New study reveals devastating power and colossal extent of a giant underwater avalanche off the Moroccan coast

An international research team has mapped a giant underwater avalanche which took place nearly 60,000 years ago in the Agadir Canyon

Peer-Reviewed Publication

University of Liverpool

 

image: 

Overview map of North West African Margin showing the pathway of the event and its erosional marks on the seafloor 

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Credit: University of Liverpool

New research by the University of Liverpool has revealed how an underwater avalanche grew more than 100 times in size causing a huge trail of destruction as it travelled 2000km across the Atlantic Ocean seafloor off the North West coast of Africa.

In a study publishing in the journal Science Advances (and featured on the front cover), researchers provide an unprecedented insight into the scale, force and impact of one of nature’s mysterious phenomena, underwater avalanches.

Dr Chris Stevenson, a sedimentologist from the University of Liverpool’s School of Environmental Sciences, co-led the team that for the first time has mapped a giant underwater avalanche from head to toe, which took place nearly 60,000 years ago in the Agadir Canyon.

Their analysis reveals the event, which started as a small seafloor landslide about 1.5 km3 in volume, grew over 100 times in size picking up boulders, gravel, sand and mud as it travelled through one of the largest submarine canyons in the world before travelling a further 1600km across the Atlantic Sea floor.

The avalanche was so powerful that it eroded the entire 400 km length of the canyon and several hundred metres up the sides – about 4500 km2 in total - and was so strong it carried cobbles more than 130m up the side of the canyon.

Unlike a landslide or snow avalanche, underwater avalanches are impossible to see and extremely difficult to measure. However, they are the primary mechanism for moving material such as sediments, nutrients and pollutants across the surface of the earth and present a significant geohazard to the seafloor infrastructure such as internet cables.

The research team analysed more than 300 core samples from the area taken during research cruises over the last 40 years. This, alongside seismic and bathymetry data, enabled them to map out the giant avalanche.

Dr Stevenson said: “This is the first time anyone has managed to map out an entire individual underwater avalanche of this size and calculate its growth factor.”

“What is so interesting is how the event grew from a relatively small start into a huge and devastating submarine avalanche reaching heights of 200 meters as it moved at a speed of about 15 m/s ripping out the sea floor and tearing everything out in its way.

“To put it in perspective: that’s an avalanche the size of a skyscraper, moving at more than 40 mph from Liverpool to London, which digs out a trench 30 m deep and 15 km wide destroying everything in its path. Then it spreads across an area larger than the UK burying it under about a metre of sand and mud.”

Dr Christoph Bottner, a Marie-Curie research fellow at Aarhus University in Denmark, who co-led the team, said “We calculate the growth factor to be at least 100, which is much larger compared to snow avalanches or debris flows which only grow by about 4-8 times. We have also seen this extreme growth in smaller submarine avalanches measured elsewhere, so we think this might be a specific behaviour associated with underwater avalanches and is something we plan to investigate further.”

Professor Sebastian Krastel, head of Marine Geophysics at Kiel University and chief scientist aboard the cruises that mapped the canyon, added: “Our new insight fundamentally challenges how we view these events. Before this study, we thought that big avalanches only came from big slope failures. But now, we know that they can start small and grow into extremely powerful and extensive giant events.

"These findings are of enormous importance for how we try and assess their potential geohazard risk to seafloor infrastructure like internet cables that carry almost all global internet traffic, which are critical to all aspects of our modern societies.”

The most recent cruises mapping the Agadir Canyon were led by the Institute of Geosciences, Kiel University, Leibniz Institute for Baltic Sea Research and GEOMAR Helmholtz Centre for Ocean Research, Germany. A suite of archive core data was analysed from the British Ocean Sediment Core Repository at NOCS Southampton, which was collected aboard NERC ships over the past 40 years.

The paper ‘Extreme erosion and bulking in a giant submarine gravity low’ is published in the journal Science Advances (doi: 10.1126/sciadv.adp2584).

