3- oceanic circulation

what causes water to move horizontally?

wind and gravity

what causes water to move vertically?

gravity and density

incoming solar radiation

at the equator, solar energy strikes Earth directly, resulting in a high influx of energy

northern vs southern hemisphere

Northern Hemisphere:

- more land and wider range of temps

Southern Hemisphere:

- less land and narrower range of temps

density of air

warm air is less dense, so it rises; cold air is more dense, so it sinks

convection cell

Coriolis Effect

- path in the Northern Hemisphere is deflected to the right (air moves in a clockwise direction)

- path in the Southern Hemisphere is deflected to the left (air moves in a counter-clockwise direction)

friction at air sea interfaces

- wind causes water to accelerate

- transfer of wind energy to water movement is 1-3%

- transfer of energy decreases with depth

- causes a spiral

Ekman Spiral/Transport

deeper layers moved more slowly and twist around; may flow opposite to surface currents

*Coriolis displacement of waters: CW in N and CCW in S

upwelling

- transport of deep ocean water to the surface

- occurs when water is blown away from shore

- cold, nutrient-filled water brought up

downwelling

- downward transport of surface waters to depth

- occurs when water is blown towards shore

- warm and nutrient-poor water

eddies

- swirling of a fluid and reverse current when fluid flows past an obstacles

- occurs behind islands and sea mounds

- effects dispersal of organisms

California currents

California current: carries cold nutrient-rich water down the coast

California counter-current: carries warm water up the coast from Baja

point of conception: mixing of the two currents

ocean gyres

circular motion of water in the major ocean basins (5 major currents)

tracking ocean circulation

eulerian: measuring fluid movement around a fixed point

lagrangian: measuring fluid movement by following particles in the fluid

how is the movement of water measured?

in millions of m^3 of water per second

wave parameters

wind waves

- shorter period waves that result from local winds

- choppy and disorganized

- often with white caps

swell

- longer period waves that build over large bodies of water as a result of major weather patterns

- well organized and smooth

- somewhat predictable

what determines the generation of waves?

wind velocity, wind duration, and the distance over which wind blows

destructive interference

peaks and troughs cancel each other, resulting in smaller waves

construction interference

peaks and trough combine, resulting in larger waves

wave refraction

- points focus wave energy

- bays diffuse wave energy

- a lot of energy in a smaller space

what factors play a role in the density of water?

temperature: warm water is less dense, cold water is more dense

salinity: high salt concentration is more dense, low salt concentration is less dense

Thermohaline Circulation

- driven by temperature and salinity

- "Global Conveyor Belt"

- 1500 yrs to cycle through

- is an example of a convection cell

how will global warming impact ocean circulation?

there will be a decrease in sea ice, which will decrease the concentration of salt resulting in less of a difference in density, therefore reducing the waterfall effect and slowing down circulation

what type of ocean circulation effects tides?

gravity/gravitational pull of the sun and the moon

spring tides

- tidal bulges are the largest

- sun and moon are aligned

neap tides

- bulges and tidal ranges are the smallest

- the moon and sun are pulling at right angles

what is the periodicty of the lunar orbit

it is a 29 day cycle that cycles every 2 weeks between spring and neap tides

semidiurnal tides

2 highs and 2 lows a day (same amplitude for both)

mixed semidiurnal tides

2 highs and 2 lows of different heights (west coast of US and Canada)

diurnal tides

1 high and 1 low tide per day (mostly in Antartica)