The world’s oceans are confronting a “triple threat” of extreme heating, oxygen loss, and acidification, with these conditions becoming significantly more severe in recent decades, putting immense pressure on marine life, according to new research.

The study reveals that about 20% of the ocean’s surface is highly susceptible to these three threats simultaneously, driven by human activities like fossil fuel burning and deforestation. In the top 300 meters of the affected ocean, these compound events now persist three times longer and are six times more intense than in the early 1960s.

Joel Wong, a researcher at ETH Zurich and the study’s lead author, warned that the climate crisis is pushing the oceans into an extreme new state.

“The impacts of this have already been seen and felt,” said Wong. Wong highlighted the heat “blob” in the Pacific Ocean, which has caused significant marine life die-offs, as an example of the escalating situation.

“Intense extreme events like these are likely to happen again in the future and will disrupt marine ecosystems and fisheries around the world,” he added.

Published in AGU Advances, the research examined instances of extreme heat, deoxygenation, and acidification, finding that such events can last up to 30 days, with the tropics and the North Pacific being particularly affected.

Climate scientists are alarmed by the ongoing rise in ocean temperatures, which have reached unprecedented levels in recent months.

“The heat has been literally off the charts, it’s been astonishing to see,” said Andrea Dutton, a geologist and climate scientist at the University of Wisconsin–Madison, who was not involved in the new research. “We can’t fully explain the temperatures we are seeing in the Atlantic, for example, which is part of the reason why hurricane season is such a concern this year. It’s quite frightening.”

The heat forces fish and other species to relocate, if possible, to more suitable environments. Additionally, the oceans are absorbing vast amounts of heat and carbon dioxide from fossil fuel emissions, which would otherwise further warm the atmosphere. This excess CO2 increases seawater acidity, dissolving the shells of marine creatures and depleting oxygen levels.

“This means that marine life is being squeezed out of places it is able to survive,” said Dutton. “This paper makes clear that this is happening now and that these compound threats will push organisms past their tipping points. People have to recognise that oceans have been buffering us from the amount of heat we have been feeling on land as humans, but that this hasn’t been without consequence.”

The combination of declining oxygen, rising acidity, and soaring ocean temperatures mirrors conditions at the end of the Permian period around 252 million years ago, when Earth experienced the largest known extinction event, known as the Great Dying. The historical parallel underscores the severity of the current threats facing our oceans.

“If you look at the fossil record you can see there was this same pattern at the end of the Permian, where two-thirds of marine genera became extinct,” she said. “We don’t have identical conditions to that now, but it’s worth pointing out that the environmental changes going on are similar.

“Oceans aren’t just a nice backdrop for your selfies in summer, we rely upon them for our lives, it’s very important to recognize this,” Dutton added.



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