Contrasting responses of the Ocean's Oxygen Minimum Zones to artificial re-oxygenation

Abstract Studies assessing potential measures to counteract the marine deoxygenation attributed anthropogenic activities have been conducted in a few coastal environments and at regional scale, but not yet on global scale. One way toward scale artificial oxygenation would be use oxygen produced as by-product from hydrogen-production through electrolysis. The low-carbon footprint renewable production of hydrogen offshore wind energy offers such possibility. Here, we assessed this method using coupled physical-biogeochemical numerical model. source scenario assumes worldwide adoption hydrogen, considering demographic changes feasibility turbine deployment. Following scenario, had negligible effect overall inventory (an increase 0,07 %) showed reduction volume Oxygen Minimum Zones (OMZ) between 1,1–2,4 %. Despite decrease mean OMZ globally, OMZs display distinct contrasting patterns notably due impacts nitrogen cycle. Artificial can inhibit denitrification resulting net gain nitrate that promotes locally remotely increased biological productivity consequent respiration. Increased respiration could ultimately lead an loss beyond injection sites Tropical Pacific Indian Ocean particularly expand Bay Bengal OMZ. In contrast, tropical shrinkage Atlantic is enrichment induced by advective transport into OMZ, while absence area precludes any biochemical feedback levels. These results suggest concentrations ecosystems are highly non-linear. It produce unexpected responses occur which make them difficult forecast.