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

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.

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Antarctic-wide survey of plant life to aid conservation efforts

The first continent-wide mapping study of plant life across Antarctica reveals growth in previously uncharted areas and is set to inform conservation measures across the region.

The satellite survey of mosses, lichens and algae across the continent will form a baseline for monitoring how Antarctica's vegetation responds to climate change.

Scientists used a European Space Agency satellite to sweep the continent, combined with field measurements taken over several summer seasons, and detected almost 45 square kilometers of vegetation -- roughly three times the size of Lake Windermere in the Lake District, UK.

The international team, led by the University of Edinburgh with the Norwegian Institute for Nature Research, British Antarctic Survey and Scottish Association for Marine Science, found that over 80 per cent of the vegetation growth was contained within the Antarctic Peninsula and neighbouring islands.

The team estimates this growth makes up only 0.12 percent of Antarctica's total ice-free area, highlighting the importance of monitoring key areas of vegetation abundance, which is inadequately protected under the existing Antarctic Specially Protected Area (ASPA) system, experts say.

Antarctic vegetation, dominated by mosses and lichens, has adapted to survive the harsh polar conditions and each type plays an important role in carbon and nutrient recycling on a local level, experts say.

Until now, their spatial coverage and abundance across the continent remained unknown.

Previous research has shown that the environmental sensitivity of Antarctica's vegetative species makes them excellent barometers of regional climate change.

Monitoring their presence in Antarctica, a minimally disturbed landscape, could provide clues as to how similar vegetation types may respond to climate in other fragile ecosystems across the globe, such as parts of the Arctic.

Charlotte Walshaw, PhD researcher from the School of GeoSciences, University of Edinburgh, who led the study, said: "Our continent-scale map provides key information on vegetation presence in areas that are rarely visited by people. This will have profound implications for our understanding of where vegetation is located across the continent, and what factors influence this distribution."

Dr Claudia Colesie, researcher at the University of Edinburgh's School of GeoSciences, who took part in the study, said: "Lichens and mosses in Antarctica encounter the harshest living conditions on the planet on a daily basis. Only the most resilient organisms can thrive there. Now that we know where to look for them, we can provide more targeted conservation measures to safeguard their future."

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How the rising earth in Antarctica will impact future sea level rise

The rising earth beneath the Antarctic Ice Sheet will likely become a major factor in future sea level rise, a new study suggests.

Despite feeling like a stationary mass, most solid ground is undergoing a process of deformation, sinking and rising in response to many environmental factors. In Antarctica, melting glacial ice means less weight on the bedrock below, allowing it to rise. How the rising earth interacts with the overlying ice sheet to affect sea level rise is not well-studied, said Terry Wilson, co-author of the study and a senior research scientist at the Byrd Polar and Climate Research Center at The Ohio State University.

In the new study, Wilson's colleagues at McGill University developed a model to predict how these interactions could impact global sea level, finding that if humans can lower greenhouse gas emissions and global warming is slowed, upward shifts in the solid earth could reduce Antarctica's contribution to sea level rise by about 40%, significantly bolstering the best case scenarios for global sea level rise. In this low-emissions scenario, land uplift slows the flow of ice from land to ocean, allowing for more of the ice sheet to be preserved.

Conversely, if humans are unable to lower carbon emissions in time, ice retreat will outpace uplift, pushing ocean water away from Antarctica and amplifying sea level rise. These events could significantly worsen the most dire models of projected sea level rise along populated coastlines, said Wilson.

"Our measurements show that the solid earth that forms the base of the Antarctic ice sheet is changing shape surprisingly quickly," said Wilson. "The land uplift from reduced ice on the surface is happening in decades, rather than over thousands of years."

The study was published today in Science Advances.

To arrive at these conclusions, the team developed a 3D model of the Earth's interior using geophysical field measurements from the Antarctic Network (ANET) of the Polar Earth Observing Network (POLENET) project. The mission is focused on studying the changing polar regions by collecting GPS and seismic data from an array of autonomous systems across Antarctica.

Researchers then performed a number of simulations to capture many possible evolutions of Antarctica's ice sheet and the extent of global sea level rise Earth may experience until the year 2500, according to those parameters.

"We can project what difference it actually will make if we all contribute to a low-emission scenario now, versus what's come to be called 'business as usual' emissions," said Wilson, who is also the lead investigator of the ANET-POLENET project.

She attributes the model's unprecedented level of detail to how deftly it incorporates data from Antarctica. GPS stations monitor how the land is moving and seismometers measure how fast seismic waves from earthquakes travel through the earth, yielding important insight into where the land uplift will be fast or slow.

Surprisingly, according to some of the team's GPS observations processed by researchers at Ohio State, Wilson said, the Antarctic Ice Sheet is currently experiencing a solid earth uplift of about 5 centimeters per year, about 5 times the rate that North America experiences.

Another significant aspect of the study is how the changes in Antarctica under different carbon emissions scenarios will impact coastlines around the world. Because sea level change will not be uniform, the study notes that nearly 700 million people around the world living in coastal regions will be most impacted by rising seas due to Antarctic ice loss.

Since some regions, such as small island nations, will be more vulnerable than others, mitigating environmental conditions like atmospheric and ocean warming is a vital issue for society, said Wilson.

"Many people are now more aware they're experiencing the effects of climate change," she said. "This work reinforces that our actions as individuals, nations and globally can make a difference in what kind of Earth our offspring will experience in their lifetimes."

The study results highlight how complex the relationship between the solid earth and the processes that happen atop it is, as well as the importance of continuing to gather enough data to make prompt and accurate predictions about what the next few centuries of our planet will look like.

"There's a lot of uncertainty in every model and every prediction that you make," said Wilson. "But to document how fast our world is changing, it's very important to continue advancing our ability to make predictions that are more certain, which is the only path that will allow us to tend to our future in a meaningful way."

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Underwater mapping reveals new insights into melting of Antarctica's ice shelves

Clues to future sea level rise have been revealed by the first detailed maps of the underside of a floating ice shelf in Antarctica.

An international research team -- including scientists from the University of East Anglia (UEA) -- deployed an unmanned submersible beneath the Dotson Ice Shelf in West Antarctica.

The underwater vehicle, 'Ran', was programmed to dive into the cavity of the 350metre-thick ice shelf and scan the ice above it with an advanced sonar. Over 27 days, the submarine travelled more than 1000 kilometres back and forth under the shelf, reaching 17 kilometres into the cavity.

An ice shelf is a mass of glacial ice, fed from land by tributary glaciers, that floats in the sea above an ice shelf cavity. Dotson Ice Shelf is part of the West Antarctic ice sheet -- and next to Thwaites Glacier -- which is considered to have a potentially large impact on future sea level rise due to its size and location.

The researchers report their findings of this unique survey in a new paper published today in the journal Science Advances.

They found some things as expected, for example the glacier melts faster where strong underwater currents erode its base. Using the submersible, they were able to measure the currents below the glacier for the first time and prove why the western part of Dotson Ice Shelf melts so fast. They also found evidence of very high melt at vertical fractures that extend through the glacier.

However, the team also saw new patterns on the glacier base that raise questions. The mapping showed that the base is not smooth, but there is a peak and valley ice-scape with plateaus and formations resembling sand dunes. The researchers hypothesize that these may have been formed by flowing water under the influence of Earth's rotation.

Lead author Anna Wåhlin, Professor of Oceanography at the University of Gothenburg in Sweden, said: "We have previously used satellite data and ice cores to observe how ice shelves change over time. By navigating the submersible into the cavity, we were able to get high resolution maps of the ice underside. It's a bit like seeing the back of the moon for the first time."

The expedition was carried out in regions of drifting ice in West Antarctica in 2022 during a research cruise for the TARSAN project, a joint US-UK funded initiative that is part of the International Thwaites Glacier Collaboration. The project is studying how atmospheric and oceanic processes are influencing the behaviour of the Thwaites and Dotson Ice Shelves -- neighbouring ice shelves which are behaving differently.

Co-author Dr Rob Hall, from UEA's School of Environmental Sciences, co-led the cruise on the RV Nathaniel B Palmer, on which the observations were made in January to March 2022. He said: "Anna and her team successfully piloted their autonomous underwater vehicle 'Ran' over 1000 km under Dotson Ice Shelf collecting a huge range of data and samples, which will take several years to process and analyse.

