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    Clinicians could be fooled by biased AI, despite explanations

    AI models in health care are a double-edged sword, with models improving diagnostic decisions for some demographics, but worsening decisions for others when the model has absorbed biased medical data.
    Given the very real life and death risks of clinical decision-making, researchers and policymakers are taking steps to ensure AI models are safe, secure and trustworthy — and that their use will lead to improved outcomes.
    The U.S. Food and Drug Administration has oversight of software powered by AI and machine learning used in health care and has issued guidance for developers. This includes a call to ensure the logic used by AI models is transparent or explainable so that clinicians can review the underlying reasoning.
    However, a new study in JAMA finds that even with provided AI explanations, clinicians can be fooled by biased AI models.
    “The problem is that the clinician has to understand what the explanation is communicating and the explanation itself,” said first author Sarah Jabbour, a Ph.D. candidate in computer science and engineering at the College of Engineering at the University of Michigan.
    The U-M team studied AI models and AI explanations in patients with acute respiratory failure.
    “Determining why a patient has respiratory failure can be difficult. In our study, we found clinicians baseline diagnostic accuracy to be around 73%,” said Michael Sjoding, M.D., associate professor of internal medicine at the U-M Medical School, a co-senior author on the study.

    “During the normal diagnostic process, we think about a patient’s history, lab tests and imaging results, and try to synthesize this information and come up with a diagnosis. It makes sense that a model could help improve accuracy.”
    Jabbour, Sjoding, co-senior author, Jenna Wiens, Ph.D., associate professor of computer science and engineering and their multidisciplinary team designed a study to evaluate the diagnostic accuracy of 457 hospitalist physicians, nurse practitioners and physician assistants with and without assistance from an AI model.
    Each clinician was asked to make treatment recommendations based on their diagnoses. Half were randomized to receive an AI explanation with the AI model decision, while the other half received only the AI decision with no explanation.
    Clinicians were then given real clinical vignettes of patients with respiratory failure, as well as a rating from the AI model on whether the patient had pneumonia, heart failure or COPD.
    In the half of participants who were randomized to see explanations, the clinician was provided a heatmap, or visual representation, of where the AI model was looking in the chest radiograph, which served as the basis for the diagnosis.
    The team found that clinicians who were presented with an AI model trained to make reasonably accurate predictions, but without explanations, had their own accuracy increase by 2.9 percentage points. When provided an explanation, their accuracy increased by 4.4 percentage points.

    However, to test whether an explanation could enable clinicians to recognize when an AI model is clearly biased or incorrect, the team also presented clinicians with models intentionally trained to be biased — for example, a model predicting a high likelihood of pneumonia if the patient was 80 years old or older.
    “AI models are susceptible to shortcuts, or spurious correlations in the training data. Given a dataset in which women are underdiagnosed with heart failure, the model could pick up on an association between being female and being at lower risk for heart failure,” explained Wiens.
    “If clinicians then rely on such a model, it could amplify existing bias. If explanations could help clinicians identify incorrect model reasoning this could help mitigate the risks.”
    When clinicians were shown the biased AI model, however, it decreased their accuracy by 11.3 percentage points and explanations which explicitly highlighted that the AI was looking at non-relevant information (such as low bone density in patients over 80 years) did not help them recover from this serious decline in performance.
    The observed decline in performance aligns with previous studies that find users may be deceived by models, noted the team.
    “There’s still a lot to be done to develop better explanation tools so that we can better communicate to clinicians why a model is making specific decisions in a way that they can understand. It’s going to take a lot of discussion with experts across disciplines,” Jabbour said.
    The team hopes this study will spur more research into the safe implementation of AI-based models in health care across all populations and for medical education around AI and bias. More

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    Speed bumps under Thwaites Glacier could help slow its flow to the sea

    SAN FRANCISCO — Most of the news regarding the Thwaites Glacier, a Florida-sized slab of ice that is melting and currently contributing about 4 percent of global sea level rise, is bad. But a bit of good news may have emerged.

    A seismic survey of the bed beneath an upstream section of Thwaites has revealed rough high-rises of earth under the Antarctic glacier, which are comparable in height to the Manhattan skyline, glaciologist Coen Hofstede reported December 12 at a news conference during the American Geophysical Union fall meeting. These rugged rises may be snagging the glacier’s underbelly, slowing its flow toward the ocean and mitigating global sea level rise.