 

3D image of giant underwater avalanche which took place nearly 60,000 years ago in the Agadir Canyon

Credit

Dr. Christoph Bottner, Aarhus University

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Journal

Science Advances

DOI

10.1126/sciadv.adp2584 

Article Title

Extreme erosion and bulking in a giant submarine gravity low

Article Publication Date

21-Aug-2024

 

To kill mammoths in the Ice Age, people used planted pikes, not throwing spears, researchers say

UC Berkeley archeologists say the findings might help resolve the debate about Clovis points and reshape how we think about what life was like roughly 13,000 years ago

Peer-Reviewed Publication

University of California - Berkeley

 

image: 

Clovis points are distinguishable, in part, due to their distinctive flute or channel flake scar near the base, as shown in these replicas. UC Berkeley researchers studied how the points functioned as part of a system and were used to bring down megafauna in the Ice Age.

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Credit: Courtesy of Scott Byram

How did early humans use sharpened rocks to bring down megafauna 13,000 years ago? Did they throw spears tipped with carefully crafted, razor-sharp rocks called Clovis points? Did they surround and jab mammoths and mastadons? Or did they scavenge wounded animals, using Clovis points as a versatile tool to harvest meat and bones for food and supplies?

UC Berkeley archaeologists say the answer might be none of the above.

Instead, researchers say humans may have braced the butt of their pointed spears against the ground and angled the weapon upward in a way that would impale a charging animal. The force would have driven the spear deeper into the predator's body, unleashing a more damaging blow than even the strongest prehistoric hunters would have been capable of on their own.

Drawing upon multiple sources of writings and artwork, a team of Berkeley archaeologists reviewed historical evidence from around the world about people hunting with planted spears. 

They also ran the first experimental study of stone weapons that focused on pike hunting techniques, revealing how spears react to the simulated force of an approaching animal. Once the sharpened rock pierced the flesh and activated its engineered mounting system, they say, the spear tip functioned like a modern day hollow-point bullet and could inflict serious wounds to mastodons, bison and saber-toothed cats.

"This ancient Native American design was an amazing innovation in hunting strategies," said Scott Byram, a research associate with Berkeley's Archeological Research Facility and first-author of a paper on the topic published today in the journal PLOS ONE. "This distinctive Indigenous technology is providing a window into hunting and survival techniques used for millennia throughout much of the world."

The historical review and experiment may help solve a puzzle that has fueled decades of debate in archaeology circles: How did communities in North America actually use Clovis points, which are among the most frequently unearthed items from the Ice Age?

Named for the town of Clovis, New Mexico, where the shaped stones were first recovered nearly a century ago, Clovis points were shaped from rocks, such as chert, flint or jasper. They range from the size of a person's thumb to that of a midsize iPhone and have a distinct, razor-sharp edge and fluted indentations on both sides of their base. Thousands of them have been recovered across the U.S. — some have even been unearthed within preserved mammoth skeletons. 

They've also been a pop culture plot point. Characters in the video game "Far Cry Primal" use spears tipped with stone points to ambush mastodons. The movie 10,000 B.C. uses a similar spear to hunt mammoths. Scholars and hobbyists reconstruct Clovis points — and some even document on YouTube the process of building them and using them to hunt bison.

Those depictions make for a good story. But they likely fail to consider the realities of life in the Ice Age, said Byram and his co-author, Jun Sunseri, a Berkeley associate professor of anthropology. 

Clovis points are often the only recovered part of a spear. The intricately designed bone shafts at the end of the weapon are sometimes found, but the wood at the base of the spear and the pine pitch and lacing that help make them function as a complete system have been lost to time. 

Plus, research silos limit that kind of systems thinking about prehistoric weaponry, Jun said.  And if stone specialists aren’t experts in bone, they might not see the full picture.

"You have to look beyond the simple artifact," he said. "One of the things that's key here is that we're looking at this as an engineered system that requires multiple kinds of sub-specialties within our field and other fields."

Building tools as strong, effective systems was likely a priority for communities 13,000 years ago. The tools needed to be resilient. The people had a limited number of suitable rocks to work with while traversing the land. They might go hundreds of miles without access to the right kind of long, straight poles from which to fashion a spear. So it stands to reason they wouldn't want to risk throwing or destroying their tools without knowing if they'd even land the animal, said Byram, who mined archival records, spanning anthropology to art to Greek history, to trace the arc of planted pikes as weapons.

