Salt:sodium chloride Salts exist as ions in seawater

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Sources & Salt Balance • Original sources include • Weathering of crustal & volcanic rock (most cations) • Gases from the mantle during earth’s formation (most anions) • Geological evidence indicates that oceanic salt composition has not changed for ~1.5 billion years. • This implies an equilibrium: Rate of salt addition = Rate 21 of salt removal Sources into and Sinks out of Ocean Land (via rivers) atmosphere OCEAN Ocean is in “Steady State” or “Dynamic Equilibrium”: Chemistry of ocean is not changing Input fluxes = Output fluxes OR Sources = Sinks hydrothermal Sediments Organisms create material that is buried 22 in sediments = Primary way that dissolved constituents are removed from ocean Sources and Sinks of Salt Ions Spreading centers and vents are sources and sinks Residence Time-how long do water and elements remain in ocean? Total Fluxes In Fluxes are in units of amount per time (e.g. grams/year) Inventory is total amount (e.g. grams) Inventory (total amount in ocean) Residence time = Inventory / Flux In The average amount of time a given constituent spends in the ocean Concentration of ions in excrement, shells, skeletons Loss to sediments 23 Ions adhere to particles such as clays (from dust) and fecal pellets Total Fluxes Out Or, the approximate time it takes for the concentration of a constituent to significantly 25 change H 2 O Bathtub analogy Turnover time = time to fill or time to drain Volume/Input Rate Volume/Output Rate Units Liters/(grams/Year) Units are in Years for Turnover time Evaporation 26 27 4
Ocean’s Residence Time RT = Reservoirs / Fluxes 28 yr -1 = 1400 x 10 6 km 3 / 434 km 3 = 3226 years -OR- RT = 4000 m / 1 m yr -1 29 = 4000 years (Back-of-the-envelope calculation, assuming a 1 m/yr surface evaporation rate over an average ocean water depth of 4000m) ∗ Do all components of seawater have the same residence time? ∗ Do ions have the same residence time as water? Why or why not? Conservative Non conservative 30 31 Summary of residence time ∗ Average length of time a molecule remains in reservoir‐or how long it takes for concentration to change ∗ Different sources and sinks mean different turnover times for different constituents ∗ What iare conservative and non‐conservative components? ∗ How do you calculate residence time? 33 Gases in Sea Water • Gas exchange occurs at the air-sea interface • Biological processes influence gas concentration below surface • Maximum amount of gas that can be held in solution is the saturation concentration • Depends on T, S and p • Increases at lower T, S and/or higher p • Thus, increases in cold, deep waters, or in cold surface waters at high latitudes 34 5
Page 1 and 2: Chemistry of Seawater OCEA 101 •
Page 3: ∗ Polar‐low evaporation, low pr
Page 7 and 8: The Marine Biological Pump 44 45 Th
Page 9 and 10: Ocean Acidification 1700s to presen

Salt:sodium chloride Salts exist as ions in seawater

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