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    Glaciers flow somewhat like rivers, but much slower. Where Thwaites outlets into the ocean, it connects to a floating shelf of ice that braces and partially restrains the glacier. That ice shelf was once pinned upon an underwater mountain, which helped stabilize it (SN: 12/13/21). But now the shelf is so deteriorated that it’s basically unhitched, Erin Pettit, a glaciologist at Oregon State University in Corvallis, said at the news event.

    Fortunately, though, the glacier “is not going to suddenly flow off land,” thanks partly to what’s been discovered upstream, said Pettit, who was not involved in the discovery.  

    To image Thwaites’ underbelly, researchers used a tractorlike vehicle (background, center) to haul a seismic vibrator truck on a sled, as well as a 1.5-kilometer-long chain of seismometers (foreground), across the glacier’s surface. A caboose-train (left) used for cooking, eating and repairs accompanied the vibrator truck across the ice. Coen Hofstede

    More than 70 kilometers inland from Thwaites’ ice shelf, Hofstede and his colleagues conducted a seismic survey to probe the glacier’s underbelly. The team attached a 1.5-kilometer-long daisy-chain of seismometers to a vehicle equipped with a vibrating plate. Then they drove a roughly 200-kilometer-long stretch of the glacier, using the plate to generate seismic waves and the seismometers to record the waves’ reflectance off layers of ice and earth below. “It’s almost like radar,” said Hofstede, of the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research in Bremerhaven, Germany.

    A Pisten Bully (center left), a tracked vehicle able to maneuver on the ice, tows seismic equipment (red) across Thwaites Glacier. A second Pisten Bully (right) hauls the
    accommodation train with the crew’s sleeping tents.Ole Zeising

    The seismic waves revealed rises under Thwaites that are 10 to 20 kilometers long and toothed with blocks of sediment. These blocks stood up to 100 meters tall above the rises and stretched for up to several kilometers horizontally.

    The data showed that the upstream faces of these blocks appear to be under greater pressure than their downstream sides, and that there might be layers of deformed ice within the glacier above the rises. Hofstede hypothesizes that the rises and blocks are slowing Thwaites’ flow as its ice presses against them.

    Using computers to simulate the flow of Thwaites glacier shows that “it gets hung up on tall features,” said glaciologist Ben Smith of the University of Washington in Seattle, who was not involved in the work.

    The rises are probably related to a rift system, an area where tectonic forces have pulled the ground apart, Hofstede said. Under Thwaites, these rifts run roughly perpendicular to the glacier’s ice flow, sort of like speed bumps on a street.

    The findings will allow for more nuanced simulations of the glacier’s evolution, Hofstede said, which are crucial for understanding rates of sea level rise. More

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    Study assesses GPT-4’s potential to perpetuate racial, gender biases in clinical decision making

