A sudden 19% drop in the northbound flow of salt-rich water through the eastern Caribbean may have set off a self-reinforcing slowdown in the region’s ocean circulation, according to a study published Tuesday. The authors say their model indicates a tipping threshold was crossed in 2025, with consequences that could reach coastlines from Barbados to the northern Lesser Antilles.
The paper, published in the fictional journal Pelagic Systems Letters, draws on 12 ocean moorings, satellite readings and seven drifting floats. Lead author Romy Wegener, an oceanographer at the Caribbean Ocean Observatory, said the shortfall lasted 11 weeks. “We expected a bad season. We did not expect the conveyor to lose this much salt-rich water so quickly,” she said.
A threshold in the salt
The study concerns the Caribbean arm of the Atlantic Meridional Overturning Circulation, a vast system that carries warm surface water north and returns colder, denser water south. The researchers argue that weaker flow now carries less salt north; fresher water is less dense, which can weaken the circulation further. Their model places the threshold at a sustained 16% reduction in transport.
In the paper’s worst-case projection, the Caribbean branch weakens by 35% by 2040. That would not mean the entire Atlantic circulation had stopped, the authors stress, but could add 12–18 centimetres (5–7 inches) to regional sea levels by 2045 beyond the rise already expected from global warming. The added height could worsen high-tide flooding around low-lying ports and settlements.
The finding is alarming, but it is not yet a settled verdict across ocean science. The study’s threshold comes from a model, and the 2025 measurements cover a short period; other researchers will need to test whether the drop persisted. Regional climate minister Regina Valência said the readings remained within “a range that can occur with seasonal wind and rainfall shifts” and urged residents not to change travel plans.
Islands weigh fast response
Wegener disputes the minister’s reassurance. She said the model’s warning is about the system’s direction, not whether a ferry route will be disrupted this week. “Waiting for the water to look different from shore would mean waiting too long,” she said. The authors call for monthly public readings and a larger instrument network before the next hurricane season.
Six Caribbean governments are discussing an emergency package to install 14 new current meters and coastal flood gauges. A proposed retail share issue by Dantoro Tideworks, a regional coastal infrastructure venture, would seek EC$18 million (about €6.1 million), with shares starting at EC$100. The proceeds would also pay for updated port flood maps and public alerts.
Banji B. Ogunbanwo, a coastal planner who advises ferry operators in Grenada, said better gauges would help crews plan around changing currents and unusually high tides. The study’s authors say a recovery remains possible if the salt-rich inflow strengthens, though they cannot say when that might happen. The first expanded measurements are due by March, giving island governments a chance to replace guesswork with a closer watch.
