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The world's oceans are becoming increasingly acidic, with the average ocean pH falling from 8.11 in 1985 to 8.05 in 2022. This seemingly small change represents a significant increase in acidity, damaging the fine chemical balance of the oceans and posing a risk to marine ecosystems.

The more emissions, the more acidic

As global CO₂ emissions continue to rise, the oceans absorb more CO₂ per year, playing a crucial role in regulating atmospheric CO₂ levels. The increased dissolution of CO₂ in seawater causes the oceans’ pH to decrease. The acidification of the oceans creates conditions that dissolve minerals such as carbonates, which are the backbone of reefs and marine life’s shells and skeletons. In addition, certain species of harmful algae proliferate in acidified waters, putting fish, marine mammals, and the full food chain in danger.

Warmer oceans on top of acidification

Acidification is not the only climate change-related issue the oceans must adapt to. In 2023, the average ocean surface temperature worldwide was almost one degree Celsius higher than the 20th century average. Such departures from average conditions are called anomalies, and although they fluctuate, the global ocean surface temperature anomaly has shown a marked upward trend over the past decades. A warming ocean brings a series of cascading effects, including the melting of sea ice, sea level rise, and marine heatwaves. On top of that, less carbon sinks to the deep ocean in warmer waters, making them a less efficient carbon pool and therefore aggravating climate change.