Saturday, January 24, 2026

Critical Atlantic Ocean currents kept going during last ice age

University College London

Recovering the Core — image:
David Thornalley, Jack Wharton, and Alice Carter Champion slicing up a sediment core into 1cm sections onboard the Research Vessel (RV) Neil Armstrong about 500 miles due east of New York City.
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Credit: Alice Carter-Champion, UCL

During the last ice age, the Atlantic Ocean’s powerful current system remained active and continued to transport warm, salty water from the tropics to the North Atlantic despite extensive ice cover across much of the Northern Hemisphere, finds new research led by UCL scientists.

The findings, published in Nature, show that despite the Earth being in an ice age, part of the ocean’s interior — known as North Atlantic Deep Water (NADW) — was only about 1.8°C colder than today, far from the near-freezing conditions previously assumed. Additionally, the NADW occupied a similar depth range as today, extending from roughly 1 to 4 kilometres below the surface.

This challenges the prevailing view that at the peak of the last ice age — the Last Glacial Maximum (LGM) — Atlantic circulation was weaker, and NADW was colder and confined to shallower depths. The researchers’ findings also more closely agree with climate model projections for these glacial conditions, supporting the models’ ability to accurately forecast future ocean circulation.

Lead author Dr Jack Wharton (UCL Geography) said: “We were amazed to find that the deep Atlantic stayed relatively warm and salty during one of Earth’s coldest periods. Taken together, our data tell us the ocean’s circulation system kept running even under extreme conditions, which is crucial for understanding how our climate engine works. The same climate models that correctly predicted this past behaviour also warn that these currents are vulnerable to weakening as the planet warms — and that could have dramatic consequences for future climate.”

Taking the ancient ocean’s temperature

To reconstruct deep Atlantic conditions during the Last Glacial Maximum, around 19,000 to 23,000 years ago, researchers analysed tiny fossil shells preserved in mud on the ocean floor. These microfossils, known as foraminifera, record the temperature and salinity of the seawater in which they lived. The team studied mud collected from sites off the coasts of the Bahamas, Bermuda, South Carolina and Iceland, from depths between 1.5 and 5 kilometres below the surface.

By analysing chemical signals locked inside these fossil shells, the team estimated deep-ocean temperature and salinity at the time the organisms were alive. These waters also carried a distinctive chemical fingerprint linking them to surface waters originating in the subtropics and Nordic Seas, indicating that large-scale heat transport through the ocean continued during this period.

Co-author Professor David Thornalley (UCL Geography) said: “The microfossils recovered from the ocean floor show that deep waters in the North Atlantic were far from freezing during the last ice age. By examining locations across the North Atlantic, we can show that warm, salty surface waters continued to sink and form North Atlantic Deep Water that reached similar depths to today.”

Ocean currents and climate forecasts

The warmer ice age ocean temperatures indicated by these microfossils reflect what climate models have previously predicted, strengthening their credibility. However, it also lends credence to another prediction of these models – that climate change will cause the currents to weaken in the future, significantly cooling Europe and North Africa and disrupting weather patterns.

The ocean currents running throughout the Atlantic Ocean – known collectively as the Atlantic Meridional Overturning Circulation (AMOC) – play a critical role in regulating Earth’s climate. The AMOC acts like a conveyor belt, transporting heat northward from the tropics and helping to keep Europe temperate. As surface waters cool in the North Atlantic, they sink and return southwards through the deep ocean as North Atlantic Deep Water.

Climate models predict that as the North Atlantic surface ocean warms, these waters become less dense and less able to sink to form deep waters, reducing the strength of the AMOC. Without this transport mechanism, heat from the tropics won’t reach Europe and North Africa, dramatically cooling their climates.

Co-author Professor Mark Maslin (UCL Geography) said: “This research helps us better understand the mechanisms that drive ocean circulation and improves our ability to predict future climate change. Many of our best climate models indicate that Atlantic circulation is likely to weaken under the type of warming we’re likely to face in the coming decades—it would have a tremendous, destabilising impact on the climate of Europe and North Africa.”

