Category: 7. Science

A major ocean current in the Southern Hemisphere has reversed direction for the first time in recorded history, in what climatologists are calling a “catastrophic” tipping point in the global climate system.

The development, which was confirmed by Spanish marine scientists at El Institut de Ciències del Mar (ICM-CSIC) in Barcelona, has triggered widespread alarm among climate scientists due to its potential to accelerate global warming and destabilise weather patterns worldwide.

“The stunning reversal of ocean circulation in the Southern Hemisphere confirms the global climate system has entered a catastrophic phase,” said climatologist Ben See in a post on social media.

The collapse involves the deep overturning circulation in the South Atlantic — part of the global conveyor belt of ocean currents — which typically pulls cold, nutrient-rich water up from the ocean floor and drives planetary heat distribution.

The study, published on July 2, identifies a collapse and reversal of the Deep Western Boundary Current (DWBC) in the South Atlantic — a key part of the Atlantic Meridional Overturning Circulation (AMOC).

This current system plays a crucial role in regulating global temperatures and storing atmospheric carbon dioxide in the deep ocean. The ICM’s data show that the flow of the DWBC current reversed from northward to southward for several consecutive months in 2023 — the first such event in 30 years of continuous monitoring.

“This is an unprecedented observation and a potential game-changer,” said physicist and lead author Dr Marilena Oltmanns, who warned the changes could “alter the Southern Ocean’s capacity to sequester heat and carbon.”

According to the ICM-CSIC, the reversal is likely linked to an ongoing weakening of the Antarctic overturning circulation, a deep-ocean process driven by the formation of cold, salty water masses near Antarctica. That system has slowed by up to 40% since the late 1990s, and the new findings suggest it may be destabilising regional ocean dynamics more rapidly than expected.

There has been a lot of speculation that the whole AMOC (otherwise known as the Gulf Stream), could come to a halt. The AMOC brings warm water to Europe from the equator, and when it stops flowing that will lead to a mini-ice age in Europe with winter temperatures dropping by 10-30C. While scientists are 98% certain that the AMOC will stop flowing by 2100, recent studies suggest that the collapse could come as soon as this year,  or at least in the next few decades.

The ICM report warns that the reversal of the DWBC could also unleash vast amounts of carbon dioxide currently trapped in deep-ocean reservoirs. The reversal will undermine the ocean’s role as a carbon sink, which currently absorbs about 25% of all anthropogenic CO₂ emissions.

“This could double current atmospheric CO₂ concentrations by releasing carbon that has been stored in the deep ocean for centuries,” the report said. Such a release would likely obliterate existing climate targets, as the additional emissions would overwhelm current carbon budgets and render mitigation strategies based on gradual reductions, obsolete.

“The planet is sending us increasingly clear signals that we are crossing critical thresholds,” the ICM warned, characterising the event as a shift from “chronic climate stress” to “acute systemic breakdown.”

The reversal threatens to weaken the ocean’s crucial role as a carbon sink — one of the Earth’s key natural defences against rising atmospheric CO₂ — and will also dramatically disrupt global weather systems, sea level patterns, and marine ecosystems.

The Mediterranean is as hot as bathwater

The event coincides with an unprecedented marine heatwave in the Mediterranean. A Spanish metrological buoy recorded a sea temperature of 31C on July 4 – as hot as a lukewarm bath. The northwestern Mediterranean Sea has recorded a temperature anomaly of +6.21°C above the 1982–2015 average, part of a pattern of record marine heatwaves that scientists say are reshaping entire ecosystems.

The northwestern Mediterranean Sea is currently 6.21°C above the 1982–2015 average, creating what scientists have called “bathwater” conditions in a historically temperate basin. Warmer surface temperatures could further stall or disrupt ocean currents, feeding a dangerous feedback loop of warming and current instability.

While ocean circulations have shifted in the deep past due to glacial cycles, the current reversal is the first to occur in modern times due to anthropogenic climate change. Researchers now warn of increased risk of abrupt changes in monsoon patterns, fisheries collapse, and a rapid sea-level rise in the Southern Hemisphere. They are calling for immediate global attention and a reassessment of climate adaptation strategies in light of what may be a new and more volatile climate regime.

“The stunning reversal of ocean circulation in the Southern Hemisphere confirms the global climate system has entered a catastrophic phase,” said climatologist Ben See on social media.

