GEO 3 - Midterm 2
Where is the deepest point in the ocean located, and how deep is it?
- The deepest point of the ocean is called the "Challenger Deep" - It is located below the 'Mariana Trench' - The Challenger Deep is 11 km deep
What is salinity?
- The measure of the concentration of dissolved salt in water - Salinity is measured in parts per thousand (ppt)
What is the average salinity of the global ocean? What is the typical range of salinities?
- The salinity of seawater is a measure of the concentration of dissolved salts - Salinity is measured in parts per thousand - The average salinity of seawater is 35 ppt - The normal range is 34 ppt- 37 ppt
Which processes of radiative transfer affect the fate of light in water?
Same as in the atmosphere: - Reflection - Scattering - Absorption
Where are the subtropical gyres located?
The subtropical gyres dominate the world's open-ocean currents 1. North Pacific 2. Indian Ocean 3. South Pacific 4. North Atlantic 5. South Atlantic - A single trip around a subtropical gyre takes ~10 years
Define wave height (h)
The vertical distance from crest and trough
Define: Relative humidity
- (RH) The ratio of the air's actual water vapor content over the maximum amount of water vapor the air can hold at a particular temperature and pressure - This can be expressed as (Amount of H2O in the air / Amount of H2O the air can hold) x 100 OR (Specific humidity / Saturation humidity) x 100 - RH ranges from 0% (Dry Air) to 100% (Saturated Air)
What percentage of the Earth's freshwater is available for human consumption? Where is the majority of freshwater stored?
- 70% (the majority) of Earth's freshwater is frozen in glaciers and ice caps - 29% of Earth's freshwater is underground - Less than 1% of Earth's freshwater is in rivers and lakes, available for human consumption
How much ocean water is there?
- 97% of all water on Earth is ocean water - Oceans cover 71% of Earth's surface
Who was Fridtjof Nansen and what observation did he make that was important for understanding ocean currents?
- A Norwegian explore on an expedition to the North Pole. He thought there would be a current flowing east-west across the NP - He designed a ship to get stuck in the ice thinking the current would take him to NP. The floating ice/ship DIDN'T move in the direction of the wind, rather it moved 20-30 degrees to the RIGHT of the prevailing winds -
What are wave trains?
- A group of waves of equal or similar wavelengths traveling in the same direction, driven by wind
What is a wave?
- A wave is the movement of energy through a medium - The particles in the medium do NOT travel with the wave, but may experience some local oscillations as the wave passes - Waves transport Energy, NOT water mass, across the ocean surface - Waves do not always travel in the same directions as the currents. Waves are created by the wind/a disturbing force and then radiate in all directions away from the disturbance
What is a rogue wave?
- Abnormally large, unexpected, and dangerous waves that form as a result of constructive interference - Greater than twice the size of surrounding waves - Very steep sided with unusually deep troughs
What is fetch?
- Area of contact between the wind and water where waves are generated
What happens to the relative humidity as the air temperature increases? decreases?
- As temperature increases, RH decreases, and vice versa (Inverse Relationship) - As temperature increases, the amount of water vapor the air can hold (AKA Saturation humidity) increases, so the Relative humidity (RH) decreases - This is shown in the equation: RH% = (Specific Humidity / Saturation Humidity) x 100
What is thermal expansion?
- As water is heated, the Kinetic energy of water molecules increases, causing the molecules to vibrate more and move farther apart - As the space between molecules increases (due to warming), water volume increases and water density decreases
What happens to the characteristics of a wave as it approaches shore? (i.e., describe changes in wave speed, wavelength, height, and period)
- As waves enter shallow water, friction slows the bottom of the wave, causing the wave crest to move ahead of the bottom of the wave. As the wave hits the bottom, the orbitals are flattened/can't move up and down - The change in orbitals slows the wave speed. Slowing of the speed causes shortening of the wavelength and an increase in height - The shortening of the wavelength/bunching up of waves allows the period to maintain - Steepness = Height/Wavelength. Waves break when the steepness is GREATER than 1/7
Explain why the ocean appears blue. What causes some bodies of water to appear greenish, brownish, or lighter blue in color?
