Sunday, December 04, 2022

Findings from 3,000-year-old Uluburun shipwreck reveal complex trade network

Findings offer glimpse into life 3,000-plus years ago

Peer-Reviewed Publication

WASHINGTON UNIVERSITY IN ST. LOUIS

Map of Eurasia during Late Bronze Age 

IMAGE: TIN FROM THE MUŠISTON MINE IN CENTRAL ASIA’S UZBEKISTAN TRAVELED MORE THAN 2,000 MILES TO HAIFA, WHERE THE ILL-FATED SHIP LOADED ITS CARGO BEFORE CRASHING OFF THE EASTERN SHORES OF ULUBURUN IN PRESENT-DAY TURKEY. view more 

CREDIT: MAP PROVIDED BY MICHAEL FRACHETTI/WASHINGTON UNIVERSITY IN ST. LOUIS

More than 3,000 years before the Titanic sunk in the North Atlantic Ocean, another famous ship wrecked in the Mediterranean Sea off the eastern shores of Uluburun — in present-day Turkey —  carrying tons of rare metal. Since its discovery in 1982, scientists have been studying the contents of the Uluburun shipwreck to gain a better understanding of the people and political organizations that dominated the time period known as the Late Bronze Age.

Now, a team of scientists, including Michael Frachetti, professor of archaeology in Arts & Sciences at Washington University in St. Louis, have uncovered a surprising finding: small communities of highland pastoralists living in present-day Uzbekistan in Central Asia produced and supplied roughly one-third of the tin found aboard the ship — tin that was en route to markets around the Mediterranean to be made into coveted bronze metal.  

The research, published on November 30 in Science Advances, was made possible by advances in geochemical analyses that enabled researchers to determine with high-level certainty that some of the tin originated from a prehistoric mine in Uzbekistan, more than 2,000 miles from Haifa, where the ill-fated ship loaded its cargo.  

But how could that be? During this period, the mining regions of Central Asia were occupied by small communities of highlander pastoralists — far from a major industrial center or empire. And the terrain between the two locations — which passes through Iran and Mesopotamia — was rugged, which would have made it extremely difficult to pass tons of heavy metal.

Frachetti and other archaeologists and historians were enlisted to help put the puzzle pieces together. Their findings unveiled a shockingly complex supply chain that involved multiple steps to get the tin from the small mining community to the Mediterranean marketplace.  

“It appears these local miners had access to vast international networks and — through overland trade and other forms of connectivity — were able to pass this all-important commodity all the way to the Mediterranean,” Frachetti said.

“It’s quite amazing to learn that a culturally diverse, multiregional and multivector system of trade underpinned Eurasian tin exchange during the Late Bronze Age.”

“To put it into perspective, this would be the trade equivalent of the entire United States sourcing its energy needs from small backyard oil rigs in central Kansas.”

Michael Frachetti

Adding to the mystique is the fact that the mining industry appears to have been run by small-scale local communities or free laborers who negotiated this marketplace outside of the control of kings, emperors or other political organizations, Frachetti said.

“To put it into perspective, this would be the trade equivalent of the entire United States sourcing its energy needs from small backyard oil rigs in central Kansas,” he said.

Uluburun excavation images showing copper oxhide ingots.

CREDIT

Cemal Pulak/Texas A&M University

About the research

The idea of using tin isotopes to determine where metal in archaeological artifacts originates dates to the mid-1990s, according to Wayne Powell, professor of earth and environmental sciences at Brooklyn College and a lead author on the study. However, the technologies and methods for analysis were not precise enough to provide clear answers. Only in the last few years have scientists begun using tin isotopes to directly correlate mining sites to assemblages of metal artifacts, he said.

“Over the past couple of decades, scientists have collected information about the isotopic composition of tin ore deposits around the world, their ranges and overlaps, and the natural mechanisms by which isotopic compositions were imparted to cassiterite when it formed,” Powell said. “We remain in the early stages of such study. I expect that in future years, this ore deposit database will become quite robust, like that of Pb isotopes today, and the method will be used routinely.”