The reversal of the current will bring cold water up from the deep in which is trapped CO₂. That means the reversal, “could double current atmospheric CO₂ concentrations by releasing carbon that has been stored in the deep ocean for centuries,” the El Institut de Ciencies del Mar said.

“The planet is sending us increasingly clear signals that we are crossing critical thresholds,” the Institut added.

Antarctica has seen a drastic environmental shift in recent years, a change that has led to an alarming loss of sea ice. In a landmark discovery, scientists have determined that since 2015, Antarctica has shed as much ice as the entire size of Greenland. This rapid ice loss, however, is only part of a larger, troubling trend. Recent studies published by the Proceedings of the National Academy of Sciences (PNAS) highlight an unexpected rise in salinity in the Southern Ocean. This change has triggered a cascade of reactions, with the most notable being the melting of sea ice from below. The consequences of these changes extend far beyond the Antarctic region, with global implications for climate patterns, sea levels, and wildlife habitats.

One of the most alarming findings is the reappearance of the Maud Rise polynya—a massive hole in the sea ice that hadn’t been seen since the 1970s. This phenomenon is a key marker of the current changes underway in the Southern Ocean. The re-emergence of the polynya signifies the growing instability in the ice-ocean system, making the Southern Ocean more susceptible to the warming trends driven by the increasing salinity. As these changes intensify, researchers are warning that Antarctica could permanently reshape the world’s oceans and climate systems.

Sudden Surge in Southern Ocean Salinity

In a surprising twist, the Southern Ocean has experienced a significant increase in surface salinity. For decades, scientists had observed a trend of freshening in the surface waters, which played a crucial role in sustaining sea ice. However, this trend has now reversed. The rise in salinity, detected by European satellites and advanced oceanographic devices, has weakened the stratification of water layers. This change has made it easier for deep, warmer ocean waters to rise to the surface, bringing with them enough heat to melt the sea ice from below.

The shift from freshening to salting has created a dangerous feedback loop: less sea ice leads to more heat absorption, which in turn melts more ice. As this loop intensifies, the effects are being felt globally. The warmer temperatures in the Southern Ocean contribute to stronger storms, more volatile weather patterns, and rising ocean temperatures. These changes not only affect the Antarctic ecosystem but also have far-reaching impacts on marine life across the planet.

The Maud Rise Polynya and Its Global Implications

The return of the Maud Rise polynya after 50 years of absence is one of the most striking indicators of the dramatic changes unfolding in the Southern Ocean. This massive hole in the sea ice is a rare and unusual occurrence, almost four times the size of Wales. Its sudden appearance is linked to the rising salinity levels, which have allowed deeper ocean heat to melt the ice from beneath.

Dr. Alessandro Silvano from the University of Southampton, who led the research, explained, “The return of the Maud Rise polynya signals just how unusual the current conditions are. If this salty, low-ice state continues, it could permanently reshape the Southern Ocean — and with it, the planet.” These changes are already being felt on a global scale. As ice retreats, it alters the albedo effect, reducing the Earth’s natural ability to reflect sunlight and accelerating global warming. This also leads to more extreme weather events, including stronger storms and shifts in ocean currents. Antarctic wildlife, including penguins and other species dependent on the ice, are facing shrinking habitats, pushing them further toward the brink of survival.

Urgency for Monitoring and Predicting Future Shifts

Given the rapid pace of these changes, scientists are calling for more robust monitoring systems to track the evolving conditions in the Southern Ocean. The rise in surface salinity and the loss of sea ice are unexpected developments that challenge previous models of Antarctic climate behavior. Professor Alberto Naveira Garabato, co-author of the study, emphasized the need for continuous observation to better predict and understand these shifts. “The new findings suggest that our current understanding may be insufficient to accurately predict future changes,” he said.

He also pointed out, “It makes the need for continuous satellite and in-situ monitoring all the more pressing, so we can better understand the drivers of recent and future shifts in the ice-ocean system.” Without real-time data and a more accurate model of these changes, scientists will struggle to forecast the long-term effects of these environmental disruptions. More research and monitoring are critical for not only understanding the causes behind the changes in the Southern Ocean but also for developing strategies to mitigate their impact on global ecosystems.

Pexels

When astronauts go to space, there’s no doctors to care for them if they get sick.

