Going with the flow: visualizing ocean currents with ECCO

This data visualization showing ocean currents around the world uses data from NASA’s ECCO model, or Estimating the Circulation and Climate of the Ocean.

The model pulls data from spacecraft, buoys, and other measurements.

Credits: Kathleen Gaeta Greer/ NASA’s Scientific Visualization Studio

From NASA by James Riordon

Historically, the ocean has been difficult to model.
Scientists struggled in years past to simulate ocean currents or accurately predict fluctuations in temperature, salinity, and other properties.
As a result, models of ocean dynamics rapidly diverged from reality, which meant they could only provide useful information for brief periods.

In 1999, a project called Estimating the Circulation and Climate of the Ocean (ECCO) changed all that.
By applying the laws of physics to data from multiple satellites and thousands of floating sensors, NASA scientists and their collaborators built ECCO to be a realistic, detailed, and continuous ocean model that spans decades.
ECCO enabled thousands of scientific discoveries, and was featured during the announcement of the Nobel Prize for Physics in 2021.

NASA ECCO is a powerful integrator of decades of ocean data, narrating the story of Earth’s changing ocean as it drives our weather, and sustains marine life.

The ECCO project includes hundreds of millions of real-world measurements of temperature, salinity, sea ice concentration, pressure, water height, and flow in the world’s oceans.
Researchers rely on the model output to study ocean dynamics and to keep tabs on conditions that are crucial for ecosystems and weather patterns.
The modeling effort is supported by NASA’s Earth science programs and by the international ECCO consortium, which includes researchers from NASA’s Jet Propulsion Laboratory in Southern California and eight research institutions and universities.

The project provides models that are the best possible reconstruction of the past 30 years of the global ocean.
It allows us to understand the ocean’s physical processes at scales that are not normally observable.

ECCO and the Western Boundary Currents

 

Western boundary currents stand out in white in this visualization built with ECCO data.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Greg Shirah/NASA’s Scientific Visualization Studio

Large-scale wind patterns around the globe drag ocean surface waters with them, creating complex currents, including some that flow toward the western sides of the ocean basins.
The currents hug the eastern coasts of continents as they head north or south from the equator: These are the western boundary currents.
The three most prominent are the Gulf Stream, Agulhas, and Kuroshio.

The North American Gulf Stream as illustrated with the ECCO model.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Greg Shirah/NASA’s Scientific Visualization Studio

Seafarers have known about the Gulf Stream — the Atlantic Ocean’s western boundary current — for more than 500 years.
By the volume of water it moves, the Gulf Stream is the largest of the western boundary currents, transporting more water than all the planet’s rivers combined.

In 1785, Benjamin Franklin added it to maritime charts showing the current flowing up from the Gulf, along the eastern U.S. coast, and out across the North Atlantic.
Franklin noted that riding the current could improve a ship’s travel time from the Americas to Europe, while avoiding the current could shorten travel times when sailing back.

A visualization built of ECCO data reveals a cold, deep countercurrent that flows in the opposite direction of the warm Gulf Stream above it.

Download this visualization from NASA Goddard’s Scientific Visualization Studio.

Credits: Greg Shirah/NASA’s Scientific Visualization Studio

Franklin’s charts showed a smooth Gulf Stream rather than the twisted, swirling path revealed in ECCO data.
And Franklin couldn’t have imagined the opposing flow of water below the Gulf Stream.
The countercurrent runs at depths of about 2,000 feet (600 meters) in a cold river of water that is roughly the opposite of the warm Gulf Stream at the surface.
The submarine countercurrent is clearly visible when the upper layers in the ECCO model are peeled away in visualizations.

The Gulf Stream is a part of the Atlantic Meridional Overturning Circulation (AMOC), which moderates climate worldwide by transporting warm surface waters north and cool underwater currents south.
The Gulf Stream, in particular, stabilizes temperatures of the southeastern United States, keeping the region warmer in winter and cooler in summer than it would be without the current.
After the Gulf Stream crosses the Atlantic, it tempers the climates of England and the European coast as well.

The Agulhas current originates along the equator in the Indian Ocean, travels down the western coast of Africa, and spawns swirling Agulhas rings that travel across the Atlantic toward South America.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Greg Shirah/NASA’s Scientific Visualization Studio

The Agulhas Current flows south along the western side of the Indian Ocean.
When it reaches the southern tip of Africa, it sheds swirling vortices of water called Agulhas Rings.
Sometimes persisting for years, the rings glide across the Atlantic toward South America, transporting small fish, larvae, and other microorganisms from the Indian Ocean.

Researchers using the ECCO model can study Agulhas Current flow as it sends warm, salty water from the tropics in the Indian Ocean toward the tip of South Africa.
The model helps tease out the complicated dynamics that create the Agulhas rings and large loop of current called a supergyre that surrounds the Antarctic.
The Southern Hemisphere supergyre links the southern portions of other, smaller current loops (gyres) that circulate in the southern Atlantic, Pacific, and Indian oceans.
Together with gyres in the northern Atlantic and Pacific, the southern gyres and Southern Hemisphere supergyre influence climate while transporting carbon around the globe.

The Kuroshio Current flows on the western side of the Pacific Ocean, past the east coast of Japan, east across the Pacific, and north toward the Arctic.
Along the way, it provides warm water to drive seasonal storms, while also creating ocean upwellings that carry nutrients that sustain fisheries off the coasts of Taiwan and northern Japan.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Greg Shirah/NASA’s Scientific Visualization Studio

In addition to affecting global weather patterns and temperatures, western boundary currents can drive vertical flows in the oceans known as upwellings.
The flows bring nutrients up from the depths to the surface, where they act as fertilizer for phytoplankton, algae, and aquatic plants.

The Kuroshio Current that runs on the west side of the Pacific Ocean and along the east side of Japan has recently been associated with upwellings that enrich coastal fishing waters.
The specific mechanisms that cause the vertical flows are not entirely clear.
Ocean scientists are now turning to ECCO to tease out the connection between nutrient transport and currents like the Kuroshio that might be revealed in studies of the water temperature, density, pressure, and other factors included in the ECCO model.

Tracking Ocean Temperatures and Salinity

When viewed through the lens of ECCO’s temperature data, western boundary currents carry warm water away from the tropics and toward the poles.
In the case of the Gulf Stream, as the current moves to far northern latitudes, some of the saltwater freezes into salt-free sea ice.
The saltier water left behind sinks and then flows south all the way toward the Antarctic before rising and warming in other ocean basins.