Aslihan K. Yener, a research affiliate at the Institute for the Study of the Ancient World at New York University and a professor emerita of archaeology at the University of Chicago, was one of the early researchers who conducted lead isotope analyses. In the 1990s, Yener was part of a research team that conducted the first lead isotope analysis of the Uluburun tin. That analysis suggested that the Uluburun tin may have come from two sources — the Kestel Mine in Turkey’s Taurus Mountains and some unspecified location in central Asia.

“But this was shrugged off since the analysis was measuring trace lead and not targeting the origin of the tin,” said Yener, who is a co-author of the present study.

Yener also was the first to discover tin in Turkey in the 1980s. At the time, she said the entire scholarly community was surprised that it existed there, right under their noses, where the earliest tin bronzes occurred.

Some 30 years later, researchers finally have a more definitive answer thanks to the advanced tin isotope analysis techniques: One-third of the tin aboard the Uluburun shipwreck was sourced from the Mušiston mine in Uzbekistan. The remaining two-thirds of the tin derived from the Kestel mine in ancient Anatolia, which is in present-day Turkey.

Findings offer glimpse into life 2,000-plus years ago

By 1500 B.C., bronze was the “high technology” of Eurasia, used for everything from weaponry to luxury items, tools and utensils. Bronze is primarily made from copper and tin. While copper is fairly common and can be found throughout Eurasia, tin is much rarer and only found in specific kinds of geological deposits, Frachetti said.

“Finding tin was a big problem for prehistoric states. And thus, the big question was how these major Bronze Age empires were fueling their vast demand for bronze given the lengths and pains to acquire tin as such a rare commodity. Researchers have tried to explain this for decades,” Frachetti said.

The Uluburun ship yielded the world’s largest Bronze Age collection of raw metals ever found — enough copper and tin to produce 11 metric tons of bronze of the highest quality. Had it not been lost to sea, that metal would have been enough to outfit a force of almost 5,000 Bronze Age soldiers with swords, “not to mention a lot of wine jugs,” Frachetti said.

“The current findings illustrate a sophisticated international trade operation that included regional operatives and socially diverse participants who produced and traded essential hard-earth commodities throughout the late Bronze Age political economy from Central Asia to the Mediterranean,” Frachetti said.  

Unlike the mines in Uzbekistan, which were set within a network of small-scale villages and mobile pastoralists, the mines in ancient Anatolia during the Late Bronze Age were under the control of the Hittites, an imperial global power of great threat to Ramses the Great of Egypt, Yener explained.

The findings also show that life 2,000-plus years ago was not that different from what it is today.

“With the disruptions due to COVID-19 and the war in Ukraine, we have become aware of how we are reliant on complex supply chains to maintain our economy, military and standard of living,” Powell said. “This is true in prehistory as well. Kingdoms rose and fell, climatic conditions shifted and new peoples migrated across Eurasia, potentially disrupting or redistributing access to tin, which was essential for both weapons and agricultural tools.

“Using tin isotopes, we can look across each of these archaeologically evident disruptions in society and see connections were severed, maintained or redefined. We already have DNA analysis to show relational connections. Pottery, funerary practices, etc., illustrate the transmission and connectivity of ideas. Now with tin isotopes, we can document the connectivity of long-distance trade networks and their sustainability.”

Uluburun excavation i

CREDIT

Cemal Pulak/Texas A&M University


More clues to explore

The current research findings settle decades-old debates about the origins of the metal on the Uluburun shipwreck and Eurasian tin exchange during the Late Bronze Age. But there are still more clues to explore.

After they were mined, the metals were processed for shipping and ultimately melted into standardized shapes — known as ingots — for transporting. The distinct shapes of the ingots served as calling cards for traders to know from where they originated, Frachetti said.

Many of the ingots aboard the Uluburun ship were in the “oxhide” shape, which was previously believed to have originated in Cyprus. However, the current findings suggest the oxhide shape could have originated farther east. Frachetti said he and other researchers plan to continue studying the unique shapes of the ingots and how they were used in trade.


