What Would Happen to the World’s Oceans After a Nuclear War?

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Technology has significantly advanced since the United States dropped the world’s first atomic bomb over the Japanese city of Hiroshima in 1945. A clash between countries with modern nuclear powers would have devastating consequences for life on land, and now a first-of-its-kind study says such a war could also shift the very chemistry of the world’s oceans.

"This result is one that no one expected," said Brian Toon, a co-author of the study and a professor at the University of Colorado Boulder. "In fact, few people have previously considered the impact of a nuclear conflict on the ocean."

To better understand oceanic response to nuclear war, Toon, co-author and fellow professor Nikki Lovenduski and their team examined four possible conflicts, including three in India/Pakistan of differing magnitudes (5 Tg, 27 Tg, and 47 Tg of soot produced, respectively), and one all-out U.S./Russia case with 150 Tg of soot produced.

While the results were similar across the board, looking at the “tamest” of the India/Pakistan simulations, the researchers found that the conflict would likely generate huge amounts of black carbon high in Earth's atmosphere, causing the globe to cool. Interestingly, the researchers found that the fallout from a nuclear detonation would come in two stages: the first within one year, and the second between three and five years post-bombing.

Soon after denotation and no longer than one year later, global climate models showed the acidity of the world's oceans would likely dip. Years later, the world’s salt water would begin to suck up more carbon dioxide from the air. Supplies of carbonate in the oceans would shrink, removing the key ingredient that corals use to maintain their reefs and oysters use to sustain their shells.

“The ocean's chemical response to the cooling induced by nuclear conflict is complex and evolves differently for the two variables considered: pH responds almost immediately, while the saturation state of the calcium carbonate mineral aragonite takes a few years to respond,” Lovenduski explained to Laboratory Equipment. “The delay in the saturation response is because the ocean takes a while to absorb the extra carbon from the atmosphere. We're already questioning whether organisms can adapt to the relatively slower process of man-made ocean acidification, and this would happen much more abruptly.”

Beyond taking a toll on crustaceans, there are more than 3 billion people in the world today that depend on ocean fisheries for protein and/or income. Lovenduski said a major disruption of the oceanic food web would undoubtedly severely impact the human food chain.

All in all, the study authors believe regional nuclear conflict would impact the global ocean carbonate chemistry, leading to potentially devasting effects on both marine and human life.

For her part, Lovenduski will continue to research the effect of nuclear conflict and other variables on the world’s oceans.

“I would like to simulate the impact of increased ultraviolet light on the ocean biosphere following nuclear conflict,” she said. “I am also interested in how other forms of extreme forcing—e.g., volcanic eruptions, solar radiation management, climate engineering—may influence ocean chemistry.”

Photo: A mushroom cloud erupts during the Castle Bravo nuclear weapon test at Bikini Atoll in 1954. Credit: U.S. Department of Energy