"People who are doing metal military artifact analysis know all about it because it was used for stopping horses in warfare," Byram said. "But prior to that, and in other contexts with boar hunting or bear hunting, it wasn't very well known. It's a theme that comes back in literature quite a bit. But for whatever reason, it hasn't been talked about too much in anthropology."

To evaluate their pike hypothesis, the Berkeley team built a test platform measuring the force a spear system could withstand before the point snapped and/or the shaft expanded. Their low-tech, static version of an animal attack using a braced, replica Clovis point spear allowed them to test how different spears reached their breaking points and how the expansion system responded. 

It was based on prior experiments where researchers fired stone-tipped spears into clay and ballistics gel — something that might feel like a pinprick to a 9-ton mammoth.

"The kind of energy that you can generate with the human arm is nothing like the kind of energy generated by a charging animal. It's an order of magnitude different," Jun said. "These spears were engineered to do what they're doing to protect the user."

The experiment put to the test something Byram had mulled for decades. When he was in graduate school and analyzing prehistoric stone tools, he crafted replica Clovis points and fashioned spears using traditional techniques. He remembered thinking how time-intensive a process it was to invest in a stone Clovis point — and how important it would be for the point to function effectively.

"It just started to make sense to me that it actually had a different purpose than some of the other tools," Byram said. "Unlike some of the notched arrowheads, it was a more substantial weapon. And it was probably also used defensively."

Conversations around a campfire early in the pandemic between Jun, a zooarchaeologist who learned from local communities during his time in Africa, and Kent Lightfoot, a Berkeley anthropology professor emeritus, prompted them to dig into the mystery. Through talks with his VhaVenda mentors, Jun learned how the engineering that went into the butt of some spears was just as critical as the work that went into the points. 

"The sophisticated Clovis technology that developed independently in North America is testimony to the ingenuity and skills that early Indigenous people employed in their cohabitation of the ancient landscape with now-extinct megafauna," said Lightfoot, a co-author of the study.

In the coming months, the team plans to further test its theory by building something akin to a replica mammoth. Using a type of slide or pendulum, they hope to simulate what an attack might have looked like as a planted Clovis-tipped pike made impact with a massive, fast-moving mammal.   

"Sometimes in archaeology, the pieces just start fitting together like they seem to now with Clovis technology, and this puts pike hunting front and center with extinct megafauna," Byram said. "It opens up a whole new way of looking at how people lived among these incredible animals during much of human history."

 

A high-speed photo sequence during a test after an 11.34 kg weight was dropped from 35 cm shows various moments as the stone point recedes into and splinters the pike shaft. Researchers said the way the stone point could have pierced animal flesh and the wood-and-bone shaft opened up suggests that the spear as a system functioned similar to a hollow-point bullet. 

Credit

Courtesy of Scott Byram

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Journal

PLoS ONE

Method of Research

Experimental study

Article Title

Clovis points and foreshafts under braced weapon compression: Modeling Pleistocene megafauna encounters with a lithic pike

Article Publication Date

21-Aug-2024

 

Using AI to link heat waves to global warming

Stanford University

Researchers at Stanford and Colorado State University have developed a rapid, low-cost approach for studying how individual extreme weather events have been affected by global warming. Their method, detailed in a Aug. 21 study in Science Advances, uses machine learning to determine how much global warming has contributed to heat waves in the U.S. and elsewhere in recent years. The approach proved highly accurate and could change how scientists study and predict the impact of climate change on a range of extreme weather events. The results can also help to guide climate adaptation strategies and are relevant for lawsuits that seek to collect compensation for damages caused by climate change.

“We’ve seen the impacts that extreme weather events can have on human health, infrastructure, and ecosystems,” said study lead author Jared Trok, a PhD student in Earth system science at the Stanford Doerr School of Sustainability. “To design effective solutions, we need to better understand the extent to which global warming drives changes in these extreme events.”

Trok and his co-authors trained AI models to predict daily maximum temperatures based on the regional weather conditions and the global mean temperature. For training the AI models, they used data from a large database of climate model simulations extending from 1850 to 2100. But once the AI models were trained and verified, the researchers used the actual weather conditions from specific real-world heat waves to predict how hot the heat waves would have been if the exact same weather conditions occurred but at different levels of global warming. They then compared these predictions at different global warming levels to estimate how climate change influenced the frequency and severity of historical weather events.

