were enjoying while they were there in the parks. If you look at post- 2020 Twitter, you can also see keywords thanking God or showing appreciation for nature, describing the birds singing or water sounds.”

What the researchers found was people seemed to have realized a newfound appreciation for nature and greenspaces, especially true for those in urban settings. As a landscape architect, Park was interested to see if there was something more to the findings and perhaps if there might be some design implications for the results.

Common features in modern parks include benches, walking paths, and sports fields, for instance. However, Park says the results of the paper seem to suggest that natural greenspaces appeal to people differently.

“We might want to go back to the origin of public parks like those Olmsted designed,” Park says. “In his time in 19th century, there was a lot of hustle and bustle in the city, and they wanted to have space for people to find respite and peace. We might want to go back to that era living with a 21st century health crisis and try to rethink about the design principles.”

Park says to imagine Manhattan’s Central Park, which hosts ponds, wooded areas, and meadows. Most of those natural features were introduced artificially and were not there in the first place. Compare this with contemporary parks:

“Modern parks may be well managed, maintained, and manicured, everything is clean and tidy,” Park says. “There are some seating areas, paved surfaces, and structures where you can play something with your friends and family members, but not really in a naturalistic style. People can feel that in public spaces.”

The outdoors as essential resource for overall well-being

Greenspaces impact mental, physical, and spiritual health, and Park reasons that these natural elements might be essential in public spaces, particularly for those who have less access to the public parks, or marginalized communities that don’t have any green areas at their residences.

“I’m arguing that parks are not only recreational spaces; greenspaces and parks serve as essential amenities for all including those with low incomes or disabilities, and the elderly,” Park says. “Parks need inclusive planning approaches that might be added to the current principles for park development.”

Park explains that many people are involved in the planning, design, and management of parks and greenspaces. The tricky part is that the more naturalistic, garden concept for public parks may require more planning and maintenance, and therefore these design features rely more heavily on resources and budgets.

“In the long term, I think that will be the direction that we need to go and now officials and park managers need to work together with those who are living nearby so that we can have some kind of co-managing type of approaches to the future,” Park says.

This study highlights the importance of those design features and their roles in our emotional and spiritual well-being, and Park says it is important for the public to advocate for our greenspaces. Research like this can inform decision-making.

“It is important for the public and decision-makers to understand that ultimately, we need to have a budget to have more natural features and nature-oriented programs in the park.  We all need to be more active in terms of the things that towns are doing. That can start with joining your town’s Conservation Commission or attending monthly meetings. Participate and make your voice heard. That makes a huge change and can impact big decisions. Sometimes these decision makers are really grounded by how the stakeholders are feeling so giving some input and feedback on the public decision-making should be the first step. It is empowering and more people need to be involved in public planning.”

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JOURNAL

Scientific Reports

DOI

10.1038/s41598-022-17077-3 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Evolving norms: social media data analysis on parks and greenspaces perception changes before and after the COVID 19 pandemic using a machine learning approach

Did primitive cetaceans feed like marine reptiles?

Research carried out at the University of Liège (Belgium) has studied the morphological similarities between the first cetaceans and ancient marine reptiles from the dinosaur era, the mosasaurs

Peer-Reviewed Publication

UNIVERSITY OF LIEGE

 

IMAGE: ANALYZES OF THE DIFFERENCES BETWEEN SKULLS. view more 

CREDIT: @ULIÈGE/EDDYLAB

Did the first ancestors of whales pick up where the mosasaurs left off 66 million years ago, after the extinction of all the large predatory marine reptiles? A study conducted by Rebecca Bennion, a PhD student at the EDDyLab of the University of Liège (Belgium), has looked into the possible convergences in morphology and behaviour that may exist between these two groups of large marine predatory animals. This research has been published in the journal Paleobiology.

Many of us are familiar with modern whales and dolphins. However, the extinct ancestors of these modern marine mammals bear an uncanny resemblance to earlier forms of marine life, notably the mosasaurs, a completely extinct group closely related to snakes and lizards. "Superficial similarities have long been noted, but the idea that these two groups might be functionally similar has never been rigorously tested," explains Rebecca Bennion, a doctoral student at ULiège's EDDyLab and first author of the study.