- Blue light is the least absorbed, as a result it is scattered by the ocean --> why the water appears blue - Dark Blue: Where the sunlight is 'scattered' by the water molecules - Lighter Aqua colors: Shallow water near the islands where the sunlight is 'reflecting' off the sand and reefs near the surface - Greenish colors: High concentrations of phytoplankton that 'absorb' red and blue light - Brownish colors: Coastal areas with high sediment loads that 'absorb' blue light - Light penetrates deeper in clear ocean waters. Light penetration is shallow in high-turbidity coastal waters with high suspended sediment loads or plankton concentration
What processes increase/decrease the density of seawater?
- Decrease: 1. Precipitation 2. River runoff 3. Heating (by solar radiation or by the atmosphere) 4. Sea ice melting - Increase: 1. Evaporation 2. Cooling 3. Sea ice formation
Describe how the tsunami warning system works (DART)
- Deep Ocean Assessment and Reporting of Tsunamis (DART): A global tsunami warning system developed by NOAA in the U.S - DART buoys are anchored to pressure sensors on the ocean-floor - The tsunami warning process begins when the ocean-bottom sensors register a change in PRESSURE associated with an ocean disturbance - Bottom sensors send data to the surface buoys, which transmit the data via satellite to regional warning centers
What determines the wave speed of deep-water waves?
- Deep-water waves: When ocean depth is greater than 1/2 the wavelength (d > L/2) - Wave speed, length, and height are relatively constant - Wave period is ALWAYS constant - Speed is dependent on WAVELENGTH (or period) --> Longer waves travel faster
Describe the wave-coastline interaction known as Diffraction, and give a local example
- Diffraction occurs when waves pass through a narrow opening (e.g. between two islands or the entrance to a bay or harbor) - The waves spread outward from the opening, spreading the energy over a wider area and weakening the waves impact - Local example: Although some south swells can pass through the Channel Islands to Santa Barbara, diffraction through the narrow island openings weakens the energy of the waves that reach our shore Key words: Narrow opening, spread outward, weakened impact
What is a disturbing force? Restoring force?
- Disturbing Force: Any force that transmits energy to the water column or sea-surface (GENERATES waves) - Wind - Landslides, undersea earthquakes (faulting) - Gravitational pull of sun and moon - Restoring Force: Any force that acts to restore the sea-surface or drain a wave of its energy (DAMPENS or removes waves) - Gravity - Surface tension
For each phase change of water, state if heat is absorbed or released to the environment. Give an example of each phase change in nature
- During Sublimation, heat is absorbed (Ex. At Mt. Everest, low temperature + dry winds + intense sunlight = sublimation of snow) - During Deposition, heat is released into the environment (Ex. Frost forming on the ground from warm most air coming into contact with a cold surface) - During Condensation, heat is released into the environment (Ex. Clouds forming when warm air + cold dust particles form cloud droplets) - During Evaporation, heat is absorbed (Ex. Water vapor forms when lakes absorb heat) - During Freezing, heat is released into the environment (Ex. Parts of the ocean freeze when it gets cold enough, forming sea ice) - During Melting, heat is absorbed (Ex. When sea ice is heated, it melts creating liquid water)
Where in the world are the lowest salinities found? Why?
- Equator and the Poles 1. At the Equator (heavy rainfall and cloudiness associated with the ITCZ) 2. At the Poles (lowest evaporation + large inflow of freshwater from rivers and ice caps)
Which wavelengths (types of radiation) are absorbed first? Which are absorbed last?
- For incoming solar radiation, the rate of absorption depends on the wavelength (Longer wavelength = faster) (Shorter wavelength = slower) - Uv and Infrared are absorbed first (longer wavelengths) - Visible light is absorbed less quickly - Shorter wavelengths penetrate further, with blue and green reaching the deepest depths/being absorbed last
Describe heat exchange during the phase changes of water between solid, liquid, and gas
- For water to change states, Hydrogen Bonds must be broken, and this requires energy - Solid --> Gas = Sublimation - Gas --> Solid = Deposition - Gas --> Liquid = Condensation - Liquid --> Gas = Evaporation - Liquid --> Solid = Freezing - Solid --> Liquid = Melting
Define: High tide, low tide, tidal range
- High Tide: (rising/flood tide) When the highest part/crest of the wave reaches a particular location, high tide occurs - Low Tide: (falling/ebb tide) Low tide corresponds to the lowest part of the wave/trough - Tidal Range: The height difference between consecutive high and low tides
Where on Earth would you expect to find areas of HIGH salinity, and why?
