week 6 - ocean circulation

Question 1

three types of water masses with different densities

Answer 1

1. stable
2. unstable
3. neutral

Question 2

stable water mass

Answer 2

low density on top, high density on the bottom
- mixing is inhibited

Question 3

unstable water mass

Answer 3

high density on top, low density on bottom
- mixing is spontaneous

Question 4

neutral water mass

Answer 4

density is medium/same on the top and bottom
- mixing is easy

Question 5

thermocline

Answer 5

a region of rapid temperature change
- separates the top mixed layer (turbulent) from the bottom deep water (calm)

Question 6

pyconocline

Answer 6

rapid change in density

Question 7

where is heat greater?

Answer 7

at lower latitudes
-because of this, winds are generated to restore equilibrium
- warm air rises near the equator and travels toward the poles (deflected by coriolis effect)

Question 8

coriolis effect

Answer 8

things moving in the northern hemisphere appear to be deflected to the right, and to the left on the southern hemisphere

Question 9

major winds

Answer 9

1. westerlies
2. trade winds

Question 10

ekman transport

Answer 10

the net motion of water at a 90 degree angle to the prevailing wind direction

Question 11

what causes coastal upwelling on the southern hemisphere and downwelling on the northern hemisphere?

Answer 11

southerly winds parallel to the coast (winds coming from the south)

Question 12

what causes coastal upwelling on the northern hemisphere and downwelling on the southern hemisphere?

Answer 12

northerly winds parallel to the coast (winds coming from the north)

Question 13

equatorial divergence

Answer 13

winds moving toward each other deflect the water away from each other (45 degrees)
- happens at the equator
- causes upwelling (ekman suction)

Question 14

upwelling

Answer 14

bringing water from the deep to the surface while surface water is being moved away due to the wind

Question 15

subtropical convergence

Answer 15

when winds are going in the opposite direction, the water moves toward each other (ekman pumping)
- westerlies and trade winds
- causes downwelling

Question 16

downwelling

Answer 16

because water cannot pile on top of itself, it is forced to go downward, creating downwelling

Question 17

basics of subtropical gyres

Answer 17

1. happens at the equator
2. coastal winds go north with deflection and westerlies deflect water to the right
3. all deflected water points to the same center, which creates a mound of water and high pressure
4. because everything is deflected to the right, it creates a circle
5. creates a pressure gradient force with high pressure on the inside and low pressure on the outside

clockwise on the north, counterclockwise on the south

Question 18

four components of subtropical gyres

Answer 18

1. equatorial current driven by tradewinds
2. western boundary current (hot) deflected
3. west wind drift driven by westerlies
4. eastern boundary current (cold) deflected

Question 19

5 major ocean gyres

Answer 19

1. indian ocean gyre
2. north pacific gyre
3. south pacific gyre
4. north atlantic gyre
5. south atlantic gyre

Question 20

basics of deep currents (6 things)

Answer 20

1. driven by bouyancy (density) forces
   - gravity is the driving force
2. also known as thermohaline circulation
   thermo = heat, haline = salt
3. both of these affect density
4. flow is much slower than surface currents (1000 years for deep water to circulate)
5. formation of deep water is due to evaporation and formation of sea ice
   - makes the water more dense and thus sinks to the bottom

Question 21

two places of deep water formation

Answer 21

1. north atlantic deep water (NADW)
   - forms near greenland; evaporation and cooling causes surface water to sink and flow south
2. anarctic bottom water (AABW)
   - densest deep water
   - cold, dense water from sea ice formation in the weddell sea sinks and mixes with NADW form AABW

Question 22

how can water masses be distinguished?

Answer 22

by their temperatures and salinities

Question 23

what are surface currents driven by?

Answer 23

winds

Question 24

what is deep ocean circulation driven by?

Answer 24

gravity