Oceanography 3

Explain why at some locations in the ocean there is downwelling. Describe 2 specific examples of downwelling with different causes.

Downwelling occurs when the water on the surface of the sea becomes denser than the water beneath it and so it sinks. Most downwelling happens at the poles. There, cold air chills the water. The water brought in by the surface gyres is pretty salty already, because it comes from the tropics, where evaporation increased salinity. And once it gets to high latitudes, the water becomes even more saline as ice forms and further concentrates sea salts. Ex: Arctic Convergence in North Atlantic caused by Thermo, Convergence in the middle of the ocean gyre caused by Ekman

Explain why western boundary currents and eastern are different

Due to Coriolis effect which is strongest near the poles water flowing eastward at high latitudes turns sooner to right Coriolis effect is nonexistant at the equator so water flowing westward near equator doesn't turn clockwise until it encounters boundary current causes a geostrophic hill to be offset to the west

Diagram and discuss how Ekman transport produces the "hill" of water within subtropical gyres that causes geostrophic current flow.

Due to wind energy, coriolis effect and pressure gradient, water is turned to the right and forms a hill of water, It cant turn further right becasue itd be going uphill and it cant turn left becasue of coriolis effect.

Define and describe geostrophic current flow

the currents of geostrophic gyres fastest are found at western boundaries of ocean basins

Using examples, explain how waves can interfere with one another constructively or destructively.

Constructive interferience between waves of diff wavelengths creates big wave Destructie Interfierence diminishes waves and makes it easier to swim out

Describe the physical changes that occur to a wave's wave speed (C), wavelength (L), height (H) and wave steepness (H/L) as a wave moves across shoaling water to break on the shore

S= decreases, L(wavelenght)- decreases, H- increases, (H/L) wave steepness increases

List the factors that influence the formation of a "fully developed sea"

maximum wave size possible for a wind of specific strength, duration and fetch ( uninterupted distance over which the wind blows w/out significant change in direction

Rip Current

may form around low spots or breaks in sandbars, and also near structures such as jetties and piers. A rip current, sometimes incorrectly called a rip tide, is a localized current that flows away from the shoreline toward the ocean, perpendicular or at an acute angle to the shoreline.

10. Using examples, explain how wave refraction is different from wave reflection

refraction- slowing and bending of waves in shallow water that break in a line parallel to shore. reflection- waves move away from an obstruction such as a large ship, or seawall in the direction that they came from.

Explain what a "wave train" is and how it travels; describe how a wave in a group / train travels compared to the way an individual wave travels.

wave train- progressing groups of swells w/ same origin and wavelength. Moves forward at only half the speed of individual waves. Individual waves- move forward with speed porportional to their wavlength dont persist in the ocean and last only as long as they take to pass through the group

Explain what determines when a wave will break.

when H/L ratio gets 1:7 too steep

Differentiate between "swell" and "wind chop"

wind chop- breaks along its lenght caused by strong offshore wind swell- smooth undulation of ocean surface- generated by storms

Describe Langmuir circulation

winds that blow steadily across the ocean and the small waves that such winds generate and induce long sets of counter rotating vortices

Differentiate between shallow water and deep water waves. Explain what determines the speed of each.

Deep water waves- waves moving through water deeper than half their wavelength. Speed is determined by the depth and wavelenths( longer in deep water waves) Shallow water waves- waves in water shallower than 1/20 their original wavelength, orbits of water molecules in waves moving through shallow water are flattened by the proximity of the bottom. Speed is reduces as crests bunch up and the wavelengths are shortened

Diagram and discuss the Ekman spiral and Ekman transport

Ekman spiral- when driven by wind, topmost layer of ocean in Northern Hemi flows at 45 degrees to the right. The layer below moves at an angle to the right of water to depth of 100 meters in Northern hemi (left in southern) each layer with a slower speed because of friction loss Ekman transport- net motion of water down to 100 meters. moves 90 degrees to the right of the wind direction in the north and 90 degrees right in southern hemi

Identify the major water masses and tell where they are found and where they formed: NADW, AABW, Med

NADW- (North Atlantic Deep Water) Found in Atlantic formed in Northern Polar ocean AABW (Antarctic Bottom Water) found in Antarctic formed near antarctic coast Mediteranean Overflow- found in Med formed in Atlantic and Antarctic

Describe the atmospheric and oceanographic changes that result in an El Nino. Differentiate between "normal", "El Nino" and "La Nina" conditions.

