Ocean101-Ch06-Part3 - CHAPTER 6 WATER(Now let's make it...

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1 CHAPTER 6 - WATER (Now (Now let let’ s make it salty! s make it salty!) Outline Outline 1. 1. What What’ s in seawater? 2. 2. Salinity and solutions Salinity and solutions 3. 3. Salinity factors Salinity factors 4. 4. Dissolved gasses Dissolved gasses & the concept of pH pH 5. 5. Residence Residence time time 6. 6. Variations in surface seawater Variations in surface seawater 7. 7. S, T, P, and S, T, P, and ! ( (“ the clines the clines”) 1. 1. What What’ s in Seawater? (besides the water) Dissolved Dissolved “ salts salts” Dissolved gasses Organic molecules Suspended sediments Suspended sediments Seawater samples are often collected using a Nansen bottle bottle . The bottle is lowered to the depth at which the scientist wants to collect a water sample. Then a small weight is sent down the line. The weight hits a trigger, which causes the bottle to flip upside down and also close off at both ends. The sealed bottle is then hauled up to the surface. Nansen Bottle Seawater Sampling Seawater Sampling See Figs. 6.14&6.15 p. 132
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2 Dissolved Substances How are “salts” added to and removed from oceans? Added Added to oceans to oceans: River input (primarily) Circulation through mid-ocean ridges Volcanic eruptions Removed Removed from ocean water from ocean water: Salt spray Recycling through mid-ocean ridges Biogenic sediments (hard parts, fecal pellets) Evaporites, adsorption, precipitation See Fig. 6.13, p. 131 What What’ s in Seawater? s in Seawater? SALINITY (S) SALINITY (S) = Total amount (or concentration) of dissolved inorganic solids in the water Salinity can expressed as a percentage (%) If you had 100 pounds of seawater consisting of 96 pounds of water molecules and 4 pounds of dissolved salts, the salinity would be “4.0%” (Per cent means “parts out of 100 ”) More commonly, units are per mil per mil (aka parts per thousand ) (‰ or ppt ppt) If 1000 pounds of seawater has 960 pounds of water molecules + 40 pounds of dissolved salts " S = “40‰” Note that 40‰ = 4.0% , because 40 / 1000 = 4 / 100 What What’ s in Seawater? s in Seawater? Salinity varies from place to place and seasonally, but: “Average” seawater : S ! 35 35 ‰ (3.5%) Brackish (hyposaline): < 33 ‰ Hypersaline: > 38 ‰ “Average” river water : S ! 0.1 0.1 ‰ (0.01%)
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3 What What’ s in Seawater? s in Seawater? This may not seem like a lot, but there are enough salts in the oceans (50 million billion tons) to cover the planet with a layer of salts >150 meters (~50 stories) thick! What What’ s in Seawater? s in Seawater? Chlorinity Chlorinity = Total weight of just the chlorine, bromine, and iodine ions in the water Why measure chlorinity? The ratio of chlorinity to salinity is constant, so we can measure chlorinity (easier to do) and calculate salinity from it: * Salinity Salinity (‰) = 1.80655 x Chlorinity Chlorinity (‰) Evaporation Evaporation = “Should” just drive off H 2 O (but…) * Principle of constant proportions Principle of constant proportions (aka Forchhammer’s principle)
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