Case studies and beyond

The researchers first put their AI method to work analyzing the 2023 Texas heat wave, which contributed to a record number of heat-related deaths in the state that year. The team found that global warming made the historic heat wave 1.18 to 1.42 degrees Celsius (2.12 to 2.56 F) hotter than it would have been without climate change. The researchers also found that their new technique accurately predicted the magnitude of record-setting heat waves in other parts of the world, and that the results were consistent with previously published studies of those events.

Based on this, the researchers used the AI to predict how severe heat waves could become if the same weather patterns that caused previous record-breaking heat waves instead occurred under higher levels of global warming. They found that events equal to some of the worst heat waves in Europe, Russia, and India over the past 45 years could happen multiple times per decade if global temperatures reach 2.0 C above pre-industrial levels. Global warming is currently approaching 1.3 C above pre-industrial levels.

“Machine learning creates a powerful new bridge between the actual meteorological conditions that cause a specific extreme weather event and the climate models that enable us to run more generalized virtual experiments on the Earth system,” said study senior author Noah Diffenbaugh, the Kara J Foundation Professor and professor of Earth system science in the Stanford Doerr School of Sustainability. “AI hasn’t solved all the scientific challenges, but this new method is a really exciting advance that I think will get adopted for a lot of different applications.”

The new AI method addresses some limitations of existing approaches – including those previously developed at Stanford – by using actual historical weather data when predicting the effect of global warming on extreme events. It does not require expensive new climate model simulations because the AI can be trained using existing simulations. Together, these innovations will enable accurate, low-cost analyses of extreme events in more parts of the world, which is crucial for developing effective climate adaptation strategies. It also opens up new possibilities for fast, real-time analysis of the contribution of global warming to extreme weather.

The team plans to apply their method to a wider range of extreme weather events and refine the AI networks to improve their predictions, including using new approaches to quantify the full range of uncertainty in the AI predictions.

“We’ve shown that machine learning is a powerful and efficient new tool for studying the impact of global warming on historical weather events,” said Trok. “We hope that this study helps promote future research into using AI to improve our understanding of how human emissions influence extreme weather, helping us better prepare for future extreme events.”

 

Acknowledgement/footer box:

Diffenbaugh is also the Kimmelman Family Senior Fellow in the Stanford Woods Institute for the Environment. Co-authors of the study also include Elizabeth Barnes and Frances Davenport of Colorado State University. The study was funded by Stanford University and the U.S. Department of Energy.

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Journal

Science Advances

DOI

10.1126/sciadv.adl3242 

Article Title

Machine Learning-Based Extreme Event Attribution

Article Publication Date

21-Aug-2024

 

NJIT biologist awarded $680,000 federal grant to save North Atlantic right whale

NJIT biologist Brooke Flammang joins a national conservation effort to advance whale tracking technology to aid in the recovery of one of the world’s most endangered large whale species

New Jersey Institute of Technology

Brooke Flammang, a biologist at New Jersey Institute of Technology (NJIT), has been awarded nearly $680,000 from the National Oceanic and Atmospheric Administration (NOAA) as part of a growing nationwide effort to save the critically endangered North Atlantic right whale (Eubalaena glacialis).

NOAA Fisheries recently unveiled a more than $9 million initiative funded by the Inflation Reduction Act to support a coalition of universities, nonprofits and scientific organizations engaged in the recovery of the species, which has seen its numbers dwindle to roughly 360 individuals today due to factors ranging from climate-driven changes to its habitat, to fishing gear entanglements and vessel strikes.

As part of the collaborative effort, Flammang's Fluid Loco Lab at NJIT will spearhead the development of non-invasive tag attachment technology to offer near real-time tracking of the species, inspired by the way certain marine life attaches to whales for their survival. The advances could improve our understanding of changes in the whales’ reproduction, distribution patterns and habitat use that have coincided with rising temperatures in its key ocean habitats in recent decades, such as the Gulf of Maine, which has warmed faster than 99% of the global ocean, according to NOAA.

