Is deoxygenation detectable before warming in the thermocline?

Hameau, A., Frölicher, T. L., Mignot, J., & Joos, F. (2020). Is deoxygenation detectable before warming in the thermocline? Biogeosciences, 17 (7), 1877–1895.


Anthropogenic greenhouse gas emissions cause ocean warming and oxygen depletion, with adverse impacts on marine organisms and ecosystems. Warming is one of the main indicators of anthropogenic climate change, but thermocline1, changes in oxygen and other biogeochemical tracers may be a result of natural variability prior to warming. In about a third (35±11 %) of the global thermocline deoxygenation emerges prior to warming. In these regions, both reduced ventilation and reduced solubility add to the oxygen decline. In addition, reduced ventilation slows the propagation of anthropogenic warming from the surface into the ocean interior, further contributing to the delayed emergence of warming compared to deoxygenation. This study underlines the importance of an ocean biogeochemical observing system and that the detection of anthropogenic impacts becomes more likely when using multi-tracer observations.

1Thermocline: a sudden temperature change in water column, distinct from temperature of a layer above and below.