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Southern Ocean Salinity Shift & Global Climate Impacts
I recently came across compelling content on TikTok where people from various fields were discussing unprecedented changes in the Southern Ocean, using phrases like ‘never seen before’ and ‘catastrophic tipping point.’ As usual when something sparks my interest on social media, I knew I needed to dig deeper into the peer-reviewed science behind these claims. What I discovered was far more concerning than the initial posts suggested.
What I discovered was that the Southern Ocean, that vast body of water surrounding Antarctica, has undergone a fundamental transformation that challenges everything we thought we understood about polar marine systems. Since 2016, something extraordinary and deeply troubling has been happening in the most remote waters on Earth.
Is It That Scary?
To be clear, we’re not talking about ocean currents literally reversing direction, but rather fundamental changes in ocean salinity that are disrupting the natural circulation patterns and density layers that have existed for millennia.
For decades, the surface waters of the Southern Ocean had been doing exactly what climate scientists expected them to do in a warming world: they were getting fresher. Melting ice and increased precipitation were diluting the salt content, creating a stable layered ocean structure that helped maintain sea ice cover. This freshening process was so consistent that it became a cornerstone of our climate models.
Then, around 2015, everything changed.
New satellite data from the European Space Agency’s SMOS mission, combined with underwater robotic floats, revealed something that caught the entire scientific community off guard. The Southern Ocean’s surface waters began getting saltier at an alarming rate. Not slightly saltier, not gradually saltier, but dramatically and rapidly saltier. This reversal has continued unabated, marking what researchers are calling a fundamental shift to a new ocean state never observed in the modern era.
Dr. Alessandro Silvano from the University of Southampton, who led the groundbreaking study published in the Proceedings of the National Academy of Sciences, described the findings as “astonishing.” The implications extend far beyond Antarctica. When ocean surface waters become saltier, they become denser and heavier, causing them to sink more readily. This breaks down the ocean’s natural layering system, allowing warm water from the depths to rise to the surface in a dangerous feedback loop that accelerates ice loss.
Since 2015, Antarctica has lost sea ice equivalent to the size of Greenland. Unlike typical seasonal variations, this ice has not returned, representing the largest environmental change on our planet in the past decade. The loss coincided perfectly with the salinity increase, providing what scientists call a “coherent explanation” for the rapid Antarctic sea ice decline that had previously puzzled researchers.e
Why This Changes Everything We Know
The research published in PNAS by Dr. Silvano’s team used data from multiple sources including the European Space Agency’s SMOS satellite mission and autonomous underwater floats, providing robust evidence for these unprecedented changes.
The Southern Ocean is like a massive layered cake. Normally, cold, fresh surface water sits on top of warmer, saltier deep water. This stratification acts like a lid, trapping heat in the ocean depths and keeping surface waters cool enough for sea ice to form and persist.
When surface waters become saltier, this balance collapses. The denser salty water sinks, stirring up the ocean layers and allowing centuries-old deep water to rise. This deep water carries with it not just heat, but also carbon dioxide that has been locked away in the ocean depths for hundreds of years. The result is a vicious cycle: saltier water brings more heat to the surface, which melts more ice, which allows more solar energy to be absorbed rather than reflected, which brings even more heat to the surface.
We witnessed this process firsthand with the return of the Maud Rise polynya in 2016-2017, a gaping hole in the sea ice nearly four times the size of Wales that hadn’t appeared since the 1970s. These polynyas are like windows into the future, showing us what a Southern Ocean without stable sea ice might look like.
The transformation extends beyond the immediate Antarctic region. The Southern Ocean plays a crucial role in the global conveyor belt of ocean currents, helping to regulate planetary heat distribution and carbon storage. Changes here send ripple effects throughout the entire global ocean system, potentially affecting weather patterns, marine ecosystems, and climate stability as far away as Europe and North America.
Is There A Fix?
This is the question that haunts every marine scientist studying this phenomenon: is there anything humanity can do to halt or reverse this process? The short answer is deeply unsettling.
Unlike some environmental problems that can be addressed through direct intervention, the Southern Ocean’s transformation appears to be beyond our immediate control. We cannot simply remove salt from vast ocean areas or artificially restore the layered structure that took millennia to develop. The scale is too immense, the processes too fundamental, and our technological capabilities too limited.
