Currents_ Tides_ Waves Review

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					Currents, Tides, Waves Review
         Tide Formation
• Gravitational pull of the moon
• Gravitational pull of the sun
• The centrifugal force of the earth
  as it rotates
• The relative positions of the moon
  and the sun
• The angle of the orbit of the moon
  around the earth
Gravity: force of attraction between two bodies
• Gravitational pull of the moon:
  – Draws moon and earth toward each other
  – Moon and earth revolve around central point –
    balancing centrifugal force is created that
    keeps them apart
     • Example: Adult and child hold hands and spin
       around together. The centrifugal force tends to pull
       them apart.
• High tide: crest of wave arrives at shore,
  raising the sea level
• Low tide: trough of wave arrives at shore,
  lowering the sea level
• Tide Range: vertical distance between
  high and low tide
• Ebb tide: outgoing tide between high
  water and low water
• Flood tide: incoming tide between low
  water and high water
 Tidal Patterns and Currents
• Diurnal Tide – single high and
  low tide daily. (ex. Gulf of Mexico)
• Semidiurnal Tide – two roughly
  equal high and low tides daily.
  (ex. east coast of U.S.)
• Mixed Tides – two unequal high
  and low tides daily. (ex. Pacific
  coast of U.S.)
 The Sun, Moon, and Types of Tide
• Spring Tides
   –Sun, moon and earth aligned
   –New moon – sun and moon aligned
    on same side of Earth.
   –Full moon – the sun and moon
    aligned on opposite sides of the
• Both positions create the highest and
  lowest tides
 The Sun, Moon, and Types of Tide
• Neap Tides
   –Moon is in a quarter phase, the
     lines from it and the sun to the
     Earth form a right angle.
• Raise the low tide and lower the high
Movements of masses of water in the ocean
Formation of Surface Currents
• The forces that move water to produce ocean
  currents are caused by:
 ▫ Rotation of the earth
 ▫ Winds
 ▫ Water density Differences
Effect of a Rotating Earth
• Turns from west to east.

• Velocity of rotation at its
  surface is
  ▫ greatest at the equator
  ▫ least at the poles.

• This is called the Coriolis
   Gyres – circular flow of water
• Clockwise in the northern hemisphere
• Counterclockwise in the southern hemisphere

5 Major Gyres
   •   North Atlantic
   •   South Atlantic
   •   South Pacific
   •   North Pacific
   •   Indian
   Gyres – circular flow of water
• Clockwise in the northern hemisphere
• Counterclockwise in the southern hemisphere

5 Major Gyres
   •   North Atlantic
   •   South Atlantic
   •   South Pacific
   •   North Pacific
   •   Indian
  Ekman Transport
• Coriolis effect – spinning of
  the earth

• Water flows to the right of
  the direction of the wind

• Water in each water column
  flows a little more to the right
  as you go down

• A down flowing spiral occurs
  Western and
Boundary Currents

• 5 major ocean gyres flow in relation to the spin
  of the earth – geostrophic currents.
• Currents on the western boundary of the ocean
  flow from the equator to the poles
• Currents on the eastern boundary of the ocean
  flow from the poles to the equator
• Western boundary currents are narrower,
  faster and deeper than other currents.
  Countercurrents and Undercurrents

• Countercurrent - water at the equator where
  lack of wind allows them to flow in the opposite
  direction of the current next to it.

• Undercurrent – water flows beneath and
  opposite of the current over it.

• Both return excess water to their source
   Upwellings and Downwellings
• Upwellings
 ▫ Form when winds parallel to shore force water
   away from shore; west coast of continents.
 ▫ Water from the bottom is brought up to replace
   the moved water
 ▫ Water brings with it nutrients from the ocean
• Downwellings
 ▫ Form when winds parallel to shore force water
   into shore; east coast of continents
 ▫ Extra water is forced down towards the bottom
Heat transport and Climate
• Currents redistribute heat throughout the globe

• Without these, Earth would have more extreme

• Cold water from the poles keeps the Galapogos
  Islands cool even though they are in the tropics

• Warm water from Gulf Stream, warms the air
  above and keeps much of Europe warmer than
  other places at similar latitudes.
  A hurricane can best be        Ok, So What Exactly Is a Hurricane?
  described as a huge
  tropical storm (up to 600
  miles in diameter)!
  Winds can be up to 200       Arrows indicate
  mph!                         “feeder bands”
                               or “rain bands”
  Storm usually doesn’t last
  for more than 7-10 days.
  It moves across the ocean
  at around 10-20 mph…not
  too fast really!
             • The winds are the strongest around the eye wall.
        • Within the eye, winds are calm and the weather is great.
• Strongest winds are on the right side, heaviest rain is usually on the left
Intertropical Convergence Zone
                           The ITCZ is an area of
                           low pressure located
                           roughly 5 degrees North
                           and South of the Equator.
                           It is a place where
                           • air converges,
                           • rises, and
                           •     condenses
                                   (forming clouds)
                           It is the rainiest place on
      So What Does a Hurricane Need in Order to Develop?

So a hurricane needs warm water, time to grow, and favorable upper
 level winds in the troposphere. If the winds are too strong, they will
          blow the hurricane apart – we call that wind shear!
       Evolution of Hurricane Development -- Stages

               Stage 3 – Category 1 Hurricane

                 Winds range from 75-94 mph.

  Well developed
 feeder bands. An
eye begins to form
   (although it is
covered in clouds).
Storm is tightening
   around center.
Saffir-Simpson Scale of Hurricane Intensity
Parts of a Wave Defined:
 Crest – highest point of a wave.
 Trough – lowest part of a wave; below the
   stillwater mark.
 Wave Height – vertical distance from crest to
 Wave Length – horizontal distance from crest
   to crest.
 Wave Frequency – the # of wave crests that
   pass a fixed point per unit of time.
 Wave Period – the time in seconds that it takes
  for one complete wave to pass a fixed point.
 Wave Speed – the speed of a wave in a certain
        Wave Patterns
• Parallel Waves – sets of waves traveling
  together in the same direction with crests
  about equally distant from each other.

• Radiating Waves – sets of waves that move
  outward in rings away from the generating
Climate – weather patterns over a long period of time

Tsunami – wave caused by an earthquake or other means
with a long wavelength and period

El Nino – waters in the eastern Pacific Ocean are warm due
to the jet stream

Greenhouse Effect – increasing temperatures of the
atmosphere due to infrared radiation trapped by gases

Seasons – changes caused by tilt of the earth’s axis and
revolution around the sun
• When waters
  in the eastern
  Pacific Ocean
  warm, the
  subtropical jet
  stream is more
  likely to dip
  south and bring
  into the

• When waters
  in the eastern
  Pacific are
  cool. In that
  case, the jet
  stream tends to
  stay further
  precipitation to
      The Wave of Disaster - Tsunami
• What is a tsunami?
 ▫ Series of waves with a long wavelength and
 ▫ Time between crests can vary from a few minutes
   to over an hour.

• What are the causes of a tsunami?
 ▫ Landslide
 ▫ Earthquake
 ▫ Volcanic Eruption

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