The Barents Sea system – gateway to the changing Arctic
New book documents 6 years of interdisciplinary research on the Barents Sea
Norwegian University of Science and Technology
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The Barents Sea system – gateway to the changing Arctic provides an overview of the interconnected elements of the Barents Sea, from microbes living in the sediments to seabirds at its surface, from the cycling of tiny particles of trace minerals to large-scale atmospheric and ocean currents. Also described are the methods and technologies used to observe and understand the system, including newly developed tools that make the Arctic Ocean more accessible to scientific inquiry than ever before. This book also explains how the region is managed: knowledge-based management is the key to maintaining a well-functioning Barents Sea.
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Credit: Fagbokforlaget
Roughly 300 scientists, students and technicians from ten Norwegian research institutions worked together in a six-year national effort to investigate the Barents Sea. The Nansen Legacy research project, which ran from 2018-2024, involved biologists, chemists, technologists, physicists, historians and cyberneticists working side by side.
Their interdisciplinary collaboration relied on a number of new methods to carry out a thorough survey of the environment in the Barents Sea management plan area.
The research results from this huge national effort are collected in the new book The Barents Sea system – gateway to the changing Arctic. Geir Johnsen, a professor of biology at the Norwegian University of Science and Technology (NTNU) is one of the book’s three editors.
“The most important thing in this major research project is interdisciplinarity. We work closely together across disciplines, and we work well with each other,” Johnsen said.
The researchers believe the book will be an important contribution to knowledge-based management of this important international resource.
Autonomous vehicles played key role
The researchers deployed instruments in the skies, on the sea surface, under sea ice, in the water column and on the seabed. These different platforms could collect data simultaneously, providing a nearly real-time understanding of what was happening in a specific place.
"Instrument-carrying robot platforms have made it possible to carry out scientific investigations in a very efficient way," says Johnsen.
The researchers used flying drones, small satellites, autonomous boats and underwater robots that could be fitted with hyperspectral cameras.
This type of camera can capture very precise images of large areas, making it possible to see nuances in the colour of the sea surface that can help researchers assess algae blooms, as one example.
The robots are also equipped with sensors that measure temperature and light, as well as acoustic meters and water samplers.The Observational Pyramid
Researchers called this combination of observational tools the Observational Pyramid. It allows researchers to scan the ocean from sky to seabed, collect water samples and perform various tests in the same area at the same time.
"The observation pyramid looks at phenomena in time and space and collects data at many different levels. We get 100 times more information compared to only information from research vessels," Johnsen said.
"The method can be scaled up and down: With the help of satellites, we can map areas of several hundred thousand square kilometers. And we can also zoom in on details and examine a drop of water or a cell," he said.
Why the Barents Sea?
The Barents Sea contains many mysteries and unanswered questions, yet it is a critical area for marine resources, geopolitics and shipping.
The Arctic is becoming increasingly ice-free, and it is precisely in the Barents Sea that the melting of sea ice is most noticeable, including with the greatest temperature increases. That makes the Barents Sea an important place for tracking environmental trends and climate change.
The researchers have studied the past and present climate and ecosystem in the Barents Sea. These data enable researchers to make better predictions about future changes and offer important information for being able to manage resources in the best possible way.
"Other sea areas in the Arctic are likely to experience similar changes as we are seeing in the Barents Sea now. This knowledge base and the book will be an important resource for understanding changes that are taking place in the ocean," Johnsen said.
The Norwegian-based Nansen Legacy Project a used combination of observational tools, from seabed to space, that they called the Observational Pyramid. Ths approach allowed researchers to scan the ocean from sky to seabed, collect water samples and perform various tests in the same area at the same time. The results are published in the new book: The Barents Sea system – gateway to a changing Arctic.
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Illustration: Frida Gnossen
This underwater robot is called the REMUS, shown here operating under the ice in Svalbard as part of the Nansen Legacy Project.