"The incredible high-resolution images of the underside of the ice shelf are the icing on the cake and will open up a whole new avenue of scientific research."

Prof Karen Heywood, also from UEA and a co-author, is UK lead scientist on the TARSAN project. She said: "This has been such an exciting project to work on. When Anna sent round the first images of the underside of the Dotson ice shelf we were thrilled -- nobody had ever seen this before. But we were also baffled -- there were cracks and swirls in the ice that we weren't expecting. It looked more like art!

"We wondered what could be causing these. All of the glaciologists and the oceanographers in the TARSAN project got together to brainstorm ideas. It's been like detective work -- using fundamental ocean physics to test theories against the shape and size of the patterns under the ice. We've been able to show for the first time some of the processes that melt the underside of ice shelves.

Prof Heywood added: "These ice shelves are already floating on the sea, so their melting doesn't directly affect sea level. However ultimately the melting of ice shelves causes the glaciers on land further upstream to flow faster and destabilise, which does lead to sea level rise, so these new observations will help the community of ice modellers to reduce the large uncertainties in future sea level."

Scientists now realise there is a wealth of processes left to discover in future research missions under the glaciers.

"The mapping has given us new data that we need to look at more closely. It is clear that many previous assumptions about melting of glacier undersides are falling short. Current models cannot explain the complex patterns we see. But with this method, we have a better chance of finding the answers," said Prof Wåhlin.

"Better models are needed to predict how fast the ice shelves will melt in the future. It is exciting when oceanographers and glaciologists work together, combining remote sensing with oceanographic field data. This is needed to understand the glaciological changes taking place -- the driving force is in the ocean."

In January 2024, the group returned with Ran to Dotson Ice Shelf to repeat the surveys, hoping to document changes. However, they were only able to complete one dive before Ran disappeared under the ice.

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Marine plankton behavior could predict future marine extinctions

Marine communities migrated to Antarctica during the Earth's warmest period in 66 million years long before a mass-extinction event.

All but the most specialist sea plankton moved to higher latitudes during the Early Eocene Climatic Optimum, an interval of sustained high global temperatures equivalent to worst case global warming scenarios.

When the team, comprised of researchers from the University of Bristol, Harvard University, University of Texas Institute for Geophysics and the University of Victoria, compared biodiversity and global community structure, they found that the community often responds to climate change millions of years before losses of biodiversity.

The study, published today in Nature, suggests that plankton migrated to cooler regions to escape the tropical heat and that only the most highly specialised species were able to remain.

These findings imply that changes on the community scale will be evident long before extinctions in the modern world and that more effort must be placed on monitoring the structure of marine communities to potentially predict future marine extinctions.

Dr Adam Woodhouse from the University of Bristol's School of Earth Sciences, explained: "Considering three billion people live in the tropics, this is not great news.

"We knew that biodiversity amongst marine plankton groups has changed throughout the last 66 million years, but no one had ever explored it on a global, spatial, scale through the lens of a single database.

"We used the Triton dataset, that I created during my PhD, which offered new insights into how biodiversity responds spatially to global changes in climate, especially during intervals of global warmth which are relevant to future warming projections."

Dr Woodhouse teamed up with Dr Anshuman Swain, an ecologist and specialist in the application of networks to biological data. They applied networks to micropalaeontology for the first time ever to document the global spatial changes in community structure as climate has evolved over the Cenozoic, building on previous research on cooling restructured global marine plankton communities.

Dr Woodhouse continued: "The fossil record of marine plankton is the most complete and extensive archive of ancient biological changes available to science. By applying advanced computational analyses to this archive we were able to detail global community structure of the oceans since the death of the dinosaurs, revealing that community change often precedes the extinction of organisms.

"This exciting result suggests that monitoring of ocean community structure may represent an 'early warning system' which precedes the extinction of oceanic life."

Read more at Science Daily

Tiny plastic particles are found everywhere

It's not the first study on microplastics in Antarctica that researchers from the University of Basel and the Alfred-Wegener Institute (AWI) have conducted. But analysis of the data from an expedition in spring 2021 shows that environmental pollution from these tiny plastic particles is a bigger problem in the remote Weddell Sea than was previously known.

The total of 17 seawater samples all indicated higher concentrations of microplastics than in previous studies. "The reason for this is the type of sampling we conducted," says Clara Leistenschneider, doctoral candidate in the Department of Environmental Sciences at the University of Basel and lead author of the study.

The current study focused on particles measuring between 11 and 500 micrometers in size. The researchers collected them by pumping water into tanks, filtering it, and then analyzing it using infrared spectroscopy. Previous studies in the region had mostly collected microplastic particles out of the ocean using fine nets with a mesh size of around 300 micrometers. Smaller particles would simply pass through these plankton nets.

The results of the new study indicate that 98.3 percent of the plastic particles present in the water were smaller than 300 micrometers, meaning that they were not collected in previous samples. "Pollution in the Antarctic Ocean goes far beyond what was reported in past studies," Leistenschneider notes. The study appears in the journal Science of the Total Environment.

What role do ocean currents play?

The individual samples were polluted to different extents. The offshore samples, which were collected north of the continental slope and the Antarctic Slope Current, contained the highest concentrations of microplastics. The reasons for this are not conclusively known. It may be that the ice that tends to form near the coast retains the tiny plastic particles, and they are only released back into the water when the ice melts. It could also be the case that ocean currents play a role. "They might work like a barrier, reducing water exchange between the north and south," suggests Gunnar Gerdts from the AWI in Heligoland, Germany.

What is certainly true is that ocean currents are an important factor and the subject of many open questions in the field. So far the researchers have only examined water samples from the ocean surface, but not from lower depths. This is primarily due to limited time on the ship expeditions for taking samples and to equipment with insufficient pumping capacity. "It would nonetheless be revealing to analyze such data, since the deep currents differ greatly from the surface currents and thermohaline circulation leads to exchange with water masses from northern regions," Leistenschneider says.

It is also still unclear how the microplastics make their way to the Weddell Sea in the first place and whether they ever leave the region. The strong Antarctic Circumpolar Current, which flows all the way around the Antarctic Ocean at a latitude of about 60° south, might prevent their departure. The researchers are also not yet able to say conclusively where the microplastics originate. Possible sources include regional ship traffic from the tourism, fishing and research industries, as well as research stations on land. However, the microplastics might also make their way to Antarctica from other regions via ocean currents or atmospheric transport.

Research leads to awareness

Clara Leistenschneider plans to focus next on analyzing the sediment samples she collected during the same expedition. This should provide information about how microplastics are accumulating on the sea floor, which is home to unique and sensitive organisms and is a breeding ground for Antarctic icefish (Bovichtidae).

With the increase in tourism in the Antarctic Ocean, pollution may increase even more in the future, further impacting the environment and the food chain.

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Climate change threatens Antarctic meteorites

Using artificial intelligence, satellite observations, and climate model projections, a team of researchers from Switzerland and Belgium calculate that for every tenth of a degree of increase in global air temperature, an average of nearly 9,000 meteorites disappear from the surface of the ice sheet. This loss has major implications, as meteorites are unique samples of extraterrestrial bodies that provide insights into the origin of life on Earth and the formation of the Moon.

Disappearing at an alarming rate

By 2050, about a quarter of the estimated of 300,000 -- 800,000 meteorites in Antarctica will be lost due to glacial melt.

By end of the century, researchers anticipate that number could rise approaching a loss of meteorites closer to three-quarters of the meteorites on the continent under a high-warming scenario.

Published in the journal Nature Climate Change, Harry Zekollari co-led the study while working under Professor Daniel Farinotti in the Laboratory of Hydraulics, Hydrology and Glaciology at the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich.

Zekollari and co-lead Veronica Tollenaar, Université Libre de Bruxelles, reveal in the study that ongoing warming results in the loss of about 5,000 meteorites a year, outpacing the collection efforts of Antarctic meteorites by a factor five.

