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Oceanography II


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What are gyres and what causes them?
Large, circular water currents. In the subtropics, the westerlies move the water from east to the west. In the tropics, the Trade Winds move the water from the west to the east. When the two are deflected by continents, they are bending into each other, causing current loops or gyres.
How many gyres exist in the oceans?
Five: The North Pacific Gyre, the South Pacific Gyre, the North Atlantic Gyre, the South Atlantic Gyre, and the Indian Ocean Gyre.
In what direction does the Corilios effect move things?
In the Northern Hemisphere, objects are deflected to the right. While in the Southern Hemisphere, they are deflected to the left.
What is the Ekman spiral?
Prevailing winds create a drag in the water and causing layers of water underneath. The deeper the layer, the more speed it looses and the more to the right it turns in the N.H. The base of the current flows in the opposite direction of the surface movement.
So what is the Ekman transport?
the net water transport is 90 degrees to the right of the wind (in the N.H.) Net transport is the average of all directions and speeds of current spiral. in other words, the bulk of the water moves at a 90-degress angle to the wind.
Surface current moves at what angle to the wind in the Ekman transport?
At a 45-degree angle.
Hows does the Ekman transport creat mounds and depression in the water? and how high or deep are they?
Mounds are creating by converging waters, sinking the water(downwelling). Depressions are created by diverging waters, where water rises and causes upwelling. Both are usually up to 1 meter
What areas have upwelling and downwelling?
The high latitudes usually have upwelling, the subtropics have downwelling, and the tropics (equator) have upwelling.
What is zone called where the surface layer of the ocean has a lot of plant photosynthesis?
Photic zone.
what is geostrophic flow?
Occuring around a mound, it is when the pressure gradient equals the Coriolis effect, making the water movement parallel to the wind around the mound .
Cold or warm currents flow on what side of ocean basins?
Warm currents flow on the western side of the ocean basins, here water also piles up due to the rotation of the Earth, Coriolis effect and the trade winds.
What is the name of the ocean current that flows around Antartica?
Antartica Circumpolar Current
What kind of pressure system is responsible for rainy and dry seasons?
Rainy seaons mean low-pressure system. Dry seasons mean high-pressure system.
Where are the 5 major monsoons?
West African, East African/Indian, East Asian, Australian, Brazilian
What are the conditions for an El Nino event?
Weak or reversed Trade Winds, thermocline is less steep, temperature's rise.
What is ENSO?
El Nino-Southern Oscillation, the phenomenon that occurs during the winters months, with huge fluctuations in climate, temperatue, sea-surface temperatures, and biological productivity.
What about NAO?
North Atlantic Oscillation, another wintery climatic phenomenon, causes stronger westerlies. The US receives mild, wet winters, Europe receives warm and wet winters, and Canada receives cold, dry winters.
Fewer, weaker storms, causing cold, snowy winters in the U.S.
What are the main characteristics of the thermocline in the different latitudes?
In the high-latitudes, there is a small and weak thermocline. Mid-latitudes has a summer thermocline that ranges around 10-20degrees Celcius. Low-latitudes has a summer thermocling in the 25-30degree Celcius range.
What is the thermohaline?
It is the density-driven circulation of the ocean, pelow the pycnocline.
So what is the pycnocline?
it is a boundary zone between the surface-water and deep-waters of the ocean. Has a sharp density gradient.
Name the different water masses in order of less dense to the most dense.
Mediterranean Intermediate Water (MIW), Antartic Intermediate Water (AAIW), North Atlantic Deep Water (NADP), Antartic Bottom Water (ABW)
How do these waters get more dense?
By cooling, evaporation, or formation of sea ice.
Why does the water in the polar region get so dense?
Since sea ice forms, it leaves behind the salt, making the water saltier than it was, so it makes it more dense.
So what is produces in the Pacific Ocean?
the waters in the Pacific Ocean are a mixture of Circumpolar Water and AABW and NADW.
In which direction does the Circumpolar water flow?
From west to east.
What is the global conveyor?
The complete circuit of global ocean circulation, includes the horizontal and vertical flow of near-surface and deep water.
Waves represent...
...the transmission of energy, not mass!!!
Waves flow through what two interfaces?
