·          Ocean Currents  Circulation of ocean water has profound effects on organisms living in the open ocean and coastal embayments.   Within bays and estuaries, tidal currents circulate and mix ocean and bay water transporting larva from offshore to bays and nutrients from bays to ocean.   http://www.youtube.com/watch?v=-hCZuYzNujI  Check it            Currents  Waves break along the shore at angles and the current flow parallel to the coast.   This is the longshore current or littoral drift which is the movement of water within the breaker zone and strictly from breaking waves.               Why Where and How Rip Currents form   Why Rip Currents Form    As waves travel from deep to shallow water, they will break near the shoreline. When waves break strongly in some locations and weakly in others, this can cause circulation cells which are seen as rip currents: narrow, fast-moving belts of water traveling offshore.        Why Rip Currents are Dangerous  Rip currents are the leading surf hazard for all beachgoers. They are particularly dangerous for weak or non-swimmers. Rip current speeds are typically 1-2 feet per second. However, speeds as high as 8 feet per second have been measured--this is faster than an Olympic swimmer can sprint! Thus, rip currents can sweep even the strongest swimmer out to sea.
      Where Rip Currents Form  Rip currents most typically form at low spots or breaks in sandbars, and also near structures such as groins, jetties and piers. Rip currents can be very narrow or extend in widths to hundreds of yards. The seaward pull of rip currents varies: sometimes the rip current ends just beyond the line of breaking waves, but sometimes rip currents continue to push hundreds of yards offshore.    

·          How to Identify Rip Currents   Look for any of these clues:  a channel of churning, choppy water   an area having a notable difference in water color   a line of foam, seaweed, or debris moving steadily seaward   a break in the incoming wave pattern       None, one, or more of the above clues may indicate the presence of rip currents. Rip currents are often not readily or easily identifiable to the average beachgoer. For your safety, be aware of this major surf zone hazard. Polarized sunglasses make it easier to see the rip current clues provided above            

·          Learn how to swim!   Never swim alone.   Be cautious at all times, especially when swimming at unguarded beaches. If in doubt, don’t go out!   Whenever possible, swim at a lifeguard protected beach.   Obey all instructions and orders from lifeguards.   If caught in a rip current, remain calm to conserve energy and think clearly.     Don’t fight the current. Swim out of the current in a direction following the shoreline. When out of the current, swim towards shore.   If you are unable to swim out of the rip current, float or calmly tread water. When out of the current, swim towards shore.   If you are still unable to reach shore, draw attention to yourself:  face the shore, wave your arms, and yell for help.         Rip Current Myth  A rip current is a horizontal current. Rip currents do not pull people under the water–-they pull people away from shore. Drowning deaths occur when people pulled offshore are unable to keep themselves afloat and swim to shore. This may be due to any combination of fear, panic, exhaustion, or lack of swimming skills.       

·          In some regions rip currents are referred to by other, incorrect terms such as rip tides and undertow. We encourage exclusive use of the correct term – rip currents. Use of other terms may confuse people and negatively impact public education efforts.            Rip Currents vs. Rip Tides  
Warning sign posted adjacent to tidal inlet in South Carolina. Photo courtesy University of Delaware Sea Grant College Program  Rip currents are not rip tides. A specific type of current associated with tides may include both the ebb and flood tidal currents that are caused by egress and ingress of the tide through inlets and the mouths of estuaries, embayments, and harbors. These currents may cause drowning deaths, but these tidal currents or tidal jets are separate and distinct phenomena from rip currents. Recommended terms for these phenomena include ebb jet , flood jet , or tidal jet .   
    

·          What is Undertow?   Undertow, an often misunderstood term, refers to the backwash of a wave along the sandy bottom. After a wave breaks and runs up the beach face, some of the water percolates into the sand, but much of it flows back down the beach face creating a thin layer of offshore-moving water with a relatively high velocity. This backwash can trip small children and carry them seaward. However, the next incoming wave causes higher landward velocities, pushing them back up on the beach.   Undertow does not pull you under water or out to sea.      

