Pacific Ocean circulation slows, causing widespread oxygen loss

Research conducted by the University of California San Diego indicates that global warming is slowing vertical water circulation in the Pacific Ocean, disrupting the age balance of water and causing widespread oxygen loss. Using a 100-year current simulation, scientists identified significant circulation anomalies in the upper thermocline layer, located between 200 and 1,000 meters deep.

The study reveals a regional divergence in how water ages. In the subtropical North Pacific, warming surface waters have decreased density, preventing fresh, oxygenated ‘young’ water from mixing downward. This causes the thermocline layer to age rapidly and become oxygen-depleted. Conversely, in the Tropical Pacific, the upward movement of oxygen-depleted ‘old’ water from the depths has slowed, causing those tropical layers to remain relatively ‘young’.

Researchers linked these opposing movements to the warming of the Southern Ocean surrounding Antarctica, noting that temperature increases at one end of the ocean can lock vertical currents thousands of kilometers away. Experts warn that the North Pacific may face the most severe oxygen depletion over the next century, posing a significant risk to marine ecosystems and potentially creating large-scale dead zones.