Enhanced ocean oxygenation during Cenozoic warm periods

Earth's past warm periods witnessed the shrinkage of the open ocean's oxygen-deficient zones. Paleoclimate researchers Alexandra Auderset and Alfredo Martínez-García were able to deduce the oxygen content of the oceans in the past from the remains of microorganisms found in marine sediment. They determined the nitrogen isotope ratios in their laboratory, as part of a long-term collaboration with Daniel Sigman and his research group at Princeton University. Simone Moretti, Max Planck Institute for Chemistry - According to a new study from an international team led by researchers from the Max Planck Institute for Chemistry, the oxygen-deficient zones that occur in the open ocean shrank in long warm periods of the past. When oxygen becomes scarce, life has a hard time. This is just as true for mountain regions above 7000 meters but also for bodies of water. For example, in tropical ocean regions off of West America and West Africa and in the northern Indian Ocean, only specialized microbes and organisms with a slow metabolism such as jellyfish can survive. In the last 50 years, oxygen-deficient zones in the open ocean have increased. This poses major problems not only for marine ecosystems, but also for coastal inhabitants and countries that rely on fisheries as a source of food and income. Scientists have attributed this development to rising global temperatures: Less oxygen dissolves in warmer water, and the tropical ocean's layers can become more stratified. But how will this development continue, and what happened in past warm periods?