Present ocean circulation
47
2.5. Exercises on chapter 2
(2.1) Wind stress
The average windspeed over the region of the Antarctic Circumpolar Current
is about 10 ms −1 .
a. Give an estimate of the mean wind-stress at the ocean-atmosphere interface
in this region.
b. If a unidirectional wind blows over an initially motionless water column of
10 m thickness, then calculate the flow velocity in this layer after 3 hours.
(2.2) Heat flux
Consider a layer of seawater (heat capacity C p =4 .2 × 10 3 Jkg −1 K −1 ,
density ρ =1 .027 × 10 3 kgm −3 ) with a thickness of 1 m and an area of 10 4
m 2 .
a. Determine how much energy is needed to raise the temperature of the water
by 1 ◦ C.
Assume that a constant heat flux Q = 400 Wm −2 is applied over the area, for
example due to a warmer atmosphere.
b. How long does it take before the temperature of the water layer has
increased by 1 ◦ C?
During a seasonal cycle, there is heat uptake in an ocean region whereas
during the winter the opposite occurs.
c. Assume that the upper 100 m of ocean water is in contact with the
atmosphere and that the seasonal temperature change in the water is about
10 ◦ C. Calculate the amount of energy which is stored (released) by the water
layer.
d. Determine the same quantity for a land surface and a seasonal temperature
change of about 20 ◦ C.
47
2.5. Exercises on chapter 2
(2.1) Wind stress
The average windspeed over the region of the Antarctic Circumpolar Current
is about 10 ms −1 .
a. Give an estimate of the mean wind-stress at the ocean-atmosphere interface
in this region.
b. If a unidirectional wind blows over an initially motionless water column of
10 m thickness, then calculate the flow velocity in this layer after 3 hours.
(2.2) Heat flux
Consider a layer of seawater (heat capacity C p =4 .2 × 10 3 Jkg −1 K −1 ,
density ρ =1 .027 × 10 3 kgm −3 ) with a thickness of 1 m and an area of 10 4
m 2 .
a. Determine how much energy is needed to raise the temperature of the water
by 1 ◦ C.
Assume that a constant heat flux Q = 400 Wm −2 is applied over the area, for
example due to a warmer atmosphere.
b. How long does it take before the temperature of the water layer has
increased by 1 ◦ C?
During a seasonal cycle, there is heat uptake in an ocean region whereas
during the winter the opposite occurs.
c. Assume that the upper 100 m of ocean water is in contact with the
atmosphere and that the seasonal temperature change in the water is about
10 ◦ C. Calculate the amount of energy which is stored (released) by the water
layer.
d. Determine the same quantity for a land surface and a seasonal temperature
change of about 20 ◦ C.