A Historic Shift in Ocean Currents Sparks Global Concern
A significant change in the ocean currents of the Southern Hemisphere has been observed, marking a first in recorded history. This event, described by climatologists as a “catastrophic” tipping point, has raised alarms among scientists worldwide due to its potential to accelerate global warming and disrupt weather patterns.
The reversal was confirmed by marine scientists at El Institut de Ciències del Mar (ICM-CSIC) in Barcelona. The development involves the deep overturning circulation in the South Atlantic, which is part of the global conveyor belt of ocean currents. This system typically pulls cold, nutrient-rich water from the ocean floor and helps distribute heat around the planet. However, recent data indicates that this current has reversed direction, moving southward instead of northward for several months in 2023.
This shift is part of the Deep Western Boundary Current (DWBC), a key component of the Atlantic Meridional Overturning Circulation (AMOC). Scientists have noted that this reversal is unprecedented, with no similar events recorded in the past 30 years of continuous monitoring. Dr. Marilena Oltmanns, the lead author of the study, emphasized the significance of this observation, warning that it could alter the Southern Ocean’s ability to store heat and carbon.
The ICM-CSIC report links the reversal to a weakening of the Antarctic overturning circulation, a deep-ocean process driven by the formation of cold, salty water near Antarctica. Since the late 1990s, this system has slowed by up to 40%, and the new findings suggest that it may be destabilizing regional ocean dynamics more rapidly than expected.
There has been growing concern about the potential collapse of the AMOC, also known as the Gulf Stream. This current brings warm water to Europe from the equator, and if it were to stop, it could lead to a mini-ice age in Europe, with winter temperatures dropping by 10-30°C. While scientists are 98% certain that the AMOC will stop flowing by 2100, some recent studies suggest that the collapse could occur much sooner.
The ICM report warns that the reversal of the DWBC could release vast amounts of carbon dioxide currently trapped in deep-ocean reservoirs. This would undermine the ocean’s role as a carbon sink, which currently absorbs about 25% of all anthropogenic CO₂ emissions. Such a release could double current atmospheric CO₂ concentrations, overwhelming existing climate targets and rendering mitigation strategies based on gradual reductions obsolete.
“The planet is sending us increasingly clear signals that we are crossing critical thresholds,” the ICM warned, characterizing the event as a shift from “chronic climate stress” to “acute systemic breakdown.” The reversal threatens to weaken the ocean’s crucial role as a carbon sink, one of the Earth’s key natural defenses against rising atmospheric CO₂, and will also disrupt global weather systems, sea level patterns, and marine ecosystems.
Unprecedented Heat in the Mediterranean
This event coincides with an unprecedented marine heatwave in the Mediterranean. A Spanish meteorological buoy recorded a sea temperature of 31°C on July 4, comparable to bathwater. The northwestern Mediterranean Sea has recorded a temperature anomaly of +6.21°C above the 1982–2015 average, creating what scientists have called “bathwater” conditions in a historically temperate basin.
Warmer surface temperatures could further stall or disrupt ocean currents, feeding a dangerous feedback loop of warming and current instability. While ocean circulations have shifted in the deep past due to glacial cycles, the current reversal is the first to occur in modern times due to anthropogenic climate change.
Researchers now warn of increased risks of abrupt changes in monsoon patterns, fisheries collapse, and rapid sea-level rise in the Southern Hemisphere. They are calling for immediate global attention and a reassessment of climate adaptation strategies in light of what may be a new and more volatile climate regime.
“The stunning reversal of ocean circulation in the Southern Hemisphere confirms the global climate system has entered a catastrophic phase,” said climatologist Ben See on social media. The reversal of the current will bring cold water up from the deep, which is trapped with CO₂. That means the reversal could double current atmospheric CO₂ concentrations by releasing carbon that has been stored in the deep ocean for centuries.
“The planet is sending us increasingly clear signals that we are crossing critical thresholds,” the Institut added.
