February 6th lecture

Question 1

How does wind generate currents?

Answer 1

When wind blows on the surface of the ocean, energy is transferred to the surface water by friction, setting the surface layer in motion and generates currents and waves

Question 2

What is wind generation current dependent?

Answer 2

• The wind speed

- The water surface tension and roughness

Question 3

How much of wind energy is converted into the ocean as kinetic energy?

Answer 3

1-3%

Question 4

if the wind is 60km/hr how fast will the ocean current generated by it be?

Answer 4

1-2km/hr

Question 5

How can wind interact with water below the surface?

Answer 5

As the surface layer of the ocean flows, it interacts with the water below it and transfers energy down, through friction.

Question 6

With wind dirven currents, does the current speed remain constant with depth? why or why not?

Answer 6

It decreases as you get deeper into the ocean.

As each layer of the ocean interacts with the one below it, it transfers less and less kinetic energy through friction, thus the speed decreases as you get deeper in the ocean

Question 7

How deep do most wind driven currents reach?

Answer 7

Most of them reach only 100-200m deep

Question 8

Will a current stop when the wind stops? why or why not?

Answer 8

No the current will continue to flow as it has generated momentum

Question 9

Due to the friction between ocean layers being small, what effect does it have on the momentum of a current?

Answer 9

energy and momentum are also slowly dissipated and last longer periods of time.

Question 10

What does the wind to the topography of the ocean as it blows over it?

Answer 10

It slopes the ocean in the direction that the wind blows

Question 11

What effect does the slope caused by wind have on ocean currents?

Answer 11

although the slope is small ( only 10’s of cm ) over then entire ocean, it is enough to create a pressure gradient - with water going from high pressure to low pressure in an attempt to flatten out the ocean

Question 12

Once currents are set in motion, what two things affect them?

Answer 12

1. ) Coriolis effect

2. ) Coasts

Question 13

What is a Ekman spiral?

Answer 13

When wind energy is transported into the ocean, each layer as it is set in motion is affect less and less by the wind direction and more by the Coriolis, deflecting each layer of water more to the right than the one above it. leading to a complete 180 of the current direction in a spiral like pattern.

Question 14

What is more powerful, Ekman transport or wind currents

Answer 14

Ekman transport as it is controlled by the Coriolis effect.

Question 15

Under ideal conditions the surface layer of water is deflected how far to the right of the wind by ekman transport?

Answer 15

45 degrees

although in real life it is often less

Question 16

As you get deeper into a current, the speed decrease. What effect does that have on the deflection of the current?

Answer 16

it gets deflected less as you go deeper.

Question 17

What is the depth of frictional influence

Answer 17

The depth where the current is opposite to the wind, and the speed is roughly 4% of the surface speed.

Question 18

If we avarge out all the currents at different depths of a Ekman spiral, what would its deflection be? what is it called?

Answer 18

it is 90 degrees

this is called Ekman transport

Question 19

What conditions must be meet in order for the Ekman motion of the Ekman sprial to happen? (three things)

Answer 19

• The water column must be nearly uniform in density over the spiral
• The wind must have blown for at least 1-2 days
• If the water is too shallow, friction with the bottom stops the Establishment of the Ekman spiral