Presentation on theme: "Physical and Chemical Oceanography"— Presentation transcript:
1 Physical and Chemical Oceanography Section 7 Part I: CHEMICAL COMPOSITIONExcellent Site for Review!
2 Salinity salt concentration in parts per thousand (ppt) Variance: ocean average: 35 ppt (35%)Variance:Sea diluted with freshwater by:RiverMelting glaciers
3 From Section 4 Nutrient Cycles Chemical Compositionfairly constant for millions of yearsSalinityMainly: sodium, chloride ionsSmaller: sulphate, magnesium, hydrogencarbonate, potassiumFrom Section 4 Nutrient Cycles
4 Chemical Composition local changes can occur Volcanic activity Runoff Atmospheric dissolution
5 1. Volcanic ActivityGases: CO2, Sulphur dioxide, hydrogen sulphide, hydrogen chloridedissolve in atmospheric H2Oenter sea by precipitationSubmerged volcanoes at plate boundaries emit gases (chlorine)Major source of chloride ions in sea
6 2. Runoff Flow of water from land Rain, melted snow & ice Drains to oceans directlyor from riversPasses through soilUrban runoff into drains
7 2. RunoffPicks up pollutants – pesticides, fertilizers and oil-derived substancesfood chains and webs increasing concentration at each trophic levelExample: industrial wastewater with mercuryMinamata BayShellfish & organismsHuman consumption – neurological disorders, paralysis and death
9 3. Atmospheric Dissolution Dissolved gases:Nitrogen (N)nitrogen-fixing microorganisms make products for other organismsCarbon Dioxide (CO2)PhotosynthesisOxygen (O)RespirationGases dissolved are at equilibrium with atmosphereConcentration of it depends on relative solubility, temperature and salinity of sea
10 Salinity Evaporation – salt stays behind hydrometer Hypersaline (increased amount of salt)Ex: lagoon – high temp. EvaporationEx: Dead Sea – extremeAccumulation of solutes10x saltier than ocean
12 Density temperature salinity Warm on top of cold, dense water Temperature gradient
13 Density If temp. abruptly as depth = thermocline Ocean surface 25 ⁰ C Shallow layer of warm on deep layer of coldOcean surface25 ⁰ C2000 m deep1⁰Cdepthtemperature
14 Density salinity density halocline – abrupt change in salinity as depthLower salinity (lower density) on top of higher salinity (higher density)Mixing occurs by wind blowing at the surface down to ~200 mTurbulence and currentsTemperature changes
17 Dissolved Oxygen Temp of H2O O2 slightly less soluble in salt than freshTemp of H2ODissolved Oxygen Concentration Freshwater0⁰C14.6 mg/dm35⁰C12.8 mg/dm310⁰C11.3 mg/dm315⁰C10.2 mg/dm320⁰C9.2 mg/dm325⁰C8.4 mg/dm3What is the pattern?
18 D.O. surface layer = high d.o. D.O. removed by respiration of marine Can be supersaturated by 2 processes:Turbulence & mixing by waves causing atmospheric O2 to dissolvePhotosynthesis by algaeO2 as byproductD.O. removed byrespiration of marineorganisms