Colors indicate temperature in this visualization of ECCO data.
Warm water near the equator is bright yellow.
Water cools when it flows toward the poles, indicated by the transition to orange and red shades farther from the equator.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Greg Shirah/NASA’s Scientific Visualization Studio

Currents also move nutrients and salt throughout Earth’s ocean basins.
Swirling vortexes of the Agulhas rings stand out in ECCO temperature and salinity maps as they move warm, salty water from the Indian Ocean into the Atlantic.

The Mediterranean Sea has a dark red hue that indicates its high salt content.
Other than the flow through the narrow Strait of Gibraltar, the Mediterranean is cut off from the rest of the world’s oceans.
Because of this restricted flow, salinity increases in the Mediterranean as its waters warm and evaporate, making it one of the saltiest parts of the global ocean.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.

Credits: Greg Shirah/NASA’s Scientific Visualization Studio

Experimenting with ECCO

ECCO offers researchers a way to run virtual experiments that would be impractical or too costly to perform in real oceans.
Some of the most important applications of the ECCO model are in ocean ecology, biology, and chemistry.
Because the model shows where the water comes from and where it goes, researchers can see how currents transport heat, minerals, nutrients, and organisms around the planet.

In prior decades, for example, ocean scientists relied on extensive temperature and salinity measurements by floating sensors to deduce that the Gulf Stream is primarily made of water flowing past the Gulf rather than through it.
The studies were time-consuming and expensive.
With the ECCO model, data visualizers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, virtually replicated the research in a simulation that was far quicker and cheaper.

A simulation built with data from the ECCO model shows that very little of the water in the gulf contributes to the water flowing in the Gulf Stream.
Download this visualization from NASA Goddard’s Scientific Visualization Studio.
Credits: Atousa Saberi/NASA’s Scientific Visualization Studio

The example illustrated here relies on ECCO to track the flow of water by virtually filling the Gulf with 115,000 particles and letting them move for a year in the model.
The demonstration showed that less than 1% of the particles escape the Gulf to join the Gulf Stream.

Running such particle-tracking experiments within the ocean circulation models helps scientists understand how and where environmental contaminants, such as oil spills, can spread.

Take an ECCO Deep Dive

Today, researchers turn to ECCO for a broad array of studies.
They can choose ECCO modeling products that focus on one feature – such as global flows or the biology and chemistry of the ocean – or they can narrow the view to the poles or specific ocean regions.
Every year, more than a hundred scientific papers include data and analyses from the ECCO model that delve into our oceans’ properties and dynamics.

DARPA's USX-1 Defiant - First fully autonomous vessel

USX-1 Defiant has officially launched! The No Manning Required Ship (NOMARS) program has built a vessel designed to operate autonomously for long durations at sea. #USV For more info and images: https://t.co/n2pIDZyata pic.twitter.com/Dijsxy0EIO

— DARPA (@DARPA) March 4, 2025

From NavalNews by Aaron-Matthew Lariosa

 

NOMARS envisions a cost-effective USV concept for the U.S. Navy through a design philosophy that excludes all crewed features.
Serco launched the Defense Advanced Research Projects Agency’s No Manning Required Ship program medium unmanned surface vessel prototype, USX-1 Defiant, at Nichols Brothers Boat Builders shipyard last month in preparation for a series of trials that aim to bring a cost-effective USV to the U.S. Navy.
From the design’s outset, the 180-foot-long, 240-ton vessel was designed without considering human habitation or protection features.

 

According to DARPA, the NOMARS program “intends to demonstrate significant advantages,” including at-sea reliability, hydrodynamic efficiency, and stealthy features.
“The NOMARS program aims to challenge the traditional naval architecture model, designing a seaframe (the ship without mission systems) from the ground up with no provision, allowance, or expectation for humans on board,” stated the DARPA release. 

Serco was selected to construct the demonstrator by DARPA over Leidos Gibbs and Cox in 2022.

 

A previously released rendering of the Defiant design. DARPA

 

The US Navy’s USVs Mariner, at rear, and Ranger, in front, sail together in 2023. USN 

 

The program, originally launched in 2020, looks to design a Medium USV with unprecedented reliability and availability.
Ryan Maatta, a Marine Engineer Manager with Serco overseeing the NOMARS project, told Naval News at the annual Surface Navy Association symposium that the program’s key features include a 90% reliability at sea for a year and an autonomous refueling capability.

USVs Mariner and Ranger demonstrated SERCO’s refueling capability in a test last September. 

Maatta also confirmed that Defiant would undergo two months of sea trials before “a very large and extensive demonstration of the vessel and its capabilities.” 

 

 

The DARPA NOMARS program has successfully launched the USX-1 Defiant, a 180’, 240-metric ton medium unmanned surface vessel designed to revolutionize autonomous operations at sea.

DARPA Photo

 

“What we’re trying to prove out here is the feasibility of completely unmanned vessels vs partially unmanned. This is a much larger form factor, more than anyone has done. A completely unmanned vessel, rather than an optionally manned vessel,”

Ryan Maata, Marine engineer manager at Serco

While the USV’s deck was covered by a tarp in photos released by DARPA, Serco’s concept models include one BAE Adaptable Deck Launcher and a container.

The company’s Large USV concept, which Maatta described as the Second World War-era destroyer escort of the future, comes equipped with four Adaptable Deck Launchers for a complement of 16 strike-length Mark 41 missile cells.

 

Defiant is unique in this regard, as previously tested USVs such as Nomad and Ranger were retrofitted offshore vessels converted for autonomous operations.

Sailors were embarked on the U.S. Navy’s Ghost Fleet Overlord during its 2023 Indo-Pacific voyage to ensure systems ran accordingly. 

 

Maatha highlighted that the removal of berths, galleys, and other facilities provides a “much larger payload fraction” on Defiant. 

“One of the historic problems with unmanned systems is, they promise to keep sailors or pilots safe, but they don’t tend to be less expensive than their manned counterparts. We really worked to change the philosophy and operating principles so that this is much less expensive to do the same mission as a manned platform,” said Maatta in a Naval News interview. 