Meteorites -- time capsules of the universe

Zekollari, now an Associate Professor of Glaciology at Vrije Universiteit Brussel, calls for a major international effort to preserve the scientific value of meteorites, "We need to accelerate and intensify efforts to recover Antarctic meteorites. The loss of Antarctic meteorites is much like the loss of data that scientists glean from ice cores collected from vanishing glaciers -- once they disappear, so do some of the secrets of the universe."

Meteorites are fragments from space that provide unique information about our solar system.

Antarctica is the most prolific place to find meteorites, and to date, about 60 percent of all meteorites ever found on Earth have been collected from the surface of the Antarctic ice sheet.

The flow of the ice sheet concentrates meteorites in so-called "meteorite stranding zones," where their dark crust allows them to be easily detected.

In addition to intensifying recovery operations, there is potential to increase the efficiency of meteorite recovery missions in the short term.

This potential relies mainly on data-driven analysis to identify unexplored meteorite stranding zones and mapping areas exposing blue ice where meteorites are often found.

Extraterrestrial heritage slipping away

Due to their dark colour, meteorites preferentially heat up with respect to the surrounding ice.

As this heat transfers from the meteorites to the ice, it can warm up the ice, and eventually cause the ice to locally melt, leading to a sinking of meteorites underneath the surface of the ice sheet.

Once the meteorites enter the ice sheet, even at shallow depths, they cannot be detected anymore, and they are thus lost for science.

As atmospheric temperatures increase, so does the surface temperature of the ice, intensifying the loss.

"Even when temperatures of the ice are well below zero, the dark meteorites warm-up so much in the sun that they can melt the ice directly beneath the meteorite. Through this process, the warm meteorite creates a local depression in the ice and over time fully disappears under the surface," says Tollenaar.

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Tanks of the Triassic: New crocodile ancestor identified

Dinosaurs get all the glory. But aetosaurs, a heavily armored cousin of modern crocodiles, ruled the world before dinosaurs did. These tanks of the Triassic came in a variety of shapes and sizes before going extinct around 200 million years ago. Today, their fossils are found on every continent except Antarctica and Australia.

Scientists use the bony plates that make up aetosaur armor to identify different species and usually don't have many fossil skeletons to work with. But a new study led by researchers at The University of Texas at Austin centers on an aetosaur suit of armor that has most of its major parts intact.

The suit -- called a carapace -- is about 70% complete and covers each major region of the body.

"We have elements from the back of the neck and shoulder region all the way to the tip of the tail," said William Reyes, a doctoral student at the UT Jackson School of Geosciences who led the research. "Usually, you find very limited material."

The research was published in The Anatomical Record.

Reyes and his collaborators used the armor to identify the specimen as a new aetosaur species -- which they named Garzapelta muelleri. The name "Garza" recognizes Garza County in northwest Texas, where the aetosaur was found, and "Pelta" is Latin for shield, a nod to aetosaurs' heavily fortified body. The species name "muelleri" honors the paleontologist who originally discovered it, Bill Mueller.

Garzapelta lived about 215 million years ago and resembled a modern American crocodile -- but with much more armor.

"Take a crocodile from modern day, and turn it into an armadillo," said Reyes.

The bony plates that covered Garzapelta and other aetosaurs are called osteoderms. They were embedded directly in the skin and formed a suit of armor by fitting together like a mosaic. In addition to having a body covered in bony plates, Garzapelta's sides were flanked by curved spikes that would have offered another layer of protection from predators. Although crocodiles today are carnivores, scientists think that aetosaurs were primarily omnivorous.

The spikes on Garzapelta are very similar to those found in another aetosaur species, but surprisingly, researchers found that the two species are only distantly related. The similarities, they discovered, are an example of convergent evolution, the independent evolution of similar traits in different species. The development of flight in insects, birds, mammals and now-extinct pterosaurs is a classic example of this phenomenon.

According to Reyes, an array of unique features on Garzapelta's plates clearly marked it as a new species. They range from how the plates fit together to unique bumps and ridges on the bones. However, figuring out where Garzapelta fit into the larger aetosaur family tree was more of challenge. Depending on which portion of the armor the researchers emphasized in their analysis, Garzapelta would end up in very different places. Armor that ran down its back resembled armor from one species, while its midsection spikes resembled armor from another.

Once the researchers determined that the spikes evolved independently, they were able to work out where Garzapelta fit best among other aetosaur species. Nevertheless, Reyes said the research shows how convergent evolution can complicate things.

"Convergence of the osteoderms across distantly related aetosaurs has been noted before, but the carapace of Garzapelta muelleri is the best example of it and shows to what extent it can happen and the problems it causes in our phylogenetic analyses," Reyes said.

Garzapelta is part of the Texas Tech University fossil collections. It spent most of the past 30 years on a shelf before Reyes encountered it during a visit. Bill Parker, an aetosaur expert and park paleontologist at Petrified Forest National Park who was not part of the research, said that university and museum collections are a critical part of making this type of research possible.

"These specimens weren't just dug in the field yesterday," he said. "They've been sitting in the museum for decades and it just takes someone like Will to come along and finally decide to study them and make them come to life."

In addition to different species having different armor, it's possible that an animal's age or sex could also affect armor appearance. Reyes is currently exploring these questions by studying aetosaur fossils in the Jackson School's collection, most of which were found during the 1940s as part of excavations done by the Works Progress Administration.

Read more at Science Daily

Significant glacial retreat in West Antarctica began in 1940s

Among the vast expanse of Antarctica lies the Thwaites Glacier, the world's widest glacier measuring about 80 miles on the western edge of the continent. Despite its size, the massive landform is losing about 50 billion tons of ice more than it is receiving in snowfall, which places it in a precarious position in respect to its stability.

Accelerating ice loss has been observed since the 1970s, but it is unclear when this significant melting initiated -- until now. A new study published in the journal PNAS, led by researchers at the University of Houston, suggests that significant glacial retreat began in the 1940s. Their results on the Thwaites Glacier coincide with previous work that studied retreat on Pine Island Glacier and found glacial retreat began in the '40s as well.

"What is especially important about our study is that this change is not random nor specific to one glacier," said Rachel Clark, corresponding author, who graduated from UH last year with a doctorate in geology. "It is part of a larger context of a changing climate. You just can't ignore what's happening on this glacier."

Clark and the study authors posit that the glacial retreat was likely kicked off by an extreme El Niño climate pattern that warmed the west Antarctic. Since then, the authors say, the glacier has not recovered and is currently contributing to 4% of global sea-level rise.

"It is significant that El Niño only lasted a couple of years, but the two glaciers, Thwaites and Pine Island, remain in significant retreat," said Julia Wellner, UH associate professor of geology and U.S. lead investigator of the Thwaites Offshore Research project, or THOR, an international collaboration whose team members are authors of the study.

"Once the system is kicked out of balance, the retreat is ongoing," she added.

Their findings also make it clear the retreat at the glaciers' grounding zone, or the area where the glaciers lose contact with the seabed and start to float, was due to external factors.

"The finding that both Thwaites Glacier and Pine Island Glacier share a common history of thinning and retreat corroborates the view that ice loss in the Amundsen Sea sector of the West Antarctic ice sheet is predominantly controlled by external factors, involving changes in ocean and atmosphere circulation, rather than internal glacier dynamics or local changes, such as melting at the glacier bed or snow accumulation on the glacier surface," said Claus-Dieter Hillenbrand, U.K. lead investigator of THOR and study co-author.

"A significant implication of our findings is that once an ice sheet retreat is set in motion, it can continue for decades, even if what started it gets no worse," added James Smith, a marine geologist at the British Antarctic Survey and study co-author. "It is possible that the changes we see today on Thwaites and Pine Island glaciers -- and potentially across the entire Amundsen Sea embayment -- were essentially set in motion in the 1940s."

Dating of Sediment Cores Plays Key Role in Study

Clark and the team used three primary methods to reach their conclusion. One of those methods was marine sediment core collection that was closer to the Thwaites Glacier than ever before. They retrieved the cores during their trip to the Amundsen Sea near Thwaites in early 2019 aboard the Nathaniel B. Palmer icebreaker and research vessel. The researchers then used the cores to reconstruct the glacier's history from the early Holocene epoch to the present. The Holocene is the current geological epoch that began after the last ice age, roughly 11,700 years ago.

