Friday, July 02, 2021

Eruption of the Laacher See volcano redated

Revised date of the Laacher See eruption 13,077 years ago provides crucial information about historical climate fluctuations at the end of the last Ice Age

JOHANNES GUTENBERG UNIVERSITAET MAINZ

Research News

IMAGE: 13,000-YEAR-OLD TREE TRUNK FROM THE VOLCANIC DEPOSITS OF THE LAACHER SEE ERUPTION IN THE VICINITY OF MIESENHEIM, GERMANY. view more
CREDIT: PHOTO/©: OLAF JÖRIS

The eruption of the Laacher See volcano in the Eifel, a low mountain range in western Germany, is one of Central Europe's largest eruptions over the past 100,000 years. The eruption ejected around 20 cubic kilometers of tephra and the eruption column is believed to have reached at least 20 kilometers in height, comparable to the Pinatubo eruption in the Philippines in 1991. Technical advances in combination with tree remains buried in the course of the eruption now enabled an international research team to accurately date the event. Accordingly, the eruption of the Laacher See volcano occurred 13,077 years ago and thus 126 years earlier than previously assumed. This sheds new light on the climate history of the entire North Atlantic and European region and requires an adaptation of the European climate archives. "We can now precisely date a drop in temperature at the end of the last glacial period, so that the information coincides with that observed from the Greenland Ice Sheet cores," said Dr. Frederick Reinig, a dendrochronologist at Johannes Gutenberg University in Mainz (JGU). An international research team with experts in archeology, climatology, ecology, radiocarbon dating, and volcanology was involved in this study. The research results were published in the renowned scientific journal Nature.

Charred remains of birch and poplar wood have been preserved to this day

The eruption of the Laacher See volcano was a natural disaster that affected large parts of Europe. The ash rain reached as far as northern Italy in the south and Saint Petersburg in the Northeast. In the immediate vicinity and the neighboring Rhine Valley, mighty deposits of ash and pumice formed, which buried all life beneath them. "During the eruption, pyroclastic flows buried the local vegetation around the Laacher See volcano. The trees were partially charred within the ash deposits and have been preserved to this day," explained Reinig, describing the eruption process that took place over several weeks in late spring to early summer and which now enables scientists to precisely date the event. "These wooden contemporary witnesses are very rare, and they are difficult to recover," said Reinig, first author of the study.

"The regional effects of the volcanic eruption have been well studied. What we have been missing so far is the certainty of when exactly this happened," emphasized Professor Ulf Büntgen, co-author of the Nature publication from the University of Cambridge. This was now determined based on samples from buried birch and poplar trees.

The analysis of tree rings reveals the precise date of the eruption

The volcanic sediments not only preserved the wood for over 13,000 years but also allowed to identify the individual tree rings. "The tree rings enable us to exactly determine the age of the samples," said Professor Jan Esper from Mainz University. In a joint initiative of the Federal Research Institute for Forests, Snow and Landscape WSL in Birmensdorf, Switzerland, together with the Archaeological Research Center and Museum for Human Behavioral Evolution MONREPOS in Neuwied, both newly discovered samples and older finds were analyzed. For this purpose, the Laboratory for Ion Beam Physics at ETH Zurich carried out radiocarbon measurements on 157 individual tree rings of the examined trees. Calibration of these results against a Swiss reference chronology then resulted in the precise dating. "The constant advances in radiocarbon measurement technology and the calibration methods used, as well as the careful handling of the sensitive samples, were the key to establish this dating with an uncertainty of less than ten years," said Lukas Wacker from ETH Zurich.

CAPTION

A charred tree trunk in the deposits of the Laacher See volcanic eruption: the individual annual rings of the sample were decisive for the exact dating of the eruption.

CREDIT

photo/©: Olaf Jöris

Revised dating of the volcanic eruption has consequences for the synchronization of European climate archives and the understanding of large-scale climate dynamics

According to the description in Nature, the eruption of the Laacher See volcano took place 13,006 years before 1950, with an uncertainty of nine years. That is 126 years earlier than the generally accepted dating based on sediments in the Meerfelder Maar from the Eifel region in Germany.