 

SERCO has claimed that it has the capabilities required to mass produce and maintain vessels similar to NOMARS and its LUSV concepts.
The NOMARS program and Defiant come amid increased calls from American policymakers and combat commands for cost-effective USVs, specifically in a potential Chinese invasion of Taiwan. Admiral Samuel Paparo, head of the U.S. Indo-Pacific Command, has detailed his use of the vessels in Hellscape, which aims to flood the Taiwan Strait with drones.

Links :

• Offshore Mag : USVs could play a major role in the future of offshore energy development
• TWZ : Mysterious Naval Vessel Spotted In Washington State Is A New DARPA Drone Ship 
• DARPA : NOMARS: No Manning Required Ship
  

Dancing turtles help us understand how they navigate around the world

Some turtles flap about when a magnetic field suggests they are about to be fed
Goforth et al., Nature (2025)

From NewScientist by Chris Simms

 

Some turtles "dance" when they anticipate food, which gives us clues as to how they navigate from A to B

Baby loggerhead turtles “dance” when they are expecting food, a behaviour that researchers have used to investigate their navigation abilities.
By learning to associate a magnetic field with a food, this cute display has helped indicate that the sea turtles have two distinct geomagnetic senses to help them navigate during their epic ocean journeys.

Young loggerheads do a “turtle dance” when they are in a magnetic field that they associate with food and the behaviour has been used to reveal their navigation secrets

 

“The turtle dance is a strange pattern of behaviour that emerges quickly in young captive sea turtles when they figure out that food comes from above,” says Ken Lohmann at the University of North Carolina at Chapel Hill.
“They would get very excited and raise their heads up out of the water and come swimming over, and often if the food wasn’t dropped in immediately, they would begin to flap their flippers and spin around.”

It's one of the greatest mysteries in the animal kingdom - how do sea turtles navigate? 

 

Lohmann and his colleagues realised that there might be a way to use this behaviour to reveal how turtle navigation works.
They put juvenile loggerhead sea turtles (Caretta caretta) in tanks surrounded by coil systems that created magnetic fields in the water, replicating those in their natural habitats.

The juveniles spent an equal amount of time in two magnetic fields, but were only fed in one of them.
Soon, when they were in a magnetic field they associated with food, the turtles started to dance in anticipation, a learned behaviour reminiscent of Ivan Pavlov‘s famous dog experiment.
“We demonstrated that the turtles can learn to recognise magnetic fields,” says team member Kayla Goforth at Texas A&M University.

The researchers then reproduced a magnetic field near the Cape Verde islands, an area where loggerheads tend to turn south-west when migrating.
The team demonstrated that the juvenile turtles also did this.
Then the researchers trained other turtles to associate the Cape Verde field with food.

One of the ideas about how some animals sense magnetic fields is that there is a complex set of chemical reactions, possibly taking place in the eye, that are influenced by Earth’s magnetic field.

To try to affect any such system, the team used an additional magnetic field that oscillates at a radio wave frequency, which should interfere with that cascade of chemical reactions.

Regardless of whether the oscillating field was turned on, the turtles could detect the underlying Cape Verde magnetic signature and would dance, which suggests their map sense isn’t dependent on this chemical reception mechanism.
But the oscillating field did make them turn in random directions, rather than south-west.

Scientists tested for this behaviour via a series of experiments in tanks
Goforth et al., Nature (2025)

“This is good evidence that there are actually two different magnetic senses in the turtles: one that is used for the map sense, one that is used for the compass sense,” says Lohmann.
“The simplest explanation would be that the magnetic map sense does not depend on this chemical magnetoreception process, but the magnetic compass sense does.”

The waters off the coast of Sri Lanka are home to a vast variety of marine life.

One resident is the green turtle, an endangered species of sea turtle.

Born on these shores, it migrates vast distances – but it always returns to the same beach.

Green turtles begin their often long lives with a risky journey from beach to ocean.

But just how do they manage to find their way home again, even from thousands of kilometers away?

The answer might surprise you…

 

“The magnetic map sense is a positional sense, kind of like a GPS, and their compass sense tells them which way to go,” says Goforth.
“This is probably how they’re getting back to important ecological locations such as feeding grounds and nesting areas.”

“It’s a new way of thinking about how turtles are using the magnetic field to navigate,” says Katrina Phillips at the University of Massachusetts Amherst.
“What’s really fascinating is we still don’t understand how they’re even perceiving the magnetic field.
So, this is getting at what is going on mechanistically.”

Links :

• Nature DOI: 10.1038/s41586-024-08554-y
• YouTube : How birds and turtles navigate across the planet
  
• GeoGarage blog  : Turtles use the Earth's magnetic field as a global GPS / Magnetic memories may guide salmon home / From East to West: scientists solve birds' ability to navigate ... /  An ocean of noise: how sonic pollution is hurting marine life /

How does life happen when there’s barely any light?

Under the sea ice during the Arctic’s pitch-black polar night, cells power photosynthesis on the lowest light levels ever observed in nature. 

Under the ice, as the first photons of spring sunlight penetrated the Arctic’s dark polar night, researchers measured algal cells harvesting light at the theoretical minimum of photosynthesis — less than one-hundred-thousandth of the light of a sunny day. 

 Mark Belan/Quanta Magazine 

 

From QuantaMag by Asher Elbein

Most of life’s engines run on sunlight.
Photons filter down through the atmosphere and are eagerly absorbed by light-powered organisms such as plants and algae.
Through photosynthesis, the particles of light power a cellular reaction that manufactures chemical energy (in the form of sugars), which is then passed around the food web in a complex dance of herbivores, predators, scavengers, decomposers and more.

On a bright, sunny day, there’s a wealth of photons to go around.
But what happens at low light?

Biologists have long been curious about just how little light photosynthesis can run on — or how many photons need to arrive, and how quickly, for a cell’s photosynthetic machinery to process carbon dioxide into oxygen and energy.
Calculations have suggested a theoretical minimum of around 0.01 micromoles of photons per square meter per second, or less than one-hundred-thousandth of the light of a sunny day.

For decades, this calculation was theoretical, given the difficulties of studying photosynthesis under low light.
No one could confirm it in the field, though there are plenty of places on Earth that light barely reaches.
Every winter in the high Arctic, for example, the sun, hidden by the tilt of the Earth, vanishes for months.
Meters of snow blanket the sea ice and block incoming light, leaving the frigid ocean below as dark as the inside of a tomb.
There, biologists assumed, photosynthesizing microalgae that live in the water and ice power down for the season and wait for warmth and light to return.