CT scans were used to take x-rays of the sediment to gather details from its history. Geochronology, or the science of dating earth materials, was then used to reach the conclusion that significant ice melt began in the '40s.

Clark used 210Pb (lead-210), an isotope that's naturally buried in the sediment cores and is radioactive, as the most important isotope in her geochronology. This process is similar to radiocarbon dating, which measures the age of organic materials as far back as 60,000 years.

"But lead-210 has a short half-life of about 20 years, whereas something like radiocarbon has a half-life of about 5,000 years," Clark said. "That short half-life allows us to build a timeline for the past century that's detailed."

This methodology is important because although satellite data exists to help scientists understand glacial retreat, these observations only go as far back as a few decades, a time frame that is too short to determine how Thwaites responds to ocean and atmosphere changes. Pre-satellite records are needed for scientists to understand the glacier's longer-term history, which is why sediment cores are used.

Study Informs Future Modeling to Reduce Uncertainty of Sea-Level Rise

Thwaites Glacier plays a vital role in regulating the West Antarctic ice sheet stability and, thus, global sea-level rise, according to Antarctic researchers.

"The glacier is significant not only because of its contribution to sea-level rise but because it is acting as a cork in the bottle holding back a broader area of ice behind it," Wellner said. "If Thwaites is destabilized, then there's potential for all the ice in West Antarctica to become destabilized."

If Thwaites Glacier were to collapse entirely, global sea levels are predicted to rise by 65 cm (25 in).

"Our study helps to better understand what factors are most critical in driving thinning and retreat of glaciers draining the West Antarctic ice sheet into the Amundsen Sea," Hillenbrand said. "Therefore, our results will improve numerical models that attempt to predict the magnitude and rate of future Antarctic ice sheet melting and its contributions to sea levels."

Researchers with THOR are part of an even larger initiative, the International Thwaites Glacier Collaboration, a joint U.S.-U.K. partnership to reduce uncertainty in the projection of sea-level rise from Thwaites Glacier.

Read more at Science Daily

Stability inspection for West Antarctica shows: marine ice sheet is not destabilized yet, but possibly on a path to tipping

Antarctica's vast ice masses seem far away, yet they store enough water to raise global sea levels by several meters. A team of experts from European research institutes has now provided the first systematic stability inspection of the ice sheet's current state. Their diagnosis: While they found no indication of irreversible, self-reinforcing retreat of the ice sheet in West Antarctica yet, global warming to date could already be enough to trigger the slow but certain loss of ice over the next hundreds to thousands of years.

"With more and more ice being lost in Antarctica over the last years, concerns have been raised whether a tipping point has already been crossed and an irreversible, long-term collapse of the West Antarctic Ice Sheet has already been initiated," explains Ronja Reese from the Potsdam Institute for Climate Impact Research (PIK) and the Northumbria University, Newcastle. "The results of our studies deliver two messages: First, while a number of glaciers in Antarctica are retreating at the moment, we find no indication of irreversible, self-reinforcing retreat yet, which is reassuring. However, our calculations also clearly indicate that an onset of an irreversible retreat of the ice sheet in West Antarctica is possible if the current state of the climate is sustained."

The main driver of ice loss in West Antarctica is relatively warm ocean water that amplifies melting underneath the ice shelves, which are the floating extensions of the grounded ice sheet. Melting of these ice shelves can enhance ice loss as it speeds up the grounded sections of the ice sheet. That is why the Antarctic margin with its grounding lines -- the zone where the grounded and the floating ice are connected -- is a key indicator of ice sheet health. An accelerated retreat of the grounding lines could indicate a forthcoming collapse of large marine regions of West Antarctica's ice sheet -- those parts of the ice sheet that are grounded below sea level.

Evolving over 10,000 years, triggered today: irreversible ice-loss and sea-level rise

Using state-of-the-art ice sheet models, the researchers not only conducted a thorough inspection of signs of irreversible retreat of marine sectors of the Antarctic ice sheet at present, they also ran simulations to investigate how the ice sheet would evolve over the next 10,000 years if current conditions remained unchanged. These hypothetical experiments indicate that even with no additional warming beyond what we have already experienced today, an irreversible collapse of some marine regions of West Antarctica's ice sheet is possible. Because the ice reacts to changes in temperature very slowly, the authors find that collapse occurs in their simulations at the earliest in 300 to 500 years from now, under current climate forcing. A full collapse would take centuries to millennia.

"The thing with sea-level rise from Antarctica is not that changes would happen overnight as an immediate threat to coastal communities. The process of melting would happen over hundreds or thousands of years. However, the cause could be human actions today, as they have the power to trigger and commit a future of 10,000 years to several meters of global sea-level rise. And stronger warming in the future would even speed up this process," Julius Garbe from PIK stresses.

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Loss of Antarctic sea ice causes catastrophic breeding failure for emperor penguins

Emperor penguin colonies experienced unprecedented breeding failure in a region of Antarctica where there was total sea ice loss in 2022. The discovery supports predictions that over 90% of emperor penguin colonies will be quasi-extinct by the end of the century, based on current global warming trends.

In a new study published today in Communications Earth & Environment, researchers from British Antarctic Survey discussed the high probability that no chicks had survived from four of the five known emperor penguin colonies in the central and eastern Bellingshausen Sea. The scientists examined satellite images that showed the loss of sea ice at breeding sites, well before chicks would have developed waterproof feathers.

Emperor penguins are dependent on stable sea ice that is firmly attached to the shore ('land-fast' ice) for the majority of the year, from April through to January. Once they arrive at their chosen breeding site, penguins lay eggs in Antarctic winter from May to June. Eggs hatch after 65 days, but chicks do not fledge until summer, between December and January.

At the beginning of December 2022, the Antarctic sea ice extent had matched the previous all-time low set in 2021. The most extreme loss was seen in the central and eastern Bellingshausen Sea region, west of the Antarctic Peninsula where there was a 100% loss of sea ice in November 2022.

Lead author of the study, Dr Peter Fretwell, said:

"We have never seen emperor penguins fail to breed, at this scale, in a single season. The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.

We know that emperor penguins are highly vulnerable in a warming climate -- and current scientific evidence suggests that extreme sea ice loss events like this will become more frequent and widespread.

Since 2016, Antarctica has seen the four years with the lowest sea ice extents in the 45-year satellite record, with the two lowest years in 2021/22 and 2022/23. Between 2018 and 2022, 30% of the 62 known emperor penguin colonies in Antarctica were affected by partial or total sea ice loss. Although it is difficult to immediately link specific extreme seasons to climate change, a longer-term decline in sea ice extent is expected from the current generation of climate models.

Understanding emperor penguin colonies

Emperor penguins have previously responded to incidents of sea ice loss by moving to more stable sites the following year. However, scientists say that this strategy won't work if sea ice habitat across an entire region is affected.

Emperor penguin populations have never been subject to large scale hunting, habitat loss, overfishing or other local anthropogenic interactions in the modern era. Unusually for a vertebrate species, climate change is considered the only major factor influencing their long-term population change. Recent efforts to predict emperor penguin population trends from forecasts of sea ice loss have painted a bleak picture, showing that if present rates of warming persist, over 90% of colonies will be quasi-extinct by the end of this century.

The five colonies of penguins studied were all discovered in the last 14 years using satellite imagery -- Rothschild Island, Verdi Inlet, Smyley Island, Bryan Peninsula and Pfrogner Point. All five colonies had been shown to return to the same location each year to breed, with only one previous instance of breeding failure at Bryan Peninsula in 2010.

Scientists now routinely use satellite imagery to discover and monitor emperor penguin colonies, as the brown stains of the birds' guano stands out clearly against the stark white of ice and snow. The team used images from the European Commission's Copernicus Sentinel-2 satellite mission, which has continuously monitored the area in Antarctica since 2018.

The impact of Antarctic sea ice loss

Over the past seven years, sea ice around Antarctica has decreased significantly. By the end of December 2022, sea ice extent was the lowest experienced in the 45-year satellite record. In the Bellingshausen Sea, the home of the penguin colonies in this study, sea ice didn't start to re-form until late April 2023.