Some researchers have explored theoretical geoengineering solutions, including marine cloud brightening, which involves spraying seawater particles into the atmosphere to create reflective clouds that could cool ocean surfaces. However, these interventions come with their own risks and uncertainties. Studies suggest that large-scale cloud brightening could disrupt natural weather patterns, potentially causing droughts in some regions while failing to address the underlying ocean chemistry changes.
Ocean fertilization, another proposed intervention, involves adding nutrients to stimulate phytoplankton growth and carbon absorption. But the Southern Ocean’s remote location, harsh conditions, and complex ecosystem dynamics make such approaches extremely challenging to implement safely. Moreover, the effectiveness of these techniques in addressing salinity-driven circulation changes remains highly uncertain.
The harsh reality is that the Southern Ocean operates on timescales and spatial scales that dwarf human intervention capabilities. The water masses involved have been circulating for centuries, and the energy contained in these systems is beyond anything we could hope to manipulate with current technology.
The Reality We’re All Going to Face
The implications of the Southern Ocean’s transformation stretch far into the future, creating a cascade of consequences that will reshape life on Earth. I have a strange feeling that we are entering uncharted territory.
The immediate effects are already visible and accelerating. Antarctic sea ice acts like a giant mirror, reflecting roughly 80% of incoming solar radiation back into space. Without this reflective surface, the dark ocean absorbs that energy instead, driving further warming in a self-reinforcing loop. This process is contributing to more intense storms, altered precipitation patterns, and accelerated melting of the Antarctic ice sheet itself.
Sea level rise, already a critical concern, will accelerate as both thermal expansion and ice sheet melting increase. Coastal cities from Miami to Mumbai will face increasingly frequent flooding, while small island nations may become uninhabitable within decades. The economic costs of adaptation and relocation will reach into the trillions of dollars.
Marine ecosystems face unprecedented disruption. Emperor penguins, which depend on stable sea ice for breeding, are already showing population declines. Krill, the tiny crustaceans that form the foundation of the Antarctic food web, rely on sea ice for their life cycle. Their decline will cascade upward through the food chain, affecting everything from whales to commercial fisheries.
Perhaps most concerning is the potential release of ancient carbon. The upwelling of deep, carbon-rich waters could eventually double atmospheric CO2 concentrations by releasing carbon that has been stored in the deep ocean for centuries. While this process would unfold over many decades, it represents a ticking time bomb that could overwhelm our efforts to reduce emissions.
When combined with other marine crises I encounter daily in my conservation work, from ocean acidification to plastic pollution, coral bleaching to overfishing, the Southern Ocean changes paint a picture of a planet in ecological freefall. Our oceans, which have buffered humanity from the worst effects of climate change by absorbing heat and carbon, are reaching their limits.
The most troubling aspect may be how this discovery exposes the gaps in our understanding. If we failed to predict this fundamental shift in one of Earth’s most important ocean systems, what other surprises await us? Climate models that policymakers rely on for planning may be systematically underestimating the pace and severity of coming changes.
Yet even in the face of this daunting reality, we cannot afford despair. The Southern Ocean crisis underscores the absolute urgency of rapid decarbonization. Every fraction of a degree of warming matters, every year of delay multiplies the consequences, and every action we take to reduce emissions helps determine how severe these changes become.
We also need massive investments in ocean monitoring and research. The satellite systems and robotic floats that revealed this transformation are threatened by funding cuts just when we need them most. Understanding these changes is our early warning system for an increasingly unstable planet.
The Southern Ocean has sent us a clear signal that we have crossed a critical threshold. The choice, quite literally, is in our hands.
Written by: Junior Thanong Aiamkhophueng
Featured Image Photo Credit: © Larissa Beumer / Greenpeace

References:
- Silvano, A., et al. (2025). “Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites.” Proceedings of the National Academy of Sciences.
- Institut de Ciències del Mar (ICM-CSIC). (2025). “A change in the Southern Ocean structure can have climate implications.”
- Newsweek. (2025). “Fact Check: Did an Ocean Current Reverse?”
- The Conversation. (2025). “Completely unexpected: Antarctic sea ice may be in terminal decline due to rising Southern Ocean salinity.”
