- Homework 2. -Answer this question and
email it to biovcc@Gmail.com
- 1. If you owned a seaside home and a
bad storm bought heavy winds and high surf to your coastline, would you
prefer it to be during a new moon or a quarter moon?
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, dont 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. Dont 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
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
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
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.
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
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
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.
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
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
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
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).
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.
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.
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.
relationship between wavelength and wave periods allow math approximations to
be made giving more insight to the behavior and properties of waves.
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.
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
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.
the wave approaches the shallow water, it changes shape. the wave length decreases. the height increases as particles encounter
resistance from the bottom.
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.
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.
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.
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.
usually has higher crests and shorter wave lengths than summer thus release
more energy on the shore.
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.
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
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.
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
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.
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
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 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.
tend to cancel each other out and the range between high and low water is
small. These are low-amplititude
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.
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.
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.)
Marine Bio HW#3
2. surface from wind/deep sea from density /temperature
8. low and high energy environments-shallow offshore and steep
topography, alignment of moon and sun
moon pases your area, crest of tide wave moves over
and you experience high tide..trough=low
2. gulf stream current
4. weakening of trade winds t
6. ekman spiral
8. about 45' to the right
they move so slowly,
14. disturbance / energy / medium 14 breaking waves returning to the sea
than half of its length
26. a fast-moving flood of water
the Pacific Rim
30. coastal estuarine sedimentation, pollutant transport , invertebrate reproduction
36. associated with river inlets, considered to be a true tidal
wave ,exposed to great tidal fluctuation