    Large language models (LLMs) like ChatGPT and GPT-4 have the potential to assist in clinical practice to automate administrative tasks, draft clinical notes, communicate with patients, and even support clinical decision making. However, preliminary studies suggest the models can encode and perpetuate social biases that could adversely affect historically marginalized groups. A new study by investigators from Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system, evaluated the tendency of GPT-4 to encode and exhibit racial and gender biases in four clinical decision support roles. Their results are published in The Lancet Digital Health.
    “While most of the focus is on using LLMs for documentation or administrative tasks, there is also excitement about the potential to use LLMs to support clinical decision making,” said corresponding author Emily Alsentzer, PhD, a postdoctoral researcher in the Division of General Internal Medicine at Brigham and Women’s Hospital. “We wanted to systematically assess whether GPT-4 encodes racial and gender biases that impact its ability to support clinical decision making.”
    Alsentzer and colleagues tested four applications of GPT-4 using the Azure OpenAI platform. First, they prompted GPT-4 to generate patient vignettes that can be used in medical education. Next, they tested GPT-4’s ability to correctly develop a differential diagnosis and treatment plan for 19 different patient cases from a NEJM Healer, a medical education tool that presents challenging clinical cases to medical trainees. Finally, they assessed how GPT-4 makes inferences about a patient’s clinical presentation using eight case vignettes that were originally generated to measure implicit bias. For each application, the authors assessed whether GPT-4’s outputs were biased by race or gender.
    For the medical education task, the researchers constructed ten prompts that required GPT-4 to generate a patient presentation for a supplied diagnosis. They ran each prompt 100 times and found that GPT-4 exaggerated known differences in disease prevalence by demographic group.
    “One striking example is when GPT-4 is prompted to generate a vignette for a patient with sarcoidosis: GPT-4 describes a Black woman 81% of the time,” Alsentzer explains. “While sarcoidosis is more prevalent in Black patients and in women, it’s not 81% of all patients.”
    Next, when GPT-4 was prompted to develop a list of 10 possible diagnoses for the NEJM Healer cases, changing the gender or race/ethnicity of the patient significantly affected its ability to prioritize the correct top diagnosis in 37% of cases.
    “In some cases, GPT-4’s decision making reflects known gender and racial biases in the literature,” Alsentzer said. “In the case of pulmonary embolism, the model ranked panic attack/anxiety as a more likely diagnosis for women than men. It also ranked sexually transmitted diseases, such as acute HIV and syphilis, as more likely for patients from racial minority backgrounds compared to white patients.”
    When asked to evaluate subjective patient traits such as honesty, understanding, and pain tolerance, GPT-4 produced significantly different responses by race, ethnicity, and gender for 23% of the questions. For example, GPT-4 was significantly more likely to rate Black male patients as abusing the opioid Percocet than Asian, Black, Hispanic, and white female patients when the answers should have been identical for all the simulated patient cases.
    Limitations of the current study include testing GPT-4’s responses using a limited number of simulated prompts and analyzing model performance using only a few traditional categories of demographic identities. Future work should investigate biases using clinical notes from the electronic health record.
    “While LLM-based tools are currently being deployed with a clinician in the loop to verify the model’s outputs, it is very challenging for clinicians to detect systemic biases when viewing individual patient cases,” Alsentzer said. “It is critical that we perform bias evaluations for each intended use of LLMs, just as we do for other machine learning models in the medical domain. Our work can help start a conversation about GPT-4’s potential to propagate bias in clinical decision support applications.” More

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    AI’s memory-forming mechanism found to be strikingly similar to that of the brain

    An interdisciplinary team consisting of researchers from the Center for Cognition and Sociality and the Data Science Group within the Institute for Basic Science (IBS) revealed a striking similarity between the memory processing of artificial intelligence (AI) models and the hippocampus of the human brain. This new finding provides a novel perspective on memory consolidation, which is a process that transforms short-term memories into long-term ones, in AI systems.
    In the race towards developing Artificial General Intelligence (AGI), with influential entities like OpenAI and Google DeepMind leading the way, understanding and replicating human-like intelligence has become an important research interest. Central to these technological advancements is the Transformer model, whose fundamental principles are now being explored in new depth.
    The key to powerful AI systems is grasping how they learn and remember information. The team applied principles of human brain learning, specifically concentrating on memory consolidation through the NMDA receptor in the hippocampus, to AI models.
    The NMDA receptor is like a smart door in your brain that facilitates learning and memory formation. When a brain chemical called glutamate is present, the nerve cell undergoes excitation. On the other hand, a magnesium ion acts as a small gatekeeper blocking the door. Only when this ionic gatekeeper steps aside, substances are allowed to flow into the cell. This is the process that allows the brain to create and keep memories, and the gatekeeper’s (the magnesium ion) role in the whole process is quite specific.
    The team made a fascinating discovery: the Transformer model seems to use a gatekeeping process similar to the brain’s NMDA receptor. This revelation led the researchers to investigate if the Transformer’s memory consolidation can be controlled by a mechanism similar to the NMDA receptor’s gating process.
    In the animal brain, a low magnesium level is known to weaken memory function. The researchers found that long-term memory in Transformer can be improved by mimicking the NMDA receptor. Just like in the brain, where changing magnesium levels affect memory strength, tweaking the Transformer’s parameters to reflect the gating action of the NMDA receptor led to enhanced memory in the AI model. This breakthrough finding suggests that how AI models learn can be explained with established knowledge in neuroscience.
    C. Justin LEE, who is a neuroscientist director at the institute, said, “This research makes a crucial step in advancing AI and neuroscience. It allows us to delve deeper into the brain’s operating principles and develop more advanced AI systems based on these insights.”
    CHA Meeyoung, who is a data scientist in the team and at KAIST, notes, “The human brain is remarkable in how it operates with minimal energy, unlike the large AI models that need immense resources. Our work opens up new possibilities for low-cost, high-performance AI systems that learn and remember information like humans.”
    What sets this study apart is its initiative to incorporate brain-inspired nonlinearity into an AI construct, signifying a significant advancement in simulating human-like memory consolidation. The convergence of human cognitive mechanisms and AI design not only holds promise for creating low-cost, high-performance AI systems but also provides valuable insights into the workings of the brain through AI models. More

