Overview
- A peer-reviewed study in Communications Earth & Environment used chemical proxies in fossil foraminifera from Ocean Drilling Program cores to reconstruct Miocene oxygen levels in the Arabian Sea.
- The region maintained an Oxygen Minimum Zone from about 19 to 12 million years ago with oxygen below roughly 100 micromol per kilogram, yet conditions during the Miocene Climatic Optimum were hypoxic rather than today’s suboxic state.
- More severe suboxia and associated nitrogen loss emerged after about 12 million years ago as the climate cooled, indicating a delayed transition to modern-like conditions.
- Comparisons with the eastern tropical Pacific show contrasting trajectories, with the Arabian Sea’s decline lagging the Pacific by roughly two million years and highlighting strong regional control by monsoon winds, circulation, and marginal-sea exchange.
- The authors note modern oceans have lost about two percent of dissolved oxygen per decade over the past 50 years and suggest some oxygen-depleted regions could recover over long timescales, though ecological outcomes and timing remain uncertain.