“Previous studies on right whale distribution have used suction cup tags that stay on for short periods of time and need to be retrieved to download the data. Predictions based on those data on where whales will be throughout the year are no longer accurate because of the changing ocean climate causing movement of the whales’ food sources,” said Flammang, an associate professor whose NOAA-funded research will include the use of satellite telemetry for improved tracking of the whales. “The possibility of near real-time monitoring would be game-changing for conservation and regulation policy decisions.”

Flammang's project builds on nearly a decade of research and development of novel tagging technology that mimics the passive forces of suction and friction that power the suction disks of remoras, or sucker fish, which are well known for hitchhiking long distances on the bodies of whales under intense drag forces.

The technology has already surpassed the fish’s notable adhesion ability in some cases, previously demonstrating up to 60% greater hold than what living remoras are able to produce on shark skin. The non-harmful tagging approach could give researchers greater capabilities for long-term monitoring of the whale, which has been protected under the Endangered Species Act since the 1970s.

Approximately $2.8 million from the initiative has been earmarked for monitoring and modeling efforts, which will include researchers from Marine Ecology and Telemetry Research and Duke University’s Marine Geospatial Ecology Lab, in addition to Flammang’s Fluid Loco Lab.

Another estimated $6.9 million will support a collaboration between the Atlantic States Marine Fisheries Commission and fishing industry partners in the development of on-demand (or “ropeless”) fishing gear technology that prevents fishing gear entanglements.

NOAA Fisheries declared an Unusual Mortality Event for the North Atlantic right whale in 2017, attributing 142 whale deaths to entanglement and vessel strikes since that time. Overall, the organization estimates that more than 85% of right whales have been entangled in fishing gear at least once in their lifetime.

The new wave of grant support comes as part of a broader $82 million in funding for North Atlantic right whale recovery efforts from the Inflation Reduction Act, unveiled by the Biden-Harris Administration in September 2023.

“North Atlantic right whales are approaching extinction with approximately 360 individuals remaining, including fewer than 70 reproductively active females,” said Assistant Administrator for NOAA Fisheries Janet Coit in a statement. “It’s imperative we advance our collective actions to help recover this species, and these partnerships will help the science and conservation community do just that.”

For more, visit NOAA's Inflation Reduction Act website.

New study provides further support for psilocybin’s potential to treat depressive symptoms

High dose psilocybin was the only psychedelic treatment to reduce depressive symptoms by more than placebo in antidepressant trials

BMJ Group

High doses of psilocybin - the active ingredient in magic mushrooms - appears to have a similar effect on depressive symptoms as the selective serotonin reuptake inhibitor (SSRI) drug escitalopram, suggests a systematic review and meta-analysis published in The BMJ today.

The findings show that patients treated with high dose psilocybin showed better responses than those treated with placebo in antidepressant trials, although the effect size was small.

The researchers point out that flaws in study designs may have overestimated the effectiveness of psychedelics, but say high dose psilocybin “appeared to have the potential to treat depressive symptoms.”

Psychedelic treatment has shown promise in reducing depressive symptoms. However, only one randomised controlled trial has so far directly compared a psychedelic drug (psilocybin) with an antidepressant drug (escitalopram) for patients with major depressive disorder.

What’s more, the subjective effects of psychedelic substances can compromise blinding, leading to overestimation of treatment effects compared with placebo. Psychedelic treatment is also usually given with psychological support which makes isolating the direct effects of psychedelics difficult.

To try and address these issues, the researchers trawled scientific databases to identify randomised controlled trials published up to 12 October 2023 that assessed the effects of psychedelics or escitalopram in adults with acute depressive symptoms.

To be eligible, psychedelic treatment (including MDMA, LSD, psilocybin, or ayahuasca) had to be given orally with no additional use of antidepressants, while escitalopram trials had to compare at least two different oral doses (maximum 20 mg/day) with placebo. Trials comparing psychedelic therapy directly with escitalopram were also included. 

Overall, 811 people (average age 42; 54% women) were included in 15 psychedelic trials and 1,968 people (average age 39; 63% women) were included in five escitalopram trials.

