15 – 2 Sea water15 – 2 Sea water

Chemical Properties of Sea Chemical Properties of Sea WaterWater

• Sea water is 96.5% water, 3.5% saltsSea water is 96.5% water, 3.5% salts

• Salinity:Salinity:– Measures the amount of dissolved salts in sea waterMeasures the amount of dissolved salts in sea water– Expressed in ppt (parts per thousand) Expressed in ppt (parts per thousand) – 35 ppt = 3.5%35 ppt = 3.5%– Most abundant salt in the ocean is sodium chloride Most abundant salt in the ocean is sodium chloride

(NaCl)(NaCl)

– Others include magnesium sulfate (MgSOOthers include magnesium sulfate (MgSO44) and ) and Calcium Chloride (CaClCalcium Chloride (CaCl22))

Salinity VariationsSalinity Variations• Actual salinities vary from place to placeActual salinities vary from place to place

• Regions of high evaporation have greater Regions of high evaporation have greater salinitysalinity– 37-38 ppt37-38 ppt

• Regions of low evaporation have lower Regions of low evaporation have lower salinitysalinity– 32-33 ppt32-33 ppt

Salinity SourcesSalinity Sources• Salinity not much different then years agoSalinity not much different then years ago

• Evaporation leaves salt behindEvaporation leaves salt behind

• Calcium shells of marine organisms Calcium shells of marine organisms dissolvedissolve

• Weathering of rocks produces salinityWeathering of rocks produces salinity

Removal of SaltsRemoval of Salts

• Small salty spray droplets from breaking waves Small salty spray droplets from breaking waves are picked up by wind and deposited on landare picked up by wind and deposited on land

• Marine organisms remove the ions to make their Marine organisms remove the ions to make their shellsshells

Physical Properties of Sea Physical Properties of Sea WaterWater• Denser than fresh waterDenser than fresh water

– Salt ions heavier than water moleculesSalt ions heavier than water molecules

• Freezing point is lowerFreezing point is lower– Salt lowers Freezing point (about -2Salt lowers Freezing point (about -2ooC)C)

Physical PropertiesPhysical Properties

• Water Absorbs light:Water Absorbs light:– Water is clear but gets Water is clear but gets

dark going downdark going down• Which color travels Which color travels

furthest?furthest?

– Light only penetrates Light only penetrates water in first 100 m downwater in first 100 m down• Photosynthesis only good at Photosynthesis only good at

toptop

•

Ocean LayeringOcean Layering

• Surface Temps. -2Surface Temps. -2ooC – 30C – 30ooCC

• Layers due to density differenceLayers due to density difference

• Temps decrease with depthsTemps decrease with depths– Surface (0-100 m ) relatively warmSurface (0-100 m ) relatively warm– Thermocline: rapid decrease in Thermocline: rapid decrease in

Temp.Temp.– Bottom Cold Temps near freezing Bottom Cold Temps near freezing

(4 (4 ooC) C)