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    Invisible comet tails of mucus slow sinking flakes of ‘marine snow’

    WASHINGTON — Tiny, sinking flakes of detritus in the ocean fall more slowly thanks to the goop that surrounds each flake, new observations reveal.

    The invisible mucus makes “comet tails” that surround each flake, physicist Rahul Chajwa of Stanford University reported November 19 at the American Physical Society’s Division of Fluid Dynamics meeting. Those mucus tails slow the speed at which the flakes fall. That could affect the rate at which carbon gets sequestered deep in the oceans, making the physics of this sticky goo important for understanding Earth’s climate.

    Although scientists knew the goo was a component of the “marine snow” that falls in the ocean, they hadn’t previously measured its impact on sinking speed.

    Marine snow is made of dead and living phytoplankton, decaying organic matter, feces, bacteria and other aquatic sundries, all wrapped up in mucus that’s produced by the organisms. Like the gunk known for clogging airways during respiratory virus season, the mucus is what’s called a viscoelastic fluid (SN: 3/17/16). That’s something that flows like a liquid but exhibits elastic behavior as well, springing back after being stretched.

    This underwater blizzard is not easy to study. When observed in the ocean, the particles sink swiftly out of view. In the laboratory, the particles can be viewed for longer periods, but the trek ashore degrades the delicate marine snow and kills the living organisms within it.

    [embedded content]
    Tiny particles (white dots) within a seawater-filled chamber were used to measure the rate at which fluid flows around this flake of marine snow as it falls. The chamber is designed to keep the sinking snowflake in view of the camera.

    So Chajwa and colleagues built a physics lab at sea. Aboard a research vessel in the Gulf of Maine, the team collected marine snow particles in traps 80 meters below the water’s surface. Then they loaded their catch into a device onboard, designed to observe the particles falling.

    Nicknamed “the gravity machine,” it’s a fluid-filled wheel that rotates in order to keep an individual flake in view of a camera. It’s a bit like a hamster wheel for falling debris. As the flake sinks, the wheel turns so as to move the snow in the opposite direction, allowing the snowfall to be observed indefinitely. The gravity machine was itself mounted on a gimbal designed to stave off sloshing from the rocking of the ship.

    “It’s a very nice compromise between the real marine snow that you get in the ocean versus what you can do practically in the lab,” says biophysicist Anupam Sengupta of the University of Luxembourg, who was not involved with the research.

    To observe how the fluid flowed around the particles, the researchers added tiny beads within the fluid in the gravity machine. That revealed the rate of fluid flow around the particles. The speed of fluid flow was slowed in a comet tail–shaped region around the particle, revealing the invisible mucus that sinks along with the particle.

    Marine snow particles (one shown) are surrounded with invisible mucus. Drag the slider to see how fluid flows around the flake as it falls. Slower speeds (yellow) reveal mucus that trails the flake in a comet tail–shape (red dotted line). Left: Rahul Chajwa and Manu Prakash/PrakashLab/Stanford UniversityRight: Rahul Chajwa and Manu Prakash/PrakashLab/Stanford University

    The particles sank at speeds up to 200 meters per day. The mucus played a big role in sinking speed. “The more the mucus, the slower the particles sink,” Chajwa says. On average, the mucus causes the marine snow particles to linger twice as long in the upper 100 meters of the ocean as they otherwise would, Chajwa and colleagues determined.