·          Currents  Surface and wind driven currents carry plankton.   The thermohaline/deep sea circulation brings O2 to abyss and disperses eggs and young of deep sea creatures and transports heat.    

·          Currents  Deep sea circulation is driven by temperature and density deficiencies within the ocean.   These are called thermohaline currents.   As the water cools it becomes more saline..some water form ice crystals so salt is left behind.   Currents  Water is more salty, higher density, sinks to a denser layer, pushes out polar water toward equator, horizontally moving deep water masses are deflected by the coriolis bending.  

·          Currents  These currents help deliver dissolved O2 to the bottom communities where there is no circulation.   Bottom water that is devoid of O2 is called anoxic/deoxygenated water.  

·          Currents  The suns irregular heating patterns of the atmosphere creates regular wind patterns around the world.   Frictional drag of prevailing wind along the ocean surface waters causes them to move.   (friction decreases with depth)               Currents  Coriolis effect-wind and water are deflected to the right in the northern hemisphere (left in Southern Hemisphere) due to the earths rotation and causes water to rotate slowly in circular rivers or gyres.   http://www.youtube.com/watch?v=pWNuBR7Sre0          

·          Currents  Ekman spiral is formed when wind driving surface currents and the coriolis effect creates additional deflection of water 100-200m below.     

·          Currents  Each succeeding layer is deflected further to the right.   In some cases this spiral is responsible for a phenomenon known as UPWELLING.

·          Currents  Movements of surface water away from the shore enables cold, dense bottom water to rise and mix with warmer surface water (UPWELLING).         

·          Currents  UPWELLING carries significant amounts of dissolved minerals to the oceans upper sunlit limit supplying fertilizer to plants near the surface...  That will grow food for the fish.   When upwelling stops, the numerous fish disappear (El Nino).                                                        http://www.popsci.com/adam-weiner/article/2008-10/physics-surfing-part-one-dropping?page=      http://www.youtube.com/watch?v=QPxLs0Cv4zY      WAVES

·           Waves are of practical significance to us...they may swamp a small boat,   smash supertankers,   damage offshore structures,   force commercial vessels to slow their speed,   damage shore structures,   WAVES  make students skip school when they want to surf and…  determine what adaptations organisms along the shoreline must have in order to exist there.   

·          WAVES  Waves are mechanical energy that has been transferred from wind, earthquakes, landslides, or other waves to the ocean water.  Most of the transfer is by wind and waves travel outward from the energy source. As more energy is supplied, waves become larger.     

·          WAVES  Properties of waves  3 factors that determine size of wind generated waves.  1. time of contact  2. velocity of wind  3. fetch-distance over which wind is in contact with water.    

·          WAVES  Any one of these factors can limit the wave height.   If the wind speed is low, it doesn't matter how far and how long the wind blows over the water, no large waves will be produced.     

·          WAVES  If the wind speed is great but short, again, no large waves will be formed and strong wind over a short area will also not produce large waves.   When no single limiting factor is present, large waves can form at sea. (40-50' S).    WAVES  A typical fetch for a local storm is about 500 miles and with the storm moving,   and the storm winds circulation around the low pressure area,             

·          WAVES   The winds can continue to follow the waves on the side of the storm which increases fetch and duration of time over which the wind can add energy to the waves.   Waves up to 49 feet are not uncommon and the wave lengths can be between 330-600 feet.   WAVES  Giant waves over 100' are rare but a Navy Tanker (USS Ramapo)in 1933 encountered a Typhoon and riding on the downside to ease the ride, was overtaken by waves that when measured against the ships superstructure by the officer on watch were 112'high.     W

·          AVES  The period was 14.8 seconds and the wave speed was 90'/sec (60 mph). While conditions to produce waves of this size occur, none have been well documented (or have survived).   

·          WAVES  PARTS OF THE WAVE  The portion of the wave that is elevated above the undisturbed sea surface is the crest.   The portion that is depressed below the surface is the trough.     