News
Seaworthy Collective Announces Cohort 7 of the Ocean Enterprise Studio & Incubator

Miami, FL, February 24, 2026 — Seaworthy Collective, a Miami-based non-profit that supports current and aspiring entrepreneurs in BlueTech (ocean innovation), is excited to announce its next wave of startups and founders selected for Cohort 7 of its flagship Startup Program, The Continuum Ocean Enterprise Studio and Incubator.
The 2026 program will once again support US-based startups developing ocean data technologies and services, in alignment with the priorities of the NOAA Ocean Enterprise Initiative. This is a result of Seaworthy’s expanded role in its $14 million NOAA partnership, The Continuum, a coordinated network of ocean enterprise accelerators that fast-tracks startups getting to market by making support for BlueTech solutions more scalable, efficient, and interconnected. The Continuum partners include Braid Theory, Ocean Exchange, Seaworthy Collective, St. Pete Innovation District, Tampa Bay Wave, World Ocean Council, and the University of South Florida.
“We are so proud of this latest wave of startups and founders to not only represent Seaworthy Collective’s seventh cohort, but our second under the umbrella of our NOAA partnership, The Continuum,” said Daniel Kleinman, Seaworthy Collective’s Founder and CEO. “Altogether, these businesses and entrepreneurs are driving forward the future of the Blue Economy and Ocean Enterprise; addressing the critical need for data and AI-driven solutions across ocean mapping and survey, water quality monitoring and reporting, fisheries and ecosystem health, and overall ocean intelligence; enabling improved decision-making and emerging markets to grow.”
The seven startups selected to be part of the Spring Ocean Enterprise Studio & Incubator are:


BathyLab – Brookfield, NH; Founded by Shannon Hoy and Patrick Cooper. BathyLab develops AI-powered tools that help seafloor mapping teams collect better data and scale their operations. Their solutions provide real-time operational intelligence for both crewed and autonomous vessels, supporting the critical seafloor mapping work that drives the blue economy and advances our understanding of the planet.

BeachLens – Gainesville, FL; Founded by Ja’Rell Felix. BeachLens brings together real time coastal, safety, and tourism data and turns them into simple, actionable insights for users. The core product is a mobile application that acts as a centralized hub for beach safety and logistics, moving far beyond basic weather apps to offer highly specific data.

Envara Scientific – Sterling, VA; Aspiring founder Marianne Dietz and her emerging venture, Envara, will leverage intelligence-informed thinking to help organizations better navigate and act upon high-stakes environmental data.

H3 – Miami, FL; Aspiring founder, Rachel Bobich, joins Seaworthy as she looks to build a collective Intelligence and resourcing platform to support the scientific community that propels the Blue Economy.


iCatch – Bozeman, MT; Founded by Dr. Mariah Meek and Dr. Nadya Mamoozadeh. iCatch is taking the guesswork out of species identification. Combining predictive AI technology with precision genomic testing allows species verification by anyone, anywhere, all along the seafood supply chain.


Marnova – San Diego, CA; Founded by Andrew Barrows and Dr. Forest Rohwer. Marnova converts harmful sargassum blooms into productive fisheries through a nature-based feeding system that strengthens the marine food web. They pair it with real-time tracking hardware and software so fishers can find these fishing grounds faster, while reducing sargassum washing ashore and disrupting coastal livelihoods.


Project Neptune – Hermosa Beach, CA; Founded by Maxwell Lynch and Ethan Young. Project Neptune provides localized beach water quality data, forecasts, and decision-ready insights to help people safely plan their time at the coast. They aggregate and interpret water quality testing, environmental conditions, and risk indicators into simple dashboards that show whether it’s safe to enter the water, and why.
“This cohort marks a pivotal moment for Seaworthy Collective as we scale the solid foundation built over the last five years supporting our first 100 founders and 50 startups. By integrating these next seven early-stage startups into The Continuum, we are proving that our model for founder success is not just repeatable, but highly scalable. We aren’t just launching startups; we are building a streamlined pipeline for the next generation of ocean intelligence,” Tamara Kahn Zissman, Director of Founder Success at Seaworthy Collective.
