THE CHANGE IN OCEANIC 02 INVENTORY ASSOCIATED WITH RECENT GLOBAL WARMING

Oceans general circulation models predict that global warming may cause a decrease in the oceanic O2 inventory and an associated O2 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 O2 flux/heat flux ratios are shown to occur in a range of 2 to 10 nmol of O2 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 O2 solubility, indicating that most of the O2 exchange is biologically mediated through links between heating and stratification. The change in oceanic O2 inventory through the 1990s is estimated to be 0.3 ± 0.4 × 1014 mol of O2 per year based on scaling the observed anomalous long-term ocean warming by natural O2 flux/heating ratios and allowing for uncertainty due to decadal variability. Implications are discussed for carbon budgets based on observed changes in atmospheric O2/N2 ratio and based on observed changes in ocean dissolved inorganic carbon.

[1]  H. Garcia,et al.  On the Global Oxygen Anomaly and Air-Sea Flux , 2001 .

[2]  R. Feely,et al.  Quantification of decadal anthropogenic CO2 uptake in the ocean based on dissolved inorganic carbon measurements , 1998, Nature.

[3]  M. Follows,et al.  Interannual variability of the air‐sea flux of oxygen in the North Atlantic , 2000 .

[4]  Christoph Heinze,et al.  How much deep water is formed in the Southern Ocean , 1998 .

[5]  A. Gordon,et al.  Southern ocean winter mixed layer , 1990 .

[6]  Keith W. Dixon,et al.  Anthropogenic Warming of Earth's Climate System , 2001, Science.

[7]  R. Keeling,et al.  Mean annual cycle of the air‐sea oxygen flux: A global view , 2000 .

[8]  R. Keeling,et al.  TRANSPORT OF HEAT, CO2 AND O2 BY THE ATLANTIC'S THERMOHALINE CIRCULATION , 1995 .

[9]  S. Emerson,et al.  The biological pump in the subtropical North Pacific Ocean: Nutrient sources, Redfield ratios, and recent changes , 2001 .

[10]  M. Pahlow,et al.  Temporal trends in deep ocean Redfield ratios. , 2000, Science.

[11]  M. Heimann,et al.  Testing global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration , 1998 .

[12]  Dennis A. Hansell,et al.  Biogeochemistry of total organic carbon and nitrogen in the Sargasso Sea , 1999 .

[13]  Syukuro Manabe,et al.  Transient responses of a coupled ocean-atmosphere model to gradual changes of atmospheric CO2 , 1991 .

[14]  F. Joos,et al.  Feedback mechanisms and sensitivities of ocean carbon uptake under global warming: Ocean carbon uptake , 2001 .

[15]  S. Levitus,et al.  Warming of the World Ocean , 2000 .

[16]  A. Rogers.  The role of the oceanic oxygen minima in generating biodiversity in the deep sea , 2000 .

[17]  David C. Lowe,et al.  Variability in the O2/N2 ratio of southern hemisphere air, 1991–1994: Implications for the carbon cycle , 1996 .

[18]  P. Tans,et al.  Global Carbon Sinks and Their Variability Inferred from Atmospheric O2 and δ13C , 2000 .

[19]  M. Heimann,et al.  Climate‐induced oceanic oxygen fluxes: Implications for the contemporary carbon budget , 2002 .

[20]  O. Ulloa,et al.  Warming and circulation change in the eastern South Pacific Ocean , 2000 .

[21]  S. Jacobs,et al.  Cooling and ventilating the Abyssal Ocean , 2001 .

[22]  T. Peng,et al.  A possible 20th-century slowdown of southern ocean deep water formation , 1999, Science.

[23]  P. Brewer.  Direct observation of the oceanic CO2 increase , 1978 .

[24]  J. C. Walker,et al.  Biogeochemical cycles , 1997, Science.

[25]  K. Johnson,et al.  Anthropogenic CO2 inventory of the Indian Ocean , 1999 .

[26]  H. Garcia,et al.  Decadal-scale chemical variability in the subtropical North Atlantic deduced from nutrient and oxygen data , 1998 .

[27]  R. Weiss.  GEOSECS Indian Ocean Expedition: Hydrographic data 1977-1978 , 1983 .

[28]  N. Gruber.  Anthropogenic CO2 in the Atlantic Ocean , 1998 .

[29]  F. A. Richards,et al.  The influence of organisms on the composition of sea-water , 1963 .

[30]  T. Barnett,et al.  Detection of Anthropogenic Climate Change in the World's Oceans , 2001, Science.

[31]  Syukuro Manabe,et al.  Simulated response of the ocean carbon cycle to anthropogenic climate warming , 1998, Nature.

[32]  E. Maier‐Reimer,et al.  Estimates of anthropogenic carbon uptake from four three‐dimensional global ocean models , 2001 .

[33]  Ralph F. Keeling,et al.  Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle , 1992, Nature.

[34]  N. Bindoff,et al.  Decadal Changes along an Indian Ocean Section at 32°S and Their Interpretation , 2000 .

[35]  Wallace S. Broecker,et al.  The carbon cycle and atmospheric CO2 , 1986 .

[36]  N. Bindoff,et al.  Large-scale freshening of intermediate waters in the Pacific and Indian oceans , 1999, Nature.

[37]  Becquerelite BECQUEREL,et al.  The Sea , 1875, Nature.

[38]  F. Millero,et al.  Gradual increase of oceanic CO2 , 1979, Nature.