General Oceanography: Salinity, Temperature, and Thermohaline Circulation

Higher salinity can rest above lower salinity water if:

1. the higher salinity water is sufficiently warm or

2. the lower salinity water is sufficiently cold

Surface temperature is controlled by:

1. Latitude: distribution of solar radiation due to shape and tilt of Earth

2. Season: as Earth revolves around the sun

3. Current flow

4. Upwelling: cold nutrient-rich deep water brought to surface

What are western boundary currents?

surface gyres that carry warm water poleward on the western side of ocean basins

What are eastern boundary currents?

Surface gyres that carry cooler water equatorward on the eastern side of ocean basins

_______ oceans are permanently layered with warm, less dense surface water separated from cold, dense deep water by a thermocline.

Tropical and subtropical

What is a thermocline?

layer in which water temperature changes rapidly with depth

______ regions have a seasonal thermocline and ____ regions have no thermocline

temperate, polar

______ thermocline weakens in winter, strengthens in summer, and is greatest at mid-latitudes

seasonal

_______ thermocline marks boundary between surface and deep (uniformly cold) water masses

permanent

_____ is more important than salinity (except in ____ environments such as estuaries, etc…) in controlling density in the ocean because it varies over a ____ range than salinity does

temperature, marginal, wide

_____ is typically where the thermocline is in lower latitudes

pycnocline

What is a pycnocline?

depth of density gradient; serves as a barrier of vertical motion between deep and surface ocean

What are isopycnals?

lines of equal water density

The surface layer is ____ dense than the layers below because it has ____ salinity or ____ temperature

less, lower, higher

Water in the ___ layer originates at the ____ in high latitudes where it ________

deep, surface

1. cools

2. becomes dense

3. sinks to the seafloor

4. flows equatorward across ocean basins

Temperature and salinity are ____ and used to trace water masses

conservative

How does caballing work with MIW?

salty warm water mixes with cool less salty water of same density, to form MIW mass that is even denser than the precursor water masses.

What is caballing?

water of equal density but differing temperature and salinity mix to form a newer denser water mass.

Both _____ and _____ mix linearly, but _____ mixes nonlinearly

heat, salt, density

What are the mechanisms of mixing?

1. salt fingering (diffusion)

2. caballing

3. internal waves

4. wind mixing

5. tidal mixing

What is salt fingering?

Mixing through diffusion. Diffusion of heat and salt between layers of density occurs very slowly. Heat diffuses faster than salt, resulting in the interfingering of layers.

_____ creates new water mass or layer (new T and S characteristics) resulting in even more layers in the stratified system

Mixing