Join Seaworthy Collective’s community via its home page at www.seaworthycollective.com to stay updated on details of its upcoming Spring slate of events featuring the members of this latest cohort, including the upcoming Spring Sea Change Makers Panel Series and Startup Showcase, Seaworthy’s biggest event of the year, at The LAB Miami on May 20, 2026.
Sponsorship opportunities are currently available, and general inquiries are also welcome via email at Info@SeaworthyCollective.com.
About the Organizations

Seaworthy Collective is a Miami-based 501c3 nonprofit that supports current and aspiring entrepreneurs driving innovation for ocean impact (AKA BlueTech). Our mission is to bring all hands on deck for BlueTech, via programs to co-create and grow early-stage startups, build regional capacity, and educate our community. We empower Sea Change Makers, founders of all backgrounds leading profitable and planet-positive businesses. Since 2021, we’ve supported 100 founders across 50 BlueTech startups, who have raised over $34 million since graduating. Altogether, our local and global community generates scalable solutions for 71% of the planet (our ocean) to regenerate 100% of the planet. Learn more at SeaworthyCollective.com

The Continuum is a coordinated network of ocean enterprise accelerators that fast-tracks startups getting to market by making support for BlueTech solutions more scalable, efficient, and interconnected. The Continuum partners include Braid Theory, Ocean Exchange, Seaworthy Collective, St. Pete Innovation District, Tampa Bay Wave, World Ocean Council, and the University of South Florida. Learn more on our website at: TheContinuum.blue
News
The Shadow Fleet Escalation: From Environmental Threat to Geopolitical Flashpoint

Six months of dramatic enforcement actions and military escalation have transformed the shadow fleet crisis, but the environmental threat remains the core concern.
In August 2025, SEVENSEAS Media published my article “The Shadow Fleet Crisis: When Ocean Conservation Meets Global Security,” which examined the emerging environmental threat posed by the global shadow fleet: more than 700 aging, poorly maintained tankers operating outside international law, carrying millions of barrels of oil through the world’s most sensitive marine ecosystems. I called for proactive intervention to prevent an uncontrollable environmental catastrophe. This article provides a six-month update on that crisis, and documents how dramatically the situation has evolved.
As I explained in that earlier piece, a single oil tanker grounding in a region such as the Caribbean could result in the destruction of acres of coral reef, the oiling of miles of island and coastal shoreline, the death of vital populations of fish and other species, and permanent harm to the economies of many coastal communities. The potential for widespread harm is amplified by the lack of response capacity and adequate funding mechanisms in the Caribbean and along trade routes through vulnerable areas.
At that time, there were fairly straightforward options for addressing the threat that vulnerable island states and the conservation community could pursue. What I could not have predicted was how rapidly the situation would escalate; not toward resolution, but toward a confrontation that has now drawn in navies, fighter jets, and the highest levels of government from multiple nations.
The shadow fleet crisis has transformed from a maritime environmental concern into a more complicated geopolitical scenario. But amid all the dramatic headlines about seizures and naval escorts, we must not lose sight of what matters most from an ocean conservation perspective: the environmental threat has grown more urgent, not less.
U.S. forces have seized seven sanctioned tankers in rapid succession. Russia has deployed military assets to protect shadow fleet vessels. France intercepted a tanker in the Mediterranean. NATO has established a new task force. These geopolitical developments complicate, but do not diminish, the environmental risks posed by aging, poorly maintained vessels carrying millions of barrels of oil.
A Note on Terminology: Shadow Fleet vs. Sanctioned Vessels
The terms “shadow fleet” and “sanctioned vessels” are often used interchangeably, but from an environmental perspective, they describe fundamentally different categories of risk.
A “sanctioned vessel” is any ship designated as violating trade sanctions, typically for carrying oil from Russia, Iran, Venezuela, or North Korea. Some sanctioned vessels continue to maintain insurance, undergo regular inspections, employ professional crews, and comply with maritime safety standards. These vessels represent a trade dispute: politically contentious, but far less threatening to marine ecosystems.
The “shadow fleet,” by contrast, refers specifically to vessels that combine sanctions evasion with wholesale abandonment of maritime safety infrastructure. These ships operate with falsified documentation, lack legitimate insurance, use aging and poorly maintained equipment, exploit their crews, and engage in dangerous practices such as turning off AIS transponders, refusing pilot services, and conducting risky ship-to-ship cargo transfers at sea.