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Photo: Martin Ludvigsen, NTNU
Strange Atlantic cold spot traced to ocean slowdown
Research confirms weakening circulation drives South Greenland anomaly
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Atlantic sea surface temperature trend between 1900-2005 (color shading in °C) for the average of six observation datasets.
view moreCredit: Kai-Yuan Li/UCR
For more than a century, a patch of cold water south of Greenland has resisted the Atlantic Ocean’s overall warming, fueling debate amongst scientists. A new study identifies the cause as the long-term weakening of a major ocean circulation system.
Researchers from the University of California, Riverside show that only one explanation fits both observed ocean temperatures and salinity patterns: the Atlantic Meridional Overturning Circulation, or AMOC, is slowing down. This massive current system helps regulate climate by moving warm, salty water northward and cooler water southward at depth.
“People have been asking why this cold spot exists,” said UCR climate scientist Wei Liu, who led the study with doctoral student Kai-Yuan Li. “We found the most likely answer is a weakening AMOC.”
The AMOC acts like a giant conveyor belt, delivering heat and salt from the tropics to the North Atlantic. A slowdown in this system means less warm, salty water reaches the sub-polar region, resulting in the cooling and freshening observed south of Greenland.
When the current slows, less heat and salt reach the North Atlantic, leading to cooler, fresher surface waters. This is why salinity and temperature data can be used to understand the strength of the AMOC.
Liu and Li analyzed a century’s worth of this data, as direct AMOC observations go back only about 20 years. From these long-term records, they reconstructed changes in the circulation system and compared those with nearly 100 different climate models.
As the paper published in Communications Earth & Environment shows, only the models simulating a weakened AMOC matched the real-world data. Models that assumed a stronger circulation didn’t come close.
“It’s a very robust correlation,” Li said. “If you look at the observations and compare them with all the simulations, only the weakened-AMOC scenario reproduces the cooling in this one region.”
The study also found that the weakening of the AMOC correlates with decreased salinity. This is another clear sign that less warm, salty water is being transported northward.
The consequences are broad. The South Greenland anomaly matters not just because it’s unusual, but because it’s one of the most sensitive regions to changes in ocean circulation. It affects weather patterns across Europe, altering rainfall and shifting the jet stream, which is a high-altitude air current that steers weather systems and helps regulate temperatures across North America and Europe.
The slowdown may also disturb marine ecosystems, as changes in salinity and temperature influence where species can live.
This result may help settle a dispute amongst climate modelers about whether the South Greenland cooling is driven primarily by ocean dynamics or by atmospheric factors such as aerosol pollution. Many newer models suggested the latter, predicting a strengthened AMOC due to declining aerosol emissions. But those models failed to recreate the actual, observed cooling.
“Our results show that only the models with a weakening AMOC get it right,” Liu said. “That means many of the recent models are too sensitive to aerosol changes, and less accurate for this region.”
By resolving that mismatch, the study strengthens future climate forecasts, especially those concerning Europe, where the influence of the AMOC is most pronounced.
The study also highlights the ability to draw clear conclusions from indirect evidence. With limited direct data on the AMOC, temperature and salinity records provide a valuable alternative for detecting long-term change, and for helping to predict future climate scenarios.
“We don’t have direct observations going back a century, but the temperature and salinity data let us see the past clearly,” Li said. “This work shows the AMOC has been weakening for more than a century, and that trend is likely to continue if greenhouse gases keep rising.”
As the climate system shifts, the South Greenland cold spot may grow in influence. The hope is that by unlocking its origins, scientists can better prepare societies for what lies ahead.
“The technique we used is a powerful way to understand how the system has changed, and where it is likely headed if greenhouse gases keep rising,” Li said.
Journal
Communications Earth & Environment
Article Title
Weakened Atlantic Meridional Overturning Circulation causes the historical North Atlantic Warming Hole
New research uncovers surprising physics of ‘marine snow’
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New research uncovers surprising insights into how particles sink in stratified fluids like oceans, where the density of the fluid changes with depth. In a study published in Proceedings of the National Academy of Sciences, researchers show that the speed at which particles sink is determined not only by resistive drag forces from the fluid, but by the rate at which they can absorb salt relative to their volume. That means that smaller particles, counterintuitively, sink faster than larger ones.
view moreCredit: Harris Lab/Brown University
PROVIDENCE, R.I. [Brown University] — The deep ocean can often look like a real-life snow globe. As organic particles from plant and animal matter on the surface sink downward, they combine with dust and other material to create “marine snow,” a beautiful display of ocean weather that plays a crucial role in cycling carbon and other nutrients through the world’s oceans.