The research, which has just been published in the journal Paleobiology and was carried out by an international team of scientists based in Europe, the USA and New Zealand, investigated the potential for convergent evolution of skull morphology between ancestral cetaceans and mosasaurs. To do this, a range of functional and biomechanical features were recorded from high-resolution three-dimensional (3D) scans of skulls from both groups. "Our laboratory has assembled a vast library of 3D scans of fossils, allowing us to explore in detail questions on large-scale evolution," explains Prof. Valentin Fischer, palaeontologist and director of the EDDy Lab at ULiège.

While cetaceans and mosasaurs initially had quite different ecological characteristics, this study found that several species had nevertheless acquired quite similar morphology and thus showed evolutionary convergence. "This convergence between early cetaceans and mosasaurs tells us more about the physical characteristics necessary for large marine predators to evolve optimally," says EDDyLab researcher Dr Jamie MacLaren, "Many members of these groups become very similar in their ecological characteristics, suggesting similar selective pressures on these animals despite being separated by tens of millions of years. Nevertheless, important differences remain between the two groups despite these examples of convergence. "Our results show what is called 'incomplete convergence', with differences remaining due to the mammalian or reptilian origin of each group," continues Rebecca Bennion.

Modern cetaceans are indeed a group that remains scientifically very interesting to study, it remains to be seen how diverse their morphology and ecology is compared to other fossil marine animals. This research is just the tip of the iceberg; further research into the convergence of marine animals through the fossil record will help us understand the constraints that evolution places on aquatic organisms and how they overcome them.

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JOURNAL

Paleobiology

DOI

10.1017/pab.2022.27 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Convergence and constraint in the cranial evolution of mosasaurid reptiles and early cetaceans

http://prehistoricpulp.blogspot.com/2007/09/ice-hunt-by-james-rollins-2003.html

Ice Hunt by James Rollins (2003) - Prehistoric Pulp 

Sep 5, 2007 ... In this case, the plot hinges around the survival of the famous "walking whale" Ambulocetus. Ice Hunt starts when an experimental U.S. Navy ...

Hidden acid-base clusters drive rapid formation of atmospheric ultrafine particles

Peer-Reviewed Publication

SCIENCE CHINA PRESS

 

IMAGE: ON SUNNY DAYS IN MEGACITIES SUCH AS BEIJING, GASEOUS ACID AND BASE POLLUTANTS FORM A LARGE AMOUNT OF NEW ULTRAFINE PARTICLES. THE CLUSTERING BETWEEN ONE ACID AND ONE BASE IS THE RATE-LIMITING STEP FOR NEW PARTICLE FORMATION. view more 

CREDIT: ©SCIENCE CHINA PRESS

A joint research team led by Dr. Jingkun Jiang from Tsinghua University and Dr. Markku Kulmala from the University of Helsinki has reported an efficient mechanism for gaseous sulfuric acid and bases to form atmospheric ultrafine particles. The findings explain the rapid formation of secondary ultrafine particles, which could further influence air quality and the climate.

The team found that acid-base reactions are the major driving forces for gaseous precursors to overcome surface tension and form ultrafine particles, and the key mechanism is the formation of hidden acid-base heterodimers. This hidden mechanism explains the high particle formation rate in Chinese megacities.

Their findings were published in National Science Review.

“There are hundreds of thousands of ultrafine particles in per cubic centimeter air in Chinese megacities, and a new particle formation event on a sunny noon can readily elevate their concentration by one order of magnitude within several hours,” Jiang says.

To explain how new particles can be so efficiently converted from gaseous precursors, Jiang and Kulmala, together with Dr. Runlong Cai, are determined to seek the key mechanism for rapid new particle formation. They have known that sulfuric acid is a primary precursor, whereas the challenge is to find the key bases among many candidates. “Urban air is a complex cocktail of chemicals with poorly understood interactions and feedbacks”, Kulmala commented.

The researchers observed highly abundant molecular clusters containing sulfuric acid during new particle formation in Beijing and Shanghai. Some of the measured clusters contain sulfuric acid and amine molecules. These provide strong evidence for amine participation in the formation of stable sulfuric acid clusters, which increases the conversion rate from gaseous sulfuric acid to new particles.

“It is intriguing that we measured fewer bases than acids in a cluster. There must be some key information hidden behind the measured signals,” Cai says. It was previously proposed that the clustering between a base molecule and a sulfuric acid homodimer is the key mechanism for new particle formation, as there were no base molecules in the measured clusters containing one sulfuric acid molecule. The research team, however, found that this was a measurement artifact.

