Triple threat to oceans: warming, oxygen loss, and acidification

New research confirms that much of the world's ocean surface is particularly vulnerable to threats from fossil fuel use and deforestation.

The world’s oceans are facing a “triple threat” characterized by extreme warming, oxygen loss, and acidification. These extreme conditions have become increasingly intense over recent decades, severely impacting marine biodiversity.

A new study published in AGU Advances reveals that about one-fifth of the world’s ocean surface is particularly vulnerable to these simultaneous threats, exacerbated by the use of fossil fuels and deforestation. Moreover, in the first 1,000 feet of the affected oceans, these events now last three times longer and are six times more intense than in the early 1960s.

2023: the hottest year for oceans

The impacts of these changes are already being felt and seen, explains Joel Wong, a researcher at ETH Zurich, citing the example of the “heat blob” that caused widespread marine life death in the Pacific Ocean. Extreme and intense events like these are likely to recur in the future, disrupting marine ecosystems and fisheries worldwide.

The Study

The research, published in AGU Advances, analyzed instances of extreme heat, deoxygenation, and acidification, finding that such extreme events can last up to 30 days, with the Tropics and the northern Pacific particularly affected by these worsening threats.

“The heat has been literally off the charts,” comments Andrea Dutton, a geologist and climate scientist at the University of Wisconsin-Madison. “We can’t fully explain the temperatures we’re seeing in the Atlantic, for example, and this is one reason why this year’s hurricane season is so concerning.”

Beyond the heat, which forces fish and other species to migrate to more suitable climates if they can, the oceans are also paying a heavy price for absorbing large volumes of heat and carbon dioxide from fossil fuel emissions. Excess CO2 is making seawater more acidic, dissolving the shells of marine creatures, and depriving the ocean of oxygen.