This difference has far-reaching consequences for the synchronization of European climate archives and the understanding of North Atlantic and European climate history. Laacher See eruption ashes were widespread over large areas of Central and Northern Europe as a result of the volcanic eruption and represent an important time marker for paleoenvironmental archives. Due to the new dating, the European archives now have to be temporally adapted. At the same time, a previously existing temporal difference to the data from the Greenland ice cores was closed.

This means that the massive cooling at the beginning of the Younger Dryas - i.e., the last Ice Age intermezzo lasting around 1,300 years before the currently prevailing warm phase, the Holocene - also occurred in Central Europe 130 years earlier, around 12,870 years ago respectively. This is in line with the onset of the cooling in the North Atlantic region identified in ice cores from Greenland. During the Younger Dryas period, temperatures in Central Europe fell by up to 5 degrees Celsius. This strong cooling did not take place time transgressively, as previously thought, but rather synchronously over the entire North Atlantic and Central European region," said Frederick Reinig. The results of the interdisciplinary research team not only set a precise date for the eruption of the Laacher See in the Eifel. The revised age of the ash deposits and the associated shift in the European climate archives now sheds new light on the climate history of the entire North Atlantic region.

CAPTION

Tree rings reveal much more than the age of a tree. For example, they allow conclusions to be drawn about the respective growing conditions and thus enable indirect climatic insight.

CREDIT

photo/©: Jan Esper

Images:

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_01.jpg
13,000 year old tree trunk from the volcanic deposits of the Laacher See eruption in the vicinity of Miesenheim, Germany. photo/©: Olaf Jöris

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_02.jpg
Recovery of a charred tree trunk that was buried by volcanic deposits during the Laacher See eruption. photo/©: Olaf Jöris

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_03.jpg
A charred tree trunk in the deposits of the Laacher See volcanic eruption: the individual annual rings of the sample were decisive for the exact dating of the eruption. photo/©: Olaf Jöris

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_04.jpg
The individual annual rings can be seen on an x-ray image of charred birch wood, recovered from the Laacher See Eruption deposits. photo/©: Frederick Reinig

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_05.jpg
Subfossil pine disc found in Zurich, Switzerland. Radiocarbon calibration of trees found within the Laacher See deposits against the Swiss radiocarbon reference based on such pines resulted in the precise eruption date. photo/©: Daniel Nievergelt

https://download.uni-mainz.de/presse/09_geograph_klimatologie_laacher_see_06.jpg
Tree rings reveal much more than the age of a tree. For example, they allow conclusions to be drawn about the respective growing conditions and thus enable indirect climatic insight. photo/©: Jan Esper

CAPTION

Portrait of Sir Patrick Geddes (c. 1888) at the age of 34, several years after publishing observations from his experiments on animals containing chlorophyll.

CREDIT

libraryblogs.is.ed.ac.uk

LaJeunesse and his colleagues used genetic information; outward physical, or morphological, characteristics; ecological traits; and geographic distributions to define the diversity found within the newly recognized Philozoon genus. They obtained animal samples -- including from soft and stony corals, jellyfish, and sea anemones -- from locations all over the world. They also obtained samples from Italy where Geddes first conducted his original research.

"Because our team comprises scientists from seven countries, we were able to collect all of these samples, and some during the global pandemic," said LaJeunesse. "This study highlights how the spirit of scientific discovery brings people together, even in times of hardship."

"The fact that these algae exist in animals from the Mediterranean Sea to New Zealand to Chile reminds us how widespread these symbioses are on Earth," said LaJeunesse. "Also, since most of the algae in the family Symbiodiniaceae have been thought to be mostly tropical where they are critical to the formation of coral reefs, finding and describing these new species in cold waters highlights the capacity of these symbioses to evolve and live under a broad range of environmental conditions. Life finds a way to persist and proliferate."

The team documented that at their northernmost and southernmost latitudinal extremes, Philozoon experience water temperatures that may reach winter lows of nearly 40 degrees F and summer highs of close to 90 F.

"The abilities of these Philozoons to withstand a wide range of temperatures is likely due to their diversification during the cooler periods of the late Pliocene and most recent Pleistocene epochs," said LaJeunesse. "This adaptation to a range of temperatures could protect them and the animals with which they associate from some of the effects of climate change, at least in the near term. Similarly, adaptation to high latitude environments may condition Philozoon species to tolerating future increases in atmospheric carbon dioxide, which could also help make them resilient to some of the effects of ocean acidification."