That’s why astronauts are given significant first aid training, with an astronaut sustaining an injury able to receive sutures, for example, from one of their colleagues in space.

It’s also the reason for the extreme cleanliness that is enforced on space stations, with astronauts expected to adhere to strict cleaning and hygiene protocols, to avoid any risk of contamination or infection while they’re situated 250 miles above ground.

If the worst should come to the worst, a rescue mission is launched; but this to be avoided, since it’s a very costly process.

Pexels

It’s surprising then, given the extreme hygiene observed on space stations, that a new strain of bacteria has been identified on board China’s Tiangong Space Station.

And what is even more surprising is that this bacterial strain has only ever been discovered onboard Tiangong.

In an article recently published in the International Journal of Systematic Evolutionary Microbiology, scientists explain their discovery:

“In this study, a Gram-positive, aerobic, spore-forming, rod-shaped strain JL1B1071T was isolated from the surface of hardware on the China Space Station. This strain belongs to the genus Niallia, with its closest relative being Niallia circulans ATCC 4513T.”

Freshly named Niallia Tiangongensis, this bacteria is not dissimilar to an earthly bacteria known as Nialla circulans, a human pathogen which can survive without oxygen and is found in sewage and human waste, food and soil.

Pexels

How did the pathogen get there?

Well this is still up for debate, with scientists suggesting that it could have adapted from Niallia circulans that naturally occur onboard Tiangong as a result of the human activities of the taikonauts (Chinese astronauts) on board the space station.

This is not uncommon practice for pathogens, which regularly mutate as a result of their evolutionary processes. In the conditions on board a space station – very different to the conditions on Earth – the pathogen could have adapted to better suit its new environment.

While on the surface the discovery of Niallia Tiangonensis could seem concerning, it is actually fascinating for our understanding of bacteria and its evolutions in space. This is vital information for future missions, and our understanding of our pathogens on Earth – though of course, as the authors state in their study, the prominent concern is the health of astronauts and taikonauts:

“Understanding the characteristics of microbes during long-term space missions is essential for safeguarding the health of astronauts and maintaining the functionality of spacecraft.”

As more people – and their respective pathogens – travel to space, it is likely that this is only the beginning.

If you thought that was interesting, you might like to read a story that reveals Earth’s priciest precious metal isn’t gold or platinum and costs over $10,000 an ounce!

Trinity College Dublin now has Ireland’s first and only BioBrillouin microscope, which will enable researchers to make giant strides in the fields of inflammation, cancer, developmental biology and biomedical materials, among others.

Cellular and tissue mechanics are potent regulators of disease, dysfunction and regeneration, and understanding them is thus a major focus of biomedical researchers. But existing methods are invasive and limited in the information that they can provide. 

However, the incredible new Brillouin microscope can map and quantify the compressibility, viscoelasticity and the detailed mechanics of materials and biological tissues, using non-invasive light. This enables researchers to assess the mechanical properties of live systems (such as cells and tissues) without interfering with them, allowing them to monitor a system and how it changes over time. It is based on light scattering from the result of interactions between a photon of light and the acoustic phonons of a material, which are impacted by the material’s mechanical properties. 

With the support of the European Research Council (ERC) and Research Ireland, the Brillouin microscopy system has been installed in the lab of Prof. Michael Monaghan in the School of Engineering at Trinity, where it is housed in the Trinity Centre for Biomedical Engineering at the Trinity Biomedical Sciences Institute. 

”Being the first commercial system in the world, we have tremendous technical support from the vendor, CellSense Technologies GmbH, with whom we have worked closely with to get the system on the ground. Our success is their success,” said Prof. Monaghan, who is a contributor to an expert consensus paper published today in leading international journal Nature Photonics.

This statement gathers the expertise of international experts in the application of Brillouin microscopy in biomedical applications. 

Studying the mechanical properties of live systems is hugely relevant in myriad fields, and promises to enable leaps forward in our understanding of the ways in which inflammation and cancer develop, for example.

However, it’s also important to understand its use is not limited to biomedical research and related applications – it will help scientists push boundaries even further in fields such as materials science, ICT, energy storage, pharmaceuticals, and medical devices and diagnostics. This groundbreaking equipment will help us advance frontier science, and we anticipate scientists will travel from all over the world to use it – we have welcomed some already.”