Estimates are that if the AMOC were to shut down, average annual temperatures in the UK could drop by as much as 7°C by the end of the century, with winters as much as 15°C colder, which could bring frozen sea ice to the shores of Scotland. Arable land across the UK and continental Europe would be significantly reduced, and it would disrupt the rainy season monsoons in Africa.

This research was supported by the Natural Environment Research Council (NERC), the Leverhulme Trust, the European Union’s Horizon Europe research and innovation programme, and the National Science Foundation (NSF), with collaboration from Utrecht University, the University of Colorado Boulder, and Woods Hole Oceanographic Institution.

Core 1

Half sediment core in pristine condition, pre-sampling and stored at WHOI.

Two sediment cores, just removed from storage at WHOI - https://www2.whoi.edu/site/seafloorsampleslab/ (link to storage facility)

Credit

Jack Wharton, UCL

Multi-coring device on the back of the R/V Neil Armstrong used to collect sediment samples from the ocean floor.

Back deck of the R/V Neil Armstrong

Ship technicians monitor the coring device being lowered into the water off the back of the R/V Neil Amrstrong.

Credit

Alice Carter-Champion, UCL

Scanning electron microscope image of the benthic foraminifer Uvigerina peregrina, one of the species used in this study. The specimen was recovered from sediments deposited around 21,000 years ago at a water depth of approximately 3 km off the coast of North Carolina.

Credit

Jack Wharton and Mark Stanley

Notes to Editors

Jack H. Wharton, Emilia Kozikowska, Lloyd D. Keigwin, Thomas M. Marchitto, Mark A. Maslin, Martin Ziegler & David J. R. Thornalley, ‘Relatively warm deep water formation persisted in the Last Glacial Maximum’ will be published in Nature on Wednesday 21 January 2026

The DOI for this paper will be: 10.1038/s41586-025-10012-2

The URL for this paper will be: https://www.nature.com/articles/s41586-025-10012-2

About UCL (University College London)

UCL is a diverse global community of world-class academics, students, industry links, external partners, and alumni. Our powerful collective of individuals and institutions work together to explore new possibilities.

Since 1826, we have championed independent thought by attracting and nurturing the world's best minds. Our community of more than 50,000 students from 150 countries and over 16,000 staff pursues academic excellence, breaks boundaries and makes a positive impact on real world problems.

We are consistently ranked among the top 10 universities in the world and are one of only a handful of institutions rated as having the strongest academic reputation and the broadest research impact.

We have a progressive and integrated approach to our teaching and research – championing innovation, creativity and cross-disciplinary working. We teach our students how to think, not what to think, and see them as partners, collaborators and contributors.

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We were the first in England to welcome women to university education and that courageous attitude and disruptive spirit is still alive today. We are UCL.

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Journal

Nature

DOI

10.1038/s41586-025-10012-2

Article Title

Relatively warm deep water formation persisted in the Last Glacial Maximum

Article Publication Date

21-Jan-2026

Scientists find extremely rapid evolution of new species after the end-cretaceous mass extinction

In a new study in Geology, researchers calculated how long it took for novel single-celled marine species to appear after the asteroid impact, and it’s surprisingly fast

Geological Society of America

Boulder, Colo., USA: Sixty-six million years ago, the dinosaurs had a really bad day when a colossal asteroid impact spurred their extinction. But even though those reptilian megafauna get all the attention, the devastation was just as bad, if not worse, for tiny marine single-celled organisms called foraminifera, or forams. These creatures, which make elaborate shells of calcium carbonate that are well preserved in the fossil record, serve as key clues for geologists working to understand the impacts of environmental change in Earth’s history.

“You can identify all these species of forams, and you can reconstruct in great detail how ocean ecosystems have changed in response to changing climate, changing ocean circulation, or changing tectonic configurations,” says Dr. Chris Lowery, a paleoceanographer at the University of Texas at Austin. “That really helps us to understand how these ocean ecosystems respond to these changes, and helps us understand, then, how they can respond in the future.”