- Highest salinity: Dry, hot regions where evaporation is high and precipitation is low, and landlocked seas - Salinity is highest in the Subtropics because of Subtropical high pressure cells (Descending branch of Hadley Cell) promote clear, dry conditions, increased evaporation and suppressed precipitation - Ex.) The Red Sea is one of the saltiest seas in the world (~40 ppt)
What happens to the relative humidity as the amount of water vapor in the air increases? decreases?
- If the amount of water vapor in the air (Specific humidity) increases, the RH increases, and vice versa (Direct Relationship) - This is shown in the equation: RH% = (Specific Humidity / Saturation Humidity) x 100
How are swells different from locally-generated wind waves?
- Longer waves travel faster than shorter waves, and leave the area of wave formation (fetch) sooner - The wave period of swells = ~10-30 seconds as opposed to the wave period of wind waves = ~5-15 seconds - For wind waves, wind speed > wave speed for energy transfer to continue. For swells, waves travel faster than the wind that created them
Where on Earth would you expect to find areas of LOW salinity, and why?
- Lowest salinity: Heavy rainfall and cloudiness, and near the mouths of rivers (freshwater runoff) - The lowest salinities are found: 1. At the Equator (heavy rainfall and cloudiness associated with the ITCZ) 2. At the Poles (lowest evaporation + large inflow of freshwater from rivers and ice caps) - Ex.) There is low salinity where rivers meet coastal areas
Explain why most places on Earth experience two high tides and two low tides per day (your answer should include tidal bulges, gravitational pull, and inertia)
- Lunar tides are responsible for the 2 high and 2 low tides per day - Gravitational pull: The moon's gravitational pull on the Earth is the strongest. The moon's gravitational pull generates tidal force which leads to tidal bulge - The tidal bulge FACING the moon is formed by the gravitational pull of the moon, which is the strongest on the side of Earth closest to the moon. Gravity pulls the ocean towards the moon and high tide occurs - The tidal bulge on the FAR side of earth/opposite the moon is caused by inertia. The water moving away from the moon resists the gravitational forces that attempt to pull it in the opposite direction. Because the gravitational pull of the moon is weaker on the far side of the earth, inertia wins, the ocean bulges, and high tide occurs - As earth rotates on its axis, any given point on the surface will rotate through the relatively fixed tidal bulges
What is Density?
- Mass of a liquid divided by its volume (the capacity of liquids in the containers) - The density of a liquid determines whether it will float on or sink in another liquid (An object will float if it is less dense than the liquid it is placed in) - The density of seawater plays a vital role in causing ocean currents and circulating heat because of the fact that dense water sinks below less dense
What factors cause sea-surface salinity to increase? Decrease?
- Ocean surface salinity varies from place to place depending on: 1. How much EVAPORATION is taking place 2. How much FRESHWATER is being ADDED (primarily from rainfall and river discharge) - This is determined by atmospheric conditions and proximity to coasts - HIGH evaporation rates = HIGH salinity - LARGE inflow of freshwater = LOW salinity
What caused the 2011 Japan Tsunami? Why was this event so destructive?
- On March 11th 2011, a magnitude 9.0 earthquake off the northeastern coast of Japan triggered a large tsunami that caused massive damage and flooding - The height of the tsunami reached up to 30 meters (100 ft) in confined harbors. In low-lying coastal areas, the tsunami traveled as far as 10 km (6 miles) inland - These events caused widespread destruction and devastation in Japan, including 16,000 deaths and tens of billions of dollars in damages - Japanese scientists had predicted a smaller earthquake, not a large tsunami. Citizens were warned of the earthquake only, then a tsunami warning came 3 minutes after, and underestimated the wave's size - The waves overtopped and destroyed protective tsunami seawalls
Describe the propagation and characteristics of tsunamis in the open ocean. What happens as they approach shore?