The distinction matters for policy. When a shadow fleet vessel reflags to Russia (as more than 40 have done since June 2025), it gains state protection but does not necessarily improve its safety profile. The environmental threat persists regardless of which flag is painted on the stern.
Geopolitical Context: A Complicating Factor
The past six months have seen extraordinary geopolitical developments that have complicated, though not fundamentally changed, the environmental calculus. Understanding these events is important, but we should view them as context rather than as the core story.
On December 10, 2025, U.S. forces seized the Venezuelan oil tanker Skipper in international waters between Grenada and Trinidad; notably, on the high seas rather than within any nation’s Exclusive Economic Zone (EEZ). In a dramatic made-for-TV move, armed law enforcement agents rappelled from helicopters onto a vessel carrying nearly 2 million barrels of crude oil. The crew, mostly Russian nationals, offered no resistance. After U.S. forces seized the oil tanker Skipper near Venezuela, they took control of the crew and cargo. They redirected the vessel to the Texas coast off Galveston for forfeiture proceedings and likely offloading.
But the Marinera chase was something else entirely. For eighteen days, U.S. Coast Guard vessels pursued the tanker (previously Guyana-flagged and known as Bella 1) across the Atlantic Ocean. During the pursuit, the crew hastily painted a Russian flag on the hull. Russia formally added the vessel to its Maritime Register and demanded the U.S. halt pursuit. Moscow dispatched a naval escort. The U.S. intercepted the vessel between Iceland and Scotland before Russian ships arrived. After U.S. and allied forces seized the Marinera in the North Atlantic, they placed the crew in U.S. custody. They moved the tanker to the United States to enter judicial forfeiture proceedings as a stateless, sanctions-violating “shadow fleet” vessel, with those involved in its escape attempt facing potential prosecution under U.S. law.
By January 21, the United States had seized seven sanctioned tankers in rapid succession. France, with UK intelligence support, intercepted the tanker Grinch in the western Mediterranean. President Macron personally ordered the operation.
Russia responded by abandoning any pretense of plausible deniability. More than 40 shadow fleet tankers have switched to the Russian flag since June 2025, with 21 reflagging immediately following the Skipper seizure. In May 2025, Russia deployed a Su-35 fighter jet in response to Estonia’s attempt to stop the tanker Jaguar, the first overt military intervention to protect a shadow fleet vessel.
All seven U.S. seizures occurred on the high seas, in international waters beyond any nation’s territorial sea or EEZ. Under traditional maritime law, flag states exercise primary jurisdiction over their vessels on the high seas. The high-seas location makes these actions legally complex, and helps explain why Russia felt emboldened to dispatch naval escorts and why France ultimately had to release the Grinch.
These geopolitical confrontations have significant implications, but from an environmental perspective, the key question remains unchanged: Are these vessels safe? The answer remains no, regardless of whose flag they fly. Vessels that operated as poorly maintained shadow-fleet tankers last month do not suddenly become environmentally sound simply because they fly a Russian flag this month. The aging hulls, inadequate maintenance, undertrained crews, and missing insurance that made them environmental hazards persist.
The Core Environmental Risks: Compounding Threats
Our ongoing research into the shadow fleet has revealed multiple compounding risks that threaten marine ecosystems worldwide. These hazards exist independently of the geopolitical drama, and in many ways are exacerbated by it.
Aging vessels and inadequate maintenance have led to Russia’s shadow fleet expanding from fewer than 100 vessels in February 2022 to over 343 vessels today. Before Russia invaded Ukraine in 2022, just three percent of the global tanker fleet was more than 20 years old. That share has more than tripled to 11%. The newly sanctioned vessels are an average of 16.8 years old. Some shadow fleet vessels have been documented using single-hull designs for oil transport, configurations banned under international regulations precisely because of their vulnerability to catastrophic failure.
Inadequate insurance: Over 70% of shadow fleet vessels lack adequate coverage through International Group P&I clubs. When tankers are uninsured or underinsured, coastal states bear the cost of environmental cleanup and damage. There is no readily available funding mechanism for rapid response mobilization.