He added that careful identification and categorization of these symbiotic algae is essential to understanding the biology and evolution of marine animals that rely on these organisms for their survival.

"The advanced molecular-genetic techniques available to us today have substantially improved our ability to study and understand these microbes," said Pilar Casado-Amezúa, researcher, HyT Association, Spain. "Our new study lays the groundwork for extensive research on the ecological role of animal-algal mutualisms in temperate marine ecosystems."

LaJeunesse noted that although there were a handful of other scientists during the late 1800s that were investigating these 'yellow cells' it was Geddes who unequivocally recognized the full significance of the evidence before him.

He explained, "In describing the associations between the cells and the host animals, Geddes called them 'animal lichens' and eloquently wrote, 'Such an association is far more complex than that of the fungus and alga in the lichen, and indeed stands unique in the physiology as the highest development, not of parasitism, but of the reciprocity between the animal and vegetable kingdoms.' Geddes vigorously contended that these algae were symbiotic in nature. Now, more than a century after their discovery, the true identities of these algae are finally being properly characterized."

CAPTION

The jellyfish, Cotylorhiza tuberculata, from Naples, Italy hosts the symbiotic algae Philozoon medusarum.

CREDIT

Marco Cannavacciuolo

Other authors on the paper include Joerg Wiedenmann, University of Southampton, United Kingdom; Pilar Casado-Amezúa, Hombre y Territorio Association, Spain; Isabella D'Ambra, Stazione Zoologica Anton Dohrn, Italy; Kira Turnham, Penn State, United States; Matthew Nitschke, University of Technology Sydney, Australia, and Victoria University of Wellington, New Zealand; Clinton Oakley, Victoria University of Wellington, New Zealand; Stefano Goffredo, University of Bologna, Spain, and The Inter-Institute Center for Research on Marine Biodiversity, Resources and Biotechnologies, Italy; Carlos Spano, Ecotecnos S.A., Chile; Victor Cubillos, Universidad Austral de Chile, Chile, and Universidad Austral de Chile, Chile; Simon Davy, Victoria University of Wellington, New Zealand; and David Suggett, University of Technology Sydney, Australia.

Funding for this research was provided by the U.S. National Science Foundation, the University of Southampton, the Association of Marine Biology Laboratories Program, the ABBaCo project, PO FEAMP Campania and the Australian Research Council.

Near-death experiences, a survival strategy ?

A study in the journal Brain Communications by Danish and Belgian researchers attributes for the first time a biological purpose to near-death experiences (NDEs)

UNIVERSITY OF LIEGE

Research News

Near-death experiences are known from all parts of the world, various times and numerous cultural backgrounds. This universality suggests they may have a biological origin and purpose, but exactly what this could be has been largely unexplored.

A new study conducted jointly by the University of Copenhagen (Denmark) and the University of Liege (Belgium) and published in Brain Communications shows how near-death experiences in humans may have arisen from evolutionary mechanisms.

"Adhering to a preregistered protocol, we investigated the hypothesis that thanatosis is the evolutionary origin of near-death experiences", says Daniel Kondziella, a neurologist from Rigshospitalet, Copenhagen University Hospital.

When attacked by a predator, as a last resort defense mechanism, animals can feign death to improve their chances of survival, one example being the opossum. This phenomenon is termed thanatosis, also known as death-feigning or tonic immobility. "As a survival strategy," Daniel Kondziella adds, "thanatosis is probably as old as the fight-or-flight response."

Charlotte Martial, neuropsychologist from the Coma Science Group at ULiège explains: "We first show that thanatosis is a highly preserved survival strategy occurring at all major nodes in a cladogram ranging from insects to fish, reptiles, birds and mammals, including humans. We then show that humans under attack by big animals such as lions or grizzly bears, human predators such as sexual offenders, and 'modern' predators such as cars in traffic accidents can experience both thanatosis and near-death experiences. Furthermore, we show that the phenomenology and the effects of thanatosis and near-death experiences overlap."

Steven Laureys, neurologist and head of GIGA Consciousness research unit and Centre du Cerveau (ULiège, CHU Liège) is excited: "In this paper, we build a line of evidence suggesting that thanatosis is the evolutionary foundation of near-death experiences and that their shared biological purpose is the benefit of survival."

