Advanced Oceanography- Unit 3

Why do hurricanes rarely strike Southern California?

Southward flowing cold California current plus upwelling just off southern California produce sea surface temps too low to sustain hurricanes.

How does bathymetry affect a shallow-water wave such as a tsunami?

-Bathymetry- measure of depth of sea bottom-When water reaches shallower depths, the wave slows and the height of the wave increases

Explain why the coast is a particularly dynamic part of the Earth system.

-area between two different environments: land and water-very active environment

Compare the restoring force for capillary waves versus tsunami waves.

-capillary waves- restoring force is water's surface tension......longer wavelength ocean waves- restoring force is gravity

How and why does the tidal range vary between a spring tide and a neap tide?

-depends on the alignment of the Earth, Sun, and Moon-Spring tide- Earth, Sun, and Moon fall along a straight line, greatest monthly tidal rangeNeap tide- Sun's pull on Earth is at a right angle to the pull of the Moon, minimum monthly tidal range

Define fetch. For the same wind speed, are higher ocean waves generated with increasing or decreasing fetch?

-distance the wind blows in the same direction over a water surface-increasing fetch

Compare the types of tides usually experienced along the U.S. Pacific coast and Atlantic coast. What might explain the difference?

.-Pacific Coast- mixed semi-diurnal tides-Atlantic Coast- semi-diurnal tides. -tidal bulges are blocked by continents and tides are different in each basin

What is a seiche?

A seiche is a rhythmic oscillation of water in an enclosed basin. Like a wave moving back in forth in a tub.

Describe the thermocline structures throughout the ocean.

A thermocline is the transition layer between the warmer mixed water at the surface and the cooler deep water below.

Define water mass. How are water masses classified?

A water mass is a large, homogeneous volume of water with limited characteristic ranges of temperature and salinity. Water masses are classified based on their source region and the relative depth in the ocean where they reach density equilibrium with surrounding waters.

What role is played by the Coriolis Effect in western boundary currents?

As currents flow westward, the Coriolis force deflecting currents towards the right.

Identify some of the costs and benefits of coastal armor.

Can disrupt littoral drift and alter flow of sediment; costly dredging may be required to replenish sediment and keep harbors openBenefits- helps prevent erosion, provides calm waters for docking, protects from storm waves, and in the case of dredging it can replenish beach sediment

Describe the role played by Ekman transport in coastal upwelling. Distinguish between coastal upwelling and equatorial upwelling.

Coastal upwelling occurs where Ekman transport moves surface waters away from the coast; surface waters are replaced by water that wells up from below. Equatorial upwelling is the process where trade winds at the Equator blow surface water both north and south, allowing upwelling of deeper water

How and why do coastal upwelling and downwelling affect sea- surface temperature?

Coastal upwelling transports cold water from below to the surface thereby lowering the sea surface temperature. Coastal downwelling transports surface waters heated by the sun toward the coastline and downward.sea surface temperatures remain relatively high.

How does water density vary with depth in the ocean?

Density is lowest at the surface, where the water is the warmest. As depth increases, there is a region of rapidly increasing density with increasing depth Differences in water density drive the deep water circulation.

Explain how tectonic activity can affect the inland progression of a tsunami.

During the initiation of an inland progression of a tsunami, a large set of ocean waves are caused by any large and sudden disturbance of the sea surface, most commonly earthquakes caused by the collision of two plates (subduction)

List some of the advantages and disadvantages of artificial beach nourishment.

Expensive an temporary solution but provides substantial protection for coastal property and businessesDredging will also allow harbors to stay open by removing sediment build-up.

Under what conditions might an extratropical cyclone cause more coastal erosion than a hurricane?

Extratropical cyclones form at the polar front, are generally strongest in the winter, and can have a significant impact on coastal areas.Extratropical cyclones generally move more slowly than hurricanes and have lower wind speeds but they also can cause storm surges and extensive wave erosion. typically considerably larger than hurricanes.

How does frictional interaction with the ocean bottom influence ocean waves?

Friction slows down a wave and it interferes with the waves circular orbital motion which causes the wave to flatten.

How and why does the profile of a beach change from winter to summer?

Gentler summer waves deposit sand from offshore bars onto the beach, ultimately widening it and increasing its elevation. Conversely, stronger winter waves with more energy, pick up those particles deposited in the summer, and carry them back offshore in bars, thus narrowing the beach

In the Northern Hemisphere, how does the direction of Ekman transport of ocean water compare to the surface wind direction?

In the Northern Hemisphere Ekman transport is 90 degrees to the right of the wind. Within the Ekman spiral, deeper water can move in a direction exactly opposite of the wind direction

Compare the direction of Ekman transport in the subtropical gyres of the Northern Hemisphere with the Southern Hemisphere. Explain the difference.

In the Northern Hemisphere, subtropical gyres rotate clockwise and the Southern Hemisphere gyres rotate counterclockwise. They rotate in opposite directions because the ekman transport acts in opposite directions in the two hemispheres.

Compare the rotation direction and productivity in warm- and cold- core rings of the Northern Hemisphere. Do cold-core rings associated with the Gulf Stream entrain waters from coastal areas or the Sargasso Sea?