- Once generated, tsunami waves radiate outward in all directions from their source. A tsunami's energy is distributed throughout the water column (surface to floor), regardless of ocean depth. As the tsunami propagates across the ocean, the wave crests can undergo refraction/bending - A tsunami's wave speed (which is directly proportional to wavelength/period) in the open ocean is faster. Tsunami waves in the open ocean have a long wavelength. Tsunami waves can travel at high speeds for long periods of time and lose little energy. The deeper the water, the faster the tsunami wave - As tsunamis approach the coast/shore, the increasingly shallow water causes the wave to slow down and forces the wavelength to shorten - Friction slows the bottom of the wave. As the wave hits the bottom, the orbitals are flattened/can't move up and down which slows the wave speed forcing the wavelength to shorten - With a shortened wavelength, the period shortens, and the wave's energy (which is being contained in a smaller volume of water) is directed upward which increases the height - The wave height may increase by up to 15 m (50 ft) or more
How does pressure change with depth in the ocean?
- Pressure increases with increasing ocean depth (Direct Relationship) - Rule of thumb: Pressure increases by 1 atm per 10 m depth in the ocean - Sea level pressure = 1 atm
Describe the wave-coastline interaction known as Reflection, and give a local example
- Reflection occurs when a water wave bounces off a hard surface, such as a seawall or sea cliff, changing the direction of the wave - Waves can reflect off steep slopes or vertical boundaries, such as shoreline cliffs or human-made structures such as a jetty or breakwater - Reflected waves can interfere with incoming non-reflected waves - Local example: At Sandspit, near the opening of the Santa Barbara harbor, the breakwater creates a reflected wave ("backwash") that interferes constructively with the incoming waves Key words: Bounces off, change in direction
Explain how salinity and sea-surface temperature affect density (in summary)
- Salinity: HIGHER salinity = HIGHER density (Direct relationship) - Sea-surface temperature: WARM temperature = LOW density (Inverse relationship)
Explain how salinity and sea-surface temperature affect density (In depth)
- Sea surface temperatures (SSTs) generally Decrease with Increasing latitude - Cold temperature = High density (Inverse) - Warm temperature = Low density (Inverse) - Thermal Expansion: As water is heated, the Kinetic energy of water molecules increases, causing the molecules to vibrate more and move farther apart - As the space between molecules increases (due to warming), water volume increases and water density decreases - Adding salts (increasing salinity) to seawater increases the mass per unit volume (AKA Density) --> Essentially because it is now NaCl + H2O rather than just H2O
What is the composition of seawater? What are the two major constituents (solutes)?
- Seawater is a solution (Solvents + Solutes = Solution) - Solvent: Pure water ("The universal solvent" - Solutes: Dissolved solids (salts) - Sea water is 96.5% pure water (solvent) and 3.5% dissolved salts (solutes) - The 2 major solutes are: 1. Mostly Sodium Chloride/NaCl/Table Salt 2. Also includes salts containing magnesium, sulfur, calcium, and potassium
What determines the wave speed of shallow-water waves?
- Shallow-water waves: When ocean depth is less than 1/2 the wavelength (d<L/2) - Wave speed and wavelength decrease - Wave height increases - Wave period stays the same - Speed is dependent on DEPTH --> waves travel faster in deeper water - Shallow-water waves "feel" the bottom
Which tides are larger, lunar or solar?
- Solar tides are expressed as a variation on lunar tides, not as a separate set of tides - The gravitational attraction between the sun and earth creates semidiurnal (2/day) tides like the earth and moon. Also creates 2 bulges - Although the sun is bigger than the moon, the sun's gravitational pull is only ~ 1/2 the moon's because the sun is a greater distance from earth - Solar tides are ~ 1/2 the height of lunar tides and are weaker than lunar tides
Where in the world is salinity the highest? Why?
- Subtropics - Salinity is highest in the Subtropics because of Subtropical high pressure cells (Descending branch of Hadley Cell) promote clear, dry conditions, increased evaporation and suppressed precipitation
How does air temperature effect the saturation (maximum) specific humidity?
- Temperature controls the maximum amount of water vapor the air can hold - Cooler air = LESSER maximum water vapor possible (Low saturation/Dry air) - Warmer air = GREATER maximum water vapor possible (High saturation/ Saturated air)
Define: Specific humidity
- The actual amount of water vapor content in the air - This is expressed as [Mass of water vapor (g)] / [Total mass of dry air + H2O (Kg)]
What is the average depth of the ocean and how does that compare to the thickness of the atmosphere?
