Lecture 10- Ocean Circulation 2

Question 1

vertical distribution of seawater density

Answer 1

directly influences the vertical movement of water in the ocean

Question 2

What determines seawater density and ocean salinity?

Answer 2

• salt concentration

- water temperature

Question 3

surface ocean temperature

Answer 3

• determined by the exchange of heat between the ocean surface and atmosphere
• measure of the heat energy contained in the ocean

Question 4

when more energy enters than leaves the ocean surface (spring/summer)

Answer 4

ocean surface warms

Question 5

when more energy leaves than enters the ocean surface (winter)

Answer 5

ocean surface cools

Question 6

What is the dominant method of heat loss?

Answer 6

evaporative cooling

Question 7

depth of light/energy penetration into surface ocean

Answer 7

relatively shallow

Question 8

depth of light/energy penetration for clearest open waters

Answer 8

150 to 200 meters

Question 9

depth of light/energy penetration for turbid coastal waters

Answer 9

50 meters

Question 10

typical vertical profile of temperature

Answer 10

• all direct solar heating takes place near the ocean surface (0-30 meters)
• seawater below 500 meters is uniformly cold

Question 11

permanent thermocline

Answer 11

the broad region at 500 meters where the seawater temperature changes from warm to uniformly cold

Question 12

seasonal thermocline

Answer 12

• temporary thermocline

- shallower thermocline only forms in the summer and is erased in the winter

Question 13

typically vertical density profile

Answer 13

less dense water “floats” above more dense water

Question 14

seasonal pycnocline

Answer 14

• region of strong change in density with depth
• net heat gains in the spring and summer
• net heat losses in the fall and winter

Question 15

permanent pycnocline

Answer 15

• remains in place at around 500 meters
• result of the long-term balance between the downward heating/mixing at the surface and upward mixing of cold water from below

Question 16

Why is the ocean more shallow in the summer?

Answer 16

heating the water makes it more buoyant so it’s harder for the wind to push it down

Question 17

location of subpolar gyres

Answer 17

north

Question 18

location of subtropical gyres

Answer 18

south

Question 19

What describes how the wind drives the surface ocean currents of very large subtropical gyres?

Answer 19

• Ekman transport

- geostrophic currents

Question 20

What causes Ekman transport?

Answer 20

• wind force
• friction force
• Coriolis force

Question 21

Ekman transport

Answer 21

• rate of total water transported in Ekman layer

- exactly 90 degrees from the wind direction

Question 22

How thick is the Ekman layer?

Answer 22

50 to 100 meters

Question 23

geostrophic balance

Answer 23

point at which currents move with steady speed with Coriolis and pressure gradient forces in perfect opposition

Question 24

geostrophic current

Answer 24

resulting current from geostrophic balance

Question 25

fully developed currents

Answer 25

move along lines of constant pressure

Question 26

What drives the Ekman layer to the center of the gyre to create a mount of surface water?

Answer 26

westerly and trade winds

Question 27

Coriolis force

Answer 27

always points toward the center of high pressure in the northern hemisphere and requires concentric CW motion

Question 28

western boundary currents

Answer 28

• currents on the western side of subtropical gyres

- swift and narrow jets that bring warm water from the tropics to high latitudes

Question 29

eastern boundary currents

Answer 29

• currents on eastern side of subtropical gyres
• broad and slow
• bring cold water from the high latitudes to the tropics

Question 30

gyres are indirect results from

Answer 30

winds