Lecture 10- Ocean Circulation 2 Flashcards
(30 cards)
vertical distribution of seawater density
directly influences the vertical movement of water in the ocean
What determines seawater density and ocean salinity?
- salt concentration
- water temperature
surface ocean temperature
- determined by the exchange of heat between the ocean surface and atmosphere
- measure of the heat energy contained in the ocean
when more energy enters than leaves the ocean surface (spring/summer)
ocean surface warms
when more energy leaves than enters the ocean surface (winter)
ocean surface cools
What is the dominant method of heat loss?
evaporative cooling
depth of light/energy penetration into surface ocean
relatively shallow
depth of light/energy penetration for clearest open waters
150 to 200 meters
depth of light/energy penetration for turbid coastal waters
50 meters
typical vertical profile of temperature
- all direct solar heating takes place near the ocean surface (0-30 meters)
- seawater below 500 meters is uniformly cold
permanent thermocline
the broad region at 500 meters where the seawater temperature changes from warm to uniformly cold
seasonal thermocline
- temporary thermocline
- shallower thermocline only forms in the summer and is erased in the winter
typically vertical density profile
less dense water “floats” above more dense water
seasonal pycnocline
- region of strong change in density with depth
- net heat gains in the spring and summer
- net heat losses in the fall and winter
permanent pycnocline
- 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
Why is the ocean more shallow in the summer?
heating the water makes it more buoyant so it’s harder for the wind to push it down
location of subpolar gyres
north
location of subtropical gyres
south
What describes how the wind drives the surface ocean currents of very large subtropical gyres?
- Ekman transport
- geostrophic currents
What causes Ekman transport?
- wind force
- friction force
- Coriolis force
Ekman transport
- rate of total water transported in Ekman layer
- exactly 90 degrees from the wind direction
How thick is the Ekman layer?
50 to 100 meters
geostrophic balance
point at which currents move with steady speed with Coriolis and pressure gradient forces in perfect opposition
geostrophic current
resulting current from geostrophic balance