The authors propose that the acquisition of language enabled humans to transform these events from relatively stereotyped death-feigning under predatory attacks into the rich perceptions that form near-death experiences and extend to non-predatory situations.

"Of note, the proposed cerebral mechanisms behind death-feigning are not unlike those that have been suggested to induce near-death experiences, including intrusion of rapid eye movement sleep into wakefulness," Daniel Kondziella explains. "This further strengthens the idea that evolutionary mechanisms are an important piece of information needed to develop a complete biological framework for near-death experiences."

No previous work has tried to provide such a phylogenetic basis. Steven Laureys concludes, "this may also be the first time we can assign a biological purpose to near-death experiences, which would be the benefit of survival."

And Daniel Kondziella adds, "after all, near-death experiences are by definition events that are always survived, without exception."

THE METHOD OF SCIENCE THE AIM OF RELIGION

Researchers identify brain circuit for spirituality

Using datasets from neurosurgical patients and those with brain lesions, investigators mapped lesion locations associated with spiritual and religious belief to a specific human brain circuit

BRIGHAM AND WOMEN'S HOSPITAL

Research News

More than 80 percent of people around the world consider themselves to be religious or spiritual. But research on the neuroscience of spirituality and religiosity has been sparse. Previous studies have used functional neuroimaging, in which an individual undergoes a brain scan while performing a task to see what areas of the brain light up. But these correlative studies have given a spotty and often inconsistent picture of spirituality. A new study led by investigators at Brigham and Women's Hospital takes a new approach to mapping spirituality and religiosity and finds that spiritual acceptance can be localized to a specific brain circuit. This brain circuit is centered in the periaqueductal gray (PAG), a brainstem region that has been implicated in numerous functions, including fear conditioning, pain modulation, altruistic behaviors and unconditional love. The team's findings are published in Biological Psychiatry.

"Our results suggest that spirituality and religiosity are rooted in fundamental, neurobiological dynamics and deeply woven into our neuro-fabric," said corresponding author Michael Ferguson, PhD, a principal investigator in the Brigham's Center for Brain Circuit Therapeutics. "We were astonished to find that this brain circuit for spirituality is centered in one of the most evolutionarily preserved structures in the brain."

To conduct their study, Ferguson and colleagues used a technique called lesion network mapping that allows investigators to map complex human behaviors to specific brain circuits based on the locations of brain lesions in patients. The team leveraged a previously published dataset that included 88 neurosurgical patients who were undergoing surgery to remove a brain tumor. Lesion locations were distributed throughout the brain. Patients completed a survey that included questions about spiritual acceptance before and after surgery. The team validated their results using a second dataset made up of more than 100 patients with lesions caused by penetrating head trauma from combat during the Vietnam War. These participants also completed questionnaires that included questions about religiosity (such as, "Do you consider yourself a religious person? Yes or No?").

Of the 88 neurosurgical patients, 30 showed a decrease in self-reported spiritual belief before and after neurosurgical brain tumor resection, 29 showed an increase, and 29 showed no change. Using lesion network mapping, the team found that self-reported spirituality mapped to a specific brain circuit centered on the PAG. The circuit included positive nodes and negative nodes -- lesions that disrupted these respective nodes either decreased or increased self-reported spiritual beliefs. Results on religiosity from the second dataset aligned with these findings. In addition, in a review of the literature, the researchers found several case reports of patients who became hyper-religious after experiencing brain lesions that affected the negative nodes of the circuit.

Lesion locations associated with other neurological and psychiatric symptoms also intersected with the spirituality circuit. Specifically, lesions causing parkinsonism intersected positive areas of the circuit, as did lesions associated with decreased spirituality. Lesions causing delusions and alien limb syndrome intersected with negative regions, associated with increased spirituality and religiosity.

"It's important to note that these overlaps may be helpful for understanding shared features and associations, but these results should not be over-interpreted," said Ferguson. "For example, our results do not imply that religion is a delusion, that historical religious figures suffered from alien limb syndrome, or that Parkinson's disease arises due to a lack of religious faith. Instead, our results point to the deep roots of spiritual beliefs in a part of our brain that's been implicated in many important functions."

The authors note that the datasets they used do not provide rich information about the patient's upbringing, which can have an influence over spiritual beliefs, and that patients in both datasets were from predominantly Christian cultures. To understand the generalizability of their results, they would need to replicate their study across many backgrounds. The team is also interested in untangling religiosity and spirituality to understand brain circuits that may be driving differences. Additionally, Ferguson would like to pursue clinical and translational applications for the findings, including understanding the role that spirituality and compassion may have in clinical treatment.

