In a warming world, freshwater production is moving deep beneath the sea

CARLSBAD, Calif. (AP) — Some four miles off the Southern California coast, a company is betting it can solve one of desalination’s biggest problems by moving the technology deep below the ocean’s surface.

OceanWell’s planned Water Farm 1 would use natural ocean pressure to power reverse osmosis — a process that forces seawater through membranes to filter out salt and impurities — and produce up to 60 million gallons (nearly 225 million liters) of freshwater daily. Desalination is energy intensive, with plants worldwide producing between 500 and 850 million tons of carbon emissions annually — approaching the roughly 880 million tons emitted by the entire global aviation industry.

OceanWell claims its deep sea approach — 1,300 feet (400 meters) below the water's surface — would cut energy use by about 40% compared to conventional plants while also tackling the other major environmental problems plaguing traditional desalination: the highly concentrated brine discharged back into the ocean, where it can harm seafloor habitats, including coral reefs, and the intake systems that trap and kill fish larvae, plankton and other organisms at the base of the marine food web.

“The freshwater future of the world is going to come from the ocean,” said OceanWell CEO Robert Bergstrom. “And we’re not going to ask the ocean to pay for it.”

It’s an ambitious promise at a time when the world desperately needs alternatives. As climate change intensifies droughts, disrupts rainfall patterns and fuels wildfires, more regions are turning to the sea for drinking water. For many countries, particularly in the arid Middle East, parts of Africa and Pacific island nations, desalination isn’t optional — there simply isn’t enough freshwater to meet demand. More than 20,000 plants now operate worldwide, and the industry has been expanding at about 7% annually since 2010.

“With aridity and climate change issues increasing, desalination will become more and more prevalent as a key technology globally,” said Peiying Hong, a professor of environmental science and engineering at King Abdullah University of Science and Technology in Saudi Arabia.

But scientists warn that as desalination scales, the cumulative damage to coastal ecosystems — many already under pressure from warming waters and pollution — could intensify.

Some companies are powering plants with renewable energy, while others are developing more efficient membrane technology to reduce energy consumption. Still others are moving the technology underwater entirely. Norway-based Flocean and Netherlands-based Waterise have tested subsea desalination systems and are working toward commercial deployment. Beyond southern California, OceanWell has signed an agreement to test its system in Nice, France — another region facing intensifying droughts and wildfires — beginning this year.

For now, its technology remains in development. A single prototype operates in the Las Virgenes Reservoir where the local water district has partnered with the company in hopes of diversifying its water supply. If successful, the reverse osmosis pods would eventually float above the sea floor in the Santa Monica Bay, anchored with minimal concrete footprint, while an underwater pipeline would transport freshwater to shore. The system would use screens designed to keep out even microscopic plankton and would produce less concentrated brine discharge.

Gregory Pierce, director of UCLA’s Water Resources Group, said deep sea desalination appears promising from an environmental and technical standpoint, but the real test will be cost.

“It’s almost always much higher than you project” with new technologies, he said. “So that, I think, will be the make or break for the technology.”

Las Virgenes Reservoir serves about 70,000 residents in western Los Angeles County. Nearly all the water originates in the northern Sierra Nevada and is pumped some 400 miles (640 kilometers) over the Tehachapi Mountains — a journey that requires massive amounts of energy. During years of low rainfall and snowpack in the Sierra, the reservoir and communities it serves suffer.

About 100 miles (160 kilometers) down the coast, the Carlsbad Desalination Plant has become a focal point in the state’s debate over desalination’s environmental tradeoffs.

The plant came online in 2015 as the largest seawater desalination facility in North America. Capable of producing up to 54 million gallons (204 million liters) of drinking water daily, it supplies about 10% of San Diego County’s water — enough for roughly 400,000 households.

In Southern California, intensifying droughts and wildfires have exposed the region’s precarious water supply. Agricultural expansion and population growth have depleted local groundwater reserves, leaving cities dependent on imported water. San Diego imports roughly 90% of its supply from the Colorado River and Northern California — sources that are becoming increasingly strained by climate change. Desalination was pitched as a solution: a local, drought-proof source of drinking water drawn from the Pacific Ocean.

But environmental groups have argued the plant’s seawater intake and brine discharge pose risks to marine life, while its high energy demands drive up water bills and worsen climate change. Before the plant came online, environmental organizations filed more than a dozen legal challenges and regulatory disputes. Most were dismissed but some resulted in changes to the project’s design and permits.

