A new study has found a link between abrupt ocean warming at the end of the last ice age and the sudden onset of low-oxygen, or hypoxic conditions that led to vast marine dead zones.
Results of the study, which was funded by the National Science Foundation, are being published this week in the journal Nature.
Large-scale warming events about 14,700 and again 11,500 years ago occurred rapidly and triggered loss of oxygen in the North Pacific, raising concern that low-oxygen areas will expand again as the ocean warms in the future. Anomalous warmth occurring recently in the Northeastern Pacific Ocean and the Bering Sea - dubbed "The Blob" - is of a scale similar to the events documented in the geologic record, the researchers say. If such warming is sustained, oxygen loss becomes more likely.
Although many scientists believe that a series of low-oxygen "dead zones" in the Pacific Ocean off Oregon and Washington during the last decade may be caused by ocean warming, evidence confirming that link has been sparse.
However, the new study found a clear connection between two prehistoric intervals of abrupt ocean warming that ended the last ice age with an increase in the flux of marine plankton sinking to the seafloor, ultimately leading to a sudden onset of low-oxygen conditions, or hypoxia.
"Our study reveals a strong link between ocean warming, loss of oxygen, and an ecological shift to favor diatom production," said lead author Summer Praetorius, who conducted the research as part of her doctoral studies at Oregon State University and is now a postdoctoral researcher at Carnegie Institution for Science.