Since then, the deviation from the norm has intensified: as of 20 August 2023 the sea ice extent was 2.2 million km2 lower than the 1981-2022 median (17.9 million km2) significantly surpassing the record winter low on 20 August 2022 of 17.1 million km2. This missing area is larger than the size of Greenland, or around ten times the size of the United Kingdom.

Dr Caroline Holmes, a polar climate scientist at BAS, said:

"Right now, in August 2023, the sea ice extent in Antarctica is still far below all previous records for this time of year. In this period where oceans are freezing up, we're seeing areas that are still, remarkably, largely ice-free.

Year-to-year changes in sea ice extent are linked to natural atmospheric patterns such as El Niño-Southern Oscillation, the strength of the southern hemisphere jet stream, and regional low-pressure systems.

We'll need years of targeted observations and modelling to know precisely how much the current conditions are being influenced by these phenomena and by natural ocean variability. However, the recent years of tumbling sea ice records and warming of the subsurface Southern Ocean point strongly to human-induced global warming exacerbating these extremes."

Climate models show a decline in Antarctic sea ice both under present and forecast human carbon dioxide emissions.

Dr Jeremy Wilkinson, a sea ice physicist at BAS, commented:

"This paper dramatically reveals the connection between sea ice loss and ecosystem annihilation. Climate change is melting sea ice at an alarming rate. It is likely to be absent from the Arctic in the 2030s -- and in the Antarctic, the four lowest sea ice extents recorded have been since 2016.

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New Antarctic extremes 'virtually certain' as world warms

Extreme events in Antarctica such as ocean heatwaves and ice loss will almost certainly become more common and more severe, researchers say.

With drastic action now needed to limit global warming to the Paris Agreement target of 1.5°C, the scientists warn that recent extremes in Antarctica may be the tip of the iceberg.

The study reviews evidence of extreme events in Antarctica and the Southern Ocean, including weather, sea ice, ocean temperatures, glacier and ice shelf systems, and biodiversity on land and sea.

It concludes that Antarctica's fragile environments "may well be subject to considerable stress and damage in future years and decades" -- and calls for urgent policy action to protect it.

"Antarctic change has global implications," said lead author Professor Martin Siegert, from the University of Exeter. "Reducing greenhouse gas emissions to net zero is our best hope of preserving Antarctica, and this must matter to every country -- and individual -- on the planet."

Professor Siegert said the rapid changes now happening in Antarctica could place many countries in breach of an international treaty.

"Signatories to the Antarctic Treaty (including the UK, USA, India and China) pledge to preserve the environment of this remote and fragile place," he said.

"Nations must understand that by continuing to explore, extract and burn fossil fuels anywhere in the world, the environment of Antarctica will become ever more affected in ways inconsistent with their pledge."

The researchers considered the vulnerability of Antarctica to a range of extreme events, to understand the causes and likely future changes -- following a series of recent extremes.

For example, the world's largest recorded heatwave (38.5°C above the mean) occurred in East Antarctica in 2022 and, at present, winter sea ice formation is the lowest on record.

Extreme events can also affect biodiversity. For example, high temperatures have been linked to years with lower krill numbers, leading to breeding failures of krill-reliant predators -- evidenced by many dead fur seal pups on beaches.

Co-author Professor Anna Hogg, from the University of Leeds, said: "Our results show that while extreme events are known to impact the globe through heavy rainfall and flooding, heatwaves and wildfires, such as those seen in Europe this summer, they also impact the remote polar regions.

"Antarctic glaciers, sea ice and natural ecosystems are all impacted by extreme events. Therefore, it is essential that international treaties and policy are implemented in order to protect these beautiful but delicate regions."

Dr Caroline Holmes, a sea ice expert at British Antarctic Survey, said: "Antarctic sea ice has been grabbing headlines in recent weeks, and this paper shows how sea ice records -- first record highs but, since 2017, record lows -- have been tumbling in Antarctica for several years.

"On top of that, there are deep interconnections between extreme events in different aspects of the Antarctic physical and biological system, almost all of them vulnerable to human influence in some way."

The retreat of Antarctic sea ice will make new areas accessible by ships, and the researchers say careful management will be required to protect vulnerable sites.

The European Space Agency and European Commission Copernicus Sentinel satellites are an essential tool for regular monitoring of the whole Antarctic region and Southern Ocean.

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Ground beneath Thwaites Glacier mapped

The ground beneath Antarctica's most vulnerable glacier has been mapped for the first time, helping scientists to better understand how it is being affected by climate change. Analysis of the geology below the Thwaites Glacier in West Antarctica shows there is less sedimentary rock than expected -- a finding that could affect how the ice slides and melts in the coming decades.

"Sediments allow faster flow, like sliding on mud," says Dr Tom Jordan, a geophysicist with the British Antarctic Survey (BAS), who led the study. "Now we have a map of where the slippery sediments are, we can better predict how the glacier will behave in future as it retreats."

The distribution of sedimentary rocks beneath the Thwaites glacier is included in a new map of the geology of the region produced by the BAS researchers and published in the journal Science Advances. The findings are important because the glacier, which is the size of Great Britain or the US state of Florida, is one of the fastest changing ice-ocean systems in Antarctica.

The Thwaites glacier's grounding zone -- the point where it meets the seafloor -- has retreated 14 km since the late 1990s. Much of the ice sheet is below sea level and susceptible to rapid, irreversible ice loss that could raise global sea-level by over half a metre within centuries.

The new analysis is based on airborne surveys using aircraft equipped with radar which can see through the ice to the rocks below, as well as sensors which can map minute variations in gravity and magnetism hundreds to thousands of metres below the ground and seabed on which the glacier rests.

The researchers then use these multiple data sources to compile a 3D picture of features, including the type and extent of different rocks.

Jordan says: "The integrated nature of the airborne surveys was one of the keys to this research. Each sensor on the aircraft provided an important but incomplete part of the picture, but by bringing them all together we could provide the detailed map of the underlying geology."

In doing so, the study effectively turns back the geological clock to examine what happened when New Zealand was ripped away from Antarctica about 100 million years ago -- long before the Thwaites glacier was formed.

Because the base of Thwaites Glacier lies far below sea level, researchers had expected that thick sediments would have been deposited there over the subsequent millions of years Similar analysis has been done on some other Antarctic glaciers, showing that these other systems were predominantly underlain by thick sediments.

But the aircraft data suggests that only about a fifth of the ground below the glacier is sedimentary rock. These lie in a series of basins between 80 and 200 km long and about 30 km wide.

The rest is made up of other types of geological bodies, including granite peaks and other hard rocks. The scientists think that these sedimentary basins were once much larger, but they have been ground down to the bedrock by movement of the glacier.

It's not yet clear how this new knowledge of the subglacial geology will affect estimates of ice flow and loss from Thwaites and other glaciers. The study does show that the geological landscape has a direct control on the basal shear stress, which influences how fast ice can flow into the ocean. Members of the research team will now carry out more detailed studies of these processes. Modellers may also be able to use the new data to make more reliable projections of future ice loss.

Jordan says: "We hope that by showing the detailed geology, and how it correlates with the basal friction, future models of glacial retreat will have lower uncertainty, as the controls of the basal processes will be better understood."

He adds: "No single scientific study could ever match she scale and challenge of climate change. But it is the incremental building of all the individual scientific studies like this that allows us to understand and tackle that challenge."

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17-pound meteorite discovered in Antarctica

Antarctica is a tough place to work, for obvious reasons -- it's bitterly cold, remote, and wild. However, it's one of the best places in the world to hunt for meteorites. That's partly because Antarctica is a desert, and its dry climate limits the degree of weathering the meteorites experience. On top of the dry conditions, the landscape is ideal for meteorite hunting: the black space rocks stand out clearly against snowy fields. Even when meteorites sink into the ice, the glaciers' churning motion against the rock below helps re-expose the meteorites near the surface of the continent's blue ice fields.

An international team of researchers who just got back from Antarctica can attest to the continent's meteorite-hunter-friendliness: they returned with five new meteorites, including one that weighs 16.7 pounds (7.6 kg).

