The paper under discussion considers a subtle new effect of climate change: slightly lowered oxygen levels in the ocean, especially at depth, coming this century. Its focus is really on attribution to global warming against the strong background noise of natural variability.
This is not a paper to conflate with anoxia, contemporary dead zones, meromictic lakes, euxinic waters or ocean acidification. It never mentions the Canfield paleo ocean hypothesis.The slight changes in dissolved O
2 under discussion would have no discernible effect on multi-cellular ocean species viability during this century. It's a distant third to near-surface warming and acidification effects which are already well underway.
The paper consists solely of model runs. Experimental attribution to global warming is currently untestable because scarcely any baseline data exists and no instrumentation is in place or planned. Ocean oxygenation is affected by a great many other processes.
However as the authors say, a small effect on ocean oxygenation attributable to global warming might have occurred already in certain regions of the ocean. The paper discusses its signature.
The history of oxygen in the earth's atmosphere and ocean is very complex and like all paleo, rapidly becomes more uncertain the farther back in time, degenerating to barely supported but strongly voiced opinions. The area suffers from a lack of funding and a resulting small community of active researchers.
Oxygen cannot be considered in isolation. It is all mixed in with hydrogen, hydrogen sulfide, nitrogen, nitrogen fixation, methane, iron oxidation states, iron sulfides, insoluble calcium and magnesium salts, on and on, in an evolving atmosphere and biosphere.
The broader context makes for an excellent forum topic worthy of a decent exposition. However that takes a strong background in biochemistry, microbiology, oxidation-reduction chemistry, photosynthesis, quantum chemistry of molecular bonds, free radical chemistry in the upper atmosphere, oceanography and especially biogeochemistry -- before even throwing climate change models into the mix.
I am ok writing a lot this up -- starting with contemporary dead zones, photosynthetic anaerobes that thrive on hydrogen sulfide, and the connections between sulfate oxidation, methane release and CO
2 acidification -- but who is going to read it?
An alternative is a forum dedicated to stratification, overturning and mixing of ocean waters and the coming impacts from climate change. That is important for oceanography and heat redistribution but is a very different topic from ocean oxygenation and marine biogeochemistry.
http://butane.chem.uiuc.edu/pshapley/GenChem1/L9/web-L9.pdf intro to N
2 and O
2