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Physical and Chemical Oceanography

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Presentation on theme: "Physical and Chemical Oceanography"— Presentation transcript:

1 Physical and Chemical Oceanography
Section 7 Part I: CHEMICAL COMPOSITION Excellent Site for Review!

2 Salinity salt concentration in parts per thousand (ppt) Variance:
ocean average: 35 ppt (35%) Variance: Sea diluted with freshwater by: River Melting glaciers

3 From Section 4 Nutrient Cycles
Chemical Composition fairly constant for millions of years Salinity Mainly: sodium, chloride ions Smaller: sulphate, magnesium, hydrogencarbonate, potassium From Section 4 Nutrient Cycles

4 Chemical Composition local changes can occur Volcanic activity Runoff
Atmospheric dissolution

5 1. Volcanic Activity Gases: CO2, Sulphur dioxide, hydrogen sulphide, hydrogen chloride dissolve in atmospheric H2O enter sea by precipitation Submerged 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 directly or from rivers Passes through soil Urban runoff into drains

7 2. Runoff Picks up pollutants – pesticides, fertilizers and oil-derived substances food chains and webs increasing concentration at each trophic level Example: industrial wastewater with mercury Minamata Bay Shellfish & organisms Human consumption – neurological disorders, paralysis and death


9 3. Atmospheric Dissolution
Dissolved gases: Nitrogen (N) nitrogen-fixing microorganisms make products for other organisms Carbon Dioxide (CO2) Photosynthesis Oxygen (O) Respiration Gases dissolved are at equilibrium with atmosphere Concentration 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. Evaporation Ex: Dead Sea – extreme Accumulation of solutes 10x saltier than ocean

11 Precipitation rain, snow Dilutes sea water, decreases salinity
Estuaries Melting glaciers

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 cold Ocean surface 25 ⁰ C 2000 m deep 1⁰C depth temperature

14 Density salinity density
halocline – abrupt change in salinity as depth Lower salinity (lower density) on top of higher salinity (higher density) Mixing occurs by wind blowing at the surface down to ~200 m Turbulence and currents Temperature changes


16 Dissolved Oxygen (DO) temperature Oxygen solubility General rule:

17 Dissolved Oxygen Temp of H2O
O2 slightly less soluble in salt than fresh Temp of H2O Dissolved Oxygen Concentration Freshwater 0⁰C 14.6 mg/dm3 5⁰C 12.8 mg/dm3 10⁰C 11.3 mg/dm3 15⁰C 10.2 mg/dm3 20⁰C 9.2 mg/dm3 25⁰C 8.4 mg/dm3 What 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 dissolve Photosynthesis by algae O2 as byproduct D.O. removed by respiration of marine organisms


20 D.O. decreases to minimum as depth increases
Increases again as depth increases Oxygen minimum layer – depth that concentration of DO is lowest Between 100m and 1000m

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