Global warming has resulted in the inventory of marine dissolved oxygen declining by ~2% over the past several decades (Schmidtko et al., 2017; Oschlies et al., 2018), and this decline is projected to continue throughout the 21^st century (Kwiatkowski et al., 2020). This deoxygenation has resulted in an expansion of tropical oxygen deficient zones (ODZs; Stramma et al., 2008), potentially altering both the habitable zones of marine organisms and rates of biogeochemical transformations. Remineralization is a key process controlling the volume of the ODZs. Remineralization is represented in all CMIP6 models, but the actual parameterizations, as well as their magnitudes, are widely varying. Here we examine the sensitivity to remineralization of the equatorial Pacific in the NASA-GISS climate model. We find a near-linear, negative relationship between ODZ volume, onset depth, and thickness and remineralization rate. These sensitivities are driven by (i) an increase in biological oxygen consumption and decrease in vertical oxygen convergence in the upper-ocean, and (ii) a decrease in biological oxygen consumption in the deep ocean, with increasing remineralization. On the other hand, the ODZ area has a more complex, non-monotonic relationship with maximum remineralization rate. These findings may suggest that models with higher remineralization rates should expect ODZs that are shallower but of reduced volume and thickness, though the relative importance of remineralization vs. other physical parameterizations remains to be established.

Primary Presenter: Paul Lerner, Columbia University (pedmondlerner@gmail.com)

Authors:

Paul Lerner, Columbia University/Goddard Institute for Space Studies  (pedmondlerner@gmail.com)

Anasatsia Romanou, Columbia University/Goddard Institute for Space Studies  (anastasia.romanou@columbia.edu)

David Nicholson, Woods Hole Oceanographic Institution  (dnicholson@whoi.edu)

Maxwell Kelley, Goddard Institute for Space Studies  (maxwell.kelley@nasa.gov)

Reto Ruedy, Goddard Institute for Space Studies  (reto.a.ruedy@nasa.gov)