·          WAVES  The distance between two successive crests or two successive troughs is the length of the wave or wavelength,   and the height of the wave is the vertical distance from the top of the crest to the bottom of the trough.    

·          WAVES  The amplitude is equal to 1/2 the wave height or the distance from the crest or trough to the still water or equilibrium surface.   The period is the time required for two successive crests (or troughs) to pass a point in space.  

·          WAVES  The relationship between wavelength and wave periods allow math approximations to be made giving more insight to the behavior and properties of waves.                                                  

·          WAVES  WAVE MOTION  The particles of water get set into motion when a wave passes across the water surface.   The ocean wave does not represent a flow of water but a flow of motion or energy from its origin to its eventual dissipation at sea or loss against land.   WAVES  The surface water particles trace an orbit whose diameter is equal to the wave height.   The same motion is transferred to the water particles below but less energy of motion is found at each succeeding depth.   The diameter of the orbits decrease and become smaller and smaller as the depth increases.    

·          WAVES   At a depth of 1/2 the wavelength, the orbital motion has decreased to almost zero.   

·          WAVES  WAVE SPEED  It is possible to relate the wavelength and period of the wave in order to determine the wave's speed.   The speed of the wave (C) is equal to the length of the wave (L) divided by the period (T):  Speed = length/period or C=L/T  

·          WAVES  Particles in the ocean are set into an elliptical motion as wind energy acts on water.   The energy of the particles move (is transferred) through the ocean, not the particles.   Their movement makes the waves shape.   WAVES  The vertical height-from the top of the crest to bottom of trough is the wave height.  The time between successive crests/troughs passing a fixed point is the period of a wave.   

 

·          WAVES  Sharp peaks are called seas and as waves move out of their area.   The crests become rounded forming a swell, a long, low wave that can travel thousands of miles.  

·          WAVES  As the wave approaches the shallow water, it changes shape. –  the wave length decreases. –  the height increases as particles encounter resistance from the bottom.    

·          WAVES  The pathway of the particles become more elliptical as it gets closer to the coastline.    ..bottom resistance slows the waves.   ..shortens wave length when depth is 1/2 wavelength.   

 

·          WAVES  When depth decreases less than 1/2 wavelength (or 1.3x height)      the frictional drag along the bottom   and forward motion of the wave and steepness of the crest causes the wave to break or collapse against the shore.  

·          WAVES  Stored energy is released as the water falls against the shore.   

·          WAVES  BREAKERS  Breakers are formed in the surf zone because the water particle motion at-depth is affected by the bottom, slowed down, and compressed vertically. The orbit speed of the particles near the crest are not slowed too much so…….  WAVES  particles move faster toward the shore than the wave itself.   The crest can curl and eventually break (fall over).   There are two types, plungers and spillers.    

·          WAVES  Plunging breakers are usually found on a steep beach, the curling crest outruns the rest of the wave curves over the air below it and breaks with a sudden loss of energy and a splash.   Spilling waves occur at flatter beaches and consists of turbulent water and bubbles flowing down the collapsing wave face.  

·          WAVES  Marine organisms along the ocean are affected by wave actions.   Sandy and rocky shores, exposed to the direct assault of strong waves are known as a high energy environment, as opposed to beaches in protected estuaries, bays and lagoons which is a low energy environment.

·          WAVES  Winter usually has higher crests and shorter wave lengths than summer thus release more energy on the shore.    

·          WAVES  In the storm center, the sea surface is jumbled with waves of all heights, lengths and periods.   There are no regular patterns.   Sailors call this a sea.   As waves are being generated, they are forced to get larger by the input of energy forced waves.   WAVES  Due to variations in the winds of the storm area, energy at different intensities is transferred to the sea surface at different rates, resulting in waves with a variety of periods and heights.   

·          WAVES  Once a wave is created with its period, the period doesn't change.   The speed may change but the period remains the same.   The period is a constant property of the wave until the wave is lost by breaking at sea, through friction, or crashing against the shore.               