- The average depth of the ocean = 4 km - Comparatively, Earth's atmosphere is ~480 km thick at the top of the atmosphere
Describe destructive wave interference
- The crest of one wave lines up with the trough of another (i.e. waves are OUT of phase with one another) - The waves cancel each other out - Resulting wave may FLATTEN completely, or may be REDUCED compared to the original waves - Subtractive interference
Describe constructive wave interference
- The crests and troughs of one wave are in alignment (or in phase) with those of another - The waves AMPLIFY each other - The resulting wave is LARGER than the original waves - Additive interference
Describe how swells travel away from the storm center or wave-generating region (i.e. wave dispersion)
- The self-sorting of waves leaving a stormy, wave-generating region is based on wavelength and period - Longer waves travel faster than shorter waves and leave the area of formation sooner. Therefore, waves naturally separate into groups (wave trains) of common direction and wavelength --> the sets of waves formed this way are called swells - As a wave group moves further away from the fetch, dispersion gives order to the waves
How does wave motion (orbitals) change with depth? What is the wave base?
- The size of wave motion/orbit DECREASES with depth - Water particles near the ocean's surface move in circular orbits with diameters ~equal to the wave height. The orbital diameter and wave energy DECREASE deeper in the water - In deep water, wave motion is insignificant BELOW a depth of 1/2 the wavelength (D = L/2) known as the Wave Base
Describe some of the unique properties of water (e.g., polarity and hydrogen bonding)
- The water molecule is 2 Hydrogen atoms and 1 Oxygen atom - Polarity: Slight positive charge on the Hydrogen side and a slight negative charge on the Oxygen side. The + and - charge on opposite ends causes molecules to attract - Hydrogen Bonding: When the - charged Oxygen atom attracts surrounding + charged Hydrogen atoms. As a result of polarity, water molecules attract each other
What is the average depth that sunlight travels in the ocean?
- There is rarely any significant light beyond *200 meters* - Light may be detected as far as 1,000 meters down in the ocean
Describe tidal waves - What are their disturbing forces? Restoring forces? Typical wave periods?
- Tides are long-period waves that move through the oceans. Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface - Disturbing force: Gravitational forces exerted by the moon (& partially the sun), and the rotation of the Earth - Restoring force: Gravity/Surface tension - Typical wave period: ~12-24 hours Additionally: - Wavelength: ~100s-1000s km
What causes the tides?
- Tides= Long-period waves that move through the oceans in response to gravitational forces exerted by the moon and sun onto the Earth - Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface
Describe tsunami waves - What are their disturbing forces? Restoring forces? Typical wave periods?
- Tsunami = a series of waves generated by a large undersea disturbance - Tsunami is a Japanese word w/ the English translation "Harbor wave". Named for the large size and devastating effects if the waves when their energy is focused un harbors - Disturbing force: Sharp, sudden movements in the sea floor caused by earthquakes, submarine landslides, eruptions of undersea volcanoes, or meteorite impacts in the ocean (Ocean floor to surface is disrupted, displacing an enormous amount of water) - Restoring force: Gravity - Typical wave period: 5-60 minutes Additionally: - Wavelength: >100 km (Tsunamis often pass unnoticed in the open ocean because their long wavelength makes the rise and fall of water hard to observe) - Wave height: ~1 meter - Wave speed: 300-800 km (375-500 mph)
What causes tsunamis?
- Tsunami: A series of waves generated by a large undersea disturbance - Examples: Sharp, sudden movements in the sea floor caused by earthquakes, submarine landslides, eruptions of undersea volcanoes, or meteorite impacts in the ocean - With a tsunami, the ENTIRE water column - from the ocean floor to the surface - is disrupted, displacing a large volume of water
At what temperature does water reach its maximum density? Explain why ice floats
- Water reaches its maximum density at 4° - Pure water reaches its maximum density ABOVE its freezing point - Frozen ice is LESS dense than the near-freezing liquid water, icebergs float and sea-ice forms a layer at the surface (rather than sinking to the bottom) --> Objects float when they're less dense
What is the relationship between wave energy and wave height?