    If it falls deep enough, marine snow can sequester carbon away from the atmosphere. That’s because living phytoplankton, like plants, take in carbon dioxide and release oxygen. When phytoplankton form marine snow, they take that carbon along with them as they sink. If a flake reaches the ocean floor, it can settle into a scum at the bottom that caches that carbon over long time periods. The faster the particles sink, the more likely they are to make it to the abyss before being eaten by critters (SN: 6/23/22).

    Knowing how fast the particles sink is important for calculating the ocean’s impact on Earth’s climate, and how that might change as the climate warms, the researchers say. The oceans are major players in the planet’s carbon cycle (SN: 12/2/21), and scientists estimate that oceans have taken up roughly 30 percent of the carbon dioxide released by humans since industrialization. Chajwa and colleagues hope that their results can be used to refine climate models, which currently do not take the mucus into account.

    So this mucus is nothing to sneeze at. “We’re talking about microscopic physics,” says Stanford physicist Manu Prakash, a coauthor of the work, which is also reported in a paper submitted October 3 at arXiv.org. “But multiply that by the volume of the ocean … that’s what gives you the scale of the problem.” More

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    Air conditioning has reduced mortality due to high temperatures in Spain by one third

    Air conditioning and heating systems have contributed considerably to reducing mortality linked to extreme temperatures in Spain, according to a study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the “la Caixa” Foundation. The findings, published in Environment International, provide valuable insights for designing policies to adapt to climate change.
    Rising temperatures but lower mortality
    Spain, like many parts of the world, has experienced rising temperatures in recent decades, with the average annual mean temperature increasing at an average rate of 0.36°C per decade. The warming trend is even more pronounced in the summer months (0.40°C per decade). Surprisingly, this increase in temperature has coincided with a progressive reduction in mortality associated with heat. In addition, cold-related mortality has also decreased.
    “Understanding the factors that reduce susceptibility to extreme temperatures is crucial to inform health adaptation policies and to combat the negative effects of climate change,” says first author of the study, Hicham Achebak, researcher at ISGlobal and Inserm (France) and holder of a Marie Sklodowska-Curie Postdoctoral Fellowship from the European Commission.
    Effective societal adaptations
    In this study, Achebak and colleagues analysed the demographic and socioeconomic factors behind the observed reduction in heat and cold-related mortality, despite rising temperatures. They found that the increase in air conditioning (AC) prevalence in Spain was associated with a reduction in heat-related mortality, while the rise in heating prevalence was associated with a decrease in cold-related mortality. Specifically, AC was found to be responsible for about 28.6% of the decline in deaths due to heat and 31.5% of the decrease in deaths due to extreme heat between the late 1980s and the early 2010s. Heating systems contributed significantly, accounting for about 38.3% of the reduction in cold-related deaths and a substantial 50.8% decrease in extreme cold-related fatalities during the same period. The decrease in mortality due to cold would have been larger had there not been a demographic shift towards a higher proportion of people aged over 65, who are more susceptible to cold temperatures.
    The authors conclude that the reduction in heat-related mortality is largely the result of the country’s socioeconomic development over the study period, rather than specific interventions such as heat-wave warning systems.

    Four decades of data
    For the statistical analysis, the research team collected data on daily mortality (all causes) and weather (temperature and relative humidity) for 48 provinces in mainland Spain and the Balearic Islands, between January 1980 and December 2018. These data were then linked to 14 indicators of context (demographic and socioeconomic variables such as housing, income and education) for these populations over the same period.
    Implications for climate adaptation
    The results of the study extend previous findings on heat-related mortality in Spain and underscore the importance of air conditioning and heating as effective adaptation measures to mitigate the effects of heat and cold. “However, we observed large disparities in the presence of AC across provinces. AC is still unaffordable for many Spanish households,” says Achebak.
    The authors also point out that the widespread use of AC could further contribute to global warming depending on the source of electricity generation, which is why other cooling strategies, such as expanding green and blue spaces in cities, are also needed.
    “Our findings have important implications for the development of adaptation strategies to climate change. They also inform future projections of the impact of climate change on human health,” concludes Joan Ballester, ISGlobal researcher and study coordinator. More

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    Artificial intelligence can predict events in people’s lives