Maria Valdes, a research scientist at the Field Museum and the University of Chicago, estimates that of the roughly 45,000 meteorites retrieved from Antarctica over the past century, only about a hundred or so are this size or larger. "Size doesn't necessarily matter when it comes to meteorites, and even tiny micrometeorites can be incredibly scientifically valuable," says Valdes, "but of course, finding a big meteorite like this one is rare, and really exciting."

Valdes was one of four scientists on the mission, led by Vinciane Debaille of the Université Libre de Bruxelles (FNRS-ULB); the research team was rounded out by Maria Schönbächler (ETH-Zurich) and Ryoga Maeda (VUB-ULB). The researchers were the first to explore potential new meteorite sites mapped using satellite imagery by Veronica Tollenaar, a thesis student in glaciology at the ULB.

"Going on an adventure exploring unknown areas is exciting," says Debaille, "but we also had to deal with the fact that the reality on the ground is much more difficult than the beauty of satellite images." Despite timing their trip for Antarctica's summertime in late December, temperatures hovered around 14° F (-10° C). Valdes notes that some days during their trip, it was actually colder in Chicago than it was in Antarctica, but spending days riding snowmobiles and trekking through ice fields and then sleeping in a tent made the Antarctic weather feel more extreme.

The five meteorites recovered by the team will be analyzed at the Royal Belgian Institute of Natural Sciences; meanwhile, sediment potentially containing tiny micrometeorites was divided among the researchers for study at their institutions.

Valdes says she's eager to see what the analyses of the meteorites reveal, because "studying meteorites helps us better understand our place in the universe. The bigger a sample size we have of meteorites, the better we can understand our Solar System, and the better we can understand ourselves."

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The formation of the West Antarctic Ice Sheet was very different than previously believed

Roughly 35 million years ago, Earth cooled rapidly. At roughly the same time, the Drake Passage formed between South America and the Antarctic, paving the way for the Antarctic Circumpolar Current. Thanks to these two factors, Antarctica was soon completely covered in ice. As a study from the Alfred Wegener Institute now shows, this massive glaciation was delayed in at least one region. This new piece of the puzzle concerning the early history of the West Antarctic Ice Sheet could help to predict its unstable future. The study was just released in the Nature journal Communications Earth & Environment.

For climate researchers, the West Antarctic has been in the spotlight for years. Here, the West Antarctic Ice Sheet lying atop the continent stretches to the adjacent Amundsen Sea. Near the coast, the ice is still in direct contact with the soil; farther toward the open sea, it floats. Because climate change progressively warms the seawater, the latter is increasingly eroding the ice shelf from below. The grounding line -the last point at which the ice still rests on the ground -moves farther and farther inland. Due to meltwater and calving icebergs, the Thwaites Glacier, which flows into the Amundsen Sea, now loses twice as much ice as 30 years ago. If the West Antarctic Ice Sheet were to collapse entirely, global sea levels would rise by more than three metres.

"The stability of the West Antarctic Ice Sheet is critical to the future development of the global sea level," says the study's first author, Gabriele Uenzelmann-Neben from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). "Accordingly, researchers around the world are working to predict the future behaviour of the ice in a warmer world using numerical simulation. The more we know about the history of the West Antarctic Ice Sheet, the more accurate we can make these models. Its more recent history is well-documented, but we still know very little about its earlier years -- particularly the formation phase. Our study delivers an important piece of the puzzle."

In the course of two research cruises on board the Polarstern, the Geophysicist and her team investigated sediments in the vicinity of Pine Island Trough, a channel-like furrow in the seafloor of the shallow part of the Amundsen Sea that stretches from north to south and leads directly toward the western coast of Antarctica. To collect data, the AWI team relied on the tried and proven reflection seismology method: the Polarstern towed a 3,000-metre-long measuring cable -- or streamer -- behind her. The streamer is equipped with hydrophones that utilise a total of 240 measuring channels. During survey cruises, an airgun is used to produce seismic pulses behind the ship. These pulses penetrate the seafloor and are reflected back at geological boundaries -- e.g. between the sediment and hard rock -- which is recorded by the streamer's hydrophones. Based on the different travel times for the waves and the respective positions of the individual channels, the internal structure of the seafloor can be mapped.

The measurement data revealed a large sediment body, a sediment drift, on the eastern flank of Pine Island Trough, one with no counterpart on its western side. "Because of the Coriolis effect produced by Earth's rotation, this asymmetrical deposition of a sediment drift on the trough's eastern side but not the western one can only have been produced by a deep-water current that flowed toward the coast from north to south," says Uenzelmann-Neben. "In order for that to occur, the ocean circulation at the time of the deposition had to be similar to today's conditions, that is, the prevailing westerlies and the Antarctic Circumpolar Current had to have been located far to the south. And similar to today, the deep water upwelled through the trough must have been comparatively warm."

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Ancient ice reveals mysterious solar storm

Through analysis of ice cores from Greenland and Antarctica, a research team led by Lund University in Sweden has found evidence of an extreme solar storm that occurred about 9,200 years ago. What puzzles the researchers is that the storm took place during one of the sun's more quiet phases -- during which it is generally believed our planet is less exposed to such events.

The sun is a prerequisite for life on Earth. But our life-giving companion can also cause problems. When there is strong activity on the surface of the sun, more energy is released, something that can give rise to geomagnetic storms. This in turn can cause power outages and communication disturbances.

Predicting solar storms is difficult. It is currently believed that they are more likely during an active phase of the sun, or solar maximum, during the so-called sunspot cycle. However, the new study published in Nature Communications shows that this may not always be the case for very large storms.

"We have studied drill cores from Greenland and Antarctica, and discovered traces of a massive solar storm that hit Earth during one of the sun's passive phases about 9,200 years ago," says Raimund Muscheler, geology researcher at Lund University.

The researchers scoured the drill cores for peaks of the radioactive isotopes beryllium-10 and chlorine-36. These are produced by high-energy cosmic particles that reach Earth, and can be preserved in ice and sediment.

"This is time consuming and expensive analytical work. Therefore, we were pleasantly surprised when we found such a peak, indicating a hitherto unknown giant solar storm in connection with low solar activity," says Raimund Muscheler.

If a similar solar storm were to take place today, it could have devastating consequences. In addition to power outages and radiation damage to satellites, it could pose a danger to air traffic and astronauts as well as a collapse of various communication systems.

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World's largest fish breeding area discovered in Antarctica

Near the Filchner Ice Shelf in the south of the Antarctic Weddell Sea, a research team has found the world's largest fish breeding area known to date. A towed camera system photographed and filmed thousands of nests of icefish of the species Neopagetopsis ionah on the seabed. The density of the nests and the size of the entire breeding area suggest a total number of about 60 million icefish breeding at the time of observation. These findings provide support for the establishment of a Marine Protected Area in the Atlantic sector of the Southern Ocean. A team led by Autun Purser from the Alfred Wegener Institute publish their results in the current issue of the scientific journal Current Biology.

The joy was great when, in February 2021, researchers viewed numerous fish nests on the monitors aboard the German research vessel Polarstern, which their towed camera system transmitted live to the vessel from the seabed, 535 to 420 metres below the ship, from the seafloor of the Antarctic Weddell Sea. The longer the mission lasted, the more the excitement grew, finally ending in disbelief: nest followed nest, with later precise evaluation showing that there were on average one breeding site per three square metres, with the team even finding a maximum of one to two active nests per square metre.

The mapping of the area suggests a total extent of 240 square kilometres, which is roughly the size of the island of Malta. Extrapolated to this area size, the total number of fish nests was estimated to be about 60 million. "The idea that such a huge breeding area of icefish in the Weddell Sea was previously undiscovered is totally fascinating," says Autun Purser, deep-sea biologist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and lead author of the current publication. After all, the Alfred Wegener Institute has been exploring the area with its icebreaker Polarstern since the early 1980s. So far, only individual Neopagetopsis ionah or small clusters of nests have been detected here.

