Salinity. See Appendix 1 of textbook x10 3 = See Appendix 1 of textbook

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1 Length Area Volume m m m foot = 0.305m yard = 0.91m square feet ~0.09m2 US pint ~ 0.47 L fl. oz. ~0.02 L Speed m/s mph Acceleration m/s mph/s Weight kg, gram pound ~0.45kg Temperature o o See Appendix 1 of textbook ,000,000,000 giga billion 1,000,000 mega million 1,000 kilo thousand 10 deka ten deci tenth milli thousandth ,001 micro millionth ,000,001 nano billionth 1.000x10 3 = 1000 See Appendix 1 of textbook Salinity

2 A few definitions Element Compound Ion Basic building block e.g., H, Na, Cl, O Combination of elements e.g., NaCl, CO Any element or compound with a charge e.g., Na Water: a powerful solvent Water is a polarized molecule (+ and - ends) Where is all Earth s water?

3 Where is all Earth s water? % of total Cubic miles Oceans million Ice cap & glaciers million Groundwater million Lakes ,000 Soils ,000 Atmosphere (vapor) ,000 Rivers Biosphere Salinity defined Salinity is the total quantity of dissolved inorganic solids (salts) in water In the ocean: 32 to 39 g/kg In rivers: approximately 0.1 g/kg! Composition of seawater Typically 35 grams of inorganic salt per liter of water Water Chemicals (salt)

4 At a salinity of 35 g/kg Six ions make up 99.8% of dissolved chemicals Known as the Major Ions Cl Na SO Mg Ca K g/kg Chloride Sodium Sulphate Magnesium Calcium Potassium ClNa+ K SO Ca Mg At a salinity of 35 g/kg In terms of number of atoms per kg of seawater Mole Cl Chloride 1.13 Na Sodium 0.98 SO Sulphate 0.06 Mg Magnesium 0.11 Ca Calcium 0.02 K Potassium 0.02 ClNa+ K Ca (one mole = 6x1023 atoms) Mg SO Surface salinity World Ocean Atlas (2005) 33.0

5 Principle of Constant Proportions Regardless of how the salinity varies from place to place, the ratios between the amounts of the six major ions (Cl -, Na +, SO4 2-, Mg +, Ca +, K + ) in the open ocean are nearly constant.! Principle of Constant Proportions For example } Everywhere! Cl [g/kg] =! Na [g/kg] =1.796 in the ocean open (excluding near rivers or local sources) The salinity can change by rainfall or evaporation, but the major ions will all change their concentrations together. Minor Ions Non-uniform distributions HCO Bicarbonate g/kg Br Bromide g/kg Sr Strontium g/kg H Borate g/kg F Fluoride g/kg Nutrients Other SiO Silica Cd Cadmium PO Phosphate 3 Tritium NO Nitrate

6 Know that Ratio of major ions is uniform everywhere in the open ocean Minor ions have non-uniform distributions Why the difference? Hydrological (water) cycle Evaporation 7 Units are L/yr 4 Rivers 11 Precipitation Volume of the ocean = 140,000 x L Hydrothermal iclicker Question The volume of the ocean is 1.4x10 21 liters, and the volume flowing into the ocean from rivers is 4x10 16 liters per year, how long would it take to fill the ocean from rivers input alone? a) 300 years b) 5,000 years c) 30,000 years d) 500,000 years e) More

7 Time it takes to fill the ocean from Rivers: 36,000 years Direct rain: 3,600 years Hydrothermal vents: 8,000,000 years Evaporation 7 11 Precipitation Rivers Units are L/yr Volume of the ocean = 1.4 x L Hydrothermal The volume of the ocean is 1.4x10 21 liters, and the volume flowing into the ocean from rivers is 4x10 16 liters per year. time to fill ocean = volume [m3 ] rate [m 3 /yr] = 14 4 = (20 16) = = 30, 000 Hypothesis: The ocean is salty because rivers carry dissolved salts, weathered from rocks on land, in to the ocean. The water then evaporates, leaving the salts behind. Test: Compare the salts in seawater with those delivered by rivers.

8 Different composition Seawater River water Concentration [mg/l] 20,000 15,000 10,000 5,000 0 Cl- Cl- K+ Na + SO 2-4 Mg 2+ Ca+ HCO 3 - SiO 2 Concentration [mg/l] So river input isn t the whole story K+ Na + SO 2-4 Mg 2+ Ca+ HCO 3 - SiO 2 Excess volatiles Components of seawater not accounted for by rivers are called excess volatiles Kilauea Volcano, courtesy Hawaii Volcano Observatory, USGS The Chloride comes from volcanism. HCl is an important part of volcanic gases. Is the ocean getting saltier? No. The ocean is in steady state, meaning over long periods stuff in equals stuff out River Flow In Flow Out Lake River

9 Residence time Residence time is the average length of time an element spends in the ocean. Residence time [yr] = Amount of element in ocean [kg] Amount of element being added or removed from ocean [kg/yr] Ocean residence times Chloride Cl 100 million years Sodium Na 68 million years Magnesium Mg 10 million years Sulphate SO 10 million years Potassium K 7 million years Calcium Ca 1 million years Bicarbonate HCO 110,000 years Aluminum Al 600 years Iron Fe 200 years Elements with long residence times:! Have a long time to accumulate in the oceans Concentrations can increase Undergo large number of stirring cycles Are well mixed Elements with short residence times: Are removed quickly Do not have time to build up concentration Not well mixed

10 Hydrothermal vents are places where high temperature water comes into the ocean. are generally found on tectonic plate boundaries that are spreading apart. Hydrothermal vents Black Smokers Water can be up to 380 o C in a Black Smoker.

11 First found in 1977 on Galapagos spreading center. Vents are often found visually using deep diving submarines, the limited visibility makes them hard to find. Alvin Some key ideas Water is a polar molecule with the remarkable ability to dissolve more substances than any other natural solvent.! Salinity is the measure of dissolved inorganic solids in water (grams of salt per kilogram of seawater).! There are six major ions that account for 99.8% of dissolved chemicals in seawater. (Hint know these).! The Principal of Constant Proportions. Why does it applies to the major ions but not to others? How does Residence Times relate to the Principal of Constant Proportions?! Where does the salt in the ocean come from?! Hydrothermal vents inject high temperature water that has been cycled though the Earth s mantle. They are normally found on tectonic plate boundaries.