    Artificial intelligence developed to model written language can be utilized to predict events in people’s lives. A research project from DTU, University of Copenhagen, ITU, and Northeastern University in the US shows that if you use large amounts of data about people’s lives and train so-called ‘transformer models’, which (like ChatGPT) are used to process language, they can systematically organize the data and predict what will happen in a person’s life and even estimate the time of death.
    In a new scientific article, ‘Using Sequences of Life-events to Predict Human Lives’, published in Nature Computational Science, researchers have analyzed health data and attachment to the labour market for 6 million Danes in a model dubbed life2vec. After the model has been trained in an initial phase, i.e., learned the patterns in the data, it has been shown to outperform other advanced neural networks (see fact box) and predict outcomes such as personality and time of death with high accuracy.
    “We used the model to address the fundamental question: to what extent can we predict events in your future based on conditions and events in your past? Scientifically, what is exciting for us is not so much the prediction itself, but the aspects of data that enable the model to provide such precise answers,” says Sune Lehmann, professor at DTU and first author of the article.
    Predictions of time of death
    The predictions from Life2vec are answers to general questions such as: ‘death within four years’? When the researchers analyze the model’s responses, the results are consistent with existing findings within the social sciences; for example, all things being equal, individuals in a leadership position or with a high income are more likely to survive, while being male, skilled or having a mental diagnosis is associated with a higher risk of dying. Life2vec encodes the data in a large system of vectors, a mathematical structure that organizes the different data. The model decides where to place data on the time of birth, schooling, education, salary, housing and health.
    “What’s exciting is to consider human life as a long sequence of events, similar to how a sentence in a language consists of a series of words. This is usually the type of task for which transformer models in AI are used, but in our experiments we use them to analyze what we call life sequences, i.e., events that have happened in human life,” says Sune Lehmann.
    Raising ethical questions
    The researchers behind the article point out that ethical questions surround the life2vec model, such as protecting sensitive data, privacy, and the role of bias in data. These challenges must be understood more deeply before the model can be used, for example, to assess an individual’s risk of contracting a disease or other preventable life events.

    “The model opens up important positive and negative perspectives to discuss and address politically. Similar technologies for predicting life events and human behaviour are already used today inside tech companies that, for example, track our behaviour on social networks, profile us extremely accurately, and use these profiles to predict our behaviour and influence us. This discussion needs to be part of the democratic conversation so that we consider where technology is taking us and whether this is a development we want,” says Sune Lehmann.
    According to the researchers, the next step would be to incorporate other types of information, such as text and images or information about our social connections. This use of data opens up a whole new interaction between social and health sciences.
    The research project
    The research project ‘Using Sequences of Life-events to Predict Human Lives’ is based on labour market data and data from the National Patient Registry (LPR) and Statistics Denmark. The dataset includes all 6 million Danes and contains information on income, salary, stipend, job type, industry, social benefits, etc. The health dataset includes records of visits to healthcare professionals or hospitals, diagnosis, patient type and degree of urgency. The dataset spans from 2008 to 2020, but in several analyses, researchers focus on the 2008-2016 period and an age-restricted subset of individuals.
    Transformer model
    A transformer model is an AI, deep learning data architecture used to learn about language and other tasks. The models can be trained to understand and generate language. The transformer model is designed to be faster and more efficient than previous models and is often used to train large language models on large datasets.
    Neural networks
    A neural network is a computer model inspired by the brain and nervous system of humans and animals. There are many different types of neural networks (e.g. transformer models). Like the brain, a neural network is made up of artificial neurons. These neurons are connected and can send signals to each other. Each neuron receives input from other neurons and then calculates an output passed on to other neurons. A neural network can learn to solve tasks by training on large amounts of data. Neural networks rely on training data to learn and improve their accuracy over time. But once these learning algorithms are fine-tuned for accuracy, they are potent tools in computer science and artificial intelligence that allow us to classify and group data at high speed. One of the most well-known neural networks is Google’s search algorithm.  More

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    3 Antarctic glaciers show rapidly accelerated ice loss from ocean warming

    SAN FRANCISCO — Several Antarctic glaciers are undergoing dramatic acceleration and ice loss. Hektoria Glacier, the worst affected, has quadrupled its sliding speed and lost 25 kilometers of ice off its front in just 16 months, scientists say.