In addition to Frachetti, Powell and Yener, the following researchers contributed to the present study: Cemal Pulakat at Texas A&M University, H. Arthur Bankoff at Brooklyn College, Gojko Barjamovic at Harvard University, Michael Johnson at Stell Environmental Enterprises, Ryan Mathur at Juniata College, Vincent C. Pigott at the University of Pennsylvania Museum and Michael Price at the Santa Fe Institute.

The study was funded in part by a Professional Staff Congress-City University of New York Research Award, in addition to a research grant from the Institute for Aegean Prehistory.

Researchers find positive legacy effects after grassland droughts

Peer-Reviewed Publication

CHINESE ACADEMY OF SCIENCES HEADQUARTERS

Conceptual framework showing how drought-induced community structure change and subsequent-year precipitation pattern interactively drive a positive legacy effect 

IMAGE: CONCEPTUAL FRAMEWORK SHOWING HOW DROUGHT-INDUCED COMMUNITY STRUCTURE CHANGE AND SUBSEQUENT-YEAR PRECIPITATION PATTERN INTERACTIVELY DRIVE A POSITIVE LEGACY EFFECT view more 

CREDIT: PAN QINGMIN

Global change-induced extreme droughts are increasing in grasslands worldwide. Severe droughts not only reduce current-year grassland productivity substantially, but also have a legacy effect on productivity in subsequent years. Such drought legacies can greatly affect the response of grassland ecosystems to climate change. In general, severe droughts tend to have a negative legacy effect on grassland productivity due to losses of meristematic tissues or plant mortality.  

However, combining a four-year precipitation manipulation experiment with a 40-year observational study in the Inner Mongolia grassland, researchers from the Institute of Botany of the Chinese Academy of Sciences (CAS) found that previous-year extreme droughts could create strong positive legacies for current-year community productivity when drought treatments were stopped.  

This result was quite different from previous findings that drought years usually had negative legacy effects on community productivity.

In this study, the researchers led by Prof. PAN Qingmin and Prof. HAN Xingguo discovered that the mechanism driving positive drought legacies was the coupled effect of a drought-induced increase in annuals in the previous year and an "early less, middle more" precipitation pattern that facilitated the flourishing of annuals in the current year.  

If such a pattern continues for several years, so will the positive legacy effect.  

In view of this, the researchers provided experimental and observational evidence that extreme drought-induced change in community structure in the previous year, as indicated by an increase in the annuals/perennials ratio, coupled with a favorable precipitation pattern for the flourishing of annuals in subsequent years, could have strong positive legacy effects on community productivity.  

In this study, positive legacy effects on grassland productivity were found in more than one-third of the past 40 years. Since global climate models predict more frequent drought extremes in grasslands worldwide, these findings may have implications for understanding the impact of extreme drought on ecosystem functioning and services in grasslands.  

Considering that annuals are becoming more abundant in a large number of grazing grasslands worldwide, drought-induced positive legacies in these systems are expected to be more evident. Thus, models forecasting ecosystem feedbacks in response to climate change should consider positive drought legacies in grasslands.  

This work was supported by National Natural Science Foundation of China and the Strategic Priority Research Program of CAS.

Catch a break: Higher vitamin K intake linked to lower bone fracture risk late in life

A long term study looking at the relationship between fracture-related hospitalisations and diet in almost 1400 older women has found vitamin K1 reduced risk of hospitalization significantly.

Peer-Reviewed Publication

EDITH COWAN UNIVERSITY

Dr Marc Sim. 

IMAGE: DR MARC SIM. view more 

CREDIT: EDITH COWAN UNIVERSITY.

Breaking bones can be life changing events — especially as we age, when hip fractures can become particularly damaging and result in disability, compromised independence and a higher mortality risk.

But research from Edith Cowan University’s Nutrition and Health Innovation Research Institute has revealed there may be something you can do to help reduce your risk of fractures later in life.

In collaboration with the University of Western Australia, the study looked at the relationship between fracture-related hospitalisations and vitamin K1 intake in almost 1400 older Australian women over a 14.5-year period from the Perth Longitudinal Study of Aging Women.

It found women who ate more than 100 micrograms of vitamin K1 consumption — equivalent to about 125g of dark leafy vegetables, or one-to-two serves of vegetables — were 31 per cent less likely to have any fracture compared to participants who consumed less than 60 micrograms per day, which is the current vitamin K adequate intake guideline in Australia for women.