“It sucks in a tremendous amount of water, and with that, sea life,” said Patrick McDonough, a senior attorney with San Diego Coastkeeper, which has participated in multiple legal challenges to the project. “We’re not just talking fish, turtles, birds, but larvae and spores — entire ecosystems.”

A 2009 Regional Water Quality Control Board order estimated the plant would entrap some 10 pounds (4.5 kilograms) of fish daily and required offsetting those impacts by restoring wetlands elsewhere. Seventeen years later, that restoration remains incomplete. And a 2019 study found the plant’s brine discharge raises offshore salinity above permitted levels, though it detected no significant biological changes — likely because the site had already been heavily altered by decades of industrial activity from a neighboring power plant.

Those impacts are especially acute in California, where roughly 95% of coastal wetlands have been lost largely to development, leaving the remaining lagoons as vital habitats for fish and migratory birds.

“When we start messing with these very critical and unfortunately sparse coastal lagoons and wetlands, it can have tremendous impacts in the ocean,” McDonough said.

Michelle Peters, chief executive officer of Channelside Water Resources, which owns the plant, said the facility uses large organism exclusion devices and one-millimeter screens to minimize marine life uptake, though she acknowledged some smaller species can still pass through.

The plant dilutes its brine discharge with additional seawater before releasing it back into the ocean, and years of monitoring have shown no measurable impacts to surrounding marine life, she said.

Peters said the Carlsbad plant has significantly cut its energy consumption through efficiency improvements and operates under a plan aimed at making the facility carbon net-neutral.

Many experts say water recycling and conservation should come first, noting wastewater purification typically uses far less energy than seawater desalination and can substantially reduce impacts on marine life. Las Virgenes is pursuing a wastewater reuse project alongside its desalination partnership.

“What we are looking for is a water supply that we can count on when Mother Nature does not deliver,” Las Virgenes' Pedersen said. “Developing new sources of local water is really a critical measure to be more drought and climate ready.”

Follow Annika Hammerschlag on Instagram @ahammergram.

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A sea lion basks in the sun in La Jolla, Calif., Wednesday, Dec. 3, 2025. (AP Photo/Annika Hammerschlag)

A sectioned-off area of the Agua Hedionda Lagoon marks the seawater intake for the Carlsbad desalination plant in Carlsbad, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

Reverse osmosis machinery operates at the Carlsbad desalination plant in Carlsbad, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

Pipes carrying brackish feed water run through the Carlsbad desalination plant in Carlsbad, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

Pipes carrying brine and other substances run through the Carlsbad desalination plant in Carlsbad, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

A drone view shows the Carlsbad desalination plant's intake lagoon on the right and the discharge canal on the left, Tuesday, Dec. 2, 2025, in Carlsbad, Calif. (AP Photo/Annika Hammerschlag)

Strands of kelp rise from a thinned kelp forest in La Jolla, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

Garibaldi, California’s state fish, which are vulnerable to impingement on desalination intake screens, swim in La Jolla, Calif., Tuesday, Dec. 2, 2025. (AP Photo/Annika Hammerschlag)

The remains of fire-damaged homes sit in a cleared-out block in the Palisades neighborhood of Los Angeles, Calif., Monday, Dec. 1, 2025. (AP Photo/Annika Hammerschlag)

This photo shows the intake screen of OceanWell's prototype reverse osmosis pod that is designed to allow microscopic organisms such as plankton to safely pass through in Westlake Village, Calif., Monday, Dec. 1, 2025. (AP Photo/Annika Hammerschlag)

A prototype OceanWell reverse osmosis pod is lowered into Las Virgenes Reservoir in Westlake Village, Calif., Monday, Dec. 1, 2025, where the deep sea desalination technology is being tested. (AP Photo/Annika Hammerschlag)

A prototype OceanWell reverse osmosis pod sits on the dock at the Las Virgenes Reservoir in Westlake Village, Calif., Monday, Dec. 1, 2025, where the deep sea desalination technology is being tested. (AP Photo/Annika Hammerschlag)

Jaden Gilliam, OceanWell project engineer, left, and Mark Golay, director of engineering projects, lower a prototype reverse osmosis pod into Las Virgenes Reservoir in Westlake Village, Calif., Monday, Dec. 1, 2025. (AP Photo/Annika Hammerschlag)

U.S., Danish and Greenlandic officials have met face to face to discuss President Donald Trump's ambitions to take control of Greenland, a semiautonomous territory of Denmark. At the same time, Denmark and several European allies are sending troops to Greenland in a pointed signal of intent to boost the vast Arctic island's security.