Effect size was expressed as standardised mean difference (0.2-0.5 indicates a small effect, 0.5-0.8 a moderate effect, and 0.8 or more a large effect).

The researchers found that placebo responses in psychedelic trials were lower than in escitalopram trials. As a result, while most psychedelics performed better than placebo in psychedelic trials on the 17 item Hamilton depression rating scale (HAMD-17), only high dose psilocybin performed better than placebo in escitalopram trials on the HAMD-17 scale, showing a small effect size (standardised mean difference 0.3), which is similar to that of current antidepressant drugs.

None of the interventions was associated with a higher rate of severe adverse events (including death, admission to hospital, or suicide attempt) or discontinuation than placebo.

The authors acknowledge several study limitations, including that only acute effects of the interventions were assessed and that the long term effects of psychedelics and escitalopram remain unclear. The sample size of the psychedelic trials was small, they add, and the effects of high dose psilocybin may have been slightly overestimated compared with other treatments.

Nevertheless, they conclude: “Serotonergic psychedelics, especially high dose psilocybin, appeared to have the potential to treat depressive symptoms. Our analysis suggested that the standardised mean difference of high dose psilocybin was similar to that of current antidepressant drugs, showing a small effect size.”

They add: “Improved blinding methods and standardised psychotherapies can help researchers to better estimate the efficacy of psychedelics for depressive symptoms and other psychiatric conditions.”

[Ends]

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Journal

The BMJ

DOI

10.1136/bmj-2023-078607 

Method of Research

Systematic review

Subject of Research

People

Article Title

Comparative oral monotherapy of psilocybin, lysergic acid diethylamide, 3,4-methylenedioxymethamphetamine, ayahuasca, and escitalopram for depressive symptoms: systematic review and Bayesian network meta-analysis

Article Publication Date

21-Aug-2024

COI Statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from National Science and Technology Council for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

 

When climate reporting fails to create impact

Some of New Zealand's biggest companies submitted their first mandatory climate-related disclosures this year, but a new study shows disclosure doesn't guarantee better behaviour.

Peer-Reviewed Publication

University of Auckland

This year, New Zealand became among the first countries in the world to force their largest companies and financial institutions (about 200 in all) to disclose their climate-related risks and opportunities in their annual reports, and make regulatory filings.

Over the last month, these reports have been filed under the disclosure regime led by the Financial Markets Authority.

But do these kinds of initiatives improve environmental outcomes?

A new study, co-authored by Professor Charl de Villiers (University of Auckland, Business School) finds that mandating social and environmental disclosures doesn’t necessarily improve businesses’ performance.

Professor de Villiers and his fellow researchers examined the effects of a prominent EU sustainability reporting initiative, Directive 2014/95/EU, which came into effect in 2017.

The legislation requires large companies to report their performance on non-financial matters, including environmental issues, social and employee matters, human rights, anti-corruption and bribery.

But after analysing a cross-country sample of businesses between 2009 and 2020, the researchers found that social and environmental outcomes didn’t meaningfully improve after the Directive.

“Despite the regulatory push, European companies didn’t exhibit substantial improvements in their social and environmental performance, nor did they improve when compared to US companies.

“The findings are surprising,” says de Villiers. “It's important that we don't assume that if we force companies to disclose information, they are actually going to do better by the environment and people.”

The study, says de Villiers, provides broad-based evidence of the ineffectiveness of mandating corporate social and environmental disclosures to enhance performance.

“We show that you can't just put out a piece of legislation like this and assume things will improve. You really have to design it in such a way that there are meaningful sanctions for non-disclosure.”

The EU Directive’s relative ineffectiveness may be partly due to its lack of detailed guidelines, auditing requirements and weak penalties for non-compliance, he says.

“For Aotearoa New Zealand, and other countries wanting to see meaningful progress, this highlights the importance of coupling clear disclosure requirements with specific guidelines, rigorous auditing and strong enforcement mechanisms.”

New Zealand’s Financial Markets Authority has indicated it will adopt a “broadly educative and constructive approach”, at least in the first year or so, only taking enforcement action against companies and financial institutions where they fail to file their disclosure statements or where the statements are misleading or deceptive.

It could start getting tougher from 2026.