"Only recently have medicine and spirituality been fractionated from one another. There seems to be this perennial union between healing and spirituality across cultures and civilizations," said Ferguson. "I'm interested in the degree to which our understanding of brain circuits could help craft scientifically grounded, clinically-translatable questions about how healing and spirituality can co-inform each other."

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Funding for this work was provided by an NIH Ruth L. Kirschstein National Research Service Award (NRSA) Institutional Research Training Grant (T32MH112510), the Shields Research Grant from the Child Neurology Foundation, the Sidney R. Baer, Jr. Foundation, the Nancy Lurie Marks Foundation, the Mather's Foundation, the Kaye Family Research Endowment, and the National Institutes of Health (grants R01 MH113929, R01 MH115949, and R01 AG060987).

Paper cited: Ferguson, M et al. "neural circuit for spirituality and religiosity derived from patients with brain lesions" Biological Psychiatry DOI: 10.1016/j.biopsych.2021.06.016

Novel technique decodes mechanisms controlling executive functions of the primate brain

Researchers devise a new technique to identify specific neural pathways involved in executive functions of the brain

THE NATIONAL INSTITUTES FOR QUANTUM AND RADIOLOGICAL SCIENCE AND TECHNOLOGY

Research News

IMAGE: IMAGE-GUIDED CHEMOGENETIC SYNAPTIC SILENCING CAN BE USED TO STUDY COGNITIVE FUNCTIONS. view more
CREDIT: NATIONAL INSTITUTES FOR QUANTUM AND RADIOLOGICAL SCIENCE AND TECHNOLOGY

The human brain is a wonderfully enigmatic organ, helping to juggle multiple tasks efficiently to help us get through a long day! This feature, called executive function, seats primates like us at the pinnacle of evolution. The prospect of losing the spectacular flow of neural information in our brains because of an accident or disease is, thus, unnerving. In the event of such an unfortunate occurrence, to restore the brain to its previous working condition with full functionality--to reboot it, so to speak--would need a better understanding of the specific neural pathways involved in our daily activities that rely on working memory and decision-making--two important executive functions.

To achieve this objective, a group of researchers from National Institutes for Quantum and Radiological Science and Technology (QST), Japan, were hard at work at devising a technique they call "imaging-guided chemogenetic synaptic silencing" to decipher the specific neural pathways involved in high-order executive functions. In a pioneering study published in Science Advances, the researchers now report successfully delineating specific neural pathways involved in working memory and decision-making using this technique.

The group, led by eminent researcher Dr. Takafumi Minamimoto from the Department of Functional Brain Imaging, QST, focused on studying the dorsolateral part of the prefrontal cortex (dlPFC) in the monkey brain, to apply their novel technique, and further identify the neural pathways of interest. It is interesting to note this choice, not only because it is the brain region partially responsible for controlling executive functions, but also since this specialized region is only present in primates.

Importantly, the role of dlPFC is supported by brain regions like the dorsal caudate (dCD) and lateral mediodorsal thalamus (MDl) too. This intricate association is further explained by Dr. Kei Oyama, who is the first author of the study, as follows, "The primate prefrontal cortex (PFC), especially its dorsolateral part (dlPFC), is well known to serve as the center of higher-order executive functions; it is uniquely developed in primates and underlies their distinctive cognitive abilities. These functions, however, do not solely rely on dlPFC neurons but also on their cooperative interactions with subcortical structures, including the dorsal caudate (dCD) nucleus and lateral mediodorsal thalamus (MDl)."

Next, the researchers wanted to understand the who-does-what for working memory and decision-making. Given that the dlPFC, MDI, and dCD neurons are connected, they selectively silenced specific neuronal synapses to disrupt the flow of information, and achieve just dlPFC-dCD and dlPFC-MDl projections, either unilaterally (involving just one side of the brain), or bilaterally (involving both sides). To achieve this, they made the dlPFC neurons express designer receptors exclusively activated by designer drugs (DREADDs). Further, the monkeys involved in the study were analyzed for behavioral changes, to understand the effect of chemogenetic silencing.