Now, researchers from Brown University and the University of North Carolina at Chapel Hill have found surprising new insights into how particles sink in stratified fluids like oceans, where the density of the fluid changes with depth. In a study published in Proceedings of the National Academy of Sciences, they show that the speed at which particles sink is determined not only by resistive drag forces from the fluid, but by the rate at which they can absorb salt relative to their volume.
“It basically means that smaller particles can sink faster than bigger ones,” said Robert Hunt, a postdoctoral researcher in Brown’s School of Engineering who led the work. “That’s exactly the opposite of what you’d expect in a fluid that has uniform density.”
The researchers hope the new insights could aid in understanding the ocean nutrient cycle, as well as the settling of other porous particulates including microplastics.
“We ended up with a pretty simple formula where you can plug in estimates for different parameters — the size of the particles or speed at which the liquid density changes — and get reasonable estimates of the sinking speed,” said Daniel Harris, an associate professor of engineering at Brown who oversaw the work. “There’s value in having predictive power that’s readily accessible.”
The study grew out of prior work by Hunt and Harris investigating neutrally buoyant particles — those that sink to a certain depth and then stop. Hunt noticed some strange behavior that seemed to be related to the porosity of the particles.
“We were testing a theory under the assumption that these particles would remain neutrally buoyant,” Hunt said. “But when we observed them, they kept sinking, which was actually kind of frustrating.”
That led to a new theoretical model of how porosity — specifically, the ability to absorb salt — would affect the rate at which they sunk. The model predicts that the more salt a particle can absorb relative to its size, the faster it sinks. That means, somewhat counterintuitively, that small porous particles sink faster than larger ones.
To test the model, the researchers developed a way to make a linearly stratified body of water in which the density of the liquid increased gradually with depth. To do that, they fed a large tub with water sourced from two smaller tubs, one with fresh water and the other with salt water. Controllable pumps from each tub enabled them to carefully control the density profile of the larger tub.
Using 3D-printed molds, the team then created particles of varying shapes and sizes made from agar, a gelatinous material derived from seaweed. Cameras imaged individual particles as they sank.
The experiments confirmed the predictions of the model. For spherical particles, smaller ones tended to sink faster. For thinner or flatter particles, their settling speed was primarily determined by their smallest dimension. That means that elongated particles actually sink faster than spherical ones of the same volume.
The results are surprising, the researchers said, and could provide important insights into how particles settle in more complex ecological settings — either for understanding natural carbon cycling or for engineering ways of speeding up carbon capture in large bodies of water.
“We’re not trying to replicate full oceanic conditions,” Harris said. “The approach in our lab is to boil things down to their simplest form and think about the fundamental physics involved in these complex phenomena. Then we can work back and forth with people measuring these things in the field to understand where these fundamentals are relevant.”
Harris says he hopes to connect with oceanographers and climate scientists to see what insights these new findings might provide.
Other co-authors of the research were Roberto Camassa and Richard McLaughlin from UNC Chappel Hill. The research was funded by the National Science Foundation (DMS-1909521, DMS-1910824, DMS-2308063) and the Office of Naval Research (N00014-18-1-2490 and N00014-23-1-2478).
New research uncovers surprising insights into how particles sink in stratified fluids like oceans, where the density of the fluid changes with depth. In a study published in Proceedings of the National Academy of Sciences, researchers show that the speed at which particles sink is determined not only by resistive drag forces from the fluid, but by the rate at which they can absorb salt relative to their volume. That means that smaller particles, counterintuitively, sink faster than larger ones.
For thinner or flatter particles, their settling speed was primarily determined by their smallest dimension. That means that elongated particles actually sink faster than spherical ones of the same volume.
Credit
Harris Lab/Brown University
Journal
Proceedings of the National Academy of Sciences
Article Title
Diffusion-limited settling of highly porous particles in density-stratified fluids
Article Publication Date
20-Jun-2025