Crew competence and exploitation: Reports indicate that forced labor and human trafficking in the maritime sector remain severe problems. Crews are often ill-equipped to handle the unique navigational challenges of regions such as the Baltic Sea, where harsh winter weather, ice cover, and narrow shipping lanes require specialized training. The data we have reviewed shows that there have been significant increases in the number of tankers refusing to use experienced Danish pilots when navigating the Baltic’s dangerous shipping straits. This troubling trend has accelerated, rising from 1 in 20 in July 2023 to 1 in 5 tankers in July 2024.
Navigation interference: GNSS jamming and spoofing (the deliberate interference with satellite navigation systems) has become endemic in certain maritime regions. The Baltic Sea has experienced persistent navigation interference that degrades situational awareness and increases the risk of collisions and groundings.
A Growing Crisis: Abandoned Vessels
A troubling new dimension of the shadow fleet crisis has emerged: the dramatic increase in abandoned vessels. According to the International Transport Workers’ Federation (ITF), ship abandonments have skyrocketed from 20 vessels worldwide in 2016 to 410 in 2025, with 6,223 merchant seafarers left stranded. Both figures were up by almost a third from the previous year.
The ITF reports that shadow fleet vessels are contributing significantly to this spike. These aging vessels of obscure ownership, often unseaworthy and uninsured, are being abandoned when operations become unprofitable or when enforcement pressure increases. Flags of convenience (FOC) vessels accounted for 82% of all abandonments in 2025.
From an environmental perspective, abandoned vessels represent a compounding risk. A tanker abandoned with cargo aboard (as has occurred with several vessels carrying hundreds of thousands of barrels of Russian crude) is an environmental time bomb. Without an active crew to maintain systems, monitor conditions, or respond to emergencies, the risk of cargo spill, leak, or loss increases dramatically. When owners disappear into shell company structures and flag states disclaim responsibility, there is no one to hold accountable for cleanup costs.
The human dimension compounds the environmental risk. Abandoned crews face shortages of food, fresh water, and essential supplies. Unpaid, hungry, and demoralized seafarers cannot be expected to maintain vessel safety systems or respond effectively to emergencies. Last year, abandoned merchant navy crews worldwide were owed a total of $25.8 million in unpaid wages.
Infrastructure Incidents: Evidence of Operational Hazards
A series of incidents in the Baltic Sea demonstrated, in dramatic fashion, the operational hazards posed by shadow fleet vessels. While media attention focused on the infrastructure damage and potential that these acts are sabotage, the incidents also reveal how poorly these vessels are operated, and what that means for environmental risk.
On Christmas Day 2024, the Russian oil tanker Eagle S, operating under a Cook Islands flag, cut the Estlink 2 power cable and four data cables by dragging its anchor for 62 miles through Finnish waters. Whether intentional sabotage or negligent operation, this incident demonstrates the reality: a vessel dragging its anchor for 62 miles is a vessel that could be dragging through even more sensitive marine habitat or run aground on a reef.
Finnish authorities seized the Eagle S and found 32 safety deficiencies, including problems with fire protection, navigation equipment, and ventilation systems. The vessel’s S-band radar did not work. Its insurance had expired months earlier. This is the condition of the vessels carrying millions of barrels of oil through our oceans. The Eagle S was released after three months of detention but was subsequently scrapped in Turkey in late 2025.
These same vessels, uninspected, poorly maintained, operated by crews who manipulate navigation systems to avoid detection, are navigating congested waterways where a single miscalculation could result in catastrophic collisions and spills. The infrastructure sabotage concern and the environmental concern are two sides of the same coin: vessels operating outside established safety systems pose threats everywhere they operate.
Beyond Sanctions Evasion: The Hybrid Warfare Dimension
Our research has also revealed concerning evidence that some shadow fleet vessels serve purposes beyond oil transport. In July 2025, Danish pilots reported crew members photographing bridge infrastructure during transit. A Danwatch investigation found that many shadow fleet crew members had backgrounds in Russian defense or intelligence services. Swedish naval authorities documented unusual antenna configurations suggesting intelligence-gathering capabilities.
