ocean currents, waves, and tides chapter 11 & 12 (highways in the sea; waves and tides)
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Ocean Currents, Waves, and Tides Chapter 11 & 12 (Highways in the Sea; Waves and Tides). Oceanography 2014. Ch 11 Key Vocabulary. Ocean Current continuous, directed movement of seawater generated by the forces acting upon it Sea Level Pressure Gradient Force Gyre Ekman Transport - PowerPoint PPT PresentationTRANSCRIPT
Ocean Currents, Waves, and TidesChapter 11 & 12
(Highways in the Sea; Waves and Tides)
Oceanography 2014
Ch 11 Key Vocabulary1. Ocean Current
continuous, directed movement
of seawater generated by the
forces acting upon it
2. Sea Level
3. Pressure Gradient Force
4. Gyre
5. Ekman Transport
6. Friction Depth
7. Geostrophic Current
8. Countercurrents
9. Upwelling
10. Downwelling
11. El Nino p11-22
12. La Nina p11-24
13. Deep Circulation
14. Contour Currents
15. Ocean Conveyor Belt
16. Doppler Shift
Ch 12 Key Vocabulary1. Wavelength
2. Crest
3. Trough
4. Period
5. Wave Speed
6. Fully Developed Sea
7. Internal Ocean Waves
8. Storm Surge
9. Seiche
10. Tsunami
Background Vocabulary (Chapter 10)1. Coriolis Effect2. Trade Winds
prevailing pattern of easterly surface winds found in the tropics
3. Westerliesprevailing winds in the middle latitudes between 30 and 60 degrees latitude
4. Easterlieswinds with an easterly component at the surface near theEarth's poles, usually at latitudes more than 60 degrees
5. Doldrums6. Horse Latitudes7. SCUBA
Self Contained Underwater Breathing Apparatus
Surface CurrentsCurrents that are 0-400 meters deep
Tend to flow right in the N hemisphere and left in the S hemisphere (Coriolis Effect)
Caused by:Wind
Cause changes in sea level across horizontal distancesDifferences in density
Also causes change across horizontal distances More dense water sinks below less dense water
GyresCombination of
currents creating a circular flow
Example: North Atlantic GyreWesterlies pushing
water eastward along the upper latitudes of the Atlantic
Trade winds pushing westward near the equator
Coriolis effect
Ekman TransportMotion of the water column
down to friction depth (90o right in N hemisphere and 90o left in S hemisphere)
Currents due to friction with the wind shift to right or left
Result of the Coriolis Effect
Ekman Spiral: thin layers of water flowing in a direction caused by the layer above down to friction depth (deepest point friction from wind affects water movement)
Boundary CurrentsCurrents with
characteristics determined by the presence of a coastlineWestern boundary
currents (occur along the eastern continental coasts) Gulf Stream
Eastern boundary currents (occur along the western continental coasts) Canary Current
Characteristic Western Eastern
Temperature Warm Cold
Width Narrow Wide
Depth Deep Shallow
Volume High Low
Speed Fast Slow
Direction Toward Poles Toward Equator
Special Current TypesCounter-currents: current that flows
in a direction opposite of the adjacent current
UpwellingUpward vertical current bringing
deep water to the surfaceOccurs when wind blowing parallel to
the shore pushes surface water out to sea (due to Ekman transport)
Downwelling: Occurs when surface water is forced
downward at the shorelineOccurs when Ekman transport causes
surface water to flow toward the shore
Deep CurrentsWater motion caused by mixing water of different
densities
Ocean is stratified into different layers
Five Primary Water Masses
1. Surface Water-0-200 meters deep
2. Central Water-Extends into the thermocline-Depth Varies with latitude
3. Intermediate Water-To about 1500 meters deep
4. Deep Water-Below Intermediate, but does not contact ocean bottom
5. Bottom Water-In contact with sea floor
Ocean Conveyor BeltConstant motion in the ocean = global ocean
conveyor beltDue to thermohaline currents:
Cold, salty water is dense and sinks to the bottom of the ocean
Warm water is less dense and rises to the surface It takes almost 1,000 years for the conveyor belt
to complete one “cycle.”
Process of the Ocean Conveyor Belt1. “Starts” in the Norwegian Sea
-Warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes -This loss of heat to the atmosphere makes the water cooler and denser, causing it to sink to the bottom of the ocean
2. As more warm water is transported north, cooler water sinks and moves south to make room for the incoming warm water
3. This cold bottom water flows south of the equator all the way down to Antarctica
4. Eventually, the cold bottom waters are able to warm and rise to the surface, continuing the conveyor belt that encircles the globe
TidesDaily variations in the ocean’s sea level
Vary by locationCauses:
Result of the gravitational pull of the moon (and to some degree, also the Sun)
Pulls the ocean into a huge wave with a wavelength the size of the entire ocean basin
Equilibrium TheoryIsaac Newton: the Sun and moon create
two opposite bulges on each side of the Earth – each rotate around the Earth as the Sun and moon change position As bulge moves toward coast, tides rise As bulge moves away from coast, tides fall
Dynamic Theory of TidesPierre-Simon Laplace modified
Newton’s theory because it was too simple to explain everything about tides on Earth
More than 2 tidal bulges
Tides occur in a pinwheel-shaped, standing-wave pattern
In addition to lunar and solar gravity, this theory accounts for:Imperfect shape of EarthSeasonsShape of Ocean BasinsCoriolis Effect
Extreme TidesBay of FundyDiffer in volume by as
much as 100 km3 (that is more than 4x the volume of all the rivers in the world combined)
Demonstrates that tides are much more complex that Newton’s simple model.
WavesWave: transmission of energy through matterThree types of waves in all matter:
LongitudinalTransverseOrbital
Ocean Waves Only in fluid – energy moves a fluid in a circular motion as it
passes
Causes and CharacteristicsCreated by “disturbing forces”Intensity and duration of forces determine wave characteristics
Disturbing forces includeWindChanges in gravitySeismic Activity
Movement of water is resisted by “restoring forces”GravityCoriolis EffectSurface Tension
Destructive WavesStorm Surge
Forms when high winds push water into shore
Seiche (pronounced SAY-sh)Motion of water in lake
or bay rocking back and forth due to earthquake or very strong wind
TsunamiSudden movement of
water caused by a landslide, iceberg falling into the sea, or Earthquake
Oceanography Feb 6, 2014Waves/Currents/Tides
1. What do you think causes tides?
2. List 2-3 facts you already know about waves.
Oceanography Feb 18, 2014Vocab Review
1. What is the Ocean Conveyor Belt?2. The average level of the ocean
between high and low tide is called what?
3. What type of circulation is caused by mixing water masses of differing densities?
4. What is Ekman Transport?5. What is El Nino?
Oceanography Feb 18, 2014Vocab Review Answers
1. What is the Ocean Conveyor Belt?-Constant motion of the ocean due to connected currents worldwide
2. The average level of the ocean between high and low tide is called what?-Sea Level
3. What type of circulation is caused by mixing water masses of differing densities?-Deep Circulation
4. What is Ekman Transport?-Motion of water due to wind motion that causes spiraling motion down to friction depth
5. What is El Nino?-Rearrangement of high and low pressure systems