HPU NCS2200 Oceans and estuaries


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HPU NCS2200 Earth science for elementary education majors summer 2014 online class oceans and esutaries

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HPU NCS2200 Oceans and estuaries

  1. 1. Chapter 16 – Oceans & Coastlines Earth Science and the Environment (4th ed) Thompson & Turk
  2. 2. 16.1 Geography of oceans ►Oceans are all connected  So really just 1 big ocean! ►5 ocean basins  Atlantic  Pacific  Arctic  Antarctic  Indian
  3. 3. Fig. 16.1, p.400
  4. 4. 16.2 Seawater ►Salinity – total amount of dissolved salts expressed as a percentage  Six main ions: Cl, Na, Mg, SO4, Ca, K  Also contains gases; CO2 & O2 mainly ►Gases in equilibrium w/atmosphere  Salinity not uniform ►Average is 3.5% (35 parts per 1000)
  5. 5. Fig. 16.3, p.401
  6. 6. What Affects Salinity? ►Salinity INCREASES:  Volume of water decreases ►Evaporation & freezing ►Salinity DECREASES  Volume of water increases ►Precipitation & melting ►Saltiest water  Cold arctic/antarctic waters  Warm subtropical waters
  7. 7. Fig. 16.4, p.402
  8. 8. 16.2 Seawater ►Temperature in oceans is layered  Warm surface – 450m  Thermocline – next 2 km, temperature drops off rapidly with depth  Cold deep layer – below thermocline and extends to poles, 1oC to 2.5oC
  9. 9. Fig. 16.5, p.402
  10. 10. Density of ocean water ► D = M/V ► Temperature affects volume  As temperature goes up volume goes up and thus density goes DOWN  As temperature goes down volume goes down and density goes UP ► Salinity affects mass  As salinity goes up density goes UP  As salinity goes down density goes DOWN ► Therefore  Most dense water is Salty and cold  Least dense water is warm and less salty
  11. 11. 16.6 Ocean currents ►Current – continuous flow of water in a given direction ►Surface currents – wind-driven flow in the top 400m of seas  Commonly used to aid ocean transport ►Gulf Stream – 80km wide by 650m deep, 5km velocity (at fastest)  Westerlies and trade winds produce gyres – broad loop currents
  12. 12. Fig. 16.14, p.407
  13. 13. Fig. 16.13, p.407
  14. 14. 16.6 Ocean currents  Coriolis effect – objects moving in a fluid are curved due to earth’s rotation.  Eckman transport – another “twist” imparted to currents due to constant Coriolis and decreasing wind effects, with depth
  15. 15. Fig. 16.15, p.408
  16. 16. 16.6 Ocean currents  Deep-sea currents – move both vertically and horizontally ►Thermohaline circulation – vertical currents caused by density differentials  Cooling – cold water is more dense than warm  Salinity – more salt = denser water ►Surface currents change in both temperature and salinity as they move ►Water takes 500 – 2,000 years to make a vertical loop  Deep current flow is responsible for the exchange of heat energy around the globe.
  17. 17. Fig. 16.12, p.406
  18. 18. 16.6 Ocean currents ►Upwelling – upward flow  in response to water sinking elsewhere  Winds blowing offshore or along shore can cause upwelling ►Brings cold water up ►Also brings nutrients up ►Exchanges gases with the atmoshere ►Redistributes heat  Weak Coriolis force at low latitudes causes equatorial upwelling
  19. 19. Fig. 16.16, p.409
  20. 20. Estuaries ► enclosed body of water formed where freshwater from rivers and streams flows into the ocean, mixing with the salty sea water ► places of transition from land to sea, and from fresh to salt water ► influenced by the tides, but protected from the full force of ocean waves, winds, and storms by the reefs, barrier islands, or fingers of land, mud, or sand that define an estuary's seaward boundary
  21. 21. Estuaries ►Subdivided into three types based upon the relative importance of river inflow and tidal mixing.  Salt-wedge estuaries are dominated by the outflow from rivers.  Partially-mixed estuaries are dominated by neither river inflow nor tidal mixing.  In well-mixed estuaries tidal turbulence destroys the halocline and water stratification.
  22. 22. Estuaries ► Estuaries are extremely fertile because nutrients are brought in by rivers and recycled from the bottom because of the turbulence. ► Stressful conditions and abundant nutrients result in low species diversity, but great abundance of the species present. ► Despite abundance of nutrients, phytoplankton blooms are irregular and the base of the food chain is detritus washed in from adjacent salt marshes.
  23. 23. Functions of Estuaries ► Estuaries are sometimes called “marine nurseries”  habitats for many juvenile organisms, especially for fishes  many fish are born and grow up in estuaries  migrate to the open ocean ► Wildlife Habitat ► Recreation
  24. 24. NC Coast to Sea ►Rivers and streams flow to sea ►Empty into bays, estuaries and sounds ►Sometimes protected by barrier islands ►Coastal areas are vulnerable
  25. 25. 16.9 Beaches ►Development along sandy shores  Beachfront property & barrier islands are “hot property” ►Many resorts, hotels, etc. built in these areas  Problems with beach development ►Erosion of the coast ►Sea level rise ►pollution
  26. 26. Fig. 16.22, p.413
  27. 27. Fig. 16.31, p.419
  28. 28. 16.8 Emergent and submergent coastlines ►Factor affecting sea-level  Tectonic processes  Isostatic adjustment  Eustatic sea-level change ►Growth or melting of glaciers ►Changes in water temperature  Changes water volume via thermal expansion/contraction ►Changes in volumes of mid-ocean ridges  Rapid spreading creates a higher ridge zone, displacing more water