2 Chapter ObjectivesI will:Compare and contrast the physical and chemical properties of seawater.Explain ocean layering.Describe the formation of deep water masses.
3 Seawater is a solution Solution is a homogeneous mixture 96.5% water 3.5% dissolved salts.Most abundant salt is (NaCl)Other salts: elementschlorides & sulfates of magnesiumPotassiumCalcium
4 Salinity Measure of the amount of dissolved salts in seawater. Expressed in grams of salt per kilogram of water or parts per thousand (ppt)Total salt in seawater: avg 35 ppt or 3.5%
5 Seawater compositionSalt Ions (ion is an atom that gains or loses an electron)Dissolved gases (oxygen, nitrogen, carbon dioxideDissolved nutrients (nitrates, phosphates, silicates)These nutrientsand gases greatlyaffect life in theoceans.
7 Variations in Salinity High salinity- areas with high rates of evaporation.Low salinity – areas where rivers empty into oceans.
8 Sources of Sea SaltSalinity of ancient seas not much different than today.Magnesium in calcium-carbonate shells of marine organisms.Volcanoes- water vapor, gases (chlorine and sulfur dioxide)Weathering of Feldspar - Na, Ca, KWeathering of mineral and rocks - Fe, MgThese ions are flushed into rivers andtransported in the oceans!
9 Removal of Sea SaltsSalinity does not increase although salt ions continuously are added to seawater.WHY? Salts are removed at same rate as addedProcess to remove salts:Precipitate – forms depositsMarine Organisms- tobuild their shells, bones,teeth.Organism die – solid partsdrift to the ocean floor
11 Physical Properties of Seawater Density - Salt ions are heavier than water moleculesTemperatureSalinityAbsorption of Light
12 Seawater vs. Freshwater More denserDensity 1.02 g/cm3 to 1.03 g/cm3This density affects oceanic processesFreezing point -20CFRESHWATER:Less denserMax density 1.oo g/cm3Freezing point 00CCalculation:d= m/V
13 Absorption of Light Water absorbs light Light penetrates only upper 100m of seawaterBelow is darknessPhotosynthesis exists top 100m
14 Ocean Layers – caused by density differences Warm, sunlitRapid temp. decreaseCold, dark, freezing temps.
15 Where does all the cold water come from? Polar seasCold temp. causes seawater to become more denseSeawater freezes, sea ice formsSalt ions form beneath the iceSaltwater sinks, it migrates toward equator as cold, deep water mass
16 Deep Water MassesAntarctic Bottom Water – forms when sea freezes – below 00CNorth Atlantic Deep Water –forms off the shore of GreenlandAntarctic Intermediate Water -least dense