Prof. Michael Monaghan, School of Engineering at Trinity

A heartbeat-like pulse has been discovered beating deep beneath East Africa – and it’s ripping the continent apart.

The strange thumping is caused by a rhythmic surge of molten mantle rock rising and falling under the Earth’s surface, according to a recent study in Nature Geoscience. The surges are so powerful that, over millions of years, they could split Africa in two and create a brand new ocean.

The geological pulse was detected in the Afar Triangle, a region where three tectonic plates – the African, Somali, and Arabian plates – meet beneath Ethiopia, Eritrea, and Djibouti. Known as a tectonic triple junction, it’s one of the few places on Earth where the planet’s crust is being pulled in three different directions at once.

As these plates drift apart, they create deep cracks called rifts, places where the Earth’s crust stretches thinner and thinner until it eventually breaks. It’s within these rifts that the discovery was made.

“We found that the mantle beneath Afar is not uniform or stationary – it pulses,” said Dr Emma Watts, a geologist from Swansea University, who led the study.

To investigate, the research team collected volcanic rock samples from the region and analysed their chemical makeup. What they found was a kind of ‘geological barcode’ – a repeating pattern of chemical signatures, showing the magma plume rising and falling over millions of years. 

In some cases, the barcode was more spread out than others, revealing the rifts were channelling the pulsing magma.

“The chemical striping suggests the plume is pulsing, like a heartbeat,” said Prof Tom Gernon from the University of Southampton, who also took part in the study.

These pulses, he explained, behave differently depending on the structure of the Earth’s crust. In places where the crust is thinner or where the rifting happens faster, such as along the Red Sea, the magma pulses travel more easily, like a pulse travelling through an artery.

“We have found that the evolution of deep mantle upwellings is intimately tied to the motion of the plates above,” said Prof Derek Keir, also from the University of Southampton and co-author of the study.

“This has profound implications for how we interpret surface volcanism, earthquake activity, and the process of continental breakup.”

Read more:

Researchers have discovered evidence of human interaction with megafauna considerably earlier than the widely accepted arrival of humans in South America. A 33,000-year-old right calcaneus (heel bone) of the giant ground sloth Lestodon armatus, discovered in Arroyo del Vizcaíno in southern Uruguay, shows a deep indentation that may have been created by a human-made weapon.

The fossil is dated to around 33,000 calibrated years ago and is from an intensely dense bone bed of more than 2,000 megafaunal remains dominated by L. armatus. The bone, CAV 45, has a circular, cone-shaped depression approximately 21 mm in diameter and almost 41 mm deep. Its characteristics include smooth entry edges and conchoidal fractures—an indicator of forceful penetration into thick, cortical bone.

Through CT scanning and silicone casting, the researchers were able to map the wound structure. Microscopic inspection showed fine parallel striations within the cavity, which revealed that the penetrating object rotated and shifted laterally during insertion.

Organic fiber residue tests also showed that plant materials are still lodged in the indentation. This suggests not only trauma, but also possible transfer of tool-making residues like wood or whisker-hardened tips.

To determine if the indentation was caused by human or natural forces, alternative causes—carnivore bites, erosion, and accidental impacts—were considered by the researchers. Carnivores such as saber-toothed cats and giant bears make specific tooth marks, none of which match this circular bore. The same applies to accidental rock impacts or trampling, where one would expect irregular fractures, not the clean, cone-shaped hole observed. The mark’s extent and uniqueness argue against involvement by natural agents.

The shape of the indentation shows that the tip must have been rounded, not sharp, so the authors suggest that it could be a hardened wooden shaft with a bone, ivory, or hardwood point being driven in with enough force and rotation to pierce thick bone.

The angle of penetration—about 60° relative to the ground—fits a possible close-range hunting scenario. It would be in line with a thrusting action, possibly aimed at immobilizing the large animal rather than butchering it.

This evidence of potential bone trauma suggests that humans were probably hunting megafauna in southern South America well before the Last Glacial Maximum (~26,500–19,000 years ago). This pushes back the earliest solid evidence of human–megafauna interaction in South America. Consensus has it that humans arrived around 23,000 cal yr BP (as at White Sands, New Mexico), but this finding supports the evidence of earlier human presence in the Americas.

