9. Western Boundary

Question 1

Which are faster, narrower and deeper?
1. Western boundary currents of subtropical gyres
2. eastern boundary currents of subtropical gyres

Answer 1

West!

The apex (top of the hill) in the middle of the gyre is not actually in the middle, it’s shifted to the west. So western boundary currents are deeper, faster, and narrower

Question 2

Explain western intensification of gyres

Answer 2

1. Variation in Coriolis effect as one moves poleward (increase) (caused by earth’s rotation)
2. Water moving eastward (in the westerly winds band) is deflected more than water moving westward in the tradewind zone
3. westerly zone= the water is transported towards the gyre center over the entire ocean width
4. Trade wind zone= little deflection; flow pushes water to west side of the ocean
5. gyre center offset to the west
6. pressure gradient is larger on the west side (steeper slope) –> stronger geostrophic currents

Question 3

Because of western intensification, the pycnocline is also pushed down, meaning the boundary current is _____

Answer 3

deeper

Question 4

Western vs eastern boundary currents of sub-tropical gyres:

Answer 4

West:
- fast, narrow, deep

East:
- slow, wide, shallow

Question 5

Give 2 examples each of western currents and eastern currents

Answer 5

west:
- Gulf stream, Kuroshio current

East:
- California current, Canary current

Question 6

Front=

Answer 6

encounter of 2 water masses/ currents with distinct characteristics

Question 7

Meander=

Answer 7

snakelike bends in a current

Question 8

If a meander is tight enough, what happens? What does it form?

Answer 8

It pinches off to form an isolated ring= an EDDIE

Question 9

T/F

Eddies contain water that is either colder or warmer than the surrounding water

Answer 9

true

Question 10

Eddies that are warm core rings spin in which direction?

Cold core rings?

Answer 10

warm= clockwise

cold= counterclockwise

Question 11

Which typically last longer, warm or cold core rings?

Answer 11

Cold

Because they aren’t limited in area
- eg. warm core rings are limited to move between the gulf stream and land

Question 12

Explain size/ speed of eddies

Answer 12

Can reach 100-300km in diameter and go all the way to the seafloor

Rotating currents at their rims can be up to 90cm/second

Question 13

Why is the ITCZ not directly on the equator?

Answer 13

The position of the continents shifts it into the northern hemisphere

Question 14

There is a region of high ___ _____ near the doldrums, produced by the northward ekman transport just north of the equator

What does this set up?

Answer 14

sea surface

equatorial current system