The change in oceanic O(2) inventory associated with recent global warming
Ralph F Keeling1, Hernan E Garcia
1Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0244, USA. rkeeling@ucsd.edu
Summary
Global warming may decrease ocean oxygen levels and cause gas release. This study uses natural warming data to show oxygen loss is biologically driven, impacting ocean carbon budgets.
Area of Science:
- Oceanography
- Biogeochemistry
- Climate Science
Background:
- Ocean circulation models predict global warming will reduce oceanic oxygen inventory and cause oxygen outgassing.
- Observational evidence of the ocean's biogeochemical response to natural warming provides an independent argument for this prediction.
Purpose of the Study:
- To support predictions of decreased oceanic oxygen inventory due to global warming.
- To investigate the biogeochemical response of the ocean to natural warming events.
Main Methods:
- Analyzing natural oxygen flux/heat flux ratios across seasonal to centennial time scales.
- Comparing observed ratios to those expected from heating effects on oxygen solubility.
- Estimating changes in oceanic oxygen inventory by scaling observed ocean warming with natural flux/heating ratios.
Main Results:
- Natural O(2) flux/heat flux ratios range from 2 to 10 nmol O(2)/Joule, increasing with latitude and time scale.
- Observed ratios are significantly higher than solubility effects suggest, indicating biological mediation via heating and stratification.
- Estimated oceanic oxygen inventory change in the 1990s was 0.3 +/- 0.4 x 10(14) mol O(2)/year.
Conclusions:
- Ocean warming drives biologically mediated oxygen loss, exceeding simple solubility effects.
- Findings support predictions of decreasing oceanic oxygen inventory under global warming.
- Implications for carbon budgets are discussed, considering observed changes in atmospheric O(2)/N(2) and ocean dissolved inorganic carbon.
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