There were even more positive results regarding hip fractures, with those who ate the most vitamin K1 cutting their risk of hospitalisation almost in half (49 per cent).

Study lead Dr Marc Sim said the results were further evidence of the benefits of vitamin K1, which has also been shown to enhance cardiovascular health.

“Our results are independent of many established factors for fracture rates, including body mass index, calcium intake, Vitamin D status and prevalent disease,” he said.

“Basic studies of vitamin K1 have identified a critical role in the carboxylation of the vitamin K1-dependant bone proteins such as osteocalcin, which is believed to improve bone toughness.

“A previous ECU trial indicates dietary vitamin K1 intakes of less than 100 micrograms per day may be too low for this carboxylation.

“Vitamin K1 may also promote bone health by inhibiting various bone resorbing agents.”

So, what should we eat — and how much?

Dr Sim said eating more than 100 micrograms of vitamin K1 daily was ideal — and, happily, it isn’t too difficult to do.

“Consuming this much daily vitamin K1 can easily be achieved by consuming between 75-150g, equivalent to one to two serves, of vegetables such as spinach, kale, broccoli and cabbage,” he said.

“It’s another reason to follow public health guidelines, which advocate higher vegetable intake including one to two serves of green leafy vegetables — which is in-line with our study’s recommendations.”

Vitamin K1-rich foods

Vegetables: Kale, spinach, broccoli, green beans

Fruits: Prunes, kiwi, avocado

‘Dietary Vitamin K1 intake is associated with lower long-term fracture-related hospitalization risk: the Perth longitudinal study of ageing women’ was published in Food & Function.

Monkeypox vaccine modelling study provides road map for vaccination

Peer-Reviewed Publication

CANADIAN MEDICAL ASSOCIATION JOURNAL

A modelling study to explore optimal allocation of vaccines against monkeypox virus (MPXV) provides a road map for public health to maximize the impact of a limited supply of vaccines. The article, published in CMAJ (Canadian Medical Association Journal) https://www.cmaj.ca/lookup/doi/10.1503/cmaj.221232, confirms that prioritizing vaccines to larger networks with more initial infections and greater potential for spread is best.

"We hope that these insights can be applied by policy-makers across diverse and dynamic epidemic contexts across Canada and beyond to maximize infections averted early in an epidemic with limited vaccine supply," says Dr. Sharmistha Mishra, MAP Centre for Urban Health Solutions, Unity Health Toronto.

As of November 4, 2022, there were 1444 cases of MPXV in Canada, disproportionately among gay, bisexual and other men who have sex with men (GBMSM). A very limited supply of smallpox vaccines is available and is being prioritized to populations experiencing disproportionate risks.

Researchers modelled two hypothetical cities as interconnected networks with a combined GBMSM community size of 100 000. The team then varied the characteristics of the two cities across a range of plausible settings and simulated roll-out of 5000 vaccine doses shortly after the first detected case of MPXV.

They found that the strongest factors for optimal vaccine allocation between the cities were the relative reproduction number (epidemic potential) in each city, share of initial cases, and city (or network) size. If a larger city had greater epidemic potential and most of the initial cases, it was best to allocate the majority of vaccines to that city. The team varied the reproduction number with a single parameter, but they highlight how many factors could influence local epidemic potential, including the density and characteristics of the sexual network, access to prevention and care, and the underlying social and structural contexts that shape both sexual networks and access.

"Under our modelling assumptions, we found that vaccines could generally avert more infections when prioritized to a larger network, a network with more initial infections and a network with greater epidemic potential," writes Jesse Knight, lead author and PhD candidate at the University of Toronto and MAP Centre for Urban Health Solutions, Unity Health Toronto. "Our findings further highlight the importance of global vaccine equity in responding to outbreaks, and also in preventing them in the first place," he says.

The study emphasizes the interconnectedness of regions and that a population-level perspective is necessary.

"Strategic prioritization of a limited vaccine supply by network-level risk factors can maximize infections averted over short time horizons in the context of an emerging epidemic, such as the current global MPXV outbreak," conclude the authors.

