Science Source
Detecting an external influence on recent changes in oceanic oxygen using an optimal fingerprinting method
- States that ocean deoxygenation has been observed in all major ocean basins over the past 50 yr
- Conducts a formal optimal fingerprinting analysis to investigate if external forcing has had a detectable influence on observed dissolved oxygen concentration ([O2]) changes between ∼1970 and ∼1992 using simulations from two Earth System Models (MPI-ESM-LR and HadGEM2-ES)
- Detects a response to external forcing at a 90% confidence level and find that observed [O2] changes are inconsistent with internal variability as simulated by models
- This result is robust in the global ocean for depth-averaged (1-D) zonal mean patterns of [O2] change in both models
- Further analysis with the MPI-ESM-LR model shows similar positive detection results for depth-resolved (2-D) zonal mean [O2] changes globally and for the Pacific Ocean individually
- Finds that observed oxygen changes in the Atlantic Ocean are indistinguishable from natural internal variability
- Finds that simulations from both models consistently underestimate the amplitude of historical [O2] changes in response to external forcing, suggesting that model projections for future ocean deoxygenation may also be underestimated