“People thought of the polar night as these desert conditions where there’s very little life, and things are all sleeping and hibernating and waiting for the next spring to come,” said Clara Hoppe (opens a new tab), a biogeochemist at the Alfred Wegener Institute in Germany.
“But really, people had never really looked at it.” 

Clara Hoppe, a biogeochemist at the Alfred Wegener Institute, probed the limits of photosynthesis in the months-long darkness of the Arctic polar night. 

Paolo Verzone

In winter 2020, Hoppe spent months living on a ship wedged into an ice floe, through the polar night, to study the limits of photosynthesis in the dark.
Her team’s recent study in Nature Communications reported microalgae growing and reproducing (opens a new tab) at light levels at or close to the theoretical minimum — far lower than had previously been observed in nature.

The study shows that in some of the coldest, darkest places on Earth, life blooms with the barest quantum of light.
“At least some phytoplankton, under some conditions, may be able to do some very useful things at very low light,” said Douglas Campbell (opens a new tab), a specialist in aquatic photosynthesis at Mount Allison University in Canada, who was not involved in the study.
“It’s important work.” 

 

The depths of the ocean are a lot brighter than you might think.

New research from the Monterey Bay Aquarium Research Institute shows that nearly three quarters of deep sea creatures emit their own light using bioluminescence.

 

The Power of the Dark Side 

Scientists have traditionally understood the Arctic to be a place of stasis for much of the year.
In winter, organisms that can flee the frigid waters do so; those that stay live off stored reserves or sink into a silent sleep.
Then, when the sun returns, the place comes back to life.
During spring bloom, an upsurge in photosynthesizing algae and other microbes kick-starts the Arctic ecosystem, fueling a yearly revel, with tiny crustaceans, fish, seals, birds, polar bears, whales and more.
It seemed to Hoppe that any phytoplankton able to get an earlier start than the competition could have a more successful summer.
This led her to wonder when, precisely, the organisms could respond to the light coming back.
Her interest received a jolt in 2015 when she tagged along on a research project led by researchers at the University of Tromsø in Norway.
The multidisciplinary team found an unexpectedly thriving ecosystem in the winter waters off the Svalbard archipelago; some organisms, particularly clams, were actually more active than they were in summer.
To everyone’s surprise, the phytoplankton were not asleep either: Hoppe measured higher levels of the pigment chlorophyll — a useful proxy for active photosynthesis — in the seawater than anyone expected.
Rather than sinking into surface sediments and overwintering in a dormant “sleep mode,” many cells Hoppe found were having an active winter, with their cellular operations fully up and running.
“If these things are active,” Hoppe said, “the question obviously becomes: When do they start to function again for the ecosystem?” 

She began to wonder about the vast, cold blackness of the polar ocean. 

 

The icebreaker ship RV Polarstern wedged itself into an ice floe in fall 2019, then turned its engines off.
For months it drifted with the sea ice and served as a base for scientists studying the physics, chemistry and biology of the Arctic’s polar night.
Alfred Wegener Institute / Lukas Piotrowski 

In early 2020, Hoppe found herself testing the limits of photosynthesis directly, camped aboard an icebreaker ship that had been deliberately rammed into an ice floe and allowed to drift with its engines off through the polar night.
A rotating crew of scientists with the expedition Mosaic (Multidisciplinary Drifting Observatory for the Study of Arctic Climate) occupied RV Polarstern on its journey to gather as much data about the Arctic winter as possible.

Hoppe and her colleagues worked in the darkness of 24-hour night, amid expanses of glittering ice and wind chills down to minus 76 degrees Fahrenheit.
Cracks and ridges in the ice constantly shifted the route to a permanent hole in the ice, named Ocean City, from which Hoppe and her team gathered hundreds of liters of seawater samples and hauled them back to the ship for analysis.

The team carried out two parallel sets of measurements.
First, they took samples of microalgae from seawater and sea ice into the shipboard lab.
There, they incubated the cells and offered them carbon (traceable by isotope, or the number of neutrons in the atomic nuclei) and minute amounts of light (though significantly more than what was available under the ice).
By measuring the cells’ carbon-uptake rates, they were able to estimate the limits of the organisms’ capacity for photosynthesis.

The researchers also took regular seawater samples in which to track the amounts of phytoplankton and chlorophyll present over time.
Throughout February, both sets of numbers remained static, Hoppe said.
By the end of March, however, the microalgae’s carbon uptake had jumped, along with the number of cells and the concentration of chlorophyll — proxies for growth and photosynthesis.
Hoppe and her team tested and ruled out many possible explanations, and recognized that the uptick in photosynthesis coincided with the return of the first springtime sunlight.

At Ocean City (left), a scientific encampment on the ice floe, researchers collected seawater from a permanent hole in the ice (right).

The sampled region changed as the floe drifted across the Arctic.
Left: Alfred Wegener Institute/Esther Horvath; Right: Alfred Wegener Institute/Michael Gutsche

Yet a key piece of evidence only emerged three years after the expedition, Hoppe said, and from researchers in another department: the physicists measuring light beneath the sea ice.
This has historically been tricky: “You can’t really measure light under the ice without disturbing the environment you’re trying to measure,” Hoppe said.
“Because you drill a hole, you walk around — even footsteps on the snow and ice are going to change the light field.”

To get around the problem, the sea ice physicist Niels Fuchs (opens a new tab) and his team aboard RV Polarstern had placed extremely precise light sensors around the ice floe early in the season and allowed them to freeze to the underside of the ice for the winter.
Like trail cameras placed in the backwoods by a wildlife biologist, the light sensors recorded data on under-ice light for months, undisturbed.

In February, the darkness of the polar night was nearly absolute, and not even photons from a bright moon or fleeting twilight could reach the dark waters below.
Then, in late March, the sun briefly surfaced over the horizon.
Beneath that ice, the light sensors recorded an astronomically small number of photons: an upper range of 0.04 micromoles per square meter per second, a number very close to the theoretical minimum amount of light that photosynthesis can run on.
The actual amount of light was probably lower.
“The light we observed, compared to a normal sunny day, is like one droplet of water compared to 3 liters,” said Fuchs, an ice specialist at the University of Hamburg and co-author on the study.