Combining long-term measurements and theory based on quantum chemistry and cluster kinetics, they found that the formation of hidden acid-base heterodimers is the key mechanism. This mechanism is far more efficient than the previously proposed mechanism with acid-acid homodimers, ensuring the rapid formation of sulfuric acid clusters and new particles.

The hidden heterodimers solve the puzzle of why new particles could be frequently formed against a high background particle loading in megacities. The hidden acid-base heterodimers with a considerable fraction in the measured sulfuric acid signals can effectively cluster with each other. This ensures a high particle formation rate approaching the theoretical maximum even at a low ambient amine concentration. The hidden heterodimers also explain the temperature dependency of new particle formation in Beijing and Shanghai. “Atmospheric measurements are often perturbed by many factors. I did not expect such an amazing consistency between the measurements and the new theory,” Cai says.

The team also sought the hidden base molecules using thermodynamic and kinetic analyses. Among the measured gaseous molecules, strong amines such as dimethylamine serve as the key bases in acid-base heterodimers, whereas the highly abundant ammonia and other weak bases are more likely to be involved in the subsequent cluster growth process.

###

See the article:

The missing base molecules in atmospheric acid-base nucleation

https://doi.org/10.1093/nsr/nwac137

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JOURNAL

National Science Review

DOI

10.1093/nsr/nwac137 

Spatiotemporal variation of mortality burden attributable to heatwaves in China, 1979-2020

Peer-Reviewed Publication

SCIENCE CHINA PRESS

 NEWS RELEASE 2-SEP-2022

 

IMAGE: HEALTH RISKS OF HEATWAVES WERE CHARACTERIZED BY RAPID GROWTH, NONLINEAR TEMPORAL EVOLUTION AND EXTREMITY. NATIONALLY, THE NUMBER OF ANNUAL ATTRIBUTABLE DEATHS WAS AN AVERAGE OF 3,679 IN 1980S BUT INCREASED TO 15,500 IN 2010S. TAKING A 5-YEAR MOVING AVERAGE, IT TOOK 2.8 YEARS FOR EVERY INCREASE OF 1,000 ANNUAL HEATWAVE-RELATED DEATHS FROM 1980S TO 2000S, BUT JUST ONE YEAR FOR THE SAME INCREASE TO OCCUR IN 2010S. ALSO, THE ATTRIBUTABLE DEATHS REACHED A HIGHEST RECORD OF 26,486 IN 2017, FOLLOWED BY THE SECOND 21,219 IN 2019 AND THE THIRD 20,431 IN 2013. REGIONALLY, EAST AND CENTRAL CHINA HAD THE LARGEST NUMBER OF ATTRIBUTABLE DEATHS IN GENERAL, ACCOUNTING FOR MORE THAN 50% OF DEATHS NATIONWIDE. AMONG THE PROVINCES, DEATHS ASCRIBED TO HEATWAVES WERE HIGHEST IN SHANDONG, FOLLOWED BY HENAN, HEBEI AND JIANGSU. A-D, THE NUMBER OF ATTRIBUTABLE DEATHS TO HEATWAVES IN GRID DURING THE PAST FOUR DECADES. E, ATTRIBUTABLE DEATHS TO HEATWAVES IN CHINA FROM 1979 TO 2020. THE SOLID LINE SHOWS THE ESTIMATED NUMBER OF ATTRIBUTABLE DEATHS TO HEATWAVES; GREY AREAS SHOW THE 95% CONFIDENCE INTERVALS; THE HORIZONTAL DASHED LINE SHOWS THE AVERAGE ANNUAL DEATHS IN 1980S, 1990S, 2000S, 2010S. F, CHANGES IN ATTRIBUTABLE DEATHS TO HEATWAVES IN 2010S RELATIVE TO THE BASELINE PERIOD OF 1980-2009. AD, ATTRIBUTABLE DEATHS TO HEATWAVES. THE MAP NO. IS GS(2019)1673. ART BY HUIQI CHEN. view more 

CREDIT: ©SCIENCE CHINA PRESS

This study is led by Dr. Cunrui Huang (Vanke School of Public Health, Tsinghua University). Heatwaves impose heavy disease burden by increasing the risk of mortality and morbidity, which has been exacerbated worldwide under climate change. "In China, evidence documenting the impact of heatwaves on the number of attributable deaths, spatiotemporal variations and their driving factors is still limited, hindering the understanding of dangerous heatwaves. " Huang says.

