Researchers have for the first time reconstructed the three-dimensional structure of powerful vertical ocean currents off Antarctica using satellite observations, finding that these flows plunge roughly 3,000 feet below the surface. The work combines wide-swath sea-surface height measurements from NASA’s Surface Water and Ocean Topography (SWOT) mission with data collected by autonomous underwater gliders deployed in the Southern Ocean. Because these vertical currents drive the exchange of heat and carbon between the atmosphere and the deep sea, the findings directly challenge existing climate models that rely on coarser satellite records and likely undercount how much energy the Southern Ocean absorbs.
Why satellite-detected vertical currents reshape Southern Ocean science
Traditional ocean-observing satellites measure sea-surface height along a narrow track directly beneath the spacecraft. SWOT broke from that design by using Ka-band radar interferometry to map height variations across a wide swath, capturing fine-scale features that older instruments could not resolve. That capability, described in NASA documentation, is what allowed the research team to detect small but energetically significant eddies and fronts in the Southern Ocean south of Tasmania.
The distinction matters because vertical velocities at these scales, often called submesoscale, are the primary mechanism pulling carbon dioxide and excess atmospheric heat into the ocean interior. Climate projections that miss these motions risk underestimating how much warming the Southern Ocean can buffer. The new study, published in a recent journal article, used SWOT surface-height data together with interior hydrographic measurements from ocean gliders to infer vertical velocities through a surface-height-based reconstruction and the quasi-geostrophic omega equation. That mathematical framework translates horizontal pressure gradients visible at the surface into estimates of how fast water moves up or down at depth.
The authors also made their analysis accessible through an online portal that routes readers to the same peer-reviewed work, underscoring the central role of SWOT-era observations in the result. By comparing reconstructions that included and excluded SWOT’s fine-scale information, they showed that resolving submesoscale features substantially changes estimates of vertical motion and, by extension, the amount of heat and carbon that can be pumped into the ocean interior.
The hypothesis that SWOT-era reconstructions would reveal submesoscale vertical velocities substantially stronger than those derived from older nadir altimetry alone aligns with the study’s approach, though the available sources do not supply a specific seasonal percentage difference between austral summer and winter. What the evidence does confirm is that the vertical currents extend to roughly 3,000 feet below the surface, a depth that places them well within the layers where long-term carbon and heat storage occurs. That reach means the newly observed motions are not confined to a thin surface skin but instead penetrate into water masses that can sequester atmospheric signals for decades to centuries.
SWOT data, ocean gliders, and ship-based validation south of Tasmania
The study did not rely on satellite data alone. CSIRO, Australia’s national science agency, deployed autonomous sea gliders into the Antarctic Circumpolar Current to collect temperature, salinity, and density profiles beneath the ocean surface. These glider deployments provided the interior measurements needed to connect what SWOT saw at the surface to what was happening hundreds of meters below. The pairing of space-based and in-water observations is what gave the reconstruction its physical grounding.
Additional validation came from CSIRO’s research vessel RV Investigator, which conducted a dedicated voyage between January and March 2024 to collect ship-based measurements alongside SWOT overpasses, as recorded in the Marine National Facility report. During that campaign, scientists launched expendable instruments and operated continuous surface sensors while SWOT passed overhead, creating a rare opportunity to compare satellite-derived sea-surface structure with direct observations of temperature and salinity.
A separate peer-reviewed study published in the Journal of Geophysical Research: Oceans used SWOT sea-surface height observations to reconstruct three-dimensional eddy structures in the Southern Ocean and validated the results against along-track expendable bathythermograph and thermosalinograph comparisons collected from ships. That ship-based validation work strengthens confidence that SWOT-derived vertical velocity estimates are not artifacts of the reconstruction method but reflect real physical motions. The consistency between satellite-inferred structures and independent in situ measurements indicates that the mathematical tools used to interpret SWOT data are performing as expected in a demanding high-latitude environment.
A related methodological paper evaluated how surface quasi-geostrophic approaches perform when reconstructing vertical velocities and heat fluxes in a Southern Ocean region south of Tasmania using high-resolution simulations. Together, these studies form a chain of evidence: the mathematical technique works in simulations, the satellite instrument captures the right scales, and in-water sensors confirm the satellite-derived estimates match real ocean conditions. The new reconstruction of vertical currents to 3,000 feet fits coherently within that chain, extending it from idealized models and regional tests to a focused real-world application in a climatically critical sector of the Antarctic Circumpolar Current.
Gaps in the vertical velocity record and what to watch next
Several questions remain open. The available reporting does not include exact numerical values for the vertical velocities or heat fluxes the 2026 study measured, making it difficult to compare the new estimates against specific figures from older climatologies. Without those numbers, the precise degree to which previous satellite-based reconstructions underestimated Southern Ocean heat and carbon uptake is not yet quantified in a way that can be directly inserted into global climate models.
There are also temporal gaps. SWOT’s current observing strategy samples the same region on multi-week cycles, while the glider and ship campaigns represent snapshots over a few months. Submesoscale motions can evolve on timescales of days, and their strength likely varies with storms, seasonal stratification, and the shifting position of major fronts. To build a complete picture of how vertical velocities change over the annual cycle and from year to year, researchers will need repeated campaigns that combine SWOT overpasses with dense in situ coverage.
Another uncertainty involves how representative the region south of Tasmania is for the broader Southern Ocean. The Antarctic Circumpolar Current spans multiple ocean basins and interacts with complex topography, sea ice, and continental shelves. The newly reconstructed 3,000-foot-deep currents occur in a particularly energetic sector, and it remains to be shown whether similarly strong vertical motions are ubiquitous or concentrated in specific hotspots. Extending the combined SWOT–glider–ship approach to other sectors, including areas nearer to the Antarctic continental margin, will be essential to answer that question.
Despite these gaps, the implications for climate science are clear. By demonstrating that fine-scale vertical motions in the Southern Ocean reach deep into layers that store heat and carbon over long timescales, the new work suggests that the ocean’s role as a buffer against atmospheric warming may be more dynamic and spatially variable than coarse-resolution models capture. Future Earth system model developments will likely need to incorporate parameterizations informed by SWOT-era observations, ensuring that unresolved submesoscale processes are represented in a way that reflects their true impact on vertical exchange.
As additional SWOT data accumulate and more coordinated field campaigns are carried out, scientists expect to refine estimates of how much heat and carbon these vertical currents transport, how their intensity responds to changes in winds and stratification, and whether they are already evolving under human-driven climate change. The emerging picture is that the Southern Ocean is not a uniform, slowly overturning reservoir, but a highly structured and intermittently turbulent system where narrow jets and small eddies can drive deep-reaching exchanges. Reconstructing those motions from space, and tying them to direct measurements in the water, marks a significant step toward resolving one of the largest uncertainties in the global climate system.
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*This article was researched with the help of AI, with human editors creating the final content.
