The world relies on a modest number of countries to keep watch over the ocean. That arrangement is starting to fail. Europe and Asia must now decide whether to let the system unravel, or to take it up together.
Right now, in every ocean basin on Earth, a global network of instruments measures the state of the sea.
Research ships steam along oceanographic transects from surface to seafloor. Anchored buoys watch the tropical oceans for the first signs of El Niño or tropical cyclones and take the pulse of the thermohaline circulation. Some four thousand autonomous floats sink every ten days to two thousand metres before rising to transmit temperature and salinity to ground stations via satellite. Underwater gliders patrol continental margins, and drifting buoys ride the surface in the most remote waters. Hundreds of elephant seals carry miniaturised sensors beneath the polar sea ice…
Together, this network produces invaluable information that allows societies to anticipate and respond to a changing ocean and weather conditions, and protect the ocean in return.
It is also far more fragile than most people, and most governments realise. A new study published in Nature Climate Change has measured for the first time just how fragile the ocean watch network is.
The result is alarming. If observations from a single major contributor, the United States, were withdrawn from the Global Ocean Observing System (GOOS), the errors in our estimate of how fast the ocean is warming would jump by 163 percent. That is worse than randomly losing 80 percent of all global ocean data. The reason is geographical: US instruments cover every ocean basin and plug critical gaps that no other nation currently fills.
This is not a theoretical concern. Proposed cuts to National Oceanic and Atmospheric Administration (NOAA) and the National Science Foundation in the United States now threaten exactly this contribution. And the situation is barely better on the other side of the Atlantic.
The pressures are not confined to one side of the Atlantic, nor to the West. In China, scientists and policymakers are working to build a more resilient national contribution to ocean observation, but without the resources the moment requires. The marine monitoring system the world relies on is under strain almost everywhere.
An observing system, not a programme
Public conversations about ocean observations often focus on Argo floats.
D. Luquet IMEV, Fourni par l’auteur
Each Argo is essentially a sealed cylinder of pressurised electronics with a clever buoyancy chamber: it floods with seawater to sink and is evacuated to rise again. These autonomous robots have transformed ocean science this century.
However, Argo is just one component of GOOS and the complementarity of its parts matters.
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Argo profiles the upper two kilometres of the open ocean.
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Research vessels go deeper: GO-SHIP cruises survey from surface to seafloor along long repeated transects, providing the high-precision reference measurements that calibrate every other instrument and help validate climate models.
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Moored buoys deliver continuous time series critical for monitoring El Niño, the Atlantic Meridional Overturning Circulation, and the conditions in which tropical cyclones form.
M Maupas Genavir.
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Underwater gliders target coastal currents, eddies and continental margins that floats cannot resolve.
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Elephant seals carry sensors into under-ice regions of the polar oceans that no other instrument can reach.
Each platform answers questions the others cannot.
C. McMahon IMOS, Author provided (no reuse)
Remove any one of these ocean watch components, and the observing system’s ability to deliver reliable information degrades not in proportion to the volume of data lost, but in proportion to where the gaps appear.
OceanOPS, Author provided (no reuse)
What this network actually delivers
The Global Ocean Observing System is too often described as “climate monitoring,” but it does so much more.
Every operational weather forecast is built on these data. The numerical weather prediction systems run by the European Centre for Medium-Range Weather Forecasts, by Météo France, and by every other major weather service ingest ocean observations many times a day.
Without them, forecasts drift quickly out of skill.
The new artificial-intelligence-based forecast systems Pangu-Weather and GraphCast, despite their impressive performance, rely entirely on the same observational stream.
AI does not replace observations; it depends on them.
Sub-seasonal to seasonal forecasting, to help anticipate harvest seasons, energy demand and water availability weeks to months ahead, depends critically on knowledge about subsurface ocean heat and salinity.
Tropical cyclone track and intensity forecasts, central to early warning and evacuation decisions, depend on ocean heat content beneath the surface, not just sea surface temperature, because hurricanes draw their explosive energy from the warm layers down to at least 200m depth.
Marine heatwave warnings, now used routinely by fisheries managers worldwide, are impossible without sustained subsurface observation.
Sea-level projections used to design coastal infrastructure require decades of consistent measurements, and salinity adds the density information essential for determining all ocean currents, including the AMOC.
In short, GOOS underpins operational services from tomorrow’s storm warnings to next century’s adaptation plan. It is not a luxury but essential.
Why models and artificial intelligence alone cannot save us
There is a persistent misconception, amplified by the rise of AI, that sufficiently advanced models can substitute for direct observations. They cannot.
Every forecast model, whether traditional or AI- based, relies on data assimilation: a continuous nudged adjustment of the simulation toward real-world measurements. An AI model trained on a richly observed past will perform poorly in a sparsely observed present. In a world of rising extremes and shifting ocean states, historical patterns become less reliable.
An observation not made is lost forever. Satellite measurements of the sea surface cannot tell us what is happening hundreds or thousands of metres below, where heat accumulates, currents reorganise, and the precursors of the next season’s weather are already forming. To see beneath the surface, we need instruments in the water.
The cheapest insurance we have
The argument that ocean observation is too expensive collapses on contact with the numbers.
The total annual cost of the global system, across all platforms and personnel, runs on the order of one billion euros worldwide. The European share is a fraction of that.
Extreme weather events linked to ocean conditions caused tens of billions of euros in damage across Europe in 2024 alone.
A single major North Atlantic hurricane season can cost the United States hundreds of billions of dollars. Marine heatwaves have collapsed fisheries worth billions and triggered mass coral bleaching on every reef system on Earth. Failed seasonal forecasts cascade through agriculture, energy and humanitarian response, with consequences rarely tallied.
Every euro spent on ocean observation returns many times its value. It is one of the highest-return public investments available.
Europe’s choice
Europe needs to treat ocean observations as critical infrastructure, equivalent to satellite navigation or meteorological services. That means stable, multi-year funding for the operational backbone of the system: the floats, ships, moorings, gliders and data centres that process and deliver the data.
France has the second-largest Exclusive Economic Zone in the world but contributes around 5 percent of global ocean temperature profile data. Present in the Atlantic, Pacific and Indian Oceans, France has five departments and regions and seven overseas collectivities, which are home to 2.7 million French citizens.
Australia contributes more than three times as much.
The European Union contributes about 12 percent, less than a quarter of the American share. Europe, and France in particular, should substantially increase its contribution.
OceanObs’29, the decadal international conference set to be held this time in China, is an opportunity to negotiate a more balanced global system, reflecting economic capacity and maritime interests rather than historical accident.
Europe-China scientific cooperation should increase, as they have largely complementary observing footprints. Together, they would cover much of the global ocean.
The narrowing window
The danger is a gradual erosion of the information on which a growing share of human activity and the blue economy now depends.
Cyclone warnings become less reliable, seasonal forecasts less skilful, sea-level projections less precise. Each loss maybe individually tolerable. Together, they amount to flying blind into the most consequential transformation of the planet’s climate in human history.
The ocean observing system is a planetary public service, built over decades by many nations. France and Europe possess the institutions, expertise and the maritime interest to play a far larger role.
What is missing is the political decision to act, while the system can still be sustained. The loss of collaboration among nations would force a rebuild far more difficult and expensive than sustained investment in what already works.
The window remains open but is narrower than it was.
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