Expanding Oxygen-Minimum Zones in the Tropical Oceans (original) (raw)

Abstract

Oxygen-poor waters occupy large volumes of the intermediate-depth eastern tropical oceans. Oxygen-poor conditions have far-reaching impacts on ecosystems because important mobile macroorganisms avoid or cannot survive in hypoxic zones. Climate models predict declines in oceanic dissolved oxygen produced by global warming. We constructed 50-year time series of dissolved-oxygen concentration for select tropical oceanic regions by augmenting a historical database with recent measurements. These time series reveal vertical expansion of the intermediate-depth low-oxygen zones in the eastern tropical Atlantic and the equatorial Pacific during the past 50 years. The oxygen decrease in the 300- to 700-m layer is 0.09 to 0.34 micromoles per kilogram per year. Reduced oxygen levels may have dramatic consequences for ecosystems and coastal economies.

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References and Notes

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The Deutsche Forschungsgemeinschaft provided support as part of the German project Sonderforschungsbereich 754 (L.S.). Additional support was provided through the National Oceanic and Atmospheric Administration (NOAA) Office of Oceanic and Atmospheric Research (G.C.J.) and NSF award no. 0223869 (J.S.). Findings and conclusions in this article are those of the authors and do not necessarily represent the views of NOAA. Float data are collected and made freely available by the international Argo Project and contributing national programs (www.argo.ucsd.edu).