While compelling, the hypothesis is still tentative. More study is required on the sloth’s cut-marked bones, which have been found at Arroyo del Vizcaíno, as well as lithic fragments and other specimens before the case can be strengthened. The site already contains more than 40 bones with cut marks, some similar to the heel bone gap, and indicates more human–megafauna contacts.

Whether this millennia-long record of hunting marks constitutes human hunting ingenuity or natural accident, it is a fascinating addition to the prehistory of the Americas. The study, published in the Swiss Journal of Palaeontology, encourages further exploration of artifacts, bones, and landscape to reveal early human activity and strategies in megafaunal environments.

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Starts With A Bang — July 5, 2025

The relic signal that first proved the Big Bang has been known and analyzed for 60 years. Join us at the frontiers of modern cosmology!

Key Takeaways

• 
  Many different alternative ideas about our cosmic origins abounded until the mid-1960s, when the discovery of the CMB, identified as the Big Bang’s leftover glow, was first identified.
• 
  In all that time since, observations have confirmed and strengthened this picture, while subsequent CMB analysis has revealed even more information about our primeval Universe.
• 
  Many think that the story of the CMB ended with Planck, but the past 10 years have shown that so much more remains to be discovered. Come join us on the frontiers in this fascinating CMB-focused podcast episode!

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Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all.

Perhaps the strongest evidence we’ve ever acquired in support of the Big Bang has been the discovery of the leftover radiation from its early, hot, dense state: today’s cosmic microwave background, or CMB. While there were many competing ideas for our cosmic origins, only the Big Bang predicted a uniform, omnidirectional bath of blackbody radiation: exactly what the CMB is.

But it turns out the CMB encodes much more information than just our cosmic origins; it allows us to map the very early Universe from when it was just 380,000 years old, and gives us vital information about what has happened to light from that time over its 13.8 billion year journey to our eyes. It encodes information about our cosmic expansion history, about dark matter and dark energy, about intervening galaxy clusters, and about the material here in our own galaxy, along with much more. It is, arguably, the richest source of information from any one single observable in our entire Universe.

Here to guide us through what CMB scientists are working on here in 2025, including what we’ve learned and what we’re still trying to find out, I’m so pleased to welcome Dr. Patricio Gallardo to the show. We’ve got more than an hour and a half of quality science to go through, and by the end, I bet you’ll be more excited about the upcoming Simons Observatory, designed to measure the CMB to higher precision than ever before, than you knew you should be. Enjoy!

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Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all.

The CMB has long been considered the Big Bang’s “smoking gun” evidence. But after what JWST saw, might it come from early galaxies instead?

Originally, the abundance of bright, early galaxies shocked astronomers. After 3 years of JWST, we now know what’s really going on.

For over 50 years, it’s been the scientifically accepted theory describing the origin of the Universe. It’s time we all learned its truths.

If you want to understand the Universe, cosmologically, you just can’t do it without the Friedmann equation. With it, the cosmos is yours.

The hunt for extraterrestrial life begins with planets like Earth. But our inhabited Earth once looked very different than Earth does today.

The CMB has long been considered the Big Bang’s “smoking gun” evidence. But after what JWST saw, might it come from early galaxies instead?

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The current state-of-the-art cosmic distance ladder requires three rungs–geometric distances, primary indicators, and Type Ia Supernovae–to achieve a 1% measurement of the Hubble constant H0.

The Habitable Worlds Observatory will have the sensitivity and resolution to reduce this to a two-step measurement, eliminating the third rung entirely and reaching into the Hubble flow with stellar distance indicators such as Cepheid variables and the tip of the red giant branch alone.

We discuss the requirements for a program to measure H0 to 1% with HWO here, including telescope and instrument design considerations. We also comment on the potential of HWO to measure distances to low-mass dwarf galaxies via their RR Lyrae stars.

Gagandeep Anand, Meredith Durbin, Rachael Beaton, Joseph Jensen, Adam Riess

Comments: Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology SCDD, to be presented at HWO2025 and submitted to Astronomical Society of the Pacific following community comments. Feedback welcomed
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2507.02056 [astro-ph.CO] (or arXiv:2507.02056v1 [astro-ph.CO] for this version)
https://doi.org/10.48550/arXiv.2507.02056
Focus to learn more
Submission history
From: Meredith Durbin
[v1] Wed, 2 Jul 2025 18:00:32 UTC (8,789 KB)
https://arxiv.org/abs/2507.02056
Astrobiology