To measure the amount of light penetrating the sea ice, the physicist Niels Fuchs froze light sensors into the ice floe and left them to record data undisturbed for months.
Courtesy of Niels Fuchs 

 
Their estimate is a conservative one, he added, and it’s possible even fewer photons got through.
“The ice cover is quite heterogeneous,” he explained.
Because some parts of the sheet might allow more light through than others, the research team selected the upper thresholds of their light measurements.
“In the end there’s some variety, and we really want to be on the safe side — to not stake on the lower limit where we’re not 100% certain that this is really the amount of light.”

Pairing Fuchs’ light data with Hoppe’s microalgae observations clinched it: At the end of March, right when the barest amount of sunlight returned, the microalgae not only had their photosynthetic machinery up and running but were also growing and building biomass.
Her team concluded that they’d made the first-ever field observation of photosynthesis at just around the theoretical minimum — where the amount of light was an order of magnitude lower than what had been observed in nature before.
 

Sleep No More

Hoppe was excited to observe photosynthesis at or near the minimum amount of light that could power life.
But the finding raised a question: How could dormant cells be ready to turn their machinery on at the very moment that spring’s first light trickled through the ice?

The light we observed, compared to a normal sunny day, is like one droplet of water compared to 3 liters.
Niels Fuchs, University of Hamburg

Her team found that during the darkest periods of polar night, the microalgae didn’t show a measurable uptick in carbon uptake — they were neither growing nor photosynthesizing.
Yet they weren’t totally dormant either.
The cells kept running on low power.
Then, as soon as the light levels rose enough to support active carbon fixation in late March, the algae were ready to explode into action.

“It’s sort of like a seedbed or an inoculation issue,” Campbell said.
“That ability to productively exploit really low light improves your ability to survive and then be ready to go fast when the light goes back.”

The researchers aren’t entirely sure how the microalgae managed to stay alive and out of dormancy through the darkest times.
Some, such as diatoms, can consume dissolved organic nutrients directly from the water.
Perhaps they could eke out a living from stray photons that passed through cracks in the ice or were emitted by some bioluminescent creature.
Or perhaps polar algae have evolved unique mechanisms that can keep their metabolism running (opens a new tab) on low at frigid temperatures so that they’re ready to activate at first light.

Such adaptations might be important to the ecology of the region, said Kevin Flynn (opens a new tab), a plankton specialist at Plymouth Marine Laboratory who was not involved in the study.
“The organisms may be getting ready earlier than we think,” he said.
The finding is “important work that’s a reality check about what nature really does.”

However, he isn’t entirely convinced that the cells’ late-March growth occurred through photosynthesis.
“The appearance of chlorophyll does not mean that they are photosynthesizing to obtain that growth,” he said.
“They may simply be making more chlorophyll from organics and in preparation for photosynthesizing.
Because as the season goes, there will be light.
And the organism which is ready for it quicker than the others is going to go the quickest.”

On the other hand, Campbell thinks it’s possible that the algae might be photosynthesizing even earlier than Hoppe’s team suggested.
Their estimates of light levels were conservative, he said, and photosynthesis may have been occurring well in advance of the kind of biomass accumulation that’s easy to measure.
It is feasible to him, then, that “these things are right at or touching below that biochemical thermodynamic limit,” he said.

The findings paint a new picture of life in the Arctic’s polar night and possibly beyond.
Life may not be packed entirely into a few short months of summer; rather, the waters may be productive — or, at the very least, still living — throughout the year.
This, Hoppe said, could rewrite our understanding of Arctic organisms’ life cycles, interactions and energy reserves.

She wonders, too, whether Arctic phytoplankton’s ability to ride out near-absolute darkness might be shared by some algae in the colder, darker waters of the deep sea.
If she’s right, the zone of productive ocean may be deeper than anyone thought.
“If polar phytoplankton were able to evolve these mechanisms,” Hoppe suggested, “I’m sure phytoplankton in other areas of the ocean can do the same.”

 

Links :

• QuantaMag :  The Voyage to the End of Ice  /  Underground Cells Make ‘Dark Oxygen’ Without Light  /  Why Are Plants Green? To Reduce the Noise in Photosynthesis /  ‘Zombie’ Microbes Redefine Life’s Energy Limits
• GeoGarage blog : All the fish we cannot see

Hydrographic data a crucial factor in the success of D-Day and beyond

From Hydro by Andrew Leitch

Accurate and up-to-date intelligence

In 2025, the world will mark 80 years since the end of World War II – a conflict defined by pivotal moments such as the Normandy invasion.
Known as D-Day, this extraordinary operation saw 156,000 Allied troops land on the beaches of Normandy, France, in the largest seaborne invasion in history.
What many may not realize is that hydrographic survey data played a critical role in its success, ensuring precise planning and execution of the landings.

Launched on 6 June 1944 under the code name Operation Overlord, D-Day set in motion the Allied campaign to liberate Western Europe, defeat Nazi Germany and bring the war to an end.
Insights from the UK Hydrographic Office (UKHO) Archives reveal how meticulous hydrographic work underpinned the Normandy landings and many other operations during World War II.
This story not only underscores the immense contribution of hydrography to the Allied victory but also highlights the enduring importance of preserving our hydrographic heritage for future generations.
Collecting hydrographic data to support D-Day

The use of hydrographic data was pivotal during the D-Day landings.
While we often focus on the immediate planning and execution of Operation Overlord, the UKHO’s archives reveal a deeper layer of detail and intricacies.
These documents, preserved in one of the world’s largest collections of navigational data, stretch back over 400 years and continue to unveil hidden details, many of which reshape our understanding of important moments in history.
There can be few of more significance than D-Day, which is particularly fresh in many of our memories following the 80th anniversary commemorations that took place this summer.

The Allied Forces required a variety of sea charts and coastal diagrams during the war and the Admiralty of the British Government tasked one of its departments, the UKHO, with gathering the appropriate information, drawing the charts and maps, printing them in great numbers – as well as great secrecy – and issuing them to the fleet for operational use.
A series of ‘Special Charts’, including top secret maps and charts of the Allied minefields, wrecks and enemy minefields were drawn by the cartographers at the UKHO to ensure that the British and Allied warships and merchant ships could navigate safely.