The unique observations are made with a so-called OFOBS, the Ocean Floor Observation and Bathymetry System. It is a camera sledge built to survey the seafloor of extreme environments, like ice-covered seas. It is towed on a special fibre-optic and power cable normally at a speed of about one half to one knot, about one and half metres above the seafloor. "After the spectacular discovery of the many fish nests, we thought about a strategy on board to find out how large the breeding area was -- there was literally no end in sight. The nests are three quarters of a metre in diameter -- so they are much larger than the structures and creatures, some of which are only centimetres in size, that we normally detect with the OFOBS system," Autun Purser reports. "So, we were able to increase the height above ground to about three metres and the towing speed to a maximum of three knots, thus multiplying the area investigated. We covered an area of 45,600 square metres and counted an incredible 16,160 fish nests on the photo and video footage," says the AWI expert.

Based on the images, the team was able to clearly identify the round fish nests, about 15 centimetres deep and 75 centimetres in diameter, which were made distinct from the otherwise muddy seabed by a round central area of small stones. Several types of fish nests were distinguished: "Active" nests, containing between 1,500 and 2,500 eggs and guarded in three-quarters of the cases by an adult icefish of the species Neopagetopsis ionah, or nests which contained only eggs; there were also unused nests, in the vicinity of which either only a fish without eggs could be seen, or a dead fish. The researchers mapped the distribution and density of the nests using OFOBS's longer-range but lower-resolution side scan sonars, which recorded over 100,000 nests.

The scientists combined their results with oceanographic and biological data. The result: the breeding area corresponds spatially with the inflow of warmer deep water from the Weddell Sea onto the higher shelf. With the help of transmitter equipped seals, the multidisciplinary team was also able to prove that the region is also a popular destination for Weddell seals. 90 per cent of the seals' diving activities took place within the region of active fish nests, where they presumably go in search of food. No wonder, the researchers calculate the biomass of the ice fish colony there at 60 thousand tonnes.

With its biomass, this huge breeding area is an extremely important ecosystem for the Weddell Sea and, according to current research, likely to be the most spatially extensive contiguous fish breeding colony discovered worldwide to date, the experts report in the publication in Current Biology.

German Federal Research Minister Bettina Stark-Watzinger said: "My congratulations to the researchers involved on their fascinating discovery. After the MOSAiC expedition, German marine and polar research has once more reaffirmed its outstanding position. German research vessels are floating environmental research laboratories. They continue to sail the polar seas and our oceans almost non-stop, serving as platforms for science aimed at generating important findings to support climate and environmental protection. Funding by the Federal Ministry of Education and Research (BMBF) provides German marine and polar research with one of the most state-of-the-art research vessel fleets worldwide. This discovery can make an important contribution towards protecting the Antarctic environment. The BMBF will continue to work towards this goal under the umbrella of the United Nations Decade of Ocean Science for Sustainable Development that runs until 2030."

For AWI Director and deep-sea biologist Prof. Antje Boetius, the current study is a sign of how urgent it is to establish marine protected areas in Antarctica. "This great discovery was enabled by a specific under-ice survey technology we developed during my ERC Grant. It shows how important it is to be able to investigate unknown ecosystems before we disturb them. Considering how little known the Antarctic Weddell Sea is, this underlines all the more the need of international efforts to establish a Marine Protected Area (MPA)," Antje Boetius classifies the results of the study, in which she was not directly involved. A proposal for such an MPA has been prepared under the lead of the Alfred Wegener Institute and is defended since 2016 by the European Union and its member states as well as other supporting countries in the international Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

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Researchers identify behavioral adaptations that may help Antarctic fishes adapt to warming Southern Ocean

At first glance, Antarctica seems inhospitable. Known for howling gales and extremely cold temperatures, the continent is blanketed with a mile-thick ice shelf. Occasional elephant seals and seabirds fleck the glacial shorelines.

Yet dipping below the waves, the Southern Ocean teems with biodiversity: vibrant swaths of sea ice algae and cyanobacteria, swarming krill and crustaceans, bristling kelp forests, gigantic polar sea spiders and sponges, whale pods, and abundant Antarctic fish fauna.

These fishes play a vital role in the Southern Ocean's food web of 9,000 known marine species, yet their subzero haven may be at risk. A 2021 climate analysis posited that by 2050 some areas of the Antarctic continental shelf will be at least 1 degree Celsius warmer.

Researchers from Virginia Tech's Fralin Biomedical Research Institute at VTC have published a new study in PLOS ONE describing how two species of Antarctic fish -- one with hemoglobin in its blood cells and one without -- respond to acute thermal stress.

The research team, directed by Virginia Tech Vice President for Health Sciences and Technology Michael Friedlander, observed that both species responded to progressive warming with an elaborate array of behavioral maneuvers, including fanning and splaying their fins, breathing at the surface, startle-like behavior, and transient bouts of alternating movement and rest.

"Remarkably, our team found that Antarctic fishes compensate for increasing metabolic demands by enhancing respiration through species-specific locomotor and respiratory responses, demonstrating resilience to environmental change and possibly to global warming," said Friedlander, who is also the Fralin Biomedical Research Institute's executive director, senior dean for research at the Virginia Tech Carilion School of Medicine, and a professor in the College of Science's Department of Biological Sciences. "Ambient warming presents a multi-faceted challenge to the fish, including increased temperature of the central nervous system and target tissues such as skeletal and cardiac muscles, but also reduced availability of dissolved oxygen in the water that passes through the gills during respiration. While these findings suggest that Antarctic fishes may be able to behaviorally adapt somewhat under extreme conditions, little is known about the effects of environmental warming on their predation habits, food availability, and fecundity,"

Iskander Ismailov, the study's first author and a research assistant professor in Friedlander's laboratory during the study, said, "Behavioral manifestations that we've described show that these fishes have powerful physiological capacities to survive environmental changes," said

Through millions of years of isolation from the rest of the world -- corralled by the Antarctic Circumpolar Current -- Southern Ocean fish species have become well adapted to their frosty ecosystem.

Blackfin icefish, Chaenocephalus aceratus, one of the two species studied by the team, have unique opalescent blood. These fish are among the few known vertebrates lacking hemoglobin, a molecule in red blood cells that efficiently carries oxygen from the lungs of land-dwelling vertebrates, or from the gills of aquatic vertebrates, throughout tissues in the body. Instead, blackfin icefish transport oxygen dissolved in blood plasma, harboring roughly 10% of the oxygen carrying capacity of hemoglobin.

Oxygen is more soluble in cold water, allowing white-blooded icefish to thrive in the Southern Ocean. As water temperature rises, however, these species experience increased metabolic demand, potentially making white-blooded fish more vulnerable to global warming. To test this hypothesis, the team examined five specimens of white-blooded blackfin icefish and five red-blooded black rockcod, Notothenia coriiceps, in a climate-controlled shoreline laboratory that circulated, and progressively warmed, saltwater straight from the Southern Ocean.

The fishes acclimated to the lab conditions, before being transferred to the experimental tank, where water temperature rose from -1.8 degrees Celsius to 13 degrees, at a rate of 3 degrees per hour. The researchers captured extensive video recordings, allowing them to examine and quantify the fishes' motility, breathing rate, maneuvers in the tank, and fin movements.

As the water temperature rose, the white-blooded icefish displayed intensive pectoral fin fanning -- a behavior previously observed in icefish during egg guarding -- that the researchers suggest may help facilitate respiration. By contrast, the red-blooded fish employed complex maneuvers, including pectoral fin fanning and splaying, followed by startle-like C-turns, which may augment gill ventilation, according to Ismailov.

"The findings provide a new perspective on the effects of rising temperature on these highly cold-adapted species," said George Somero, professor emeritus of marine biology at Stanford University and a leader in studying how marine life adapts to thermal stress, who was not involved in the research.

Preparation for the expedition began in early 2014. The research team designed, custom-built, and shipped laboratory equipment to Palmer Station in Antarctica before living there for three months in 2015. The journey included a flight to Punta Arenas, Chile, then crossing the Drake Passage by boat during the austral fall.

Ismailov was the first to arrive, setting up experimental rigs. Six weeks later, he was joined by Jordan Scharping, then a second-year Virginia Tech Carilion School of Medicine student conducting research in Friedlander's lab. The pair worked in overlapping 12-hour shifts running experiments in the laboratory at near-freezing temperatures.