Between the atmostphere and the surface layer, and between the different water masses in the pycnocline creating internal waves.
What are the three main causes for surface waves?
Wind, earthquakes, and gravitational attraction of sun and moon.
What are the different wave classifications?
Capillaries, swells, tsunamis, internal waves, and tides
In waves, water molecules move how?
They usually stay in one place, and they move in a circular motion.
What is the wave period?
It is the time it takes two successive crests to pass a fixed point.
Where is the base of the wave?
At the top of the thermocline.
Do you know the equation for wave velocity in deep water?
C=L/T, C=1.56T
What is the water depth for shallow water waves?
Water depth is less than or equal to (1/20)
What three things happen when the waves feel the bottom?
1) speed increases
2) wavelength decreases
3) wave height increases
How are winds generated?
Deep water waves are wind generated, while shallow water waves are wind generated, seismic sea waves, tide waves (caused by the pull of the moon)
What are swell waves and how are they formed?
Swell waves are long wavelength waves that form in the surface of the sea by tropical storms.
How do waves evolve?
First there are storm waves, where the energy is put in by the strong winds. Then it goes on to become a swell wave, which is moving away from the sea that generated them, and can travel long distances. Then it becomes a surf wave, where it meets shallower bed and energy is put out.
What are rogue waves?
Dangerous, huge waves that come spontaneously and are created by wave interference.
How long is the tide period? and how long are they?
It is 12 hr. and 25 minutes, and they are about 1/2 of Earth's circumference.
What are characteristics of neap tides?
Minimum tidal range (lower high tide, higher low tide) and occur during first quarter and last quarter stages of moon.
Moon, Sun, and Earth are at quadrature, creating vertical tidal bulges.
What are characterists of spring tides?
Maximum tidal range (higher high tide, lower low tide) and occur during new and full moons. Moon, Sun and Earth are in syzygy, creating horizontal tidal bulges.
What are the three tidal patterns? describe them.
Semi-diurnal tide which happens twice daily, two high tides and two low, and the tidal period is 12hr and 25 minutes. Common in Atlantic.
Diurnal tides occur once daily, with one high tide and one low tide. The tidal period is at 24hr and 50 min. Common in Gulf of Mexico.
Mixed tide, 1 or 2 high tides may occur. Common in Pacific.
What is tidal behavior influenced by?
-coriolis effect/friction
-interference of the continents
-size, shape, and depth of ocean basins, continental shelves, and coastlines.
What is a progressive tide?
a wave moving progressively down the ocean basin.
What is a rotary standing wave?
a wave confined to an ocean basin, rotates around a node where is no tidal influence.
What is an amphidromic point?
where the waves rotate around a node where there is no tidal influence.
Place the following in order from the most offshore to the most inshore: beach scarp, sand bar, dunes, low-tide terrace.
Sand Bar, low tide terrace, beach scarp, dune
Where do the longshore currents form?
Between the shore and the breakers.
Why do waves bend?
Because a part of them has entered shallow water, while the remainder is still in deep water.
What does the beach look like during the summer?
the gentle weather waves more sand shoreward, creating a longer, more hilly beach.
What does the beach look like during the winter?
Waves break further offshore due to sand bars that are created further offshore. the storm waves move sand seaward. The beach is flattened and smaller.
Explain groins.
they are short structures built perpendicular to the shore, and its purpose is to trap sand from longshore transport and widen an eroding beach. the problem is, sand accumulates on the up-drift side and cause erosion on the down-drift side, causing a groin field to be built.
Explain jetties.
long structures built perpendicular to the shore to protect harbor or channel inlet from erosion by incoming swell. the problem is that sand tends to accumulate on the up-drift side, creating a sand spit. this has to be dredged occasionally.
Explain breakwaters.
rigid structures built parallel a short distance from the shore to provide quiet water for boat anchorage. the problem is that sand accumulates in quieter water behind the breakwater because the wall disrupts the incoming swell that provides the energy to move the sand.
Explain seawalls.
solid walls built onshore and parallel to the shore to protect structures and buildings from washing into the sea with rising sea level. the problem is the incoming wave energy reflects off the wall, causing the reflected waves to crash with the incoming waves making even bigger and stronger waves. will destroy beaches. sand washes away from the front of the seawall.
