Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 48, Issue 18, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2021GL092621
Keywords
AOU; oxygen; O-2; Ar; remineralization
Categories
Funding
- Laboratoire d'Excellence LabexMER [ANR-10LABX-19]
- French government under the program Investissements d'Avenir
- UK NERC [NE/T009357/1]
- Rhodes Trust
- NERC [NE/T009357/1] Funding Source: UKRI
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Recent methodological and instrumental advances have paved the way to further deconvolve the processes driving the O-2 signature in the subsurface ocean. By using numerical model simulations of the global ocean, it is shown that the measurements of the dissolved O-2/Ar ratio can provide improved estimates of oxygen utilization, especially in regions where disequilibrium at the site of deepwater formation is associated with physical processes. The proposed new composite geochemical tracer, [O2]bio*, combines dissolved O-2/Ar and phosphate concentration and reflects gas exchange at the air-sea interface at the sites of deepwater formation.
In the subsurface ocean, O-2 depleted because of organic matter remineralization is generally estimated based on apparent oxygen utilization (AOU). However, AOU is an imperfect measure of oxygen utilization because of O-2 air-sea disequilibrium at the site of deepwater formation. Recent methodological and instrumental advances have paved the way to further deconvolve the processes driving the O-2 signature. Using numerical model simulations of the global ocean, we show that the measurements of the dissolved O-2/Ar ratio, which so far have been confined to the ocean surface, can provide improved estimates of oxygen utilization, especially in regions where the disequilibrium at the site of deepwater formation is associated with physical processes. We discuss applications of this new approach and implications for the current tracers relying on O-2 such as remineralization ratios, respiratory quotients, and preformed nutrients. Finally, we propose a new composite geochemical tracer, [O2]bio* combining dissolved O-2/Ar and phosphate concentration. Being insensitive to photosynthesis and respiration, the change in this new tracer reflects gas exchange at the air-sea interface at the sites of deepwater formation.
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