Interestingly, the researchers observed that silencing the bilateral dlPFC-MDl projections in the monkeys, but not their dlPFC-dCD projections, caused problems in the working memory related to their surroundings. On the contrary, silencing their unilateral dlPFC-dCD projections, but not their unilateral dlPFC-MDl projections, altered their preference in decision-making. These results reveal that the two higher-brain functions, working memory and decision-making, which are essential for our daily lives, are controlled by different neural pathways linking specific brain areas.

Overall, this study lays the foundation for further explorations of the intricacies of the complex primate brain. In this regard, Dr. Oyama explains the potential clinical and research applications of these findings, "Many psychiatric disorders, including depression, are thought to be associated with disturbances in the transmission of neural information through neural circuits between specific brain regions. Our findings are expected to deepen our understanding of mental disorders and lead to the discovery of treatments and remedies. The successful development of a novel technique in our study will serve as a key technology for the next-generation of researchers to investigate primate brain functions, which will contribute to broad areas in life by dramatically deepening our understanding of the mechanism of higher-brain functions."

The world will indeed wait with bated breath for future mysteries to unravel as explorations take researchers deeper into the labyrinthine maze that is the mind.

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Research Article:
"Chemogenetic dissection of the primate prefronto-subcortical pathways for working memory and decision-making"
Kei Oyama, Yukiko Hori, Yuji Nagai, Naohisa Miyakawa, Koki Mimura, Toshiyuki Hirabayashi, Ken-ichi Inoue, Tetsuya Suhara, Masahiko Takada, Makoto Higuchi and Takafumi Minamimoto
Science Advances: June 23, 2021, DOI: https://doi.org/10.1126/sciadv.abg4246

About National Institutes for Quantum and Radiological Science and Technology:

The National Institutes for Quantum and Radiological Science and Technology (QST) was established in April 2016 to promote quantum science and technology in a comprehensive and integrated manner. QST's mission is to raise the level of quantum and radiological sciences and technologies through its commitment to research and development into quantum science and technology, the effect of radiation on humans, radiation emergency medicine, and the medical use of radiation. To ensure that research and development delivers significant academic, social and economic impacts, and to maximize benefits from global innovation, QST is striving to establish world-leading research and development platforms and explore new fields.

Website: https://www.qst.go.jp/site/qst-english/

About Dr. Kei Oyama from National Institutes for Quantum and Radiological Science and Technology, Japan:

Dr. Kei Oyama is a reputed researcher at the Department of Functional Brain Imaging. Specifically, Dr. Oyama is an active member of the Neural Systems and Circuits Research Group. He is an expert in different facets of behavioral and cognitive neuroscience, like learning and memory, behavior analyses, neuropharmacology, electrophysiology etc. His expertise is bolstered by around 20 publications in these fields, in reputed journals.

Funding information:

This study was funded by MEXT/JSPS KAKENHI grant numbers JP18K15353 and JP21K07268, JP17H02219, JP19H05467, JP15H05917 and JP18H04037, JP18H05018, and JP19K07811; QST President's Strategic Grant (Creative Research); AMED grant numbers JP20dm0307007, JP20dm0307021, JP18dm0207003, and JP20dm0107146; JST PRESTO grant number JPMJPR1683; cooperative research program at PRI, Kyoto University; and National Bio-Resource Project "Japanese Monkeys" of MEXT, Japan

Last ice-covered parts of summertime Arctic Ocean vulnerable to climate change

UNIVERSITY OF WASHINGTON

Research News

IMAGE: THE STUDY LOOKED AT THE WANDEL SEA NORTH OF GREENLAND, WHICH IS INSIDE WHAT'S KNOWN AS THE "LAST ICE AREA " OF THE ARCTIC OCEAN. view more
CREDIT: SCHWEIGER ET AL./COMMUNICATIONS EARTH & ENVIRONMENT

In a rapidly changing Arctic, one area might serve as a refuge - a place that could continue to harbor ice-dependent species when conditions in nearby areas become inhospitable. This region north of Greenland and the islands of the Canadian Arctic Archipelago has been termed the Last Ice Area. But research led by the University of Washington suggests that parts of this area are already showing a decline in summer sea ice.

Last August, sea ice north of Greenland showed its vulnerability to the long-term effects of climate change, according to a study published July 1 in the open-access journal Communications Earth & Environment.