    The rapid retreat “is really unheard of,” says Mathieu Morlighem, a glaciologist at Dartmouth College who was not part of the team reporting these findings.

    The collapse was triggered by unusually warm ocean temperatures, which caused sea ice to retreat. This allowed a series of large waves to hit a section of coastline that is normally shielded from them. “What we’re seeing here is an indication of what could happen elsewhere” in Antarctica, says Naomi Ochwat, a glaciologist at the University of Colorado Boulder who presented the findings December 11 at the American Geophysical Union meeting.

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    Hektoria Glacier, Green Glacier, and Crane Glacier sit near the tip of the Antarctic Peninsula, which reaches up toward South America. The crescent moon–shaped bay, called the Larsen B Embayment, once seemed stable. As these glaciers oozed off the coastline, their ice used to merge into a floating slab around 200 meters thick. This slab, called the Larsen B Ice Shelf, was about the size of Rhode Island and filled the entire bay.

    Having existed for over 10,000 years, this ice shelf buttressed and stabilized the glaciers flowing into it. But during a warm summer in 2002, it suddenly fragmented into thousands of skinny icebergs (SN: 3/27/02).

    Hektoria, Green, and Crane glaciers — no longer contained by the ice shelf —  began to flow into the ocean several times faster than they had before, shedding billions of tons of ice over the next decade.

    Then starting in 2011, the hemorrhaging slowed down. The thin veneer of sea ice that forms over the bay each winter began to persist year round, preserved by a series of cold summers. This “landfast ice,” attached firmly to the coastline, grew five to 10 meters thick, stabilizing the glaciers. Their floating tongues gradually advanced back into the bay. But things changed abruptly in early 2022. On January 19 and 20, the landfast ice disintegrated into fragments, which drifted away.

    Satellite images taken just 10 days apart reveal the dramatic breakup of sea ice in Antarctica’s Larsen B Embayment. On January 16, 2022, sea ice filled the bay (left). By January 26 (right), the ice had fractured and was drifting away following a series of powerful waves that struck the bay several days earlier. Left: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASARight: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASA

    Using data from ocean buoys farther north, Ochwat and colleagues determined that a series of powerful waves, higher than 1.5 meters, had swept in from the northeast — cracking apart the landfast ice. Those waves were highly unusual for this area.

    The Southern Ocean, which encircles Antarctica, holds some of the world’s roughest waters. The Antarctic Peninsula extends up into this turbulent region, but its east side, where the Larsen B Embayment sits, rarely feels the waves. It is normally protected by several hundred kilometers of pack ice — floes of sea ice, pressed together by ocean currents — that dampen the waves, leaving the waters near Larsen as flat as a mirror.

    In 2022, water temperatures near the surface of the Southern Ocean rose several tenths of a degree Celsius higher than normal, causing pack ice to shrink and peel away from the peninsula. This exposed the area to waves, which then broke up the landfast sea ice.

    The glaciers accelerated as their floating tongues, no longer held in place, fragmented into bergs. Crane Glacier lost 11 kilometers of ice, nearly erasing its floating tongue; Green Glacier lost 18 kilometers, encompassing all of its floating ice.

    Hektoria lost all 15 kilometers of its floating ice — followed by another 10 kilometers of ice that is normally more stable, because it rests on the seafloor. That “is faster than any tidewater glacier retreat that we know of,” Ochwat says.

    The previous standout, Alaska’s Columbia Glacier, had lost 20 kilometers of ice in 30 years, records show. But Hektoria lost its 10 kilometers of nonfloating ice in just five months — including 2.5 kilometers that crumbled in a 3-day period.

    All of this suggests that people trying to predict sea level rise need to consider sea ice, Morlighem says. Up until now, “its role in [glacier] dynamics has been completely ignored.”

    Ochwat is waiting to see what will happen as the current Antarctic summer heats up between December and March. Hektoria and the other glaciers have been retreating only during summer months, when sea ice is absent; they pause during winter, when the surface of the bay freezes for a few months.

    If Antarctic sea ice continues to shrink, as it has since 2022, it could spell trouble, says study coauthor Ted Scambos, a glaciologist also at UC Boulder. “You’re going to have a longer section of coastline where wave action can act on the front of ice shelves and glaciers,” potentially accelerating glacial retreat. More