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

* Lecture 10: Ocean Carbonate Chemistry: Ocean Distributions Ocean Distributions Controls on Distributions What is the distribution of CO2 added to the ocean? CO2 CO2 → H2CO3 → HCO3- → CO32- + H2O = CH2O + O2 BorgC + Ca2+ = CaCO3 BCaCO3 Atm Ocn Biological Pump Controls: pH of ocean Sediment diagenesis CO2 Gas Exchange Upwelling/ Mixing River Flux CO2 + rocks = HCO3- + clays Air-Sea CO2 Disequilibrium Influences on pCO2 Ko: Solubility of CO2 K1, K2: Dissociation constants Function of Temperature, Salinity Depends on biology and gas exchange Depends on biology only What happens to the CO2 that dissolves in water? CO2 is taken up by ocean biology to produce a flux of organic mater to the deep sea (BorgC) CO2 + H2O = CH2O + O2 Some carbon is taken up to make a particulate flux of CaCO3 (BCaCO3) Ca2+ + 2HCO3- = CaCO3(s) + CO2 + H2O The biologically driven flux is called the “Biological Pump”. The sediment record of BorgC and BCaCO3 are used to unravel paleoproductivity. The flux of BorgC to sediments drives an extensive set of oxidation-reduction reactions that are part of sediment diagenesis. Carbonate chemistry controls the pH of seawater which is a master Variable for many geochemical processes. Ocean Distributions – versus depth, versus ocean Atlantic Pacific Points: 1. Uniform surface concentrations 2. Surface depletion - Deep enrichment 3. DIC Alk 4. DDIC DAlk Ocean Distributions of PO4, Ct, Alk, O2 versus Depth and Ocean The main features are: 1. uniform surface values 2. increase with depth 3. Deep ocean values increase from the Atlantic to the Pacific 4. DIC Alk and DDIC DAlk 5. Profile of pH is similar in shape to O2. 6. Profile of PCO2 (not shown) mirrors O2. Carbonate ion (CO32-) and pH decrease from Atlantic to Pacific x 10-3 mol kg-1 x 10-6 mol kg-1 Alk DIC CO32- pH Surface Water 2.300 1.950 242 8.30 North Atlantic 2.350 2.190 109 8.03 Deep Water Antarctic 2.390 2