How are sand dunes formed?
by winds blowing sand landward from the dry part of the beach. (primary and secondary dunes are created)
What is the environment in a barrier island going from sea to lagoon?
First is the nearshore zone, then the dune field that protects the rest of the island from the ocean. Followed by back-island flats where all the green and foresty parts are, and finally are the salt marshes.
What are three ways that barrier islands form?
1) sand ridges isolated by rising sea level
2) sand spits breached during a storm
3) the vertical growth and emergence of longshore sand bars.
When do hurricanes occur and what feeds them?
During the June to November months. they are fed by the heat of the ocean.
Hurricanes are low or high pressure systems?
What is the area of greatest damage?
To the right of the eye of the storm
What is a Nor'easter?
It is a storm that comes from the northeast. occurs during the fall/winter months. weaker then hurricanes, but still strong.
What is a storm surge?
when water is pushed strongly landward by winds in the forward direction of the storm. water is domed-up under the intense low pressure of the storm, creating washovers.
Sea level rise affects what type of coast the most?
low-lying coastal plains, as opposed to mountainous coast.
What are fertile oases? and give me four examples.
It is abundant in nutrients. Estuaries, lagoons, salt marshes, and mangrove swamps.
What is an example of fragile oases? and why is it one?
coral reefs because nutrients are scarce.
What is the intertidal zone? the supratidal zone? and the subtidal zone?
the intertidal zone is area between low tide and high tide. the supratidal zone is just above the high tide. subtidal zone is below low tide.
What are examples of phytoplankton?
Diatoms and dinoflagellates.
Example of benthic algae?
brown and green algae or seaweed. also turtle grass and eel grass.
What is detritus?
dead and decaying algae and grasses covered with bacteria.
What is the word for organisms that live buried in the sediment? and name examples.
Infauna, such as clams, sand dollars, crabs, and worms.
What about those that live above the sediment?
They're called epifauna, and consists of snails, mussels, salt marshes grasses.
How are estuaries formed?
they can be formed by drowned river valleys, fjords (glacial valley), bar-built estuaries (sand spits), and tectonic estuaries.
characteristics of lagoons
isolated, semi-enclosed shallow water, that receives little fresh water inflow. exists on landward side of barrier island. salinity is from brackish to hypersaline. sediment is sand or mud.
What are salt marshes?
they are intertidal flats covered by vegetation, usually protected areas. they are immersed daily by high tide, and drowned by low tide.
Why is detritus from the mangroves important?
detritus forms the base of the food chain.
What are two main biozones?
Pelagic, which refers to the water column, and benthic, which refers to the seafloor.
Within the pelagic biozone, what is the name for the zone that overlies the continental shelf, and the one that extends beyond the shelf break?
Neritic zone and oceanic zone.
If we're talking about light penetrating zones in the pelagic zone, name them in order from highest to the deepest zones.
Epipelagic zone (illuminated surface layer), Mesopelagic zone (twilight, no photosynthesis), bathypelagic zone (totally dark, no plants) abyssalpelagic zone (makes up 1/2 ocean volume) and hadalpelagic zone (deep-sea trenches)
Now about the benthic zones, there is a shallow zone and a deep zone, what are the two zones in the shallow zone?
littoral (intertidal) zone which is between high and low tide. and the other is sublittoral zone, which is from the beach to shelf break.
What are they in the deep zone?
There is the bathyal zone (continental slope and rise), abyssal zone (average deap ocean bottom) and the hadal zone (which is in the deep-sea trenches.
What is the photic zone?
It is the depth where there is enough light to produce photosynthesis, consists of epipelagic zone.
What is the name of the depth where illumination is too weak for photosynthesis?
it is called the dysphotic zone and consists of mesopelagic zone.
What is the name of the depth where light doesn't penetrate anymore?
It is the aphotic zone, and consists of bathypelagic zone, abyssalpelagic zone, and hadalpelagic zone.
What are heterotrophs?
They are organisms that require other organisms for food.
So what are autotrophs?
They are organisms that can make their own food, plants! (photosynthetic organisms, and chemosynthetic organisms)
What do the passive floaters consist of?
