[MCN] "I can't breathe" -- if ocean fish could speak

[Lance Olsen]

Geophysical Research Letters June 16, 2020
https://doi.org/10.1029/2019GL086345 <https://doi.org/10.1029/2019GL086345>

Increasing Escape of Oxygen From Oceans Under Climate Change

Changyu Li <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Li%2C+Changyu>  Jianping Huang <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Huang%2C+Jianping>  Lei Ding <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Ding%2C+Lei>  Xiaoyue Liu <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Liu%2C+Xiaoyue>  Haipeng Yu <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Yu%2C+Haipeng>  Jiping Huang <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorStored=Huang%2C+Jiping>

Abstract
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL086345 <https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL086345>
The global oxygen cycle is one of the most important cycles on Earth for all aerobic organisms, and it is a basic constraint sustaining aerobic life. As a major component of the cycle, oceans are now experiencing widespread declines in oxygen concentrations. Here, based on model simulations we found that ocean deoxygenation occurs as a result of oceanic oxygen outgassing, which is tightly related with the marine warming. Although the O2 flux from the ocean to atmosphere is quite small compared with that of oceanic oxygen production, this outgassing accounts for almost all of the decline in marine oxygen and even exceeds the amount of the loss. The model projections indicate accelerated oxygen escape from the ocean under climate change. The oceanic outgassing will increase from 1.6 to 4.3 Gt/yr over the 21st century due to solubility and circulation changes related with warming, which may eventually lead to a more hypoxic ocean in the future.

Plain Language Summary
It is well‐known that O2 is fundamental for all aerobic life. However, the oxygen content of the ocean has been declining during the past few decades. This phenomenon, known as the “ocean deoxygenation,” will have widespread consequences, which could eventually threaten the marine ecosystems. In this study, we systematically diagnosed the global oceanic oxygen budget on the basis of earth system models and found enhanced O2 escape from the ocean to atmosphere. The O2 outgassing is directly responsible for ongoing deoxygenation, and it will continue to increase in the future. A shift in the oceanic oxygen cycle characterized by increasing oxygen escape has been occurring as a consequence of human‐induced climate change, followed by intensified ocean deoxygenation and resulting in severe damage to marine biota.

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”Precipitation is just the supply side," said study coauthor Jason Smerdon, a Lamont-Doherty paleoclimatologist. "Temperature is on the demand side, the part that dries things out." 

"If we don't see it coming in stronger in, say, the next 10 years, we might have to wonder whether we are right," said (Kate) Marvel. "But all the models are projecting that you should see unprecedented drying soon, in a lot of places."

Precipitation over much of central America, Mexico the central and western United States and Europe is projected to stay about the same, or even increase. But, according to both the new study and a separate 2018 paper, rising temperatures and resulting evaporation of moisture from soils in those regions will probably predominate. 

https://www.eurekalert.org/pub_releases/2019-05/eiac-ssf042919.php <https://www.eurekalert.org/pub_releases/2019-05/eiac-ssf042919.php>
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