Ninety percent of foraminifera species died off during the mass extinction event that ended the dinosaurs’ reign. The sudden disappearance of foraminifera species at the end-Cretaceous mass extinction and the reappearance of new species just after are a primary way geologists identify the event in marine rocks around the world. But just how quickly those new species evolved in the wake of the asteroid impact has long been debated by scientists.

Lowery and his colleagues’ new research, published today in the journal Geology, in a paper titled “New species evolved within a few thousand years of the Chicxulub Impact,” determined that the rise of new species was remarkably quick, occurring in some places in less than two thousand years. For reference, in normal evolutionary conditions it takes around two million years on average for a new species to develop.

“When you take away all the constraints,” asks Lowery, “how quickly can you get new species forming? The answer seems to be very, very fast. And that's important to understand throughout Earth history—it’s also important for us.” Lowery says that as anthropogenic warming of Earth’s climate potentially moves the planet toward another mass extinction, looking to the past record of how species respond to rapid change could help us understand what might happen in the near future.

To figure out how long after the asteroid impact new foraminifera species originated, the team measured the amount of an isotope of helium, 3He, in sediments deposited just after the asteroid at six sites around the world. 3He only occurs on Earth through a steady delivery of interstellar dust and wasn’t increased by the material brought in by the asteroid. In sediments deposited slowly, there’s a higher concentration of 3He. When sediments are deposited more quickly, the isotope is diluted. By precisely measuring the 3He concentration in the rock layer between the asteroid impact and the first new species, the scientists were able to determine how long it took for the novel foraminifera to emerge.

Previously, the geologic time scale for this period was determined by extrapolating between the known ages of magnetic reversals hundreds of thousands of years before and after the asteroid impact. That approach, though, doesn’t account for changes in the rate of sedimentation during one of the most catastrophic events in Earth history. In this paradigm, the new foram species emerged about 10,000 years after the impact. That’s still remarkably quick in terms of normal rates of evolution, but still an order of magnitude slower than what Lowery and his team found.

“Why does this matter? It helps us understand how quickly evolution can occur,” says Lowery. “It helps us understand how the environment changed after the impact and how brief and extreme that disturbance actually was.”

Geology: https://doi.org/10.1130/G53313.1

About the Geological Society of America

The Geological Society of America (GSA) is a global professional society with more than 17,000 members across over 100 countries. As a leading voice for the geosciences, GSA advances the understanding of Earth's dynamic processes and fosters collaboration among scientists, educators, and policymakers. GSA publishes Geology, the top-ranked geoscience journal, along with a diverse portfolio of scholarly journals, books, and conference proceedings—several of which rank among Amazon's top 100 best-selling geology titles.

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Journal

Geology

DOI

10.1130/G53313.1

Article Title

New species evolved within a few thousand years of the Chicxulub Impact,

Article Publication Date

21-Jan-2026

World’s oldest rock art holds clues to early human migration to Australia

A hand stencil on the wall of a cave in Indonesia has become the oldest known rock art in the world, exceeding the archaeologists’ previous discovery in the same region by 15,000 years or more.

Griffith University

image:
67,800 yr old hand stencil, Muna, Sulawesi
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Credit: Supplied by Max Aubert

An international team, co-led by Griffith University researchers, Indonesia’s national research and innovation agency (BRIN) and Southern Cross University, discovered and dated cave paintings made by our species on the island of Sulawesi at least 67,800 years ago.

The research team said the findings advance our understanding of how and when Australia first came to be settled, with the Sulawesi art very likely created by a population closely linked to the ancestors of Indigenous Australians.

Preserved in limestone caves in southeastern Sulawesi on the satellite island of Muna, a fragmentary hand stencil was found surrounded by painted art of a much more recent origin.

