Oceans - Pt 2 Flashcards
true or false? Tides are a type of wave?
True
what is the usual frequency of the tides?
Occur once every 12 hr and 24 hr
Main driving force of tides?
gravitational interaction between the earth and the sun or moon
define tide:
periodic rise and fall of ocean water levels
How much stronger are moon tides than sun tides?
twice as strong because the moon is closer
What are the 2 kinds of tidal bulges?
1) spring tide
2) neap tide
Spring tide
- highest high tide and lowest low tide
- occur when the sun and moon line up
Why does the tidal bulge appear on both sides of the earth if the moon is not present on both sides of the earth?
The bulge results from the moon’s gravitational pull on one side, and is present on the other due to the rotation of the earth beneath the bulge that generates a centrifugal force that prevents the bulge from collapsing.
Neap tide
- lowest high tide and highest low tide
- occur when the sun and the moon line up at 90 degree angle from the earth
true or false? Tidal waves interact with the bottom of the ocean?
true
Types of tides? (3)
1) semi-diurnal tides
2) diurnal tides
3) mixed tides
Semi-dirunal tides
2 high tides and 2 low tides per day
Diurnal tides
1 high tide and 1 low tide per day
Mixed tides
semi-diurnal signal modulated by a diurnal signal
What impaires tidal waves?
Interaction with land masses and friction at the bottom of the ocean. This causes tidal waves to break into cells and rotate around an amphidromic point (point of no amplitude)
What type of tidal waves does the Gulph of St. Lawrence (Ottawa-ish area) receive?
mixed tides
What other areas experience mixed tides (I don’t imagine this is super duper important)
Atlantic Coast, Caribbean Sea, and some of the Gulph of Mexico
True or false? The Bay of Fundy experiences the largest tidal range?
True. 15 m range. This is due to the natural frequency of the funnel-shaped bay
What is a tidal current?
Horizontal water movement caused by tides
What are the 2 kinds of tidal currents?
1) flood current (high tide)
2) ebb current (low tide)
Tidal bore
A steep fronted wave that moves up a river as tides rise
What are the 2 driving forces of ocean currents?
1) Wind, and the drag it creates at the surface
2) density differences
What are the 2 categories of ocean currents?
1) surface currents
2) Deep-water currents
What is the primary driving force of surface ocean currents?
wind
What is the primary driving force of deep-water ocean currents?
density differences
Water is more dense when it ____ and _____
a) has a high salt concentration
b) has a lower temperature
What is the cause for the Coriolis force? In what direction does it deflect objects in the Northern hemisphere? What about the Southern hemisphere?
- Earth’s rotation is the cause of this force.
- This force deflects moving objects to the right (clockwise) in the N.H, and to the left (CCW) in the S. H
What are the effects of the Coriolis force? (3)
1) Results in the decoupling between travelling object and the earth spinning underneath it
2) the effects are greater at longer distances and higher latitudes
3) impacts large-scale atmospheric and ocean circulation
What is the Ekman spiral?
Coriolis force as applied to wind driven surface currents
What are 2 assumptions made regarding the ekman spiral?
1) the ocean s of unlimited depth
2) uniform viscosity
What are the 2 results of the ekman spiral?
1) The surface current moves at a 45 degree angle from the direction of wind movement. Notice that each successive layer of water moves further to the right (at a greater angle from the direction of wind) due to Coriolis effect
2) ekman Transport (net water movement) occurs at a 90 degree angle from the direction of wind
Coastal upwelling
If winds are moving parallel to coast, Ekman transport causes surface water to move away from the shore. Upwelling of deep, cold, nutrient rich water replaces the surface water.
Coastal downwelling
If winds are moving parallel to coast, Ekman transport causes surface water to move towards the shore. As surface waters move towards the shore, downwelling of deep, cold, nutrient rich water occurs, moving it deeper, and allowing warmer, nutrient poor water to remain at the surface.
El Nino (warm phase)
Reduction or revesal of southeast trade winds
4 consequences of El Ninos
- Cooler, nutrient rich upwelling waters get forced downward, This has an incredible impact on fishing industry
- coral bleaching
- increased rain in America (floods)
- decreased rain in Australia (droughts)
Deep Ocean currents
- slow moving (- km/yr)
- density driven
Deep water accounts for ___% of ocean water
90%
Describe thermohaline circulation
- 100-1000 yr cycle: Cold, salty waters of N. Atlantic sink and flow south along bottom. These waters become heated gradually and rise to rejoin surface currents. They cool again and sink. They move from high to low salt concentrations as well.
- THINK OF IT AS A GIANT CONVEYOR BELT CIRCULATION (UP-DOWN-UP-DOWN; HEATING (rising)-COOLING (sinking)-HEATING(rising)-COOLING(sinking))
What is the function of this thermohaline circulation?
Transfers heat from the equator to the poles
What influences the thermohaline circuation? (2 things)
position of continents and seafloor topography
In addition to temperature, what else drives thermohaline circulation?
Salt concentrations; freshwater productions.
ie. melting glaciers increase production of freshwater, creating a layer of water that won’t sink. This changes the circulation pattern, which in turn strongly influences climate
