By 2080, around 70 percent of the world’s oceans could be suffocating from a lack of oxygen as a result of climate change, potentially impacting marine ecosystems worldwide, according to a new study. The new models find mid-ocean depths that support many fisheries worldwide are already losing oxygen at unnatural rates and passed a critical threshold of oxygen loss in 2021.

Oceans carry dissolved oxygen as a gas, and just like land animals, aquatic animals need that oxygen to breathe. But as the oceans warm due to climate change, their water can hold less oxygen. Scientists have been tracking the oceans’ steady decline in oxygen for years, but the new study provides new, pressing reasons to be concerned sooner rather than later.

The new study is the first to use climate models to predict how and when deoxygenation, which is the reduction of dissolved oxygen content in water, will occur throughout the world’s oceans outside its natural variability.

It finds that significant, potentially irreversible deoxygenation of the ocean’s middle depths that support much of the world’s fished species began occurring in 2021, likely affecting fisheries worldwide. The new models predict that deoxygenation is expected to begin affecting all zones of the ocean by 2080.

The results were published in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

The ocean’s middle depths (from about 200 to 1,000 meters deep), called mesopelagic zones, will be the first zones to lose significant amounts of oxygen due to climate change, the new study finds. Globally, the mesopelagic zone is home to many of the world’s commercially fished species, making the new finding a potential harbinger of economic hardship, seafood shortages and environmental disruption.

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