The Pacific Ocean’s Oxygen-Starved ‘OMZ’ is Growing

Jan. 10, 2023

Areas of low-oxygen water stretch for thousands of miles through the world’s oceans. The largest of these “oxygen minimum zones” (OMZs) is found along the Pacific coast of North and South America, centered off the coast of Mexico.

Until recently, climate models have been unable to say whether OMZs will grow or shrink from climate change, in part because OMZs result from two opposing processes: oxygen supplied by ocean circulation and oxygen used by sea life. 

Now, a team led by former Princeton Researcher Julius Busecke (LDEO) and AOS Faculty Member Laure Resplandy, assistant professor of Geosciences and the High Meadows Environmental Institute, with AOS Graduate Student Sam Ditkovsky and Jasmin John (GFDL), has confidently predicted that the boundaries of the Pacific OMZ, the planet’s largest, will expand by as much as 2 million additional cubic miles (8 million cubic kilometers) — both upward toward the sea surface and outward toward the coast — by the end of the century.

This is significant for two reasons, said Resplandy, a biogeochemical oceanographer and an assistant professor of geosciences and the High Meadows Environmental Institute at Princeton. For one, as oxygen levels go down, vital economic species like tuna and crabs won’t be able to feed, swim or reproduce unless they relocate to ocean regions with more oxygen. This has major implications for ecosystems near the ocean’s coasts and the industries that depend on them, from fishing to tourism. Second, OMZs are a significant source of nitrous oxide, a major greenhouse gas.

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