OCEANOGRAPHY 1080 FINAL

Iowa State 40% new, 60% whole course

The time between two successive waves (i.e. the time it takes to complete one wave cycle) is called the

period

What is the definition of fetch with regards to wave generation?

the distance over which the wind blows in the same direction

A tsunami may result from:

tectonic activity on the seafloor

Which of the following is the best description of the path of a water molecule at location B as the wave moves through it (ignore Stokes Drift)?

the water molecules moves in a counterclockwise orbit

Match the letter with the appropriate term

• wave crest: B

• wave height: E

• wavelength: A

• trough: C

• amplitude: D

As a wave approaches the shoreline, it eventually breaks because it:

reaches its critical steepness as friction causes waves to slow down and pile up

The duration of time it takes to reach a fully developed sea is influenced by:

both the distance of the fetch and the speed of the winds

Capillary waves:

• have a restoring force that is primarily surface tension.

• are also known as ripples

• are the first waves to form when the wind starts to blow.

A region of the ocean is considered a fully developed sea when:

the energy imparted by the wind equals the energy dissipated by the breaking whitecaps

The differences between seas and swells include:

seas describe wave conditions in areas where the wind is blowing (locally-generated) and swells describe wave conditions in areas where the wind is not blowing (remotely-generated) and seas have waves that have steep sides whereas swells have symmetrically shaped waves.

Constructive interference results in larger waves while destructive interference results in:

smaller waves

What is Stokes Drift?

It describes the gradual net transport of material and water particles in the direction that the wave is moving.

A neap tide would occur:

during the scenario represented in B

The gravitational attraction of ______ with the Earth results in the largest tide producing force on Earth.

the Moon

At amphidromic points: 

the amplitude of the tidal wave is 0 (i.e. high and low tides do not influence sea level at these points)

What physical characteristics affect the magnitude of a gravitational attraction between two objects?

both the mass of the objects and the distance between the objects

A spring tide is characterized by:

very high high-tides and very low low-tides.

During full moons and new moons:

there are larger tidal ranges because the Earth, the Moon and the Sun are in line with each other

Which of the following descriptions is most accurate when describing the orbital relationship between the Earth and the Moon.

the Earth and the Moon rotate around each other with a center of gravity that is beneath the surface of the Earth

In one day, an area that experiences semidiurnal tides will have:

two high tides of nearly equal height and two low tides of nearly equal height

The two tidal bulges (two high tides and two low tides) on an idealized earth (without continents) occur because_________.

gravitational pull of the moon and sun on the Earths oceans creates bulges (2) of water

Which of the following statements is true with regards to respiration?

respiration releases energy that is then stored in the high-energy chemical bonds of the molecule ATP.

When does the spring phytoplankton bloom happen?

when the mixing depth is above the critical depth

The spring phytoplankton bloom (an increase in biomass) occurs because: 

• nutrients have been mixed to the surface during the winter so nutrient concentrations are high in surface waters during the spring.

• light levels increase during in the spring.

• the thermocline shoals (gets shallower) during the spring, allowing phytoplankton to live closer to the surface where there is more light for photosynthesis.

Where are rates of primary productivity higher (compared to the average ocean)?

along coastlines, the equator and higher latitudes

Why do dissolved nutrient concentrations (dissolved nitrate and phosphate) in ocean waters increase with depth in the ocean?

• nutrients are incorporated into cells during biosynthesis at the surface and released by decomposition at depth.

• because the water column is often stratified (i.e. a thermocline exists), it is difficult to get nutrients that are at depth back to the surface.

Why are rates of primary productivity higher (compared to the open ocean) along the coastlines?

Ekman upwelling and tidal mixing occurs along coastlines, bringing nutrients to the surface.

What answer best describes the role of the open ocean in primary productivity, compared to coastal and upwelling zones?

the open ocean has lower rates of primary productivity but a higher percentage of total ocean production.

Why are rates of primary productivity higher at higher latitudes?

there is more winter convective mixing at higher latitudes due to a deeper or absent thermocline during the winter months or, in some very high latitudes, throughout most of the year.

Why is nitrogen often the limiting nutrient in biological production?

• phosphorous is released relatively quickly after organisms die and therefore it is more available in the surface waters.

• according to the Redfield Ratio, phytoplankton cells need 16 nitrogen atoms for every 1 phosphorous atom.

What process releases nutrients (stored in cells) back into the ocean?

decomposition

An autotroph is an organism that:

makes its own food through photosynthesis (or chemosynthesis).