Danish Foreign Minister Lars Løkke Rasmussen said after a meeting in Washington on Wednesday with his Greenlandic counterpart, U.S. Vice President JD Vance and Secretary of State Marco Rubio that a “fundamental disagreement” remained. He acknowledged that “we didn't manage to change the American position” but said he hadn't expected to.

However, Wednesday's events did point to ways ahead.

Denmark, Greenland and the U.S. agreed to form a high-level working group “to explore if we can find a common way forward,” Løkke Rasmussen said. He added that he expects the group to hold its first meeting “within a matter of weeks.”

Danish and Greenlandic officials didn't specify who would be part of the group or give other details. Løkke Rasmussen said the group should focus on how to address U.S. security concerns while respecting Denmark's “red lines.” The two countries are NATO allies.

“Whether that is doable, I don't know,” he added, holding out hope that the exercise could “take down the temperature.”

He wouldn't elaborate on what a compromise might look like, and expectations are low. As Danish Defense Minister Troels Lund Poulsen put it Thursday, having the group is better than having no working group and “it's a step in the right direction.” It will at least allow the two sides to talk with each other rather than about each other.

Trump has argued repeatedly that the U.S. needs control of Greenland for its national security. He has sought to justify his calls for a U.S. takeover by repeatedly claiming that China and Russia have their own designs on Greenland, which holds vast untapped reserves of critical minerals.

Just as the talks were taking place in Washington on Wednesday, the Danish Defense Ministry announced that it was increasing its military presence in Greenland, along with NATO allies. France, Germany, Norway and Sweden announced that they were each sending very small numbers of troops in a symbolic but pointed move signaling solidarity with Copenhagen.

The U.K. said one British officer was part of what it called a reconnaissance group for an Arctic endurance exercise. The German Defense Ministry, which dispatched 13 troops, said the aim is to sound out “possibilities to ensure security with a view to Russian and Chinese threats in the Arctic.” It said it was sending them on a joint flight from Denmark as “a strong signal of our unity.”

Poulsen said that "the Danish Armed Forces, together with a number of Arctic and European allies, will explore in the coming weeks how an increased presence and exercise activity in the Arctic can be implemented in practice,” he said.

On Thursday, he said the intention was “to establish a more permanent military presence with a larger Danish contribution,” and to invite allies to take part in exercises and training on a rotating basis, according to Danish broadcaster DR.

While the European troops are largely symbolic at this point, the timing was no accident.

The deployment “serves both to send a political signal and military signal to America, but also indeed to recognize that Arctic security should be reinforced more," said Maria Martisiute, an analyst at the European Policy Center in Brussels. "And first and foremost, this should be done through allied effort, not by the U.S. coming and wanting to take it over. So it complicates the situation for the U.S.”

The European efforts are Danish-led and not coordinated through NATO, which is dominated by the United States. But the European allies are keen to keep NATO in play, and Germany said that “the aim is to obtain a well-founded picture on the ground for further talks and planning within NATO."

Poulsen has said he and Greenland's foreign minister plan to meet NATO Secretary General Mark Rutte in Brussels on Monday to discuss security in and around the Arctic. NATO has been studying ways to bolster security in the Arctic region.

“I’m really looking forward for an announcement of some kind of military activity or deployment under NATO’s framework,” Martisiute said. “Otherwise there is indeed a risk that ... NATO is paralyzed and that would not be good.”

Sylvain Plazy in Brussels contributed to this report.

Denmark's Foreign Minister Lars Løkke Rasmussen and Greenland's Foreign Minister Vivian Motzfeldt speak at a news conference at the Embassy of Denmark, Wednesday, Jan. 14, 2026, in Washington. (AP Photo/John McDonnell)

An Airbus A400M transport aircraft of the German Air Force taxis over the grounds at Wunstorf Air Base in the Hanover region, Germany, Thursday, Jan. 15, 2026 as troops from NATO countries, including France and Germany, are arriving in Greenland to boost security. (Moritz Frankenberg/dpa via AP)

Denmark's Foreign Minister Lars Løkke Rasmussen and Greenland's Foreign Minister Vivian Motzfeldt speak at a news conference at the Embassy of Denmark, Wednesday, Jan. 14, 2026, in Washington. (AP Photo/John McDonnell)

A man rides by on a quad bike past a row of Greenlandic national flags in Nuuk, Greenland, Wednesday, Jan. 14, 2026. (AP Photo/Evgeniy Maloletka)