Salt:sodium chloride Salts exist as ions in seawater

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Fig. 6.16 Total Dissolved Inorganic Carbon • Dissolved CO 2 in seawater is present in small amounts since it rapidly dissociates to HCO 3- and CO 3 2- • Thus, the carbonate system in seawater is dominated by HCO 3- along with some CO 2- 3 (H 2 CO 3 is always very low) • The equilibrium between dissolved CO 2 , HCO 3- and CO 3 2- provides a buffer against sudden or large changes in pH • However, the pH level itself depends on the concentration of CO 2 (e.g., higher CO 2 , lower pH and vice-versa) 50 51 Increasing Acidity with Depth • Surface waters have a pH of 8.2 to 8.5 due to CO 2 draw-down by photosynthesis and/or warmer surface waters holding less CO 2 • The more alkaline condition allows the release of carbonate ions, which then bond with calcium ions to form calcium carbonate tests • Deep waters have low pH, high CO 2 , thus the more acidic conditions results in calcium carbonate dissolution Increasing Ocean Acidity Increases in anthropogenic CO 2 in atmosphere will lead to increases in ocean CO 2 decreases in pH increases in acidity CCD will rise towards the surface 52 53 IPCC, 2007 WG1 Report Chapter 5 29N, 15W Figure 5.9 Anthropogenic CO 2 23N, 158W 31N, 64W 0.1 pH ~30% change in [H + ] 54 55 8
Ocean Acidification 1700s to present day Most important sources of CO 2 in Seawater • Direct transfer of the gas from the atmosphere • Respiration i of marine organisms • Oxidation of organic matter 56 57 Other components of seawater ∗ Nutrients for growth Nutrients • Nutrients are ions required for phytoplankton growth: Nitrate, NO - 3 Phosphate, PO 3- 4 Silicate, SiO 4 4- • Brought to the sea by rivers & land runoff • Present in very low concentrations (usually reported as ppb) 58 59 Due to the Biological Pump: • Nitrate, phosphate & iron are bio-limiting nutrients in the surface mixed layer • Decomposition of organic matter below the surface mixed layer consumes O 2 and releases nutrients • Nutrients and carbon rich waters are returned to the surface by the global ocean circulation (e.g., upwelling) 62 Man and salt ∗ Making salt ∗ Making freshwater from seawater 63 9
Page 1 and 2: Chemistry of Seawater OCEA 101 •
Page 3 and 4: ∗ Polar‐low evaporation, low pr
Page 5 and 6: Ocean’s Residence Time RT = Reser
Page 7: The Marine Biological Pump 44 45 Th

Salt:sodium chloride Salts exist as ions in seawater

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