In August 2025, drawing on the accumulating evidence from DanPilot reports, the Danwatch investigation, and Swedish Navy observations, the U.S. Naval Institute’s Proceedings published an analysis concluding that shadow fleet vessels should be viewed as “multirole tools” for sanctions evasion, intelligence collection, and potential sabotage.
NATO responded by announcing its “Baltic Sentry” operation. Germany established Commander Task Force (CTF) Baltic, a shore-based tactical maritime headquarters at Rostock that coordinates frigates, patrol aircraft, submarines, and naval drones to protect undersea infrastructure.
This hybrid warfare dimension is concerning in its own right, but for ocean conservation purposes, it reinforces a key point: these are not normal commercial vessels subject to normal oversight. They operate in a gray zone where the usual assumptions about vessel behavior, crew competence, and emergency response cannot be trusted. This uncertainty compounds environmental risk.
When Disaster Strikes: The Response Capacity Gap
The January 2026 seizures in the Caribbean highlighted a vulnerability that extends far beyond enforcement. What happens when a shadow fleet vessel spills its cargo in waters that lack the infrastructure to respond?
In European waters, the European Maritime Safety Agency operates 20 pollution response vessels and maintains satellite monitoring through its CleanSeaNet service. But even this capacity has gaps; remarkably, there are currently no EMSA pollution response vessels stationed in the Baltic Sea, despite the concentration of shadow fleet activity in those waters.
The Caribbean and Latin America would face even greater challenges in the event of a catastrophic spill. When U.S. forces seized the Skipper between Grenada and Trinidad, they intercepted a vessel carrying enough oil to devastate marine ecosystems and the economies that depend on them. These coastal states lack response infrastructure, equipment pre-positioning, and coordinated contingency planning. Local and migratory fisheries, fragile reef and mangrove areas, and coastal tourism remain at serious risk.
The insurance gap compounds this vulnerability. With no guarantee of repayment, communities may have to choose between mounting expensive cleanup efforts with uncertain cost recovery and continuing to provide ordinary but necessary services to their residents.
The Enforcement Paradox
The Grinch case exposed a critical gap in the legal framework. When France intercepted the vessel, President Macron declared it a triumph of sanctions enforcement. Three weeks later, he informed Ukrainian President Zelensky that France would be forced to release the tanker because current French and international maritime law do not permit prolonged detention of civilian vessels, even when under sanctions.
This is not an argument against enforcement. It is an observation that enforcement alone cannot solve the environmental crisis. The shadow fleet continues to grow. Russia’s seaborne oil exports now account for almost 70% of shipments via shadow-fleet vessels. Iran maintains exports of approximately 1.6 million barrels per day. The total reaches approximately 3.7 billion barrels annually: 6 to 7 percent of global oil flows moving in vessels that operate outside safety systems designed to protect marine environments.
The Path Forward: Focusing on Environmental Protection
The conservation community faces the same choice I outlined six months ago, but with greater urgency. The shadow fleet crisis has attracted the attention of governments, militaries, and international institutions. It has become a subject of great power competition. But amid all this geopolitical attention, the environmental dimension remains neglected.
What the crisis demands is not a political position on sanctions. It is a relentless focus on the environmental consequences of vessels operating outside established safety systems, regardless of whose flag they fly or whose cargo they carry.
What can nations do? Coastal states can strengthen Port State Control regimes: refusing entry to suspicious vessels, demanding proof of adequate insurance, and requiring comprehensive documentation of cargo origin. The EU’s approach of denying port access to vessels that turn off their AIS transponders provides a model. Nations can enforce MARPOL requirements, including the 48-hour notification for ship-to-ship transfers in their territorial seas or EEZ. Financial pressure matters too: targeting insurance providers, financiers, and service providers that enable shadow fleet operations can significantly increase operational costs and risks.
What should the ocean conservation community do? First, we must acknowledge this issue as part of our mandate. The shadow fleet threat is not separate from ocean conservation; it is a direct and growing threat to marine ecosystems. Second, we need to invest in monitoring and documentation. Organizations like SkyTruth have demonstrated how satellite imagery and remote sensing can expose environmental violations. Third, we must develop and advocate for risk-based policy frameworks that distinguish between environmental compliance and political affiliation, frameworks that create incentives for safety even within sanctioned trade. Fourth, we should build regional response capacity, particularly in vulnerable areas such as the Caribbean. Finally, we need to bring our collective voice to international forums (the IMO, UNCLOS processes, and bilateral negotiations) to ensure that environmental protection remains central to any framework addressing the shadow fleet crisis.