Huang, together with his group member Chen and meteorological expert Zhao, sought to identify what was the spatial and temporal trends of heatwave-attributable deaths in China over the past four decades. The team performed event-based attributable loss estimation to quantify the gridded attributable deaths.

The team found that health risks of climate change were characterized by rapid growth, nonlinear evolution and extremity. The attributable deaths to heatwaves in China have increased dramatically by four times in the past four decades, with the rising trends becoming more apparent in the recent decade but some fluctuations among individual years. Regionally, east and central China had the largest number of attributable deaths in general, accounting for more than 50% of deaths nationwide. Among the provinces, deaths ascribed to heatwaves were highest in Shandong, followed by Henan, Hebei and Jiangsu.

The researchers also decomposed the driving factors to changes in attributable deaths. The increase in attributable deaths to heatwaves in China over time was primarily due to increased heatwave exposure, followed by population growth, population aging and the mounting baseline mortality. Notably, population aging has played an increasingly important role in attributable deaths over time. This work could serve important information for policy-makers to develop effective climate mitigation and adaptation measures in response to increasing heatwaves, especially for the most vulnerable elderly populations.

See the article:

Spatiotemporal Variation of Mortality Burden Attributable to Heatwaves in China, 1979-2020

https://doi.org/10.1016/j.scib.2022.05.006

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JOURNAL

Science Bulletin

DOI

10.1016/j.scib.2022.05.006 

CAPTION

The increase in attributable deaths to heatwaves in China was primarily due to increased heatwave exposure, followed by population growth, population aging and the mounting baseline mortality. Notably, population aging has played an increasingly important role in attributable deaths over time, increased from 10.6% in the period between 1980s and 1990s to 15.8% afterward, reaching as high as 20.8% in the period between 2000s and 2010s. a, Decomposition of the contribution of driving factors in seven regions (left) and for the whole nation (right) from 1980s to 1990s. b, Decomposition of the contribution of driving factors in seven regions (left) and for the whole nation (right) from 1990s to 2000s. c, Decomposition of the contribution of driving factors in seven regions (left) and for the whole nation (right) from 2000s to 2010s. AD, attributable deaths to heatwaves. The Map NO. is GS(2019)1673. Art by Huiqi Chen.

CREDIT

©Science China Press

Mortality caused by heatwaves in China has increased since 1979

Peer-Reviewed Publication

INSTITUTE OF ATMOSPHERIC PHYSICS, CHINESE ACADEMY OF SCIENCES

 

IMAGE: HEATWAVES SWEEPS THROUGH NORTHERN CHINA. PHOTO TAKEN IN BEIJING ON JULY 20. view more 

CREDIT: LIANG ZHAO

Since the beginning of the summer in 2022, China has been sweltering under the worst heatwave in decades. A number of people in Zhejiang, Henan, Jiangsu, and Sichuan provinces were diagnosed with thermoplegia, the most severe form of heatstroke, and some even died of this disease.

In a warming world, the threat of heatwaves to human health is increasing. Researchers led by Liang Zhao from the Institute of Atmospheric Physics of the Chinese Academy of Sciences and Cunrui Huang from Tsinghua University investigated the spatial and temporal variation of heatwaves-related human deaths in China from 1979 to 2020.

The study was published in Science Bulletin.

They also explored the relative contributions of drivers such as heatwaves exposure, population growth, population aging, and baseline mortality to changes in attributable mortality.

"We found that the number of deaths caused by heatwaves in China has increased rapidly since 1979, from 3,679 persons per year in the 1980s to 15,500 persons per year in the 2010s," said Zhao. "We also found strong spatial heterogeneity across the country, with more human deaths in East and Central China."

Then what are the main drivers of the large increase in heatwaves-related deaths in China over the past four decades?

"The main drivers are the rapid increase in the frequency of heatwaves, followed by population growth, population aging, and rising baseline mortality. From the 2000s to the 2010s, these four factors accounted for 40.6%, 22.4%, 20.8%, and 16.2% of the change in attributed human deaths, respectively," said Huang.

The research team hopes this study's accurate assessment of the number of heatwaves-related deaths in China and the contribution of their different drivers can help policy makers to fully understand human health hazards of heatwaves and to develop response policies to reduce health losses from increased heatwaves exposure under climate change.

