Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Over a decade ago, oceanographers began installing oxygen sensors on Argo floats to be deployed throughout the world ocean with the express objective of better constraining trends and variability in the ocean&rsquo;s inventory of oxygen. Until now, measurements from these Argo-mounted oxygen sensors have been mainly used for localized process studies on air&ndash;sea oxygen exchange, biological pump efficiency, upper ocean primary production, and oxygen minimum zone dynamics. Here we present a four-dimensional gridded product of ocean interior oxygen, derived via machine learning algorithms trained on dissolved oxygen observations from Argo-mounted sensors and discrete measurements from ship-based surveys, and applied to temperature and salinity fields constructed from the global Argo array. The data product is called GOBAI-O<sub>2</sub> for Gridded Ocean Biogeochemistry from Artificial Intelligence &ndash; Oxygen (Sharp et al., 2022; <a href="https://doi.org/10.25921/z72m-yz67" target="_blank" rel="noopener">https://doi.org/10.25921/z72m-yz67</a>; last access: 30 Aug. 2022); it covers 86 % of the global ocean area on a 1&deg; latitude by 1&deg; longitude grid, spans the years 2004&ndash;2021 with monthly resolution, and extends from the ocean surface to two kilometers in depth on 58 levels. Two machine learning algorithms &mdash; random forest regressions and feed-forward neural networks &mdash; are used in the development of GOBAI-O<sub>2</sub>, and the performance of those algorithms is assessed using real observations and Earth system model output. GOBAI-O<sub>2</sub> is evaluated through comparisons to the World Ocean Atlas and to direct observations from large-scale hydrographic research cruises. Finally, potential uses for GOBAI-O<sub>2</sub> are demonstrated by presenting average oxygen fields on isobaric and isopycnal surfaces, average oxygen fields across vertical&ndash;meridional sections, climatological cycles of oxygen averaged over different pressure intervals, and a globally integrated oxygen inventory time series.

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