In the Northern Hemisphere, warm-core rings form on the current's landward side and rotate clockwise as seen from above whereas cold-core rings form on the current's ocean side and rotate counterclockwise. Cold-core rings associated with the Gulf Stream entrain waters from coastal areas and have higher productivity.

Describe the weather conditions that would favor upwelling along the Wisconsin coast of Lake Michigan.

Lakes experience seasonal turnover, referring to the vertical mixing of water in a lake driven by seasonal changes in the water temperature and density. spring and fall turnover

Describe the halocline structure throughout the ocean

Most of the ocean is divided into three horizontal depth zones based on density: the mixed layer, upper water (thermocline and pycnocline), and deep layer. Halocline separates ocean layers of different salinity. If an increase in salinity is responsible for the increase in density with depth, the pycnocline is referred to as a halocline.

Describe the pycnocline structure throughout the ocean

Most of the ocean is divided into three horizontal depth zones based on density: the mixed layer, upper water (thermocline and pycnocline), and deep layer. Pycnocline is the abrupt change of density with depth. The pycnocline is very stable and inhibits blending of ocean waters between the mixed layer and the deep layer

How are most waves produced in the surface ocean? What type of energy is transferred from this source to the surface waters? .

Most waves are wind-driven waves in which kinetic energy of the wind is transferred to surface waters

What are the dominant geological processes operating in tectonically active coastlines and passive coastlines? Which U.S. coastline is tectonically active?

Mountain buildng and volcanic activity are some of the geological proccesss in tectonically active coastlines. On passive shore lines erosion, transport and deposition of sediments are the geological processes that happen. The pacific west coast is more tectonically active

Explain how an undeveloped barrier island is a continually changing system.

Powerful storm and high winds can cause washover into tidal flats, where fine sediments accumulate. Waves breaking dissipate their energy by shifting sands and modifying the shape of the shore

Describe the halocline, thermocline, and pycnocline structures in the ocean.

Pycnocline - abrupt change of density with depth Thermocline - abrupt change of temperature with depth Halocline- separates ocean layers of different salinity

Describe rip currents and why they are potentially hazardous for swimmers.

Rip currents are dangerous, offshore flows of waterare found at beaches where waves break across a surf zone. They often occur in deeper channels, between areas of breaking waves. Rip currents can be hazardous to swimmers because speeds can vary from moment to moment andpull people away from shore

Distinguish among the types of estuaries in terms of freshwater and seawater flow and vertical stratification.

Salt wedge estuary: where river inflow is strong and tidal currents are weak. This water is stratified into two layers: fresh water over the sea water. Seaward flow of freshwater is much stronger than landward movement of sea water. there is little vertical mixing. Partially mixed estuary: where tidal currents are stronger than river flow compared to a salt wedge estuary. Vertical mixing reduces stratification and the halocline is weak. Well mixed estuary: where a strong tidal current dominates inflow There is no vertical stratification or halocline. The fresh water is completely mixed with salt water. Fjords: large walled glacial valleys filled with ocean water. They are almost never well mixed and have halocline that separates the bottom from the top. Vertical mixing doesn't even impact the bottom waters. Inverse Estuaries: forms in arid regions that receive less freshwater input than is lost through evaporation. Ocean water replaces freshwater lost. The vertical circulation pattern is opposite to other estuaries.

What is the origin of the sediment that forms a beach? How do human activities disrupt the supply of this sediment?

Sediment comes from waves, tides, and currents erode cliffs, wash away dunes, and transport sand to and from the beach.Artificial structures built by humans can disrupt the supply of sediment (breakwaters, jetties, and dams)

Distinguish between semidiurnal and mixed tides

Semidiurnal Two high tides/two low tides per day.Tidal range about same Mixed Two high tides/two low tides per day Tidal range different Most common

Distinguish among a standing wave and progressive wave, and provide an example of each.

Standing wave- stationary with respect to the medium in which it is embedded, EX: seiche. -Progressive wave- move through a body of water, EX: wind-driven waves

Identify coastal hazards associated with hurricanes.

Storm surge heavy rainfall inland flooding high winds loss of habitat loss of human life

Astronomical tides are caused by the gravitational attraction between the rotating Earth and what two bodies in space? Which one of these celestial bodies produces greater ocean tides on Earth? Why?

Sun and Moonthe Moon has greater gravitational pull because it is closer to Earth

Contrast the surface ocean currents on the eastern and western sides of the subtropical gyres.

Surface currents flow poleward on the western side of subtropical gyres and equatorward on the eastern side. Surface currents on the western sides of these gyres (western boundary currents) are faster, deeper, and narrower than their eastern counterparts.

Suppose that the surface wind is blowing from the north along the Oregon coast. Predict the direction of Ekman transport of surface waters. Would you expect coastal upwelling or downwelling?

Surface wind is blowing from the north along the Oregon coast Ekman transport would move surface seawater away from shore. Coastal upwelling would occur because of the cool, nutrient-rich deep water coming up to replace displaced surface waters.

Describe the path of North Atlantic Deep Water.

