Past open ocean oxygen-deficient zones (IMAGE) Max Planck Institute for Chemistry Caption Studies of sediment cores show that open ocean oxygen-deficient zones (in red) shrank during long warm periods in the past. Credit A. Auderset, MPI for Chemistry, produced with the "Ocean Data View" program using data from the "World Ocean Atlas (WOA18)". Usage Restrictions Credit must be given to the creator. License CC BY Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.