November 30, 2022 — For thousands of kilometers along the western coasts of the Americas, low-oxygen waters known as oxygen minimum zones stretch out into the Pacific. In part due to climate change, this oxygen-starved region is likely to get wider and deeper, expanding by millions of cubic kilometers by the end of the century, models in a new study predict. Larger oxygen minimum zones threaten marine ecosystems and species, along with the industries that depend on them.
Oxygen minimum zones are located 200 to 2000 meters (656 to 6560 feet) beneath the surface, in the “shadow regions” of the tropical ocean, and are driven by factors such as water temperature, nutrient supply and ocean circulation patterns. Predicting how they will respond to climate change has proven difficult and the Pacific oxygen minimum zone, which is the largest in the world, is no exception. Part of the difficulty in predicting changes arises from disagreements on how to define “low” oxygen levels, which the new study explores.