The window for proactive intervention remains open, but it will not remain open indefinitely. The current period of heightened attention offers an opportunity to establish frameworks before a catastrophic incident forces reactive responses. The question is whether the conservation community will rise to meet this challenge, or whether we will wait for the next spill, the next grounding, the next preventable disaster to force our hand.
The Ocean Foundation will continue to monitor developments and share what we learn. The ocean deserves better. The choice, as always, belongs to all of us.
By: Mark J. Spalding, J.D.
About the Author
Mark J. Spalding, President of The Ocean Foundation, was part of the group that founded the Shipping Safety Partnership and has responded to shipwrecks, such as the MV Selendang Ayu, and worked on addressing forced labor on ships and chronic noise pollution from shipping. He co-led Project Tangaroa and has authored several publications on sustainability in the maritime domain. His previous article, “The Shadow Fleet Crisis: When Ocean Conservation Meets Global Security,” was published by SEVENSEAS Media in August 2025.
News
Interaction of Carbon and Nutrient Cycles Overlooked in Marine Carbon Dioxide Strategies
There is growing interest in the scientific community and private sector in biological approaches to marine carbon dioxide removal, strategies designed to enhance the ocean’s natural ability to absorb carbon from the atmosphere. However, a study led by Megan Sullivan, a postdoctoral researcher in the University of Rhode Island’s Graduate School of Oceanography (GSO), suggests that some proposals may overlook an important factor.
“Most conversations only focus on how much carbon sinks out of the surface ocean,” said Sullivan. “We show that it’s just as important to consider how nutrients cycle through the system. Understanding these differences will help scientists better predict how effective ocean-based climate interventions might be over decades or centuries.”
One widely discussed carbon removal approach is ocean fertilization, particularly adding iron to certain regions of the ocean to stimulate phytoplankton growth. Like planting trees on land, the idea is that increased growth will pull more carbon dioxide from the atmosphere. This biologically captured carbon then sinks to the deep ocean, where it can remain stored for decades to centuries.
Sullivan and her colleagues developed a modeling framework to run large-scale ocean simulations on high-performance computing systems. Their model tracked how both carbon and phosphorus, a key nutrient required for phytoplankton growth, move through the ocean over time. Because carbon uptake is tightly linked to nutrient availability, the simulations helped the researchers understand how carbon and nutrient cycles interact.
They found that carbon and nutrients do not follow the same timeline. Biologically captured carbon may return to the surface ocean relatively quickly, while nutrients such as phosphorus remain trapped in the deep ocean for much longer.
“This mismatch matters,” Sullivan explained. “If nutrients like phosphorus are locked away in the deep ocean, phytoplankton growth is suppressed, reducing the ocean’s ability to continue absorbing carbon dioxide.” The team describes this as a potential “productivity hangover,” where an initial boost in carbon uptake is followed by a longer-term slowdown. In other words, an intervention that appears successful in the short term may not deliver sustained climate benefits.
The findings suggest that some proposed marine carbon removal strategies, including iron fertilization, could overestimate their long-term impact if they focus only on carbon export without accounting for nutrient redistribution. As interest grows in ocean-based carbon removal projects, understanding these long-term nutrient feedbacks will be critical for accurately assessing climate benefits.
Sullivan’s research, which began as part of her Ph.D. dissertation at the University of California, Irvine and has continued at URI as a postdoctoral fellow, was published in the journal PNAS in February. At UC Irvine, Sullivan worked closely with her advisors, François Primeau and Adam Martiny. At URI, Sullivan worked with Keisuke Inomura, an assistant professor of oceanography, to further develop and refine her manuscript.

Source: University of Rhode Island | Original Press Release
Study: Sullivan, M.R., Primeau, F.W., Seo, H., Camps-Castellà, J., Inomura, K., Martiny, A.C. (2026). Decoupled timescales of organic carbon and phosphorus recycling in the global ocean. Proceedings of the National Academy of Sciences, 123(8), e2514991123. https://doi.org/10.1073/pnas.2514991123
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