They consists of phytoplankton (diatoms, dinoflagellates, cocolithophorids), zooplankton (copepods, krill, jellies, as well as forams) bacterioplankton (heterotrophic bacteria and some cyanobacteria), and meroplankton (larval stage of benthotic and nektonic animals)
What does MOCNESS stand for?
Multiple Opening/Closing Net and Environmental Sampling System
What do active swimmers consists of?
organisms capable of moving independently of ocean currents, some inverebrates like squid, and many vertebrates like pelagic fish, marine mammals, and marine reptiles.
What are benthons?
Bottom dwellers, like epifauna, epiflora, or infauna. including ground fish.
What is stenothermal and stenohaline?
Organisms that can tolerate only a narrow range of temperatures, and only a narrow range of salinity.
What is eurythermal and euryhaline?
Organisms that can tolerate a wider range of temperatures, and a wider range of salinities.
What is a hypotonic cell?
It is when the ionic concentration becomes greater within the cell than the environment.
What is a hypertonic cell?
It is when the ionic concentration becomes greater in the environment, then within the cell.
Diatoms have what kind of shell?
Opaline silica, and eventually form deposits of siliceous ooze.
Coccolithophores have what kind of shell?
They have shells made of calcium carbonate and exist above the CCD to form deposits called calcareous ooze.
How is primary production measured?
By grams of Carbon per square meter per day (gC/m^2/day)
What is the compensation depth?
It is the bottom of the euphotic zone.
Where is the euphotic zone deeper and widerand why?
It is deeper in the low latitudes because the sun is shinning directly above as opposed the euphotic zone in the higher latitudes, which is smaller but wider, because the sun is more at an angel, covering more area but less directly.
In ocean waters, what is the limiting nutrient for plant growth?
Nitrogen is, because the ratio is 16:1, which means that there needs to be more nitrogen then phosphorus.
What relationship is there between chlorophyll abundance and sea surface temperatures?
The cooler the sea surface temperatures, the more productivity due to a weaker thermocline. The warmer the temperatures, the less productivity.
If there is a strong thermocline, what happens to the nutrients?
The strong thermocline creates a density gradient and barrier to nutrient difussion.
True or False, in high latitudes, productivity is limited by nutrients and solar radiation.
False, productivity is limited by available solar radiation.
Describe the nutrient and solar radiation availability in the mid-latitudes.
During the winter, nutrients are available but not enough solar radiation.
During the spring, nutrients and solar radiation are available creating a spring bloom (high productivity)
During the summer, solar raditioan is available, but nutrients are cut-off by seasonal thermocline.
During the fall, the thermocline breaks down and there is renewed productivity.
What does the solar radiation and nutrient availability look like in the tropis?
There is always enough solar radiation but due to the strong thermocline, nutrients availability is cut-off.
What are coral reefs?
They are rigid, wave resistant structures of calcium carbonate built by colonial corals and calcareous algae.
What is the word for the intimiate co-existence of two differente organisms, or the dependence of one organism on another? name examples
Symbiosis. Some examples are clown fish and the anemone, also microscopic algae live on the tissue of coral polyps.
What is zoothanthellae?
They are microscopic dinoflagellates (algae or plants) that produce oxygen gas and use up waste, and provides food and oxygen for polyps. Photosynthesize.
What is a coral polyp?
It is the animal of a coral that has an exoskeleton made up of calcium carbonate, and give off CO2 and nutrients. Respire.
What is a fringing reef?
THey are coral reefs that form in shallow water of the tropics and subtropics where there is little sediment input or reduced salinities from river runoff. They are created around a dormant volcano.
What is a barrier reef?
It is a hard, resistant coral reef that grows nearly to sea level and drops off abruptly to the adjacent seafloor. It tends to make a lagoon between the outer sides of the coral reef and the subsiding volcano.
What is an atoll?
It is the continuous upward growth of the coral reef as the volcano subsides, creating a lagoon above the volcano enclosed by the shallow lagoon.
What is the Lost City?
It is a newly found hydrovent field in the Atlantic, formed by faulting and uplift between the Mid-Atlantic Ridge and Atlantis Fracture Zone, and has chimneys made entirely of calcium carbonate.
How are tsunamis created?
They are seismic sea waves generated by undersea movements, such as earthquakes, landslides, and volcanoes.
As land approaches, what happens to a tsunami?
Wave height increases, but velocity decreases.

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