The team applied advanced uranium-series dating techniques, analysing microscopic mineral deposits that formed both on top of and, in some cases, beneath the paintings from Liang Metanduno, providing a time period during which the art was made.

The hand stencil was dated to a minimum of 67,800 years ago, making it the oldest reliably dated cave art yet discovered, significantly older than the rock painting found in Sulawesi by the same researchers in 2024.

The new finding also revealed the Muna cave was used for making art over an exceptionally long period, with paintings produced repeatedly for at least 35,000 years, continuing until about 20,000 years ago.

“It is now evident from our new phase of research that Sulawesi was home to one of the world’s richest and most longstanding artistic cultures, one with origins in the earliest history of human occupation of the island at least 67,800 years ago,” said Professor Maxime Aubert, an archaeologist and geochemist from the Griffith Centre for Social and Cultural Research (GCSCR), who co-led the study.

The team also observed the hand stencil was a globally unique variant of this motif.

After the stencil was created, it was altered to deliberately narrow the negative outlines of the fingers, creating the overall impression of a claw-like hand.

Professor Adam Brumm, from Griffith University’s Australian Research Centre for Human Evolution (ARCHE), who co-led the study, said the symbolic meaning of the narrowed fingers was a matter for speculation.

“This art could symbolise the idea that humans and animals were closely connected, something we already seem to see in the very early painted art of Sulawesi, with at least one instance of a scene portraying figures that we interpret as representations of part-human, part-animal beings,” Professor Brumm said.

Dr Adhi Agus Oktaviana, a rock art specialist in BRIN and a team lead, whose doctoral research at Griffith University formed part of this study, said the paintings had far-reaching implications for our understanding of the deep-time history of Australian Aboriginal culture.

“It is very likely that the people who made these paintings in Sulawesi were part of the broader population that would later spread through the region and ultimately reach Australia,” Dr Oktaviana said.

There had been considerable archaeological debate about the timing of initial human occupation of the Pleistocene-era landmass that encompassed what is now Australia, Tasmania and New Guinea, known as Sahul.

Scholarly opinion was divided between the so-named short chronology model, whereby the first people entered the Sahul ‘supercontinent’ about 50,000 years ago, and the opposing long chronology model, in which they arrived at least 65,000 years ago.

“This discovery strongly supports the idea that the ancestors of the First Australians were in Sahul by 65,000 years ago,” Dr Oktaviana said.

There were two main migration routes into Sahul proposed by researchers: a northern route to the New Guinea portion of this landmass via Sulawesi and the ‘Spice Islands’ and a more southerly route that took the sea voyagers directly to the Australian mainland via Timor or adjacent islands.

Professor Renaud Joannes-Boyau from the Geoarchaeology and Archaeometry Research Group (GARG) at Southern Cross University, who co-led the research, said the discovery sheds light on the most likely course of humans’ ancient island-hopping journey from mainland Asia to Sahul via the northern route.

“With the dating of this extremely ancient rock art in Sulawesi, we now have the oldest direct evidence for the presence of modern humans along this northern migration corridor into Sahul,” Professor Joannes-Boyau said.

“These discoveries underscore the archaeological importance of the many other Indonesian islands between Sulawesi and westernmost New Guinea,” said Professor Aubert, who, together with professors Brumm and Joannes-Boyau, continues to search for more evidence of early human art and occupation along the northern route with funding from the Australian Research Council (ARC).

The ARC’s backing forms part of a broader investment in human origins research, including the recently awarded ARC Centre of Excellence for Transforming Human Origins Research, with Griffith University as lead institution, and the ARC Training Centre for Advancing Archaeology in the Resources Sector at Southern Cross University, aiming at advancing our global understanding of human evolution and preserving our heritage.

The research was also supported by Google Arts & Culture and the National Geographic Society.

The research on early rock art in Sulawesi has been featured in a documentary film, ‘Sulawesi l'île des premières images’ produced by ARTE, released in Europe today.

The study titled ‘Rock art from at least 67,800 years ago in Sulawesi’ has been published in Nature.