"Current thinking is that this area may be the last refuge for ice-dependent species. So if, as our study shows, it may be more vulnerable to climate change than people have been assuming, that's important," said lead author Axel Schweiger, a polar scientist at the UW Applied Physics Laboratory.

How the last ice-covered regions will fare matters for polar bears that use the ice to hunt for seals that use the ice for building dens for their young, and for walruses that use the ice as a platform for foraging.

"This area has long been expected to be the primary refuge for ice-dependent species because it is one of the last places where we expect summer sea ice to survive in the Arctic," said co-author Kristin Laidre, a principal scientist at the UW Applied Physics Laboratory.

The study focused on sea ice in August 2020 in the Wandel Sea, an area that used to be covered year-round in thick, multi-year ice.

"Sea ice circulates through the Arctic, it has a particular pattern, and it naturally ends up piling up against Greenland and the northern Canadian coast," Schweiger said. "In climate models, when you spin them forward over the coming century, that area has the tendency to have ice survive in the summer the longest."

Like other parts of the Arctic Ocean, the ice here has been gradually thinning, though last spring's sea ice in the Wandel Sea was on average slightly thicker than previous years. But satellite images showed a record low of just 50% sea ice concentration on Aug. 14, 2020.

The new study uses satellite data and sea ice models to determine what caused last summer's record low. It finds that about 80% was due to weather-related factors, like winds that break up and move the ice around. The other 20%, or one-fifth, was from the longer-term thinning of the sea ice due to global warming.

The model simulated the period from June 1 to Aug. 16 and found that unusual winds moved sea ice out of the area, but that the multiyear thinning trend also contributed, by allowing more sunlight to warm the ocean. Then, when winds picked up, this warm water was able to melt the nearby ice floes.

The record-low ice concentration in 2020 was surprising because the average ice thickness at the beginning of summer was actually close to normal.

"During the winter and spring of 2020 you had patches of older, thicker ice that had drifted into there, but there was enough thinner, newer ice that melted to expose open ocean," Schweiger said. "That began a cycle of absorbing heat energy to melt more ice, in spite of the fact that there was some thick ice. So in years where you replenish the ice cover in this region with older and thicker ice, that doesn't seem to help as much as you might expect."

The results raise concerns about the Last Ice Area but can't immediately be applied to the entire region, Schweiger said. Also unknown is how more open water in this region would affect ice-dependent species over the short and long terms.

"We know very little about marine mammals in the Last Ice Area," said Laidre, who is also an associate professor in the School of Aquatic and Fishery Sciences. "We have almost no historical or present-day data, and the reality is that there are a lot more questions than answers about the future of these populations."

CAPTION

This photo of sea ice on the Wandel Sea north of Greenland was taken Aug. 16, 2020, from the German icebreaker Polarstern, which passed through the area as part of the year-long MOSAiC Expedition. This area used to remain fully covered in ice throughout the year. Satellite images show that Aug. 14, 2020, was a record low sea ice concentration for this region, at 50%.

CREDIT

Felix Linhardt/Kiel University

Other co-authors are Michael Steele and Jinlun Zhang at the UW; and Kent Moore at the University of Toronto. The research was funded by the U.S. National Science Foundation, NASA, the Natural Sciences and Engineering Research Council of Canada; the National Oceanic and Atmospheric Administration; the Office of Naval Research; and the World Wildlife Fund Canada.

CAPTION

A polar bear is perched on a thick chunk of sea ice north of Greenland in March 2016. These thicker, older pieces of sea ice don't fully protect the larger region from losing its summer ice cover.

CREDIT

Kristin Laidre/University of Washington

Fecal records show Maya population affected by climate change

Findings suggest that Maya settlement in city of Itzan started earlier and lasted longer than previously known

MCGILL UNIVERSITY

Research News

IMAGE: FECAL RECORDS FROM LAKE SEDIMENT SHOW THAT MAYA LIVED IN THE AREA FOR LONGER THAN PREVIOUSLY BELIEVED. view more
CREDIT: ANDY BRECKENRIDGE

A McGill-led study has shown that the size of the Maya population in the lowland city of Itzan (in present-day Guatemala) varied over time in response to climate change. The findings, published recently in Quaternary Science Reviews, show that both droughts and very wet periods led to important population declines.