·          Wave Buoys        Station 41009 - CANAVERAL 20 NM East of Cape Canaveral, FL   Funding provided by the National Aeronautics and Space Administration  What is a Tsunami?

·          WAVES  WATER TRANSPORT  Waves transport water toward the beach in the surf zone.   There is a drift of water in the direction the waves are traveling and is intensified in the surf zone and with the waves approaching the beach at an angle, the transport of water moves both toward and along the beach.   WAVES  REFRACTION  Waves usually approach the shore at an angle and when one end of the crest comes in and feels the bottom and the other end is still in deeper water, the shallow water end slows and because the deep water part is still traveling the same speed, the wave crests bend, or refract.   

·          WAVES  DIFFRACTION  When a wave passes its energy though a narrow opening, some wave energy will pass through to the other side and once through the energy radiates out and away from the gap.     

·          WAVES  REFLECTION  A steep, vertical barrier in water deep enough to prevent waves from breaking will reflect the waves..   

·          WAVES  STORM SURGES   Periods of excessive high water due to changes in the atmospheric pressure and the wind's action on the sea surface are called storm surges or storm tides.   These are not typical waves but share characteristics of curving sea surfaces and produce like effects to that of tsunamis.   WAVES  SWELL  Once energy or generating forces no longer effect the waves, the forced waves become free waves moving at speeds due to their periods and wavelengths.   Some waves produced have long wavelengths and long periods and have a greater speed than those with short.  

·          WAVES  They gradually move through and ahead of the slower ones and escape the storm and appear as a regular pattern of undulating crests and troughs moving across the sea surface.   Once away from the storm these waves are called swell.   WAVES  They carry considerable energy which they lose very slowly..   The movement of the faster through and ahead of the slower waves is called sorting or dispersion.   Groups of these faster waves move as wave trains or packets of similar waves with about the same period and speed (sets).   

·          WAVES  TSUNAMI  Earthquakes are often responsible for producing seismic sea waves or tsunamis. They are called tidal waves (incorrectly) and formed if in an area the earths crust suddenly raised or lowered.     WAVES    Energy is transferred to water as the coastal plates shift.   Travel through the sea at 100+ mph with a wave length of 100miles when reaching the coast, wave lengths shorten and heights can increase to 100'.   WAVES  The displacement causes a sudden rise or drop of the sea level and gravity causes the water to quickly fill it in. Waves with long wave lengths are produced (100-200km) and periods of 10-20 min    WAVES  As the wind blows, energy is transferred to the water over large areas, for varying lengths of time, and at different intensities.   As waves form, the surface becomes rougher, and its easier for the wind to grip the roughened water surface and add energy .       The rhythmic rise and fall of the oceans water at a fixed location is known as the tide.  

·          TIDES    

·           Tides  Tides are long waves moving through the ocean.   When the crest of the moving tide reaches a location, high tide occurs.   Low tide is when the trough reaches the location.     Tides  Best known as the rise and fall of these around the edge of land, the tides are caused by the gravitational attraction between   the earth and the sun and between the earth and the moon.   While tides go unnoticed far out at sea, they are easily observed along the shoreline.   Tides  Three types of tides occur.   1. Semi-diurnal 2 high and low tides per day about equal range. Most.EC   2. Diurnal 1 high and 1 low tide per day (24hrs) Gulf of Mexico/Vietnam/Manila   3. Mixed 2 high and 2 low tides per day but different ranges...1 high high, 1 low low 1 high 1 low west coast   Tides  Tides behave differently in different places.   In some coastal areas there is a regular pattern of one high and one low tide each day known as a diurnal tide.    Tides  In other areas there is a high-low water sequence repeated twice a day...semidiurnal tide and these tides usually reach about the same level at high and low tides each day.       Tides  The third type of tide has two high and low tides a day but the tides reach different high and low levels during a daily rhythm.     