Virtual overdose monitoring may help reduce opioid deaths

Peer-Reviewed Publication

CANADIAN MEDICAL ASSOCIATION JOURNAL

Virtual overdose monitoring has the potential to reduce the risk of death from opioids and other substances by offering timely and anonymous access to emergency care. An article reviewing the latest evidence is published in CMAJ (Canadian Medical Association Journal) https://www.cmaj.ca/lookup/doi/10.1503/cmaj.220579.

Isolation and solitary use of opioids and other substances are the main driver of overdose deaths, as people are unable to seek help. Virtual overdose monitoring using phone lines or smartphone apps can connect people anonymously with people who can develop personalized emergency response plans and supervise substance use. These services operate 24 hours a day and have no restrictions on the type of substances or how they are used.

"Virtual overdose monitoring services are novel public health interventions capable of providing timely and accessible harm reduction and overdose prevention services for people who use substances," writes Dr. Monty Ghosh, an internist and addiction specialist, Department of Medicine, University of Alberta, Edmonton, and the Cumming School of Medicine, University of Calgary, Calgary, Alberta, with coauthors. "Evidence, including pilot data from the National Overdose Response Service, suggests that virtual overdose monitoring services have promise as an adjunct to supervised consumption services in the continuum of care for people who use substances."

The authors call for more high-quality research to better understand potential benefits and risks of virtual overdose monitoring services.

People with depression are less likely to have children

Peer-Reviewed Publication

UNIVERSITY OF HELSINKI

Women are at their greatest risk for depression during their childbearing years, and according to a recent study published in the prestigious American Journal of Obstetrics and Gynecology, depression is indeed associated with a lower likelihood of having children among men and women.

Drawing on the unique Finnish register data, this study with over 1,4 million participants examined the associations between diagnosed depression and the likelihood of having children, the number of children, and the age at first birth for all men and women born in Finland between 1960 and 1980.

“One of the main results was that depression was associated with a lower likelihood of having children and a lower number of children among men and women. Depression was also linked to a slightly lower age at first birth”, says principal investigator Kateryna Golovina from the Helsinki Collegium for Advanced Studies.

Men with even mild depression have a lower likelihood of having children

Men diagnosed with depression had 33% lower odds of having a child compared to men without depression; women diagnosed with depression had 15% lower odds of having a child than women without depression.

An important observation was that the severity of depression was associated with a likelihood of having children: for men, even mild depression was related to a lower likelihood of having children, whereas for women the link was found only for severe depression.

Socioeconomic differences in the association between depression and the likelihood of having children

The study further examined whether there were any educational differences in the association between depression and the likelihood of having children.

“Among men and women with secondary and higher education, depression was related to a lower likelihood of having children and having fewer children. As for the participants with basic education, no associations were observed for men, whereas for women depression was related to a higher likelihood of having children” says Kateryna Golovina.

Early prevention and on-time treatment of depression are crucial

The findings have clinical implications, suggesting that depression is one of the factors contributing to the likelihood of having children, which is why early prevention and on-time treatment of depression are crucial. For example, timely screening for depression can be implemented by increasing the availability of mental health professionals or it can be done by obstetrician-gynecologists and women’s health providers. For men, the severity of depression should be considered, given that already milder depression may have more negative health and behavioral effects for them compared to women. 

“Overall, our results give another motivation to provide accessible mental health services to young people and implement low-threshold interventions and therapies”, states Professor Marko Elovainio from the Faculty of Medicine.

The study was conducted in collaboration between the University of Helsinki and the Finnish Institute for Health and Welfare. Funding was provided by the Helsinki Collegium for Advanced Studies, University of Helsinki, and the Academy of Finland.

Diamonds and X-rays open a new window into the Earth's inner core

Peer-Reviewed Publication

TOHOKU UNIVERSITY

Figure 1 

IMAGE: THE COMPRESSIONAL VELOCITY OF PURE IRON AT HIGH PRESSURE AS DETERMINED IN THE PRESENT WORK (BLUE SYMBOLS) COMPARED TO THE HIGHEST PREVIOUS DETERMINATION USING THESE METHODS (OPEN SYMBOL) AND TO THE KNOWN RELATION OF THE INNER CORE DETERMINED FROM SEISMIC OBSERVATIONS (DASHED RED LINE WITH STARS). view more 

CREDIT: DAIJO IKUTA

A collaborative research group has succeeded, for the first time, in measuring the speed of sound of pure iron under pressures similar to the Earth's inner core boundary.

