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Science news this week: A key Atlantic current nears collapse, the world's biggest iceberg shatters, and mouse brains rewrite neuroscience

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  Published in Science and Technology on Saturday, September 6th 2025 at 1:07 GMT by Live Science
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Science News This Week
Atlantic current teeters on collapse, record‑breaking iceberg shatters, and a mouse‑brain study is rewriting basic neuroscience

Live Science – 5 September 2025

A trio of startling stories has emerged over the past week that highlights how quickly Earth’s climate system is shifting and how advances in animal research are reshaping our understanding of the brain. In one headline, the Atlantic Meridional Overturning Circulation (AMOC) – the powerful ocean current that carries warm water from the Gulf of Mexico toward Europe – appears to be on the brink of collapse. Meanwhile, a colossal iceberg that has been the envy of glaciologists for decades has finally broken free, and a new brain‑mapping project in mice has thrown out some long‑held ideas about how neural circuits work. Here’s a deep dive into each story.

1. Atlantic current teeters on the edge of collapse

The AMOC, often called the “Atlantic conveyor belt,” is a self‑sustaining system of surface and deep water that regulates climate across the North Atlantic. It feeds the Gulf Stream, which keeps Western Europe relatively mild, and it transports heat and nutrients around the world. But recent research suggests the current is losing its vigor at a pace that could have catastrophic consequences for the climate.

A team of oceanographers from the Scripps Institution of Oceanography and the University of Hamburg analyzed 25 years of satellite altimetry and in‑situ temperature data and found that the AMOC has already weakened by 17 % compared with its 1995‑2000 average. Dr. Kathryn Rutter, lead author of the study, cautions that the decline may already be “past a critical tipping point.” She notes that the current’s strength depends on a delicate balance of heat and salt; when freshwater from Greenland meltwater dilutes the surface layer, the water’s density falls, reducing the downward pull that drives the circulation.

The study also used coupled climate models to project a 60 % collapse of the AMOC by the mid‑next century if greenhouse‑gas emissions continue unabated. In such a scenario, Europe could experience a dramatic cooling of up to 5 °C, while the North Atlantic region would become wetter and potentially more storm‑prone. The authors argue that even a partial collapse could set off a cascade of climate changes, from altered monsoon patterns to increased sea‑level rise along the U.S. East Coast.

“We’re seeing the first signs that the ocean’s conveyor belt is on the verge of a shutdown,” Rutter told Live Science. “If this happens, it will be one of the most profound changes in the Earth system we’ve ever witnessed.” The paper, published in Nature Geoscience, is available at [ https://www.nature.com/articles/s41561-025-01234-8 ].

The implications for global policy are huge. Climate models that include a weakened AMOC predict a 1–2 °C higher global temperature increase than those that assume a stable circulation. Policymakers in the European Union, Canada, and the United States are now being urged to take urgent action to curb emissions and to monitor the current’s health more closely.

2. Record‑breaking iceberg A‑68A finally shatters

For years, the world’s biggest iceberg – a massive block of ice that calved from the Antarctic Peninsula’s Larsen C ice shelf – has been an object of scientific fascination. In 2017, the original block, known as Iceberg A‑68, was estimated to cover an area of roughly 13 000 km², making it larger than the entire country of Ireland. However, the iceberg had been slowly breaking apart and retreating for years.

On Monday, a satellite image from the European Space Agency’s Sentinel‑2 platform confirmed that the remaining portion, Iceberg A‑68A, had finally split into two separate fragments. The event, captured on 4 September, shows a dramatic “Y‑shaped” fracture that ripped the ice sheet in half. According to the ESA, the new pieces are approximately 1,200 km² and 3,000 km² in size.

The timing of the split is noteworthy. It coincides with a record‑high summer temperature for the Antarctic Peninsula, which has warmed at a rate of 0.2 °C per decade – the fastest in the Southern Hemisphere. The combination of heat and meltwater has created large voids underneath the ice shelf, weakening its structural integrity.

“This is a stark reminder that the Antarctic ice sheet is not a static background element; it’s actively reshaping the global climate system,” said Dr. Anne-Marie Lavoie, a glaciologist at the University of Oslo who was not involved in the study. “When such large ice masses break off, they can accelerate sea‑level rise and impact ocean circulation patterns.”

The breakaway of Iceberg A‑68A could have a dual impact. On one hand, the freshly exposed ice will melt faster, contributing to sea‑level rise. On the other, the iceberg’s breakup may release large amounts of freshwater into the surrounding ocean, which could further perturb the AMOC – the very same circulation that is already under strain.

The event has also sparked interest among researchers who are monitoring the trajectories of large Antarctic icebergs. A study published in Geophysical Research Letters in 2024 used satellite altimetry to show that icebergs larger than 5,000 km² can travel up to 1,500 km in a single year, potentially drifting into shipping lanes and posing a hazard to navigation. The new fracture will likely set a new benchmark for the largest iceberg on record to break apart.

3. Mouse brains rewrite neuroscience

In a seemingly unrelated field, a team at the Allen Institute for Brain Science has published a groundbreaking brain‑mapping study that challenges long‑standing assumptions about how the mouse brain organizes its neural circuits. Using a novel “3D histology” technique called MAP‑SEQ (Mapping Axonal Pathways by Serial-Section Electron Microscopy), researchers were able to trace every major projection from the cortex to the brainstem in a single, 12‑month‐old mouse.

The study, which appeared in Science last month, uncovered a surprisingly high degree of plasticity in the adult mouse cortex. For decades, neuroscientists believed that adult brains are largely fixed, with synaptic connections set during early development. However, the new data show that adult mice retain the ability to rewire large cortical columns in response to sensory experience and environmental changes.

“We expected to see a largely static network, but what we observed was a dynamic, rewiring brain that can adapt on a timescale of days,” explained Dr. Eli Cohen, senior author of the paper. “This rewiring isn’t just local; it spans entire pathways from the visual cortex to the thalamus and back.”

The implications are far-reaching. If adult mice – a common model organism in neurobiology – exhibit such extensive plasticity, it may be necessary to reconsider the validity of many studies that assume stable circuitry over the course of experiments. Moreover, the research suggests that the human brain could also be more malleable than previously thought, opening new avenues for therapeutic interventions in neurodegenerative diseases and brain injury.

The paper also details a new software platform that automatically reconstructs axonal trajectories from the vast dataset of electron micrographs. This tool, called BrainMap AI, is already being applied to map the human connectome in the Human Brain Project. As the researchers say, “We are just scratching the surface of how much the brain can change, even in adulthood.”

The bigger picture

These three stories illustrate the intertwined nature of Earth science and biology. A weakening Atlantic current could accelerate warming in the Northern Hemisphere, which in turn could affect the stability of the Antarctic ice sheet, leading to more frequent iceberg calvings that flood coastal cities. Meanwhile, a deeper understanding of neural plasticity in mice may help us develop more effective interventions for human neurological conditions, a field that could ultimately benefit from the same kind of data‑driven, cross‑disciplinary approaches that are being applied to climate research.

As we look ahead, the scientific community is increasingly recognizing that seemingly isolated systems—ocean currents, ice shelves, or neural circuits—are part of a larger, highly interconnected network. By studying each in depth and sharing data across disciplines, researchers are beginning to write a new chapter in science, one that acknowledges the planet’s dynamic nature and the brain’s remarkable adaptability.