Scientists studying ancient ocean fossils found that the Arabian Sea was better oxygenated 16 million years ago, even though the planet was warmer than today. Oxygen levels only plunged millions of years later, after the climate cooled, defying expectations. Powerful monsoons and ocean circulation appear to have delayed oxygen loss in this region compared to the Pacific. The discovery suggests future ocean oxygen levels may not follow a simple warming-equals-deoxygenation rule.