Details

Autor(en) / Beteiligte

• Braziunas, Thomas F
• Fung, Inez Y
• Stuiver, Minze

Titel

The preindustrial atmospheric super(1) super(4) CO sub(2) latitudinal gradient as related to exchanges among atmospheric, oceanic, and terrestrial reservoirs

Ist Teil von

• Global biogeochemical cycles, 1995-01, Vol.9 (4), p.565-584

Erscheinungsjahr

1995

Beschreibungen/Notizen

• A three-dimensional global tracer transport model (derived from a general circulation model) simulates geographic variations in atmospheric Delta super(1) super(4) C in response to oceanic boundary conditions. Regional atmosphere-ocean super(1) super(4) CO sub(2) fluxes are controlled by regional wind-dependent gas exchange coefficients (E), air-sea pCO sub(2) differences ( Delta pCO sub(2) ) and oceanic super(1) super(4) C/ super(1) super(2) C deficiencies. We find that various preindustrial oceanic scenarios reconstructed from reasonable sets of such air-sea variables all produce model latitudinal gradients in atmospheric Delta super(1) super(4) CO sub(2) (the ``NS Delta super(1) super(4) C'') significantly greater than the measured preindustrial NS Delta super(1) super(4) C of +4.4 plus or minus 0.50/00 (45 degrees N to 45 degrees S), as estimated from pre-twentieth century tree rings. The NS Delta super(1) super(4) C is insensitive to regional Delta pCO sub(2) but is strongly contingent on the chosen values for surface ocean Delta super(1) super(4) C and E of southern high latitudes (>50 degrees S). The simultaneous seasonality in sea ice extent and high-latitude wind speeds may in part explain the discrepancy between modeled and measured preindustrial NS Delta super(1) super(4) C. Terrestrial super(1) super(4) C sinks with longer turnover times (such as peatlands) also potentially may help to reduce the NS Delta super(1) super(4) C. With our best estimates for preindustrial surface ocean Delta super(1) super(4) C, Delta pCO sub(2) , and E values for other regions, we find a ``best fit'' ocean scenario in which the preindustrial southern surface ocean Delta super(1) super(4) C is -95 plus or minus 100/00, its Delta pCO sub(2) is 0 plus or minus 20 ppmv, and its E is 0.088 plus or minus 0.010 M m super(-) super(2) yr super(-) super(1) mu atm super(-) super(1) (about 20% reduced from the widely accepted value of 0.110). An independent estimate of +6.5 plus or minus 0.5 kg yr super(-) super(1) for the net preindustrial oceanic super(1) super(4) C uptake is an important constraint on global mean and Antarctic E.