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DOI

10.1016/j.scib.2022.05.006 

ARTICLE TITLE

Spatiotemporal variation of mortality burden attributable to heatwaves in China, 1979–2020

Dragons and brain evolution

A molecular atlas of an Australian dragon’s brain sheds new light on over 300 million years of brain evolution

Peer-Reviewed Publication

MAX-PLANCK-GESELLSCHAFT

 

IMAGE: THE AUSTRALIAN BEARDED DRAGON POGONA VITTICEPS. view more 

CREDIT: MAX PLANCK INSTITUTE FOR BRAIN RESEARCH / G. LAURENT

These days, dragons are keeping Game of Thrones fans on their toes. But they are also providing important insights into vertebrate brain evolution, as revealed by the work of Max Planck scientists on the brain of the Australian bearded dragon Pogona vitticeps. Vertebrate evolution took a major turn 320 million years ago when early tetrapods (animals with four limbs) transitioned from water to land, eventually giving rise to three major clades: the reptiles, the birds (an offshoot of the reptilian tree) and the mammals. Because of common ancestry, the brains of all tetrapods share a similar basal architecture established during early development. Yet, how variations on this common “Bauplan” contributed to clade-specific attributes remains unclear. Neuroscientists at the Max Planck Institute for Brain Research in Frankfurt tackled this question by generating a molecular atlas of the dragon brain and comparing it with one from mice. Their findings suggest that, contrary to popular belief that a mammalian brain consists of an ancient “reptilian” brain supplemented with new mammalian features, both reptilian and mammalian brains evolved their own clade-specific neuron types and circuits, from a common ancestral set.

“Neurons are the most diverse cell types in the body. Their evolutionary diversification reflects alterations in the developmental processes that produce them and may drive changes in the neural circuits they belong to”, says Prof. Gilles Laurent, Director at the Max Planck Institute for Brain Research who led the new study published in Science. “For example, distinct brain areas do not work in isolation, suggesting that the evolution of interconnected regions, such as the thalamus and cerebral cortex, might in some way be correlated. Also, a brain area in reptiles and mammals that derived from a common ancestral structure might have evolved in such a way that it remains ancestral in one clade today, while it is “modern” in the other. Conversely, it could be that both clades now contain a mix of common (ancient) and specific (novel) neuron types. These are the sorts of questions that our experiments tried to address”, Laurent adds.

While traditional approaches to compare developmental regions and projections in the brain do not have the necessary resolution to reveal these similarities and differences, Laurent and his team took a cellular transcriptomic approach. Using a technique called single-cell RNA sequencing that detects a large fraction of the RNA molecules (transcriptomes) present in single cells, the scientists generated a cell-type atlas of the brain of the Australian bearded dragon Pogona vitticeps and compared it to existing mouse brain datasets.

CAPTION

Reptiles and mammals are evolutionary separated by over 300 million years. Max Planck scientists generated a cell type atlas from the brain of a lizard. Computationally integration of this data with mouse transcriptomics revealed that multiple brain areas contain mixtures of similar and divergent neurons, suggesting ubiquitous neuron diversification in these brain regions.

CREDIT

Max Planck Institute for Brain Research / G. Laurent; Hain et al. Science 2022 DOI: 10.1126/science.abp8202

Transcriptomic comparisons reveal shared classes of neuron types

“We profiled over 280,000 cells from the brain of Pogona and identified 233 distinct types of neurons”, explains David Hain, graduate student in the Laurent Lab and co-first author of the study. “Computational integration of our data with mouse data revealed that these neurons can be grouped transcriptomically in common families, that probably represent ancestral neuron types”, says Hain. In addition, he found that that most areas of the brain contain a mix of common (ancient) and specific (novel) neuron types, as shown in the figure below.

Graduate student Tatiana Gallego-Flores used histological techniques to map these cell types throughout the dragon brain and observed (among other) that neurons in the thalamus could be grouped in two transcriptomic and anatomical domains, defined by their connectivity to other regions of the brain. Because these connected regions have had different fates in mammals and in reptiles, one of these regions being highly divergent, comparing the thalamic transcriptomes of these two domains proved to be very interesting. Indeed, it revealed that transcriptomic divergence matched that of the target regions.

