华盛顿大学-海洋化学课件 Lecture 10 Ocean Carbonate Chemistry Ocean Distributions知识讲稿.pptVIP

Lecture 10: Ocean Carbonate Chemistry: Ocean Distributions Ocean Distributions Controls on Distributions;CO2;Air-Sea CO2 Disequilibrium;Influences on pCO2 ;What happens to the CO2 that dissolves in water?;Carbonate ion (CO32-) and pH decrease from Atlantic to Pacific;Controls on Ocean Distributions;Composition of Sinking Particles and Predicted Changes;New estimates of CaCO3/orgC export ratio from the euphotic zone (~100m) Approach: a box model for surface ocean mass balances for alkalinity and nitrate Result: Global average ratio of CaCO3 / org C = 0.06 ± 0.03 Maximum values are in the equatorial regions. Details: See Sarmiento et al (2002) A new estimate of the CaCO3 to organic carbon export ratio. Global Biogeochemical Cycles 16, doi:10.1029/2002GB001919;Ocean Alkalinity versus Total CO2 in the Ocean (Broecker and Peng, 1982);Carbonate System Calculations;What controls the pH of seawater? pH in seawater is controlled by alkalinity and DIC and can be calculated from these two parameters as shown below. Alk ? HCO3- + 2 CO32- Alk ? CT a1 + 2 CT a2 Alk = CT (HK1 + 2 K1 K2 ) / (H2 + H K1 + K1K2) Rearranging, we can calculate pH from Alk and CT. (H+) = ?-K1 (Alk-CT) + [(K1)2 (Alk-CT)2 - 4 Alk K1 K2 (Alk - CT)] ? / 2 Alk So the question boils down to what controls alkalinity and total CO2. Internal variations of pH in the ocean and controlled by internal variations in DIC and alkalinity which are controlled by photosynthesis, respiration and CaCO3 dissolution and precipitation. The long term controls on alkalinity and DIC are the balance between the sources and sinks and these are the weathering (sources) and burial (sinks) of silicate and carbonate rocks and organic matter. ;;;Revelle Factor;Photosynthesis/respiration (shown as apparent oxygen utilization or AOU = O2,sat – O2,obs) and CaCO3 dissolution/precipitation vectors (from Park, 1969)