These results are based on using a relatively new technique involving looking at stanols (organic molecules found in human and animal faecal matter) taken from the bottom of a nearby lake. Measurements of stanols were used to estimate changes in population size and to examine how they align with information about climate variability and changes in vegetation drawn from other biological and archaeological sources.

By using the technique, the researchers were able to chart major Maya population changes in the area over a period starting 3,300 years before the present (BP). They were also able to identify shifts in settlement patterns that took place over the course of hundreds of years that are associated with changes in land use and agricultural practices.

They discovered, moreover, that the land had been settled earlier than previously suggested by archaeological evidence.

New tool provides surprising information about human presence in Maya lowlands

The evidence from faecal stanols suggests that humans were present on the Itzan escarpment about 650 years before the archaeological evidence confirms it. It also shows that that the Maya continued to occupy the area, albeit in smaller number, after the so-called "collapse" between 800-1000 AD, when it had previously been believed that drought or warfare caused the entire population to desert the area. There is further evidence of a large population spike around the same time as a historical record of refugees fleeing the Spanish attack of 1697 AD on the last Maya stronghold in the southern Maya lowlands (Nojpeten, or modern-day Flores in Guatemala) - something that had not been known before.

Estimates of ancient population size in the Maya lowlands have traditionally been obtained through ground inspection and excavation. To reconstruct population dynamics, archaeologists locate, map, and count residential structures, and they excavate them to establish dates of occupation. They compare population trends at the site and regional levels. And they then use techniques such as pollen analysis and indicators of soil erosion into lakes to reconstruct the ecological changes that took place at the same time.

"This research should help archaeologists by providing a new tool to look at changes that might not be seen in the archaeological evidence, because the evidence may never have existed or may have since been lost or destroyed," said Benjamin Keenan, a PhD candidate in the Department of Earth and Planetary Sciences at McGill, and the first author on the paper. "The Maya lowlands are not very good for preserving buildings and other records of human life because of the tropical forest environment."

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Diagram showing how fecal stanol molecules are transported from human intestines to lake sediments, where they are then recovered in sediment cores.

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Benjamin Keenan et al.

Maya population size affected by both droughts and wet periods

The faecal stanol from the sediment in Laguna Itzan confirms that the Maya population in the area declined due to drought at three different periods; between 90-280 AD, between 730-900 AD and during the much less well studied drought between 1350-950 BC. The researchers also found that the population declined during a very wet period from 400--210 BC, something which has received little attention until now. The population decline in response to both dry and wet periods shows that there were climatic effects on population at both climate extremes, and not only during dry periods.

"It is important for society generally to know that there were civilisations before us that were affected by and adapted to climate change," said Peter Douglas, an assistant professor in the Department of Earth and Planetary Sciences and the senior author on the paper. "By linking evidence for climate and population change we can begin to see a clear link between precipitation and the ability of these ancient cities to sustain their population."

The research also suggests that the Maya people may have adapted to environmental issues such as soil degradation and nutrient loss by using techniques such as the application of human waste (also known as night soil) as a fertiliser for crops. This is suggested by a relatively low amount of fecal stanols in the lake sediment at a time when there is archaeological evidence for the highest human populations. One explanation for this is that human waste was applied to soils as fertilizer and therefore the stanols were not washed into the lake.

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Benjamin Keenan, the lead researcher, collecting a lake sediment core on Lake Izabal, the largest lake in Guatemala.

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Elisandra Hernández

About this study

"Molecular evidence for human population change associated with climate events in the Maya lowlands" by Benjamin Keenan et al. was published in Quaternary Science Reviews. The research was funded by the Eric Mountjoy Fellowship, McGill startup funds, and an NSERC Discovery Grant.

DOI: https://doi.org/10.1016/j.quascirev.2021.106904

About McGill University

Founded in Montreal, Quebec, in 1821, McGill University is Canada's top ranked medical doctoral university. McGill is consistently ranked as one of the top universities, both nationally and internationally. It?is a world-renowned?institution of higher learning with research activities spanning two campuses, 11 faculties, 13 professional schools, 300 programs of study and over 40,000 students, including more than 10,200 graduate students. McGill attracts students from over 150 countries around the world, its 12,800 international students making up 31% of the student body. Over half of McGill students claim a first language other than English, including approximately 19% of our students who say French is their mother tongue.

https://www.mcgill.ca/newsroom/

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