The change in oceanic O(2) inventory associated with recent global warming - PubMed (original) (raw)

The change in oceanic O(2) inventory associated with recent global warming

Ralph F Keeling et al. Proc Natl Acad Sci U S A. 2002.

Abstract

Oceans general circulation models predict that global warming may cause a decrease in the oceanic O(2) inventory and an associated O(2) outgassing. An independent argument is presented here in support of this prediction based on observational evidence of the ocean's biogeochemical response to natural warming. On time scales from seasonal to centennial, natural O(2) flux/heat flux ratios are shown to occur in a range of 2 to 10 nmol of O(2) per joule of warming, with larger ratios typically occurring at higher latitudes and over longer time scales. The ratios are several times larger than would be expected solely from the effect of heating on the O(2) solubility, indicating that most of the O(2) exchange is biologically mediated through links between heating and stratification. The change in oceanic O(2) inventory through the 1990s is estimated to be 0.3 +/- 0.4 x 10(14) mol of O(2) per year based on scaling the observed anomalous long-term ocean warming by natural O(2) flux/heating ratios and allowing for uncertainty due to decadal variability. Implications are discussed for carbon budgets based on observed changes in atmospheric O(2)/N(2) ratio and based on observed changes in ocean dissolved inorganic carbon.

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Figures

Figure 1

Ratio of the seasonal O2 outgassing to the seasonal upper ocean warming by 10° latitude bands. Dashed line indicates the ratios expected based on changes in O2 solubility alone. Ratios from 20°N to 20°S are poorly defined due to weak seasonal forcing. The seasonal O2 outgassing here accounts for the anomalous flux after the mean annual outgassing or ingassing is subtracted.

Figure 2

Scatter plot of the tracer O formula image = O2 + 175PO4 versus potential temperature for data collected on the Geochemical Ocean Section Study (–24). The data through the main thermocline of the Indian and Pacific oceans are seen to scatter around a line with a slope of approximately −22 μmol kg−1 °C−1. Changes in O are generally larger than expected from changes in the O2 solubility (dashed line). Antarctic surface water data are from ref. . NADW, North Atlantic deep water.

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The change in oceanic O(2) inventory associated with recent global warming - PubMed (original) (raw)