- Wave energy: wave energy is proportional to the square of wave height - E∝h² - The higher the wave, the larger the diameter of the water particle orbit, and the greater the speed of the orbitals; Therefore, the greater the kinetic and potential energy - HIGHER wave = GREATER energy
What is wave energy?
- Wave energy: wave energy is proportional to the square of wave height - E∝h² - The higher the wave, the larger the diameter of the water particle orbit, and the greater the speed of the orbitals; Therefore, the greater the kinetic and potential energy - HIGHER wave = GREATER energy
What is the relationship between wave period and wave frequency?
- Wave period: (T) The time it takes a single wave, from crest to crest, to travel past a fixed point (seconds) - Wave frequency: (f) The number of wave crests that travel past a fixed point per unit time (# of waves/second) - The LONGER the period, the LOWER the frequency. The SHORTER the period, the HIGHER the frequency ( f = 1/T )
Describe the wave-coastline interaction known as Refraction, and give a local example
- Wave refraction is the bending of shallow-water wave fronts due to a change in water depth (Deep to shallow) - Shallow-water wave speed only depends on bottom depth (The shallower the bottom depth, the slower the wave speed) - Local example: At Rincon, Santa Barbara; As waves approach the coastline, the shoreline end of the wave enters the shallow water and slows down, while the portion of the wave in deeper water continues to move at a faster speed. The difference in velocity refracts (bends) the wave fronts to become parallel with bottom depth contours Key words: Bending, difference in velocity, parallel
What is wave speed?
- Wave speed: In the open ocean, wave speed is directly proportional to wavelength or period - LONGER waves travel FASTER than shorter waves - The longer the wave period, the faster the wave speed (Waves have less height/potential energy in deeper water, so the speed increases)
How are waves classified?
- Waves are classified by their disturbing and restoring forces, and wave period
Define: Humidity
A general term used to describe the amount of water vapor in the air
What causes waves to break? Describe two different types of breakers
- Waves break when they reach shallow water where the steepness (height/wavelength) is greater than 1/7 - Greater wave height and decreased wavelength sharpens the wave crest, the wave front gets steeper until the crest tumbles forward and the wave breaks - Two kinds of breakers: 1. Plunging breaker: Break VIOLENTLY against the shore, leaving an air-filled tube, or channel, between the crest and food of the wave. STEEPLY-sloped bottom (aka "Barreling") 2. Spilling breaker: The crest of the waves slides down the face of the wave as it breaks onshore. GRADUALLY-sloped bottom. Long and SLOW
What are swells?
- Waves that have obtained enough energy to travel beyond their generation area/fetch. A swell is an organized series of waves with a characteristic height and period. They are "wave trains" of common direction and wavelength - They no longer need additional wind to push them onward - May be generated by prevailing winds or by storms - Once formed, swells may carry the energy of storms thousands of kilometers - Not significantly affected by local wind at that time - Generated far from open ocean storms with a wide fetch - Travel across ocean until reaching land
Describe the motion of water as a wave passes
- Waves transport energy, NOT water mass, across the ocean surface - Energy moves through the water, but the water through which the wave travels remains relatively still, other than the circular motion of individual water molecules (Orbitals) - The orbital motion occurs because water waves have both longitudinal and transverse waves, leading to a circular motion - Water molecules in the crest (peak of wave) move in the SAME direction as the wave. Water molecules in the trough (valley of wave) move in the OPPOSITE direction as the wave
Describe the process of wind-wave development from ripples to stormy seas (local wind waves) to swells
- When wind blows across the sea surface, the friction between the air and water kicks up a series of small ripples - As the wind picks up, a few molecules of water move colliding with other, setting them in motion (Increased motion = choppier water) - The ripples/bumps on the sea give the wind something to push against, and soon the ripples grow into waves - A stormy area at sea can be a generating region for large wave trains (waves move away from the storm center in sets) - The waves grow higher, longer, and faster, reaching their maximum size when they nearly match the speed of the wind. The longer and further the wind blows, the bigger and faster the waves become - Storm waves begin as turbulent, rough seas bear a storm site. As they move away from the storm center in wave trains they become swells
Describe wind-waves - What are their disturbing forces? Restoring forces? Typical wave periods?