·          Tides  This is called a semidiurnal mixed tide.  It is caused by a diurnal (daily) inequality by combining a semidiurnal and diurnal tide.   Tides  In the uniform tidal system (semi and diurnal) the greatest height to which the tide rises on any day is known as high water and the lowest point is low water.   In a mixed system it refers to higher high and lower high water and higher low and lower low waters.   Tides  Tidal observations made over a period of time are used to calculate the average or mean tide levels.   Since the depth of coastal waters is important for navigation, an average low-water reference is established:   depths are measured from this level and recorded on navigational charts   Tides  This area is usually established at mean low water and the zero reference or tidal datum, is established at this point.   In mixed tidal areas, mean lower low water is used as the tidal datum.   Sometimes the low tide level may fall below the mean value used as the tidal datum producing a minus tide .   

·          TIDAL CURRENTS  When the tide is rising, it is called a flooding or flood tide and  when its falling it is an ebbing tide.  Currents associated with the rising and falling of the tide in coastal waters is a tidal current.     

·          TIDAL CURRENTS    They can be very swift and dangerous.     When the tide turns, reverse direction, there is a period of slack water during which the tidal currents slow and then reverse.  MOON TIDE  Water particles on the side of the earth facing the moon are closest to the moon and are acted on by the larger moon gravitational force.   Because water is liquid and deformable,the force is applied to water particles toward a point directly under the moon.   Tides  It produces a bulge in the water covering.   At the same time, the centrifugal force of the earth moon system acting on the water particles at the earths surface opposite the moon creates a bulge too .  

·          Tides  TIDAL DAY  The moon and earth are moving in the same direction along its orbit during a 24 hr period but the earth must turn an extra 12' and 50 minutes for the moon to be directly over the same place.    

·          Tides  Therefore the tidal day is not 24 hours long but 24 hr and 50 minutes explaining why tides arrive at a location about an hour later each day 

·          Tides  The tide wave  The crest of the wave is high water   (tide) and the trough is low water (tide).   The wavelength of this wave is 1/2 the circumference of the earth and period 12 hr and 25 min.   

·          Tides  The SUN TIDE  While the moon plays a greater role in tide producing, the sun also produces its own tide wave.   Though it is large, the long distance away means its tide raising force is only 46% that of the moon and the average time is 24 hours not 24h50m.   

·          Tides  The tide wave produced by the moon is greater magnitude and continually moves eastward relative to tide wave produced by the sun and   therefore the tide forces produced by the moon are greater and more important than that of the sun (therefore tidal day 24h50m).   Tides  SPRING AND NEAP TIDES  During the 29 1/2 days it takes the moon to orbit the earth, the sun, the earth and the moon move in and out of phase with each other.    

·          Tides  During the period of the new moon, the moon and sun are lined up on the same side of the earth so that the high tides, or bulges, produced independently of each, coincide.   Since the water level is the result of adding the two wave forms together..  

·          Tides  tides of maximum height and greatest depression, or tides with the greatest range between high and low water are produced.   These are spring tides.               

·          Tides  In a weeks time, the moon is in its 1st quarter and moved about 12' per day, until its at a right angle to the sun wave.   Now the crests of the moon tide will coincide with the troughs produced by the sun and the same is true of the sun's crests and moons troughs.   

·          Tides   They tend to cancel each other out and the range between high and low water is small.   These are low-amplititude neap tides.   

·          Tides  At the end of another week, the moon is full and the sun, moon and earth are again lined up, producing crests that coincide and tides with the greatest range between high and low waters, or spring tides.   

·          Tides  These are followed by neap tides seven days ;  later and the cycle, 4 weeks, continues with a spring tide every two weeks...etc.   This 4 week progression creates a tidal cycle of changing tidal amplitude.   

·          Tides  DECLINATION TIDES  If the earth and moon are aligned so that the moon stands north or south of the earth's equator, one bulge is in the Northern Hemisphere and one in the Southern Hemisphere.   A point in the middle latitudes passes through only 1 crest and one trough during the tidal day.  

