25 percent. That's how much larger the Southern Ocean's summer CO2 uptake appears to be when researchers used direct air-sea flux measurements rather than indirect methods. The finding comes from a July 24, 2024 study led by the University of East Anglia and Plymouth Marine Laboratory, which used seven research cruises and direct eddy covariance measurements to argue the ocean's summer sink was underestimated. The result matters because it changes the carbon budget for the planet even as other work shows regional cooling, new seafloor maps and expanding krill fishing are reshaping the Southern Ocean's climate and ecosystems.

Stronger uptake means the Southern Ocean is removing more human carbon than models had suggested, but that bigger sink sits alongside surprising local changes that make the picture. The University of East Anglia and Plymouth Marine Laboratory team published their Science Advances paper on July 24, 2024, reporting that direct measurements on seven cruises captured short, intense CO2 uptake events missed by shipboard sampling, floats and many models. Lead author Dr Yuanxu Dong said the eddy covariance approach reduced uncertainty about how much carbon the Southern Ocean pulls from the atmosphere.

Carbon sinks and a cooler Southern Ocean

At the same time scientists are trying to reconcile a seeming contradiction: parts of the Southern Ocean have cooled over recent decades even as the planet warms. A March 27, 2025 study in Geophysical Research Letters from Stanford University researchers attributes roughly 60 percent of a decades-long mismatch between climate model projections and observed sea surface temperatures to increased Antarctic meltwater and heavier local precipitation. Assistant professor Earle Wilson of Stanford explained that freshening of the top ocean layer makes surface water less dense, reducing mixing and allowing cooler waters to sit at the surface despite global warming. The paper warns that melting and rainfall processes are underrepresented in many climate models, and that getting them right is important for projecting future sea level rise and regional ocean changes.

The two findings aren't mutually exclusive. More CO2 can be absorbed at the sea surface during short, intense events while freshening and altered circulation keep surface temperatures lower in some areas. That combination matters because temperature, stratification and carbon flux together determine how the ocean stores heat and carbon and how it responds to changes such as ice shelf melt.

Better maps of the seafloor are sharpening scientists' view of how water moves under and around Antarctic ice. The Alfred Wegener Institute coordinated an international release of the second version of the International Bathymetric Chart of the Southern Ocean, IBCSO v2, published in Scientific Data. The high-resolution bathymetry reveals previously undocumented deep troughs and large seamounts. Dr Boris Dorschel-Herr, Head of Bathymetry at the Alfred Wegener Institute, said accurate bottom topography is essential because these landforms channel warm water toward ice shelves and concentrate biological productivity, with consequences for ice melt and biodiversity.

Mastheads

Those advances come even as observing capacity around Antarctica has been strained. In 2023 researchers and program leaders reported cancellations and reduced ship time that limited field campaigns. An Australian Antarctic research program noted a planned 60-day mission using the icebreaker RSV Nuyina was canceled, leaving fewer opportunities for direct measurements on sea ice and under ice shelves.

Scientists at conferences and funding inquiries have argued that a single icebreaker that doubles as a cargo vessel isn't enough to meet the scale of observational need, especially when satellites simultaneously register some of the most dramatic sea-ice changes on record.

All of that matters for life at the top and base of the Southern Ocean food web. Antarctic krill form the base of a high-latitude system that feeds whales, seals and penguins. Reporting on the fishery documents a rapid expansion over roughly the past 15 years, enabled by industrial-scale trawling. Supertrawlers have the capacity to harvest up to 1,000 tons of krill a day, and estimates put the broader krill industry at as much as $900 million annually. Norway has lobbied the Commission for the Conservation of Antarctic Marine Living Resources, CCAMLR, to increase allowable krill take in the Southern Ocean, a move that has prompted alarm among scientists.

Matthew Savoca, a whale researcher at Stanford University, warned that current harvest math could harm recovering baleen whale populations. His calculation, cited by researchers and conservationists, suggests pressure on krill stocks could undermine predator recovery. In response to growing concern, the European Union has passed a resolution calling for a five-year moratorium on krill fishing in the Southern Ocean while more data are gathered.

For readers weighing personal choices, the implications are immediate and practical. If you take krill oil or use other Antarctic-derived products, check product labels and company disclosures about sourcing and stock assessments. Consider plant-based or algal omega-3s as alternatives while scientific assessments and policy debates proceed. The science community has recently produced more direct CO2 flux data, a new detailed seafloor map and an attribution study showing meltwater and rain explain much of the local cooling trend, so following publications from the University of East Anglia, Plymouth Marine Laboratory, Stanford University and the Alfred Wegener Institute will keep you current.

This isn't a simple story of improvement or decline. The Southern Ocean appears to be a stronger carbon sink in summer than we thought, a finding that reduces one set of uncertainties in the global carbon budget.

But freshening, seafloor pathways and industrial fishing introduce other risks. Limited ship time leaves gaps in the direct observations scientists rely on to link these processes and to advise managers and policy makers.

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For now the clearest, hardest figure to carry forward is operational: some supertrawlers can harvest up to 1,000 tons of krill a day, a scale that helps explain why scientists and the European Union are pressing for a pause while more data are collected.

This article was created with AI assistance.