Salinity Evaporation Evaporation salt stays behind Hypersaline increased

Salinity - Evaporation • Evaporation – salt stays behind • Hypersaline (increased amount of salt) • Ex: lagoon – high temp. Evaporation • Ex: Dead Sea – extreme • Accumulation of solutes • 10 x saltier than ocean hydrometer

Salinity - Precipitation • Rain, snow • Dilutes sea water, decreases salinity • Estuaries • Melting glaciers

Salinity

Density • Warm on top of cold, dense water • Temperature gradient CONCENTRATION GRADIENTS: https: //ed. ted. com/lessons/the-motion-of-the-oceanthe-concentration-gradient-sasha-wright THERMOHALINE CIRCULATION: https: //www. youtube. com/watch? v=Lk. RQj. Td. Tv. FE THERMO HALINE Circulation • temperature • salinity

Density salinity density • halocline – abrupt salinity as depth change in • 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

Density • If temp. abruptly as depth = thermocline • Shallow layer of warm on deep layer of cold depth temperature • Ocean surface 25 ⁰ C • 2000 m deep 1⁰C

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

Dissolved Oxygen • O 2 slightly less soluble in salt than fresh Temp of H 2 O Dissolved Oxygen Concentration Freshwater 0⁰C 14. 6 mg/dm 3 5⁰C 12. 8 mg/dm 3 t a p he t is t ha 10⁰C 15⁰C n r e t W ? 11. 3 mg/dm 3 10. 2 mg/dm 3 20⁰C 9. 2 mg/dm 3 25⁰C 8. 4 mg/dm 3

D. O. • surface layer = high d. o. • Can be supersaturated by 2 processes: • Turbulence & mixing by waves causing atmospheric O 2 to dissolve • Photosynthesis by algae • O 2 as byproduct • D. O. removed by respiration of marine organisms

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