The hydrographic data used in the D-Day landings was a combination of long-established charts and ‘borrowed’ German and French records, based on both existing survey data and intelligence, and highly detailed, newly collected information.
Accurate and up-to-date intelligence was essential to the success of the planned assault on the Normandy beaches, and the information shown on these maps had to be gathered without betraying a hint of interest in the area.

D-Day Naval ship movement and navigation channel chart showing routes to the beaches from the south coast of the UK.
The large circle south of the Isle of Wight was a mustering area known as ‘Picadilly Circus’ and represented a gathering point for most of the landing craft on their way to the beaches of Normandy.

In the years leading up to D-Day, reconnaissance missions and covert operations were carried out to gather fresh data on the English Channel and the waters off the Normandy coast.
A variety of methods were used, including x-craft submarines that surveyed the shoreline depths and evaluated defensive and shoreline features, and aerial recon from Mosquitos and Spitfires for photographic records.
Perhaps most daring of all, hydrographic surveyors were sent by the Admiralty to make rapid reconnaissance surveys of the coast under the cover of darkness, though at the time they were kept blissfully unaware of the significance of their work.

In August 1943, a special covert unit was set up to gather this information, code-named Operation Neptune.
Based at Cowes on the Isle of Wight, two hydrographic surveyors, Lieutenant Commander Berncastle and Lieutenant Glen, were issued with two 32-foot landing craft in which to operate.
The low profile of these vessels made them difficult to detect by German radar and canoes were used when daring landings on the beaches were required.

The surveying could only take place under certain conditions, such as when there was no moon and a high tide during the small hours.
On dark nights, the craft were towed halfway across the Channel, then motored quietly the rest of the way using silenced engines and underwater exhausts.
The surveyors would begin their work just before midnight and were under strict instructions to leave the French coast by 04:00 hours to meet the gun boat and be towed back to safety.
The top secret information they gathered was added to the charts and landing maps by draughtsmen at the UKHO.

The missions to the French coast were carried out without major injury or attack, although they were spotted one night and flares were sent up by the Germans.
The only injury suffered was when someone burnt himself on a tin of the self-heating soup supplied to sustain the men on the long dark nights at sea.

When combined with other sources of intelligence, the information that made its way onto these charts went far beyond what would normally feature.
It is remarkable to consider the intricacies that were involved in calculating every aspect of the operation, reflecting the breathtaking complexities required if D-Day was to succeed.
This included every gun emplacement along the Normandy coast, the direction and distances covered by artillery shells, the size of the shells and the overlapping arcs of impact, all of which were meticulously mapped.
This was crucial in informing the choice of the landing sites, given the belief of the German forces that it would be impossible to successfully execute a landing and bring ashore the volume of material required to sustain operations anywhere other than a major port.

 

Chart of Arromanches-les-Bains, Calvados, Normandy, France 

(Gold Beach, D-Day landing site), 1944.

Supporting the success of D-Day

This data was critical in charting the best possible navigation routes for the enormous fleet, which comprised over 4,000 vessels of various sizes.
The UKHO’s navigational charts detailed everything from the south coast of England, through to rendezvous points such as the mid-channel mustering point south of the Isle of Wight, named Piccadilly Circus, to the precise landing points on the Normandy coast.

The incredible coordination on the day of the landings involved not only mapping and planning but also the precision of naval bombardments.
Shelling began from the battleships, many of which had been uniquely prepared to adjust the angle of their guns to hit their targets accurately.

Each vessel involved in the landings carried custom-made charts, produced by the UKHO at its printing facilities in Taunton, Somerset.
By the time D-Day arrived, over 1.5 million charts had been printed; a reminder of the critical role played in the war effort by so many away from the front line of the conflict.
These charts ensured that commanders could lead their forces and fulfil their role in the operation, navigating minefields and hazards while guiding troops to their designated landing beaches.
Even the troops themselves carried charts of the shores and inland areas to facilitate post-landing navigation.

The documents that were created, particularly the charts used by the invasion forces, demonstrate how multi-layered the operation was.
The charts were not simply guides for navigating the waters; they combined geographical, geological and military intelligence into a single resource.
Using these charts, the landing craft were directed to precise sections of the beach, and every soldier knew their role based on these detailed instructions.

These historical records, now housed in the UKHO’s collection, preserve not only the physical artefacts of that time but also the stories of the bravery and coordination that made D-Day possible.
Every detail, from the depth of the water to the positions of the troops, was considered and mapped with an astonishing level of precision and detail, which therefore led and contributed to the success of the landings and the eventual victory.

Juno Beach Landing Craft designation chart showing the sections of beach and area for navigation on D-Day.
Ships were given designated locations to come ashore (e.g. Mike red), and in this way the landings and troops could be directed to specific points.

 

The role of hydrography following D-Day

The days after D-Day placed continued reliance on the UKHO’s hydrographic data.
The surveyors continued their work along the coast to ensure the ports and beaches were well surveyed for potential dangers to the following fleet.
After the beachheads were secured, the Allies had to establish supply lines and reinforce their positions.
To do this, they constructed two massive artificial harbours, known as the Mulberry Harbours, on the Normandy coast.
Hydrographic data was crucial to positioning these harbours and other offshore breakwaters, ensuring that supplies could flow in while the Allies pushed further inland.

The planning, management and execution of these ongoing operations, including the use of sunken ships as breakwaters and wave-deflecting systems, known as bombardons, was another triumph of hydrographic intelligence.
These were charted meticulously by the UKHO and new charts were issued showing the positions of the Mulberry Harbours and breakwaters, as well as the new wrecks of landing craft where six weeks before the area had been littered with German sea defences.
These historic charts stand as a testament to the ongoing importance of hydrography in the crucial days and weeks after D-Day.
Hydrography in conflict and humanitarian operations

While D-Day was a prominent example, hydrographic data played a broader role in the wider Allied war effort.
Throughout World War II, knowledge of shorelines, underwater features and ocean conditions was essential for military operations across all aspects of the war.
The UKHO’s charts facilitated safe navigation, mission planning and coordination of naval forces, and continue to do so to this day.

The UKHO’s data remains crucial for humanitarian operations.
Whether responding to natural disasters or supporting peacekeeping efforts, hydrographic data enables the safe navigation of humanitarian aid vessels, ensuring timely relief to disaster-stricken areas.
This data is used globally to protect oceans, support global commerce and aid in defence operations.