“This suggests that neuronal transcriptomic identity somewhat reflects, at least in part, the long-range connectivity of a region to its targets. Since we do not have the brains of ancient vertebrates, reconstructing the evolution of the brain over the past half billion years will require connecting together very complex molecular, developmental, anatomical and functional data in a way that is self-consistent. We live in very exciting times, because this is becoming possible”, concludes Laurent.

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JOURNAL

Science

DOI

10.1126/science.abp8202 

METHOD OF RESEARCH

Meta-analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Molecular diversity and evolution of neuron types in the amniote brain.

From wound healing to regeneration

Heidelberg scientists demonstrate how injuries are converted to regeneration signals at the molecular level

Peer-Reviewed Publication

HEIDELBERG UNIVERSITY

The phenomenon of regeneration was discovered over 200 years ago in the freshwater polyp Hydra. Until now, however, it was largely unclear how the orderly regeneration of lost tissues or organs is activated after injury. In its investigations of Hydra, an interdisciplinary research team at Heidelberg University was able to show how wound healing signals released upon injury are converted into specific signals of pattern formation and cell differentiation. Essential components are the mitogen-activated protein kinases (MAPK) and the Wnt signalling pathway – molecular mechanisms that have remained relatively unchanged throughout evolution.

The ability to regenerate varies widely in animals. Most mammals and vertebrates have only limited regeneration capacity, while basal and simple animals that emerged early in evolution, like cnidarians and planarians, can regenerate their whole body. In all cases, the process of regeneration begins with wound healing. The cells at the site of injury proliferate and form an undifferentiated mass – a blastema – from which the missing structures are re-patterned. This activates genetic processes that also control embryonic development. To determine the molecular mechanisms involved, the research team led by Prof. Dr Thomas W. Holstein studied the freshwater polyp Hydra to understand the basic features of this activation of regeneration.

The core of their investigations is the doctoral thesis of Anja Tursch. She repeated the key experiment of Geneva naturalist Abraham Trembley (1710 to 1784) which led him to discover the regeneration phenomenon. The Hydra polyp is bisected, prompting the upper half to regenerate a new “head” and the lower half a new “foot” – hence totally different body parts can grow from the exact same tissue at the cut surface in the middle. Building on their previous work on Hydra regeneration, the researchers at the Centre for Organismal Studies (COS) of Heidelberg University have now shown how this is possible.

Regardless of where it occurs, any damage triggers nonspecific signals for an injury response, i.e. wound healing, via calcium ions and the production of reactive oxygen species. The signals are transmitted intracellularly by three mitogen-activated protein kinases – p38, JNKs, and ERK. Activation of these three molecules is required for both head and foot regeneration. Wnt signalling pathways are then activated that are important during embryonic development for the formation of rudimentary organs and the body axis. The generic signals of wound healing are thus transferred into position-specific signals of patterning and cell differentiation for regeneration.

“Our experiments show that the Wnt signalling pathway is a main component of the initially general injury response and, depending on signal strength, directs the tissue toward head or foot development,” explains Prof. Holstein. This is why, in the case of MAPK inhibition, the otherwise absent regeneration can be induced by artificially generated, recombinant Wnt proteins. “It was also surprising that in middle body parts that had both head and foot removed, heads can be induced at both ends in this way,” adds Dr Suat Özbek, a member of Prof. Holstein’s “Molecular Evolution and Genomics” research group at the COS.

Wnt/β-catenin, one piece of the Wnt signalling pathway, was already known to encode positional information for new head structure formation. In collaboration with mathematicians led by Prof. Dr Anna Marciniak-Czochra, the research team of Prof. Holstein and Dr Özbek developed a model that shows how basal positional information in the tissue transforms the initially undifferentiated injury response into a differential patterning process via the Wnt signalling pathway. “Because MAPKs and Wnts are highly evolutionarily conserved, this mechanism is likely deeply embedded in our genome, which is important for regenerative processes in vertebrates and mammals as well,” stresses Thomas Holstein.

The research was done under the auspices of the “Mechanisms and Functions of Wnt Signaling” Collaborative Research Centre (CRC 1324) funded by the German Research Foundation. The results were published in the “Proceedings of the National Academy of Sciences” (PNAS).

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2204122119 

ARTICLE TITLE

Injury-induced MAPK activation triggers body axis formation in Hydra by default Wnt signaling