"Dr. Friedlander drew me to this project. I remember him presenting the Antarctic project proposal to us medical students and everyone just lighting up about it. It was an incredible opportunity and I appreciate him giving it to me," said Scharping, who is now a physician at Northwestern Memorial Hospital.

Researchers were responsible for collecting their own fish specimens during a series of four, week-long fishing trips. At sea, with the help of the research vessel crew, the researchers worked around the clock -- sometimes during harsh conditions.

"One stormy night while we were fishing, a two-story wave overtook the stern, drenching me from head to toe in ice-cold seawater -- the captain of the boat stopped the fishing after that," Ismailov recalled. "As a graduate of medical school, I never could have imagined that my career would lead me to Antarctica to study fish, but this research project has become one of the most extraordinary and memorable in my life."

The field work was funded by a National Science Foundation Grant awarded to Elizabeth Crockett, professor emerita at Ohio University, and Kristin O'Brien, professor at the University of Alaska Fairbanks. Crockett and O'Brien -- both former graduate students of Bruce Sidell, who was trained by C. Ladd Prosser -- invited Friedlander to join the expedition along with collaborators from the University of British Columbia, the University of Leeds, and Valdosta State University.

But the underpinnings of this recent study started 45 years ago. Friedlander, then a graduate student under the mentorship of Prosser at the University of Illinois at Urbana-Champaign -- a pioneer in the field of comparative animal physiology and thermal biology -- conducted research to advance experimental approaches to evaluate how temperature change affects molecular, cellular, and behavioral processes in an entire organism. Their landmark study, published in the Journal of Comparative Physiology in 1977, examining the common goldfish, was lauded by Somero in a 2015 review in the Journal of Experimental Biology.

"I find it gratifying that the pathbreaking studies of temperature effects on goldfish behavior carried out by Dr. Friedlander several decades ago have evolved into this fascinating new work on fishes of the Southern Ocean," Somero said.

While the research team observed that stenothermal Antarctic fishes show remarkable capacity to withstand acute thermal stress, Ismailov warns that these vulnerable species still need protection.

"There's a history of severe overexploitation in the Southern Ocean in the '70s and '80s due to unregulated commercial fishing. These activities had depleted the populations of some fish species so badly that the prospects of their recovery are still unclear," Ismailov said.

Friedlander expounds on this, noting that all species play important roles in a fragile ecosystem.

"If left unregulated, anthropogenic activities could produce irreversible damage, impacting not just icefish, but many other species in the Antarctic food webs as well," Friedlander said. "By doing these types of proof of principle experiments now to begin to understand the physiological repertoire available to species at risk, we can begin to make more informed predictions about what sort of perturbations within complex ecosystems that climate change may trigger, and what type of reserve and adaptive capacity individual species may deploy,"

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Antarctic ice-sheet destabilized within a decade

After the natural warming that followed the last Ice Age, there were repeated periods when masses of icebergs broke off from Antarctica into the Southern Ocean. A new data-model study led by the University of Bonn (Germany) now shows that it took only a decade to initiate this tipping point in the climate system, and that ice mass loss then continued for many centuries. Accompanying modeling studies suggest that today's accelerating Antarctic ice mass loss also represents such a tipping point, which could lead to irreversible and long-lasting ice retreat and global sea level rise. The study has now been published in the journal Nature Communications.

To understand what the consequences of current and future human-induced climate warming may be, it helps to take a look at the past: how did sea-level changes look like during times of natural climate warming? In a recent study, an international research team led by Dr. Michael Weber from the Institute of Geosciences at the University of Bonn investigated this question. In doing so, they focused on the Antarctic Ice Sheet as the largest remaining ice sheet on Earth.

There, they searched for evidence of icebergs that broke off the Antarctic continent, floated in the surrounding ocean and melted down in the major gateway to lower latitudes called "Iceberg Alley." In the process, the icebergs released encapsulated debris that accumulated on the ocean floor. The team took sediment cores from the deep ocean in 3.5 km water depth from the area, dated the natural climate archive and counted the ice-rafted debris.

The scientists identified eight phased with high amounts of debris which they interpret as retreat phases of the Antarctic Ice Sheet after the Last Glacial Maximum about 19,000 to 9,000 years ago, when climate warmed and Antarctica shed masses of icebergs repeatedly into the ocean. The result of the new data-model study: each such phase destabilized the ice sheet within a decade and contributed to global sea-level rise for centuries to a millennium. The subsequent re-stabilization was equally rapidly within a decade.

The research team found three other independent pieces of evidence for such post-glacial tipping points: Model experiments showing the melting of the entire Antarctic ice sheet, a West Antarctic ice core documenting ice-sheet elevation draw-down and drill cores revealing a step-wise ice-sheet retreat across the Ross Sea shelf.

Today's ice mass loss could be start of long-lasting period

The results are also relevant for ice retreat observed today: "Our findings are consistent with a growing body of evidence suggesting the acceleration of Antarctic ice-mass loss in recent decades may mark the begin of a self-sustaining and irreversible period of ice sheet retreat and substantial global sea level rise," says study leader Dr. Michael Weber from the University of Bonn.

Combining the sediment record with computer models of ice sheet behaviour the team showed that each episode of increased iceberg calving reflected increased loss of ice from the interior of the ice sheet, not just changes in the already-floating ice shelves. "We found that iceberg calving events on multi-year time scales were synchronous with discharge of grounded ice from the Antarctic Ice Sheet," said Prof. Nick Golledge from the University of Wellington (New Zealand), who led the ice-sheet modelling.

Dr. Zoë Thomas, a co-author of the study from the University of New South Wales in Sydney, Australia, then applied statistical methods to the model outputs to see if early warning signs could be detected for tipping points in the ice sheet system. Her analyses confirmed that tipping points did indeed exist. "If it just takes one decade to tip a system like this, that's actually quite scary because if the Antarctic Ice Sheet behaves in future like it did in the past, we must be experiencing the tipping right now," Thomas said.

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Trace gases from ocean are source of particles accelerating Antarctic climate change

Scientists exploring the drivers of Antarctic climate change have discovered a new and more efficient pathway for the creation of natural aerosols and clouds which contribute significantly to temperature increases.

The Antarctic Peninsula has shown some of the largest global increases in near-surface air temperature over the last 50 years, but experts have struggled to predict temperatures because little was known about how natural aerosols and clouds affect the amount of sunlight absorbed by the Earth and energy radiated back into space.

Studying data from seas around the Peninsula, experts have discovered that most new particles are formed in air masses arriving from the partially ice-covered Weddell Sea -- a significant source of the sulphur gases and alkylamines responsible for 'seeding' the particles.

A new study shows that increased concentrations of sulphuric acid and alkylamines are essential for the formation of new particles around the northern Antarctic Peninsula. High concentrations of other acids and oxygenated organics coincided with high levels of sulphuric acid, but by themselves did not lead to measurable particle formation and growth.

An international team of researchers from the University of Birmingham; Institute of Marine Science, Barcelona, Spain; and King Abdulaziz University, Jeddah, Saudi Arabia studied summertime open ocean and coastal new particle formation in the region, based on data from ship and land stations, and today published its findings in Nature Geoscience.

The researchers revealed that the newly discovered pathway is more efficient than the ion-induced sulphuric acid-ammonia pathway previously observed in Antarctica and can occur rapidly under neutral conditions.

Study co-author Roy Harrison OBE, Professor of Environmental Health at the University of Birmingham, commented: "New particle formation is globally one of the major sources of aerosol particles and cloud condensation nuclei. This previously overlooked pathway to natural aerosol formation could prove a key tool in predicting the future climate of polar regions.

"The key to unlocking Antarctica's climate change lies in examining particles created in the atmosphere by the chemical reaction of gases. These particles start tiny and grow bigger, becoming cloud condensation nuclei leading to more reflective clouds which direct outgoing terrestrial radiation back to earth and warm the lower atmosphere."

New particle formation is globally one of the major sources of aerosol particles and cloud condensation nuclei. Existing research suggests that natural aerosols contribute disproportionately to global warming, whilst sulphuric acid is thought to be responsible for most aerosol seeding observed in the atmosphere.

The research team identified numerous sulphuric acid-amine cluster peaks during new particle formation events -- providing evidence that alkylamines provided the basis for sulphuric acid nucleation.

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