The NADW flows through the south through the Atlantic and over the deep water near Antarctica. After Antarctica it heads north into the Indian and Pacific Ocean. The deep water is warmed, mixed upward and returned to the North Atlantic.

Why does an irregular coastline tend to straighten with time?

The forces of erosion from waves converging toward the headlands, cut back the headlands and sediment fills in the coves and bays so that the coastline straightens

Describe the significance of the meridional overturning circulation (MOC) in Earth's climate system.

The meridional overturning circulation (MOC) begins with the formation and subsequent sinking of cold, salty water at high latitudes flows equator-ward and eventually warms and rises to the surface. This system transports heat from low latitudes to high latitudes of the North Atlantic Ocean.

How does the speed of water motion in the thermohaline circulation compare to that of wind-driven surface ocean currents?

The ocean's thermohaline circulation is generally much slower than surface ocean currents.

Briefly describe the origins of a longshore current.

The origins of longshore current is the zigzag motion of a wave swath and backwash that moves particles along the beach in the same direction as sand transport.

Are barrier islands found on tectonically active or passive continental margins? Justify your choice.

The passive continental margins found on the Atlantic and Gulf coasts are where barrier islands are abundant. The islands occur where the supply of sand is abundant, the seafloor slopes gently, constant deposition of sand and waves

Describe the relationship between trade winds and biological productivity along the equator.

The trade winds converge near the equator giving rise to upwelling. Coastal upwelling transports waters rich in dissolved nutrients from the ocean depths into the photic zone (an area of high biological productivity.

How might rings (warm-core and cold-core eddies) influence the intensity of storm systems over the ocean?

These spinning rings can last for years and can influence storm development (such as intensifying or reducing hurricane intensity) Warm core rings might increase the intensity of storms

Distinguish between the directions of the trade winds in the Northern Hemisphere versus those in the Southern Hemisphere. What is the significance of the intertropical convergence zone?

Trade winds Northern Hemisphere: northeast (toward the southwest) Southern Hemisphere: southeast (toward the northwest) intertropical convergence zone is where the trade winds of the Northern and Southern Hemispheres come together. responsible for the wet and dry seasons in the tropics

In which ocean basin do most tsunamis originate? What type of tectonic activity is responsible for most tsunamis?

Tsunamis happen most frequently in the Pacific Ocean because of the many large earthquakes and volcanic eruptions associated with subduction zones along the margins of the Pacific Ocean basin, which is called the "Ring of Fire"

What is the "fuel" that powers both tropical cyclones and extratropical cyclones

Warm waters from the Gulf Stream

Distinguish between wave height and wavelength.

Wave height is the vertical distance between a wave trough and crest. Wavelength is the horizontal distance between successive wave troughs or wave crests.

Do astronomical tides behave as deep- or shallow-water waves? Explain your answer.

behaves as a shallow water wave because the length of a tide wave is greater that the depth of the ocean. continents separate the ocean into separate basins with variable depth

Explain how wave interference influences the height of ocean waves.

constructive wave influence occur when 2 or more wave crests coincide to form composite waves with heights greater than any of the original waves

Why does a wave crest refract as it approaches the shoreline?

crest refracts or bends, because of the change in water depth slows down the wave.

Speculate on some of the ways rising sea level might impact the coastal zone.

erode and inundate coastal ecosystems and eliminate wetlands.saltwaterintrusion

During winter months, monsoon winds over the Indian Ocean:

flow from sea to land and are wet.

How does the wind direction over the Arctic Ocean compare to the direction of motion of the underlying ice floes?

ice floes 20-40° to the right of the prevailing wind direction.

Which of the following will decrease the velocity of the longshore current?

increased wave period

What is the significance of resonance for the tidal range in coastal inlets?

meaning the period of the disturbance (such as wind) matches the period of oscillation of the basin. tidal range can grow as a consequence of resonance.

Why are tsunamis more common in the Pacific Ocean basin than the Atlantic Ocean basin?

more active, "Rim of Fire", subduction zones, underwater earthquakes and volcanic eruptions take place

For deep-water waves, the depth of no wave motion (wave-base) is approximately equal to _______ the wavelength.

one-half

What role is played by the ocean in the development of tropical cyclones?

origination from a uniform mass of warm humid air over the tropical ocean. The ocean places a role because tropical cyclones need warm water to develop.

Hurricanes are an efficient way to:

redistribute heat from one area to another.

Geostrophic circulation is within a gyre driven by:

the Coriolis effect.

Define thermohaline circulation and describe how it is maintained in the ocean.

thermohaline circulation - The density driven movement of water with depth in the ocean; ocean water density increases with decreasing temperature and increasing salinity

For deep-water waves, the diameter of the orbit of a water particle at the ocean surface is equivalent to the _______.

wave length.

Wave speed is equal to:

wavelength divided by period.

The circular motion of water molecules extends to a depth that is equal to:

wavelength/2.

Explain how wave refraction affects erosion and sediment deposition along an irregular coastline.

waves approaching an irregular coastline are refracted and concentrate at the headlands and spread out as they enter coves or bays. Wave energy is therefore concentrated on the headlands, causing undercutting and erosion