Throughout the past 80 years since D-Day, there have been many examples of the vital role of hydrography in disaster relief.
In recent times, this has been most evident in the support that the UKHO has been able to provide to relief and recovery efforts following extreme weather events.
In the aftermath of the devastating impact of Cyclone Pam on the South Pacific island chain of Vanuatu, the UKHO rapidly produced and freely distributed two special purpose charts of Vanuatu to assist with the humanitarian relief effort.

Similarly, when the British Virgin Islands were struck by Hurricane Irma, the UKHO was able to provide emergency assistance.
This was initially through the team of surveyors who coincidentally were already located in the area and took immediate action by conducting a lead-line survey that supported the reopening of ports, jetties and coastal facilities for the relief efforts, with the support of the Royal Navy.
The UKHO’s team subsequently returned to gather data on bathymetric profiles, tidal information and navigational aids that enabled the reopening of Road Harbour, one of the islands’ main hubs.

Hydrography continues to play an important role in today’s conflicts.
Last year, the UKHO donated £1.6 million worth of equipment, including two full singlebeam echosounder systems and two multibeam echosounder systems, to the State Hydrographic Service of Ukraine, to assist with efforts to keep the seas around Ukraine safe and to protect Ukraine’s ports and shipping lanes, including attempts to establish a humanitarian grain corridor.

Secret June 1944 mustering chart of the Solent and surrounding areas showing the locations where D-Day landing vessels and support craft were to gather in advance of being given the ‘go signal’ to move off on their routes to the beaches at Normandy.

Learning for the future by preserving the past

The UKHO’s extensive archival collection, one of the largest in the world, has continued to inform and support our understanding of the importance of hydrography to the world around us.
Though initially compiled as part of an imperial mandate to chart the globe for British interests, these records now serve a more global purpose.
Modern hydrographic work involves collaboration with international partners, using historical data as a foundation for modern safety standards, innovative navigation tools and new partnerships.
For example, hydrographic charts from the eighteenth century once used during military engagements are now being shared with our counterparts in the United Arab Emirates, ensuring safer navigation, a shared understanding of our history and improved cooperation.

Our archives continue to educate us, not just about historical operations such as D-Day, but also about the value of historic records in shaping our understanding of the past and our approach to meeting today’s hydrographic needs.
The work of cataloguing these archives is far from complete, but every new discovery adds another chapter to the story of hydrography’s importance in our history.

 

Aerial photo of Arromanches-les-Bains, Calvados, Normandy, France (Gold Beach, D-Day landing site), 13 October 1944.
The surviving artificial Mulberry Harbour at Gold Beach allowed the continuous supply of equipment, supplies and troops to service the Allied invasion of Europe until early 1945.
The Hydrographic Office has all the planning, designs and logistical charts showing its inception, delivery and operations.

Links :

• GeoGarage blog :'Top Secret' maps reveal the massive Allied effort behind D ... / Turning the tide: D-Day from an oceanographer's perspective / D-Day: the largest seaborne invasion in History / Historian uncovers covert D-Day chart maker's tale / Mapping out a vital part of D-Day history / The dominance of chaos : Weather prediction will always have a ...

DOGE’s chaos reaches Antarctica

Photograph: Wolfgang Kaehler/Getty Images

From Wired by Leah Feiger

Daily life at US-run Antarctic stations has already been disrupted.
Scientists worry that the long-term impacts could upend not only important research but the continent’s delicate geopolitics.

 

Few agencies have been spared as Elon Musk’s so-called Department of Government Efficiency (DOGE) has ripped through the United States federal government.
Even in Antarctica, scientists and workers are feeling the impacts—and are terrified for what’s to come.

courtesy of @redgeographics

The United States Antarctic Program (USAP) operates three permanent stations in Antarctica.
These remote stations are difficult to get to and difficult to maintain; scattered across the continent, they are built on volcanic hills, polar plateaus, and icy peninsulas.

But to the US, the science has been worth it.
At these stations, over a thousand people each year come to the continent to live and work.
Scientists operate a number of major research projects, studying everything from climate change and rising sea levels to the cosmological makeup and origins of the universe itself.
With funding cuts and layoffs looming, Antarctic scientists and experts don’t know if their research will be able to continue, how US stations will be sustained, or what all this might mean for the continent’s delicate geopolitics.

from National Geographic

“Even brief interruptions will result in people walking away and not coming back,” says Nathan Whitehorn, an associate professor and Antarctic scientist at Michigan State University.
“It could easily take decades to rebuild.”

The USAP is managed by the National Science Foundation.
Last week, a number of NSF program managers staffed on Antarctic projects were fired as part of a wider purge at the agency.
The program managers are critical for maintaining communication with the infrastructure and logistics arm of the NSF, and the contractors for the USAP, as well as planning deployment for scientists to the continent, keeping track of the budgets, and funding the maintenance and operations work.
“I have no idea what we do without them,” says another Antarctic scientist who has spent time on the continent, who along with several others WIRED granted anonymity due to fears of retaliation.
“Without them, everything stops,” says a scientist whose NSF project manager was fired last week.
“I have no idea who I am supposed to report to now or what happens to submitted proposals.”

Scientific research happens at all of the stations.
At the Amundsen-Scott South Pole Station, scientists work on the South Pole Telescope and BICEP telescope, both of which study the cosmic background radiation and the evolution of the universe; IceCube, a cubic-kilometer detector designed to study neutrino physics and high energy emission from astrophysical sources; and the Atmospheric Research Observatory that studies climate science and is run by the National Oceanic and Atmospheric Administration.
(Mass firings are also expected at the NOAA.)

 

 

I am alarmed by what is happening in Antarctica where the evidence overwhelmingly shows that there is an acceleration of melting of ice, which could be catastrophic to coastal communities everywhere.

What happens in Antarctica doesn’t stay in Antarctica.
pic.twitter.com/VMJ5c7wmT9

— António Guterres (@antonioguterres) November 24, 2023

“The climate science [at the South Pole Station] is super unique,” an Antarctic scientist says.
“The site has so little pollution that we call it ‘the cleanest air on Earth,’ and they have been monitoring the ozone layer and CO2 content in the atmosphere for many decades.”

 

McMurdo Valley

Other directives from the Donald Trump administration have directly affected daily life on those stations.
“Gender-inclusive terms on housing documents” have been removed from Antarctic staffer forms, a source familiar with the situation at McMurdo Station tells WIRED.
“It asked if you had a preference with which gender you housed with,” the source says.
“That’s all been removed.”

