Ocean Turning Points

What can be done · Monitoring

Who is watching the ocean?

About 8,000 floats, buoys, ships and tide gauges report from the ocean, more than half of them run by the United States. Most measure the surface or the top 2,000 m. The big changes play out where coverage is thin: the deep ocean, around Antarctica, in winter and along coasts. The direct record of the Atlantic circulation starts only in 2004.

Coverage

Gaps in monitoring for each big change

The map looks crowded, but each network was built for a particular job: weather forecasts, seasonal forecasts, the heat in the upper ocean. Most were designed for the top 2,000 m of the open, ice-free ocean, over months to years. The big changes happen largely outside that design: in the deep ocean, next to Antarctic ice, in high-latitude winters, along coasts, and in trends that take decades to emerge.

TopicWhat needs measuringWhat existsThe gap
Atlantic circulationNeedsFlow across the whole Atlantic, without breaks, for decades.ExistsFive measurement lines; the first to measure the full overturning, at 26.5°N, began in 2004.GapTelling a decline apart from natural swings needs 29–67 years of record (Lobelle et al., 2020); the measured weakening is not expected to stand out clearly until the 2040s (McCarthy et al., 2025). The main arrays face funding gaps within 18 months (Gunnarsson et al., 2026).
Subpolar North AtlanticNeedsWinter mixing in a few small basins south of Greenland.ExistsThe OSNAP array since 2014, plus floats.GapUntil OSNAP, the key sinking was thought to happen mainly in the Labrador Sea; it happens mostly further east (Lozier et al., 2019). Floats alone may be too sparse for these small regions (Gunnarsson et al., 2026).
Ice sheetsNeedsWarm water reaching the Antarctic ice shelves, and the deep ocean.ExistsA few floats under sea ice; about 200 deep floats worldwide.GapFew floats work under sea ice, almost no sensors are fixed to the ice, and there is little data outside summer (Newman et al., 2019).
Coral reefsNeedsHeat stress, and what it does to corals.ExistsDaily satellite sea temperature; surveys at more than 12,000 sites in 73 countries since 1978.GapSatellites track heat on every reef: 84% of reef area had bleaching-level heat in 2023–2025 (NOAA). Surveys of what the corals did are patchy, and only coral and algal cover are measured consistently enough for a global picture (GCRMN, 2021).
El NiñoNeedsHeat and winds across the tropical Pacific, every day.ExistsMoored buoys along the equator, floats and satellites.GapIn 2012–2014 the mooring array delivered about 40% of its data instead of the usual 80–90%. The redesign that followed doubled floats near the equator (Smith et al., 2019).
Fish on the moveNeedsWhere fish stocks are, and how many.ExistsScientific stock assessments, which cover some regions far better than others.GapAssessed stocks make up only about half of the world’s catch, and stocks without assessments tend to be in worse shape (Hilborn et al., 2020).
Ocean carbon sinkNeedsCarbon taken up by the ocean, in every season.ExistsShip measurements at the surface, and floats with carbon-related sensors.GapAdding winter float data cut the estimated Southern Ocean uptake by about a third (Bushinsky et al., 2019). Ship-based CO2 coverage has fallen back to early-2000s levels (Global Carbon Budget 2024).

The system today

Status of the global observing system

  • 9,389platforms in the Global Ocean Observing System, from 64 contributing countries, making more than 120,000 observations a day (GOOS, 2025). The map above shows only platforms OceanOPS lists as currently operating, plus the GLOSS core tide gauges.
  • 55%of the way to a complete Argo array: global, full-depth, and measuring chemistry and biology as well as heat (GOOS, 2025).
  • Over halfof the world’s ocean temperature profiles come from the United States. Removing them would raise the error in the ocean heating rate by 163% (Zhu et al., 2026).
  • 83%of the multi-sensor biogeochemical floats now operating are US floats, funded by a project that ends in October 2026 (GO-BGC).

