Marine heatwaves are supposed to mean less carbon absorbed by the ocean, and mostly, they do. A new global study led by Zhentao Hu, mostly out of Helmholtz-Zentrum Hereon in Germany, analyzed 45 coastal regions worldwide across 35 years, 1985 to 2020, and found a sharp split. In the open ocean, CO2 uptake drops about 8% during a heatwave, matching the expected pattern. But in coastal shelf seas, uptake rises 11%, and more than 90% of that boost comes from one place: the poles. Heatwave-driven sea-ice loss opens more water to the atmosphere and triggers a burst of phytoplankton growth, and that biological activity pulls carbon down. Lower-latitude coasts, including the tropics and Florida's upwelling zone, see the opposite effect, releasing more CO2 as water warms. We break down what the finding means and why a single headline can't capture a story this regional.
Then, our Ocean People Profile: meet Emily Cunningham MBE, whose two-decade conservation career started with unpaid turtle patrols in Sri Lanka and a volunteer post with the Sea Watch Foundation. From there, her path ran through Ascension Island, the Wildlife Trusts, and leading a UK Local Government Association group representing 57 coastal councils. She co-founded #Motion4theOcean, which pushed more than 30 UK local governments to formally declare ocean recovery commitments. Today she leads a global conservation initiative for WWF, was awarded an MBE for services to marine conservation and coastal communities in 2025, and has a debut book, Our Ocean to Save, landing October 29. Her career is a case study in what conservation work can look like before the credentials and the title arrive.
Finally, kelp forest restoration gets a lot of positive press as a climate solution. A new PLOS Biology essay says the math doesn't support that framing. Kelp forests are major natural carbon sinks, and climate-driven losses are running 1,000 to 10,000 times greater than what restoration can currently replace. Since 1958, the entire world has restored roughly 4,200 hectares of kelp. The loss projected by 2050 alone, 25 million hectares, is more than 6,000 times that. The researchers aren't arguing against restoration; they're arguing against treating it as a climate fix, warning that doing so can pull funding and attention away from the more effective option: protecting the kelp forests still standing.
Takeaways:
A new global study (Hu et al., analyzing 45 coastal regions across 35 years) found marine heatwaves cut open-ocean CO2 uptake by about 8%, but raise coastal shelf sea uptake by 11%, with more than 90% of that boost coming from polar and subpolar seas.
The mechanism: heatwave-driven sea-ice loss opens water to the atmosphere and kicks off a phytoplankton bloom that pulls carbon down; lower-latitude coasts see the reverse effect, releasing more CO2 as water warms.
Emily Cunningham MBE built a two-decade marine conservation career starting with unpaid turtle patrols in Sri Lanka and volunteer roles in North Wales, before leading a UK Local Government Association coastal group and co-founding #Motion4theOcean, which moved more than 30 UK local governments to declare ocean recovery commitments.
She now leads a global conservation initiative for WWF, received an MBE in 2025 for services to marine conservation and coastal communities, and has a debut book, Our Ocean to Save, out October 29.
A new PLOS Biology essay finds climate-driven kelp forest losses are running 1,000 to 10,000 times greater than what restoration can currently replace: roughly 4,200 hectares restored worldwide since 1958, against a projected loss of 25 million hectares by 2050.
The researchers argue restoration is worth supporting for biodiversity, but shouldn't be framed as a climate solution; protecting the kelp forests still standing is the more effective climate lever.
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