It may be surprising, but we do not have much information about the center of the planet that we live on. One can dig down a few kilometers, and volcanoes and plate tectonics can bring up material from depths of a few hundred km, but what lies beneath, down to the center of the Earth, some 6000 km beneath our feet, is not well understood.

It is generally accepted that the core some 3000 km below us is mostly iron: a sea of liquid iron, the outer core, around an inner core of solid iron. The best information we have is from tracking the progress of seismic waves from earthquakes, as they propagate through the planet. This tells us the density and the speed of sound. But those values do not exactly agree with what people expect for pure iron; there needs to be something else present in the core. What that material is, and how much of it there may be, are active areas of investigation as they have implications for understanding the present properties of the Earth and the evolution of the solar system.

Many research teams try to recreate the conditions of the center of the Earth in their laboratories. But this is difficult, requiring keeping materials under extreme pressure, millions of atmospheres, and extreme temperatures, similar to the surface of the sun, all while doing sensitive measurements.

The collaboration between Tohoku University, the RIKEN SPring-8 Center, Ehime University and the Japan Synchrotron Radiation Research Institute succeeded, for the first time, in measuring the speed of sound of pure iron under pressures similar to the Earth's inner core boundary, 330 GPa (the pressure if one supported 33,000 metric tons on a 1mm×1mm area).

After years of work, the researchers were able to effectively combine diamond anvil cell technology - something used to generate high pressures but which requires considerable skill to achieve pressures comparable to the Earth's core - with an X-ray scattering technique known as inelastic X-ray scattering. This technique allows scientists to observe the atomic motions in materials using X-rays and is the only method for accurately measuring the sound velocity of metals under static compression in a diamond anvil cell. This was done at RIKEN's world-leading facility for inelastic X-ray scattering, the Quantum NanoDynamics Beamline at SPring-8 in Hyogo Prefecture.

The researchers showed that the sound velocity of the inner core determined from seismological studies is 4±2% slower in compressional velocity and 36±17% slower in shear velocity than that of metallic iron.

Combining the new result with previous work suggests the Earth's core may be enriched in silicon and sulfur consistent with the existing outer core model with oxygen, as the growth of the inner core may have created a secular enrichment of oxygen in the outer core.

Details of the group's research were published in the journal Nature Communications on November 25, 2022.

Comparison of density‒velocity relations of iron at inner core conditions with Preliminary reference Earth model (PREM). The vp difference (A) and the vs difference (B) in the inner core.

CREDIT

Daijo Ikuta

BL43LXU, the RIKEN Quantum NanoDynamics Beamline at the RIKEN SPring-8 Center.

CREDIT

Alfred Q. R. Baron

The diamond anvil cell used in this experiment. (A) Symmetric Diamond Anvil Cell, (B) Schematic diagram of a diamond anvil. The orange circle is the area corresponding to (C, D) (C) Image of the top of the (stepped beveled) diamond anvil designed for IXS measurement at ultrahigh pressure, (D) Cross-section of the diamond anvil corresponding to (C).

CREDIT

Daijo Ikuta

Understanding polar species’ behavior to reduce risk of extinction: HKU Scientists discovered the southward migration of Arctic Ocean species during the last glacial period for the first time

Peer-Reviewed Publication

THE UNIVERSITY OF HONG KONG

Arctic Ostracods 

IMAGE: AN IMAGE OF ARCTIC OSTRACODS PRODUCED BY SCANNING ELECTRON MICROSCOPE (SEM). view more 

CREDIT: DR HE WANG

In order to survive, a species must find the most favourable habitat to pass on its genes. Therefore, learning how species migrated with climate change is very important for protecting species from environmental threats.