·          Tides  This type of diurnal tide is called a declination tide, because the moon is said to have declination when it stands above or below the equator.   

·          Tides  The sun also influences these tides as it sits over 23.5N/S at summer and winter solstice and the variation causes the bulge created by the sun to oscillate north/south (making a more diurnal sun tide during winter and summer.    

·          Tides  The moons declination is at 28.5N/S and because the orbit is inclined 5' to the earth sun orbit, it takes 18.6 yrs for the moon to complete its cycle of maximum declination.    

·          Tides  When the sun and moon coincide, both tide waves become more diurnal.   Also the moon doesn't move around the Earth in a perfectly circular orbit or even does the earth circle the sun at a constant distance.  

·          Tides  TIDE TABLES  Because of all the combinations, its not possible to predict the earths tides from our knowledge of tide raising bodies alone.   But with a combination of actual local measurements with known astronomical data, tide predictions are quite accurate.  

·          Tides  Water level recorders are installed at coastal sites and the rise and fall are measured over a period of years..  .At least 19 years are needed to allow for the long 18.6 year period of declination of the moon.  

·          Tide Tables are published annually by NOAA.   Tides  The tables give the dates, times, and water levels for high and low water at a primary tide station.   There are only 196 of these but consulting a list for other 6000 auxiliary stations applying corrections to the times and heights of the primary stations helps more localities get accurate tide predictions.                 

·          Tides  Tidal predictions are based on recorded high measurement from past records which are used in the future.  Tide Current Tables  Like tides, these currents are measured at primary locations and data is published similar to tide tables.   Useful for moving in and out of estuaries.    

·          Tides  Summary  Without land, 2 bulges , 1 on side of the earth closest to the moon, 1 on the other side would appear.   Bulge is high tide from mutual attraction between earth and moon.   Moon gravitational attraction pulls and moves the water.   Tides  The opposite bulge, centrifugal force created as the earth and moon revolve around a common point...barycenter-4670 km (2900miles) from earths center.   

·          Tides occur at different times because the moon goes around the earth in 24h50m or 1 lunar day. (freq 12h25m)  

·          Tides  Due to friction between earth and tidal bulges, High tide is given about 50 minutes after the moon passes over that point. known as a lunar semidiurnal tide.  

·          Tides  Vertical height ...high to low water is the tidal range and varies day to day because of the sun and the moon.   Solar tides are 1/2 the size of lunar tides.   When the sun and moon line up (2x per month) tides are higher and lower than usual...spring tide.

·          Tides  When the moon is at right angles to the sun, there is less gravitational effect that lessens the tidal range (neap tides)     

·          Tides  Between these tides the height varies throughout the month.  Differences in tidal frequencies and range occur because of the shape of the ocean basins and coastline (Hawaii is a few cm while the Bay of Fundy is 20m.)   

 

 

Review Even Answers

Marine Bio HW#3

2.             surface from wind/deep sea from density /temperature differences

4.             left

6.             fetch/wind speed/wind duration

8.             low and high energy environments-shallow offshore and steep offshore

10.           bottom topography, alignment of moon and sun

12.           after moon pases your area, crest of tide wave moves over and you experience high tide..trough=low tide///diurnal/semi-diurnal-mixed

Review Questions

2.             gulf stream current

4.             weakening of trade winds t

6.             ekman spiral

8.             about 45' to the right

10.           ,, they move so slowly,

12. Coriolis effect

14.           disturbance / energy / medium     14 breaking waves returning to the sea

16.           sea

18.           112

20.          deeper than half of its length

22.          fully-developed sea

24.          bottom-oriented pressure sensors

26.          a fast-moving flood of water

28.          around the Pacific Rim

30.          coastal estuarine sedimentation,  pollutant transport ,  invertebrate reproduction

32.          TWICE

34.          TIDAL CURRENT

36.          associated with river inlets, considered to be a true tidal wave ,exposed to great tidal fluctuation

38.          TIDAL RANGE

Reading---read it!