Surface currents - 6

Question 1

Why does equatorial low pressure occur?

Answer 1

• intense heating
• high moisture content
• rising air here

Question 2

Why does polar high pressure occur?

Answer 2

• cold, dry dense air sinking

- creates an area of divergence at the surface

Question 3

What is Coriolis deflection?

Answer 3

The apparent deflection of objects moving across Earth’s surface

Question 4

Where is the maximum rotational velocity of the earth?

Answer 4

At the equator

Question 5

Where is the minimum rotational velocity of the earth?

Answer 5

At the poles

Question 6

Why does a zonal wind system develop?

Answer 6

Due to unequal surface heating and Coriolis deflection

Question 7

What are the doldrums?

Answer 7

A belt around the earth near the equator with low pressure due to rising air here

Question 8

What are the horse latitudes?

Answer 8

Latitudes around 30º where cooler and dense air sinks

Question 9

What latitude does the Ferrel extend to?

Answer 9

30º to 50º

Question 10

What latitude does the polar cell extend to?

Answer 10

50º to 900

Question 11

What produces wind driven ocean currents?

Answer 11

Frictional interaction between wind and water

Question 12

How does the speed of the wind and the induced current differ?

Answer 12

The induced ocean current is about 3-4% of the velocity of the wind

Question 13

What are zonal wind flows?

Answer 13

Winds that move nearly parallel to latitude as a result of the Coriolis deflection

Question 14

What generates westward ocean currents?

Answer 14

Easterly trade winds

Question 15

What generates eastward ocean currents?

Answer 15

Westerly trade winds

Question 16

How are gyres created?

Answer 16

Westward and eastward driven ocean currents are deflected by continents, creating a circular flow around basins

Question 17

What height difference is observed over the ocean surface, from mounds to depressions?

Answer 17

1 metre

Question 18

How are ocean mounds formed?

Answer 18

Due to convergences where water sinks (downwelling)

Question 19

How are ocean depressions formed?

Answer 19

Due to divergences where water rises (upwelling)

Question 20

What is the Ekman Sprial?

Answer 20

The resultant pattern caused by changes in current direction and speed with depth

Question 21

What is Ekman transport?

Answer 21

The net transport of water by wind-induced motion. Net transport is perpendicular and to right in the northern hemisphere and perpendicular and the left in the southern hemisphere

Question 22

What effect does Ekman transport have at the coast?

Answer 22

Can induced upwelling or downwelling

Question 23

When is upwelling induced?

Answer 23

• When nearshore surface water is driven seaward

- When gyres diverge (Ekman divergence)

Question 24

When is downwelling induced?

Answer 24

• When nearshore surface water is driven landward

- When gyre converge (Ekman convergence)

Question 25

What is Langmuir circulation?

Answer 25

- Horizontal, helical motion of water - Created when wind blows more than 3.5ms-1 - Flows paralle to the generating wind - Creates alternate zones of convergence and divergence - Forms sea stripes (material that collects in bands parallel to wind direction)

Question 26

Where do ocean mounds form?

Answer 26

In the centre of gyres where Ekman transport of water convergences

Question 27

What is geostrophic current?

Answer 27

The circulation of water around ocean mounds due to a balance between pressure gradient force and Coriolis

Question 28

What way do gyres rotate in the N and S hemisphere?

Answer 28

Clockwise in the N hemisphere and Anticlockwise in the S hemisphere

Question 29

What are currents like along the western edge of basins?

Answer 29

Narrow, deep and swift (e.g. Gulf Stream)

Question 30

What are currents like along the eastern edge of basins?

Answer 30

Broad, shallow and slow (e.g. Canary current)

Question 31

What is western boundary intensification?

Answer 31

The geostrophic mound of water is deflected to the western part of the ocean basin because of the eastward rotation of the earth on its axis

Question 32

What % of currents are driven by winds? by density?

Answer 32

- 10% by winds | - 90% by density

Question 33

What is the Sargasso Sea?

Answer 33

Large lens of warm water that circulates clockwise around the North Atlantic gyre; it is separated from cold water below and to the sides by a strong thermocline

Question 34

What is a warm core ring?

Answer 34

A meander that has broken free from a gyre and encloses a mass of warm water

Question 35

What is a cold core ring?

Answer 35

A meander than has broken free from a gyre and encloses a mass of cold water

Question 36

How wide and deep are cold wand warm core rings?

Answer 36

100-300 km in diameter and 3 km, or less, thick

Question 37

How quickly do the cold and arm core rings rotate?

Answer 37

1 ms-1

Question 38

Typically, how many warm and cold rings are generated form the Gulf stream each year?

Answer 38

- 8 warm rings | - 10 cold rings

Question 39

What is the Sargasso Sea named after?

Answer 39

The brown sea weed, Sargassum, that is found there