- When wind blows over an area of the ocean's surface, wind waves are generated by transferring some of the wind's energy from the air to the water (Friction between wind and surface water) - Disturbing force: Wind (Most common disturbing force) - Restoring force: Gravity - Typical wave period: ~5-15 seconds Additionally: - Wavelength: ~60-150 m - Wave height: ~1-15 m (3.3-50 ft)
Describe the generation of wind-driven currents
- Wind driven currents carry energy AND water - Their fastest current speeds = 3-4 m/s (Surface current speed ~ 3% of wind speed) Generated: 1. Winds blow on ocean surface 2. Frictional drag causes surface waters to move with wind 3. Orbitals at the surface drag along water molecules in layer below them 4. Each successive layer is dragged by friction from the layer above it 5. Frictional drag and the strength of the current decrease with depth
Explain how the wind, the Coriolis force, and frictional drag influence the movement of ocean currents (balance of forces) - Ekman Theory
- Winds impart motion to the surface layer of water --> starts to move in direction of the wind - Once water starts moving, Coriolis kicks in, deflecting the current right or left (based on hemisphere) - A balance of forces sets up between the wind stress, Coriolis, and frictional drag - Surface currents: 45 degrees to the right of the wind direction in NH, 45 to the left in SH
What factors affect the size of the wind wave development?
1. Wind strength: Wind speed must be faster than the speed of the wave for energy transfer to continue (Wind speed > wave speed) 2. Wind duration: The length of time the wind blows over the same part of the ocean; winds that only blow for a short time will NOT generate large waves (Wind blown a long time --> Big waves) 3. Fetch: The uninterrupted distance over which the wind blows WITHOUT changing direction (Area of contact between the wind and water where the wind-generated waves begin, AKA the wave generating region) Stronger winds + longer duration + greater distance = LARGER wave
What are the primary drivers of surface currents and deep-ocean currents?
1.) Wind: The primary driver of surface currents 2.) Density gradients: Salinity and temperature gradients drive deep-ocean currents
Where do most tsunamis occur?
80% occur in the tectonically active region known as the Pacific Ring of Fire
iClicker: What is the average sea-surface salinity? A.) 35% (parts per hundred) B.) 35 ppt (parts per thousand) C.) 35 ppm (parts per million)
B, 35 ppt (parts per thousand)
iClicker: What happens to sea-surface salinity when it rains? A.) Salinity increases B.) Salinity decreases
B, Salinity decreases - Adding freshwater
iClicker: The highest salinities are associated with areas of... A.) Low atmospheric pressure B.) High atmospheric pressure
B, The highest salinities are associated with areas of High atmospheric pressure - Dry, hot regions, Ex.) Subtropics
Describe the net transport of water in the Ekman layer (Ekman transport). How is the direction of Ekman transport related to the direction of winds in the Northern Hemisphere? Southern Hemisphere?
Ekman Transport: Average direction (net transport) of water in the Ekman layer - Always 90 degrees to the right of the wind direction in the NH (Left in SH)
Explain how winds and Ekman transport create areas of coastal upwelling and downwelling in both the Northern and Southern hemisphere
Coastal winds produce upwelling/downwelling of coastal waters through Ekman transport (Depends on wind direction) - Coastal Upwelling: Wind direction is parallel to the coast (ALONGSHORE winds). Ekman transport moves the coastal water to RIGHT of wind direction NH, causing the net transport of surface water to flow AWAY from shore - Coastal Downwelling: Winds are still parallel to the coast, but in opposite direction. Ekman transport moves the coastal water to the RIGHT of the wind direction NH, this time causing the net transport of surface water to flow ONSHORE
iClicker: What type of wave interference produces rogue waves?
Constructive interference
iClicker: How much more energy does a 20 foot wave at Maverick's have compared to a 2 foot wave in Malibu? A.) 2 times more energy B.) 10 times more energy C.) 40 times more energy D.) 100 times more energy
D, 100 times more energy - Wave energy is proportional to the square of wave height - (20)^2 / (2)^2 = 400 to 4 = 100 to 1
What is the difference between diurnal, semidiurnal, and mixed semidiurnal tides? - What is the period of each? - Describe where each type of tide occurs (U.S. only) - What type of tide occurs in Santa Barbara?