In light of this, a research team led by Dr He WANG and Dr Moriaki YASUHARA from the School of Biological Sciences (SBS) and the Swire Institute of Marine Science (SWIMS) of The University of Hong Kong (HKU) studied the impact of East Asian winter monsoon (EAWM) along with their collaborators (note), identified two southward migration events of polar species Arctic ostracods in the Last Glacial Period and determined the ages of these two events for the first time. The results would help better understand Asian monsoon dynamics and their impacts on the marine ecosystem and polar species, thereby reducing the risk of species extinction. The study has recently been published on Geophysical Research Letters.

EAWM is a determining factor of wintertime weather and climate in East Asia, affecting crop and livestock productivity and socioeconomic activities over large areas of East Asian countries. The impacts of climatic conditions on marine ecosystems and the distribution of marine species are major concerns due to ongoing anthropogenic climate change; however, the impacts of EAWM variability on marine biota remain poorly known, which hinders the understanding of future climate change and its impact on polar species or cold water species.

The Yellow Sea is a great location to study the evolution of the EAWM, as it is sensitive to climate change, and its environment is strongly influenced by the EAWM. It also has been regarded as an ideal location to track changes in cold-adapted marine species (polar species), as it is located at the southern end of the distribution of Arctic circumpolar species. Furthermore, the abundance of fossil records in the area provides direct evidence of past climate impacts. Therefore, the research team selected eight spots from the Yellow Sea and the Sea of Japan to reconstruct the temporal and spatial changes of Arctic ostracods in the northwestern Pacific Ocean, which helps to better understand the biogeographic distribution of Arctic ostracods and their responses to climate change.

By using microfossil proxies in sediment cores from the northwestern Pacific Ocean to better understand the relationship between EAWM dynamics and marine biota, the research team identified two southward migration events of Arctic ostracods in the Last Glacial Period and determined the ages of these two events for the first time: 120 to 100 and 30 to 15 thousand years ago — intervals that are consistent with the periods of strengthened East Asian winter monsoon (EAWM) during the Last Glacial Period. Therefore, the team suggests that the stronger EAWM during these periods enhanced the formation of Yellow Sea Bottom Cold Water and/or lowered the winter temperatures of the Yellow Sea, allowing cold water species Arctic ostracods to inhabit more southern regions of the Yellow Sea.

Dr He Wang, the lead author of the study and the former Postdoctoral Fellow at SBS explains: ‘In order to understand the above topics, one of the challenges is that we need to find a good proxy. Fortunately, we find many well-preserved ostracod specimens from a new core in the Yellow Sea, including both Arctic species and Subtropical and temperate species. Ostracods have fully calcified, bivalved carapaces, and thus have been the most common fossil arthropods, which provide an excellent fossil record for detailed paleoecological reconstructions.’

"Understanding polar species’ behaviour is important because they are sensitive to climatic warming and cooling. Numerous evidence shows that species respond to ongoing human-induced warming by changing their latitudinal distribution. So, polar species distributions are getting narrower to poleward with warming compared to the wider ice-age distribution we showed in this study. These narrower habitats may result in a higher extinction risk of polar species in the near future," said Dr Moriaki Yasuhara.

The results help better understand Asian monsoon dynamics and their impact on marine ecosystems in the past, present, and future on this rapidly changing planet. Learning how these cold-adapted species (polar species) migrated with climate change is very important for protecting polar species from threats by the ongoing human-induced climate change.

The research paper can be accessed from:
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL100818

Note: Other contributors of HKU and collaborators: Dr Penghui ZHANG from Hohai University; Dr Huai-Hsuan M. HUANG from National Museum of Natural History, Smithsonian Institution; Dr Yuanyuan HONG and Miss Skye Yunshu TIAN from HKU SBS and SWIMS;Professor Jian LIU, Professor Jianwen CHEN and Professor Jie LIANG from China Geological Survey; Professor Yong Il. Lee from Seoul National University.

Image download and caption: https://www.scifac.hku.hk/press

For media enquiries, please contact Ms Casey To, External Relations Officer (tel: 3917 4948; email: caseyto@hku.hk / Ms Cindy Chan, Assistant Director of Communications of HKU, Faculty of Science (tel: 3917 5286; email: cindycst@hku.hk).