Staffers have already pushed back.
“People have been painting waste bins saying “Antarctica is for ALL” in rainbow, people’s email signatures [have] pride additions, [others] keep adding preferred pronouns to emails,” the source says.

“There’s a sense of unease on the station like people have never felt before,” they add.
“The job still has to get done, even though people feel like the next shoe can drop at any moment.”

That unease extends to their own job security.
“There are some people currently at the South Pole that are worried about losing their jobs any day now,” a source with familiarity of the situation tells WIRED.
Workers present at the station aren’t able to physically leave until October, and a midseason firing, or loss of funding, would present a unique set of challenges.

Sources are also bracing for at least a 50 percent reduction in the NSF’s budget due to DOGE cuts.
These cuts are sending Antarctic scientists with assistants and graduate students scrambling.
“We didn’t know if we could pay graduate students,” says one scientist.
While research is conducted on the continent, scientists bring their findings back to the US to process and analyze.
A lot of the funding also operates the science itself: For one project that requires electricity to run detectors, the scientist “was paranoid we would not be able to literally pay bills for an experiment starved for data.” That hasn’t come to fruition yet, but as funding cycles restart in the coming weeks and months, scientists are on tenterhooks.

Sources tell WIRED that Germany, Canada, Spain, and China have already started taking advantage of that uncertainty by recruiting US scientists focused on Antarctica.

“Foreign countries are actively recruiting my colleagues, and some have already left,” says one Antarctic scientist.
“My students are looking at jobs overseas now … people have been coming [to the US] to do science my whole life. Now people are going the other way.”

“Now is a great time to see if anyone wants to jump ship,” another Antarctic scientist says.
“I do worry about a brain drain of tenured academics, or students who are shunted out.”

“The damage caused by gutting the [Antarctic] science budget like this is going to last generations,” says another.

Throughout DOGE’s cuts to the federal government, representatives have said that if something needs to be brought back, it could be.
In some cases, reversals have already happened: The US Department of Agriculture said it accidentally fired staffers working on preventing the spread of bird flu and is trying to rehire them.

But in Antarctica, a reversal won’t necessarily work.
“One of the really scary things about this is that if the Antarctic program budget is cut, then they’ll very quickly get to the point where they can’t even keep the station open, much less science projects going,” an Antarctic scientist tells WIRED.
“If the South Pole [station] is shut down, it’s basically nearly impossible to bring it back up.
Everything will freeze and get buried in snow.
And some other country will likely immediately take over.

Got a Tip?

Are you a current or former government employee who wants to talk about what's happening?

We'd like to hear from you.
Using a nonwork phone or computer, contact the reporter securely on Signal at leahfeiger.86.

Others share this fear of a station takeover.
“Even if science funding is cut back, there is an urgent need for the US to invest in icebreakers and polar airlift capability otherwise at some point the US-managed South Pole station might not be serviceable,” says Klaus Dodds, an Antarctic expert and professor of geopolitics at Royal Holloway University of London.

Experts are concerned that countries like Russia and China—who have already been eagle-eyed on continental influence—will quickly jostle to fill the power vacuum.
“Presumably it would be humiliating for anyone who wishes to promote ‘America First’ to witness China offer to take over the occupation and management of the base at the heart of Antarctica.
China is a very determined polar power,” says Dodds.

 

The political outcome of the US pulling back from its Antarctic research and presence could be dire, sources tell WIRED.

Antarctica isn’t owned by any one country.
Instead it’s governed by the Antarctic Treaty System, which protects Antarctica and the scientific research taking place on the continent, and forbids mining and nuclear activity.
Some countries, including China and Russia, have indicated that they would be interested in rule changes to the Treaty system, particularly around resource extraction and fishing restrictions.
The US, traditionally, has played a key role in championing the treaty: “Many of the leading polar scientists and social scientists are either US citizens and/or have been enriched by contact with US-led programs,” says Dodds.

That leadership role could change quickly.
The US also participates in a number of international collaborations involving major Antarctic scientific projects.
A US pullback, Whitehorn says, “makes it very hard to regard the US as a reliable partner, so I think there will be a lot less interest in accepting US leadership in such things … The uncertainty will drive people away and sacrifice the leadership the US already has.”

“If the NSF can’t function, or we don’t fund it, projects with long lead times can just die,” another scientist says.
“I’m sure international partners would be happy to partner elsewhere.
This is what it means to lose US competitiveness.” 

 

Links :

• Medium : The Day We Chose Ignorance: NOAA, Science, and the Price of Stupidity
• NPR : Trump administration layoffs hit NOAA, agency that forecasts weather, hurricanes 
• The Guardian : ‘Cruel and thoughtless’: Trump fires hundreds at US climate agency Noaa
• Maritime Executive : After NOAA Layoffs, Experts Warn of Impacts on Shipping and Fisheries 
• InsideClimateNews : Experts Say Attempted Mass Firing of NOAA Workers May be Illegal and Threatens Public Safety
  
• GeoGarage blog : Elon Musk is coming for our weather service / For-profit companies can’t easily replace NOAA’s weather-forecasting process / Can Trump just order new names for Denali and the Gulf of Mexico? A geographer explains who decides what goes on the map

Image of the week : this bird’s eye view of a shark hunt won a photo contest

A school of hardyhead silverside fish (Atherinomorus lacunosus) flees from four blacktip reef sharks near the shore of the Maldives in this aerial photo.

 A. Albi & A. Paula

From ScienceNews by Tina Hesman Saey

The image is part of work to understand whether sharks coordinate their attacks on prey

A school of hardyhead silverside fish (Atherinomorus lacunosus) flees from four blacktip reef sharks near the shore of the Maldives in this aerial photo.

Behavioral biologists Angela Albi and August Paula of the Max Planck Institute of Animal Behavior in Konstanz, Germany, captured the image, a still frame from drone footage, during a study of how sharks interact with each other and their prey.
Blacktip reef sharks (Carcharhinus melanopterus) are social animals, and juveniles, such as these four, often gather and circle within schools of fish.

Albi is trying to determine whether the sharks coordinate their attacks.
The snapshot won the 2024 Royal Society Publishing Photography Competition.

Scientists from around the world submitted images from their research in five categories.