Diurnal tides: - One low tide and one high tide per day - Period = 24 hours - Where = In the Gulf Coast Semidiurnal tides: - Two low tides and two high tides per day of approximately equal height - Period = 12 hours - Where = In the US East Coast Mixed Semidiurnal tides: - Two low tides and two high tides per day of different heights - Period = 12 hours - Where = In the US West Coast and Santa Barbara
Describe the distribution of saltwater vs. freshwater on Earth
Earth's water supply is 97% saltwater and 3% freshwater
What is the Ekman spiral? Describe how the speed and direction of the current changes with depth (from the surface to the Ekman depth)
Ekman Spiral: When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them In each successive layer: 1. Current speed DECREASES with depth 2. Current direction is pulled a little to the right (in NH) by Coriolis - As a result, plots of current vectors with depth result in an Ekman spiral pattern - Ekman Depth: Depth at which current moves in opposite direction of the wind. (Speed = ~4% of surface current) (Usually occurs around 100 m) - Ekman Layer: layer of water in between the surface and the Ekman depth
What processes influence the formation of a marine layer or coastal fog?
Marine Layer: Cold water brought by upwelling currents, promotes formation of a marine layer/temperature inversion over the ocean (Cold air below warm air) Coastal Fog: Forms when theres cold SSTs (driven by upwelling) and warm air temperature. The cold SSTs drive cooling of overlying air and condensation/fog develops
Define Neap tides - What phase of the moon is associated with them? - Describe and/or draw the alignment of the Earth, Sun, and Moon during Neap tides - Describe and/or draw the lunar and solar tidal bulges during Neap tides - Describe the tidal ranges associated with Neap vs Spring (i.e. when will tides be more or less extreme?)
Neap tides: The sun, earth, and moon are at RIGHT angles to each other (Earth in the middle) - This occurs during a FIRST QUARTER or THIRD QUARTER moon - During Neap tides, the solar tide partially cancels out the lunar tide (SUBTRACTIVE effect) - Neap tides are associated with MODERATE high and low tides
What is a gyre?
Ocean gyres are large system of circular rotating ocean currents formed by global wind patterns and forces created by Earth's rotation
Which ocean basin is the largest?
Pacific Ocean
Define Spring tides. - What phase of the moon is associated with them? - Describe and/or draw the alignment of the Earth, Sun, and Moon during Spring tides - Describe and/or draw the lunar and solar tidal bulges during Spring tides - Describe the tidal ranges associated with Neap vs Spring (i.e. when will tides be more or less extreme?)
Spring tides: The sun, earth, and moon are in alignment - This occurs during a NEW or FULL moon (aka twice a month) - During Spring tides, the solar tide has an ADDITIVE effect on the lunar tide - Spring tides are associated with EXTREME tides (very high and very low) - As the moon revolves around the Earth and New and Full moon, it reinforces the sun's bulge causing the tides to get really big
What is the Coriolis Effect?
The effect of Earth's rotation on the direction of winds and ocean currents - Air deflects toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere, resulting in curved paths
Define wave crest
The high point or peak of the wave
Define wavelength (L)
The horizontal distance from crest to crest
Define wave trough
The low point or valley of the wave
Describe the SSTs and biological productivity associated with areas of upwelling and downwelling
Upwelling: Deep, COLD, nutrient-rich water rises from below replacing surface water moving away from shore. High biological productivity/stimulate growth of phytoplankton/ ^ chlorophyll --> West coast US) Downwelling: As WARMER surface water moves towards the shore, it has no place to go but down. Downwelling= Warm and low biological productivity
Does warmer air hold more or less moisture?
Warmer air holds MORE moisture
Compare the wavelength, speed, and period of a tsunami with that of wind-generated waves
Wavelength: >100 km (Large!) - Wind wave wavelength = ~60-150 m - Tsunamis often pass unnoticed in the open ocean because their long wavelength makes the rise and fall of water hard to observe Speed: 300-800 km/hr (375-500 mph) - Wave speed is directly proportional to wavelength or period (Longer wave = faster speed) - Because tsunami waves have a much longer wavelength --> longer period --> a tsunami wave will consequently be faster Period: 5-60 minutes - Wind wave period = ~ 5-15 seconds - With a longer periods, tsunami waves are faster. Also, the longer the period, the lower the frequency
Define: Saturation humidity
When a volume of air at a given temperature holds the maximum amount of water vapor