Normal- surface winds across pacific move from east to west and trade winds blow from high pressre to low pressure over western pacific El Nino- when pressure areas change (3-8 years) winds reverse direction and blow from west to east. Eastward warm water arries in south america coast around cristmas La Nina- when conditions to the east cool off, ocean to west rapidly warms. Water is upwelled upon iteself depressing upper curve of thermocline

Explain what thermohaline circulation is, and what the ocean conveyer belt is, and their significance.

Thermohaline- movement of water due to temperature and salinity differences. ( large scale vertical movement of ocean water and circulation of the ocean globe) Ocean conveyer belt- carries surface water to the depths and back again. Gradually warms and mixes upward to be returned to the North Atlantic by surface circulation. Important in transporting water and heat

Compare a tsunami to other types of waves, in terms of generating force, type wave (shallow water or deep water and why), speed, wavelength, and appearance / behavior. Explain why Hilo Bay is likely to have particularly big impacts from tsunami.

Tsunami- long wavelength, shallow water progressie wave caused by rapid displacement of ocean water shallow (seismic sea waves) where speed depends on water depth and gravity. When waves come ashore a wall of water forms not a breaking wave

Explain why at some locations in the ocean there is upwelling. Describe 2 specific examples of upwelling with different causes.

Upwelling- brings deep, cold, nutrient-laden water toward surface Equatorial upwelling- coriolis effect is weak near the equator so upwelling occurs in westward flowing surface currents Coastal upwelling- caused by wind blowing parallel to shore or offshore. Friction of wind blowing along the ocean surface causes he water to begin moving, coriolis deflects it to the right Ex: Antarctic divergence caused by Ekman, Tropical divergence caused by thermo

Contrast eastern and western boundary currents and explain why their characteristics are different. Give examples of each.

Western boundary currents: Fastest and deepest geostrophic current that moves water poleward in each of the gyres, eddies form Ex: gulf stream is the largest Eastern boundary current: Opposite of western boundary currents. Carry cold water toward equator, shallow and broad no eddies form Ex: California Current *coriolis effect is strongest near the poles so and non existant at equator so thats why western boundary currents are faster

Describe the parts of a wave, and describe how a wave moves across water.

crest- peak wavelength-one part on a wave to another height-top of crust to bottom of trough trough- lowest point amplitude- position from rest position to crest how waves move-generating force causes a transfer of energy from one water particle to the next

Differentiate between a "disturbing" or "generating" force and a restoring force; give examples of waves generated by different generating forces and restoring forces.

disturbing force- energy that causes ocean waves ( wind) Ex: Seismic Sea wave or sudden change in atm pressure restoring force- dominant force that returns water surface to flatness after a wave has been formed Ex: for small waves is cohesion

wind chop

first small waves created when the wind blows on the sea.

Differentiate between free waves and forced waves; give examples of each

free wave- wave that is formed and then propagates across the sea surface w/out further influence of the force that formed it Ex: tsunamis Forced wave- maintained by its disturbing force Ex: tides

Contrast the climate of a mid-latitude coastal city at a western ocean boundary with a mid-latitude coastal city at an eastern ocean boundary - explain.

greatest amount of heat transfer occurs at mid-latitutes Coastal city on eastern boundary- san Francisco is cool- upwelling cools the city Western boundary current- D.C. is humid