Against each network’s own target, Argo and weather-reporting ships are above 85%, drifting buoys and repeat ship surveys 70–85%, tide gauges, coastal radars and gliders 30–50%. GOOS rates the system as “subcritical”, with declining drifting buoy and ship-based observations, reliance on a few contributors and no secure long-term funding (GOOS 2025 Status Report). Removing all US data would degrade ocean heat monitoring more than removing 80% of all data at random (Zhu et al., 2026).

Satellites and sensors in the water

Satellite and in-water observations compared

From space

Satellites see the surface of the whole ocean, often every day.

  • Sea-surface temperature: marine heatwaves and coral bleaching alerts.
  • Sea level: the rise of the ocean and the shape of currents, from radar altimeters.
  • Ocean colour: algae and productivity near the surface.
  • Sea ice, surface salinity and winds.
  • Ships at sea: radar and optical images reveal fishing vessels that do not broadcast their position.

Only from inside the ocean

Most of the ocean’s heat, carbon and movement lies below the surface, out of a satellite’s view.

  • Heat below the surface, which sets up El Niño and marine heatwaves months ahead.
  • Ocean heat content, the main measure of how fast the planet is gaining energy.
  • The Atlantic overturning, measured by moored arrays across whole ocean basins.
  • Carbon, oxygen and nutrients at depth, from biogeochemical floats and research ships.
  • Sea level at the coast, where people live, from tide gauges.

Why continuity matters

Long-term decisions rest on short records

Decisions that are revisited often, such as coral bleaching alerts, can draw on satellite records several decades long. Seasonal forecasts of El Niño and marine heatwaves need heat measured below the surface by moorings and floats.

Decisions that play out over decades, on the Atlantic circulation, the carbon budget and the ocean carbon sink, rest on direct records only 12 to 22 years long. Direct measurement of the Atlantic circulation began in 2004 at 26.5°N and in 2014 in the subpolar North Atlantic. Earlier changes have to be inferred from indirect evidence, and those inferences disagree.

For these decisions a gap cannot be made up later. A missing year at 26.5°N is a year permanently lost from a record that is already too short to separate a trend from natural swings.

How far ahead the decision looks1 day1 week1 month1 year10 years100 yearsDetecting untracked industrial fishingCoral bleaching alerts for reef managersMarine heatwave preparednessEl Niño preparednessFishery quotas under warmingEarth’s energy imbalance and carbon budgetOcean carbon sink in mitigation accountingPlanning for AMOC weakeningCoastal adaptation pathways
  • Adaptation
  • Mitigation
  • Disaster risk
  • Marine protection
  • ○ mainly satellite
  • ◐ mixed
  • ● mainly in situ
How long the record is19801990200020102020Sea surface temperatureSatellite radiometers45 yrSea levelSatellite altimeters34 yrTropical Pacific upper oceanTAO moored array32 yrTemperature and salinity, 0–2,000 mArgo floats21 yrAMOC at 26.5°NRAPID array22 yrCarbon, oxygen and nutrientsBiogeochemical Argo✕ 12 yrAMOC in the subpolar North AtlanticOSNAP array12 yr
  • Satellite record
  • Direct (in situ) record
  • Partial coverage
  • Reduced data return
  • ✕ US funding ends October 2026
Short-horizon decisions draw largely on satellite records several decades long. Long-term decisions on the AMOC, Earth’s energy imbalance and the ocean carbon sink rely on direct records of only about 12–22 years. Indicative. Redrawn from Jongman (forthcoming).
Crew members deploy an Argo profiling float over the side of NOAA Ship Ronald H. Brown.
Crew deploy an Argo float from NOAA Ship Ronald H. Brown. Each float profiles the top 2,000 m of the ocean every ten days. Photo: Lt. Elizabeth Crapo, NOAA Corps/NOAA Photo Library, public domain

2026

Funding changes in 2026

  1. The US National Science Foundation begins removing four of the five arrays of its Ocean Observatories Initiative, including the Irminger Sea array south of Greenland.

  2. After the US Senate passes a bill to save the observatories, NSF stops the removal; one array already out of the water is to be redeployed.

