Oceans

• Ocean circulation balances

  • global heat budget
  • temperature
  • nutrients

  It generates cycles = glacials and interglacials
• Antarctic bottom water:

  • very cold
  • saline
  • very dense
  • forms polynyas
• Polynys

  • ice free area of sea
  • cools surface waters forming AABW
• NADW

  • in the labrador sea
  • less cold than AABW
  • more saline than AABW
  • forms in Nordic Sea
  • warm salty water from gulf stream as water cools and sinks
  • warm water continues to Fran Strait
• Lowest water densities are in the equatorial regions
• Isopynals is water density as a function of temperature and salinity
• Deep water sinking

  • causes a decerase in density
  • therefore previous deep water rises
• No deep water formation in the North Pacific
• Ocean common water = mixed water masses
• Deep water formation

  • surface water density increases
  • causing water to sink
• Surface ocean currents

  • wind driven
• Which way do ocean gyres rotate in the northern hemisphere?

  clockwise
• Ocean gyre:

  • large ciruclatory cell in the ocean
  • cuased by
  • trade winds
  • westerlies
• What does the Coriolis force affect?

  Non frictionally bound items
• What is the speed revolution of the Earth at the equator?

  1000 mph
• What is the speed revolution of the Earth at 60 degrees latitude?

  500 mph
• What is Ekman transport?

  rise of the ocean in the middle of ocean gyres
• What is Ekman transport caused by?

  Coriolis force in waters less than 100m deep
• What type of pressure can sea surface height variations generate?

  horizontal pressure gradient forces
• What is geostrophic flow?

  gradient induced pressure gradient force where water flows to create balance

  • increased height causes downwelling by dynamic toplogy
• Where is the highest point in the ocean gyre geographically?

  westwards intensification
• What does vertical ciruclation of diverging water?

  • downwelling
  • upwelling nutreint deep waters
• What does vertical circulation of converging water?

  • upwelling
  • low productivity as poor nutrient supply
• What are the two ocean mixing scales of diffusion?

  Molecular diffusion - cm scale

  Turbulent diffusion - m-100km
• Ocean mixing scales

  • driven by
  • wind
  • currents
  • irregular seabed
  • tide
• What are ocean mixing scales tracked by?

  fluorescent dyes
• Is horizontal mixing or vertical mixing more prevelent due to density?


  horizontal mixing
• Stratification is 2 or more layers with different densities that prevents mixing

  • inhibits vetical mixing
• What is primary production in stratification?

  Phytoplankton cycles in N Atlantic as stratification allows nutrients upwelling creating blooms
• What are the vertical changes in seawater density?

  colder = more dense

  increased salinity = more dense
• what is the net change in surface temperature below 30 degrees latitude?

  gain
• what is the net change in surface temperature above 30 degrees latitude?

  loss
• What are isotherms?

  lines joining points of equal temperature
• What are isohalines?

  lines joining points of equal salinity
• Which ocean is more saline: North Atlantic or North Pacific?

  North Atlantic
• Temperature depth profiles change in the mixed surface:

  • in mixed surface
  • little temperature variation
  • 10-300m
  • absorbs solar radiation
• How is heat trasnfered to the deeper ocean?

  Via a water column by turbulent mixing and downwelling
• What are the three thermocline levels and their latitudes?

  1. permanent thermocline - lower latitudes
  2. seasonal thermocline - mid latitues
  3. no thermocline - high latitudes
• How does salinity change with depth?

  Decrease salinity wiht depth at low and mid latitudes

  In the different sections of the ocean respond to salinity change:

  • surface = constant
  • Halocline = rapid change
  • Pycnocline = rapid density change
• Oceanic diffusion:

  • molecular diffusion
  • acts from motion of indicidual molecules
  • heat diffusion
  • 100 times faster than salinity