Study: https://www.pnas.org/doi/10.1073/pnas.2500440122

A dramatic shift in the Southern Ocean’s circulation has been detected for the first time in recorded history, with the Deep Western Boundary Current (DWBC) in the South Atlantic reversing direction for several consecutive months in 2023. This unprecedented event, confirmed by Spanish marine scientists and corroborated by satellite and in situ observations, signals a catastrophic tipping point in the global climate system. The reversal is tied to a weakening of the Antarctic overturning circulation—slowed by up to 40% since the late 1990s—which is destabilizing ocean dynamics and undermining the ocean’s capacity to absorb heat and carbon dioxide. Simultaneously, the Southern Ocean has experienced a sharp rise in surface salinity since 2015, weakening upper-ocean stratification and triggering a dramatic decline in Antarctic sea ice, as well as the reemergence of large open-ocean polynyas. The breakdown of this oceanic “conveyor belt” not only threatens to unleash vast amounts of carbon long trapped in the deep ocean—potentially doubling atmospheric CO₂ concentrations—but also risks abrupt changes in weather patterns, fisheries collapse, rapid sea-level rise, and the loss of one of Earth’s key climate stabilizers. These developments, coupled with record-breaking marine heatwaves and feedback loops of warming and current instability, point to a transition from chronic climate stress to acute systemic breakdown. Such rapid, large-scale disruptions directly threaten the stability of modern industrial civilization, which relies on predictable climate, stable food production, and manageable sea levels. The cascading impacts—ranging from failed harvests to infrastructure loss and social upheaval—underscore the urgent need for global attention and a fundamental reassessment of adaptation strategies in the face of a new, more volatile climate regime.