  3. The GO-BGC project, which deployed most of the world’s biogeochemical floats, confirms it will end on 31 October 2026 with no near-term US deployments planned.

  4. The European Union and Canada launch the OceanEye International Alliance for the Global Ocean Observing System in New York: 30 countries and the EU, with pledges of at least €211 million.

OceanEye

OceanEye is an EU initiative, announced in March 2026, to strengthen global ocean observation. Its international alliance, co-chaired at launch by the President of the European Commission and the Prime Minister of Canada and organised with UNESCO’s Intergovernmental Oceanographic Commission and the World Meteorological Organization, aims to maintain existing platforms, close data gaps and strengthen the coordination of the Global Ocean Observing System, including OceanOPS. Members include ocean countries from every region, among them Angola, Brazil, Cabo Verde, Madagascar, Mauritius, Namibia and Palau. Further pledges are expected at COP31, the Our Ocean Conference and the 2028 UN Ocean Conference.

Sources: European Commission, Reinforcing global ocean observation; Prime Minister of Canada, 23 September 2026. The Commission’s press release of 24 September gives “almost €220 million”.

What would make it stronger

Treat ocean observation as critical infrastructure

Protect the long records

A gap in a seasonal forecast input degrades one season’s forecasts. A gap in the Atlantic circulation arrays, deep and biogeochemical floats, repeat ship surveys or long tide-gauge records is permanent. These are best funded through stable, multi-year arrangements.

Connect observations to decisions

Observations deliver most when observing needs are set with the people who act on them, and when monitoring is linked to decision points in adaptation plans, early action, risk finance and mitigation accounting, including in small island and coastal developing states.

Broaden who contributes

When losing one country’s data would do more harm than losing 80% of all data at random, the system is fragile. Lower-cost sensors, observations from commercial and fishing vessels, regional programmes and the capacity-building provisions of the High Seas Treaty can widen the base.

Keep the data open

Free, timely data sharing, as Argo has practised since 2000, is what turns individual national platforms into a global system that every country can use.

This section follows Jongman (forthcoming). Brenden Jongman is the curator of Ocean Turning Points.

About these data and sources

Map: platform positions from OceanOPS, the WMO-IOC centre for the Global Ocean Observing System, reproduced for non-commercial use with acknowledgement; refreshed weekly. Satellite missions are not shown.

Sources: Global Ocean Observing System, 2025 Status Report; Zhu et al. (2026), Nature Climate Change 16, 657–660; Argo (2000), Argo float data and metadata from the Global Data Assembly Centre, SEANOE, doi:10.17882/42182; GO-BGC project notice, 28 August 2026; US National Science Foundation, update on the Ocean Observatories Initiative, 18 June 2026; McCarthy et al. (2015), Progress in Oceanography 130; Lozier et al. (2019), Science 363, 516–521; IPCC AR6 Working Group I, Chapter 9; Lobelle et al. (2020), Geophysical Research Letters 47, e2020GL089974; McCarthy et al. (2025), Geophysical Research Letters 52, e2025GL115055; Gunnarsson et al. (2026), AMOC Observation as Critical Infrastructure, Reykjavik Institute (policy report); Owens et al. (2022), Marine Technology Society Journal 56(3), 84–90; Roemmich et al. (2019), Frontiers in Marine Science 6, 439; Argo Steering Team (2024), AST-25 report; Newman et al. (2019), Frontiers in Marine Science 6, 433; Moltmann et al. (2019), Frontiers in Marine Science 6, 291; Smith et al. (2019), Frontiers in Marine Science 6, 31; Souter et al. (eds) (2021), Status of Coral Reefs of the World: 2020, GCRMN; NOAA Coral Reef Watch (2026); Hilborn et al. (2020), PNAS 117, 2218–2224; Bushinsky et al. (2019), Global Biogeochemical Cycles 33, 1370–1388; Friedlingstein et al. (2025), Global Carbon Budget 2024, Earth System Science Data 17, 965–1039; Jongman (forthcoming).