 

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Journal

The British Accounting Review

DOI

10.1016/j.bar.2024.101437 

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Does mandating corporate social and environmental disclosure improve social and environmental performance?: Broad-based evidence regarding the effectiveness of directive 2014/95/EU

 

Antarctica vulnerable to invasive species hitching rides on plastic and organic debris

University of New South Wales

Antarctica’s unique ecosystems could be threatened by the arrival of non-native marine species and marine pollution from Southern Hemisphere landmasses, new oceanographic modelling shows. 

In a study published today in Global Change Biology, scientists from UNSW Sydney, ANU, University of Otago and the University of South Florida suggest that floating objects can reach Antarctic waters from more sources than previously thought.

“An increasing abundance of plastics and other human made debris in the oceans means there are potentially more opportunities for biota to reach Antarctica,” says lead author Dr Hannah Dawson, who completed the study as part of her PhD at UNSW, and is now based at the University of Tasmania.

Non-native species – including a range of small marine invertebrates – can reach Antarctica by catching a ride on floating objects like kelp, driftwood, pumice, and plastic. Previously, scientists thought these species only drifted from remote and unpopulated islands in the Southern Ocean. However, this new research suggests they can reach the Antarctic coastline from all southern continents.

“We knew that kelp could raft to Antarctica from sub-Antarctic islands, such as Macquarie and Kerguelen Islands, but our study suggests that floating objects can reach Antarctica from much further north, including South America, New Zealand, Australia, and South Africa,” says Dr Dawson.

Co-author Professor Crid Fraser from the University of Otago says that kelp could deal a potential double whammy blow to Antarctica’s marine ecosystem.

“Southern bull kelp and giant kelp are very big – often more than 10 m long – and create forest-like habitat for a lot of small animals, which they can carry with them on the long rafting trips to Antarctica,” she says.

“If they colonise Antarctica, marine ecosystems there could change dramatically.”

Southern Ocean modelling

Using modelled surface current and wave data from 1997 to 2015, the team tracked the movement of floating debris from various Southern Hemisphere land sources toward Antarctica, providing valuable new insight into the frequency and pathways of marine dispersal.

“We were able to analyse how frequent these rafting connections are by simulating dispersal pathways across 19 years of differing oceanographic conditions,” ANU co-author Dr Adele Morrison says.

“We found that rafting objects reached the Antarctic coastline in each of the years simulated. There seems to be a constant bombardment of anything that floats – whether it’s kelp or a plastic bottle.”

Dr Dawson likens the computer modelling process to the game ‘Poohsticks’ from the children’s classic Winnie the Pooh.

“Imagine dropping a stick into a river and then running downstream to see where it ends up – that’s essentially what we do with our modelling, using simulated ocean currents, instead of a river.”

“We released millions of virtual particles – representing drift objects – from each of the source land masses and modelled their trajectories across 19 years of estimated surface ocean currents and surface waves. After running the simulations, we were able to see where they would likely end up.

“The shortest time it took for particles to reach the Antarctic coastline was from Macquarie Island, south of New Zealand, some of which arrived in just under 9 months. On average, the longest journey was for objects released from South America,” she says.

Warmer waters

The research also sheds light on which regions of the Antarctic coastline are most at risk to non-native species arrivals.

“Most of these rafting objects arrive at the tip of the Antarctic Peninsula, a region with relatively warm ocean temperatures and often ice-free conditions. These factors make it a likely area for non-native species to first establish,” says UNSW Scientia Professor Matthew England, who is also a co-author.

The dramatic drop in Antarctic sea ice over the last couple of years makes these rafting connections particularly concerning.

“Sea ice is very abrasive and so acts as a barrier for many non-native species to successfully establish around Antarctica,” Dr Dawson says.

“If the recent decline in Antarctic sea ice continues, then living things floating at the surface, or attached to floating objects, could have an easier time colonising the continent, which may have big impacts on ecosystems.”

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Journal

Global Change Biology

DOI

10.1111/gcb.17467 

Method of Research

Computational simulation/modeling

Subject of Research

Animals

Article Title

Floating debris and organisms can raft to Antarctic coasts from all major Southern Hemisphere landmasses

Article Publication Date

22-Aug-2024