Transcript Chapter 14 – The Movement of Ocean Water

Chapter 14 – The Movement of
Ocean Water
Ocean Currents – The stream like movement of water in the
oceans that are influenced by many factors.
Thor Heyerdahl – A Norwegian explorer who proved that people
from Peru could have migrated to settle Polynesia by following the
ocean currents of the Pacific.
Surface Currents – The horizontal movement of ocean water
caused by the friction of the wind along the surface of the water.
The Gulf Stream Current carries 25 times the volume of water
than all of the rivers in the world combined!
Factors that control currents:
1. Global winds – Global winds cause the water to move
in different directions. Near the Equator, the winds blow the water
from the East to the West.
2. Coriolis Effect – Due to the rotation of the Earth, global
winds and hence currents, move in a curved path rather than in
straight lines.
3. Continental Deflection – When currents flow into
Deep Currents – The movement of waters below the
surface that are NOT influenced by the wind but
rather by density of the water. Cold temperatures and
high salinity produce denser water. As water increases
in density, it will sink due to gravity. Usually, these
currents will flow along the bottom of the oceans
however, when meeting denser waters, they will flow
above them.
Currents & Climates – Surface currents greatly affect
the climate in many parts of the world. Warm-water
currents create warmer climates along the coastal
regions of many continents which would normally be
colder. The Gulf Stream carries warm water from the
tropics and warms the British Isles. Conversely, the
California current is a cold water current and cools our
west coast!
Upwelling – The process in which cold, nutrient-rich,
deep ocean waters rise up to replace warmer surface
waters moved away by local winds. These nutrients
include iron and nitrates essential to the life process of
phytoplankton that form the base of the marine
ecosystem food web.
El Nino - A change in the water temperature of the
Pacific that produces warmer currents. Responsible for
disasters such as heavy rains producing floods and
mudslides in normally arid regions and droughts in
areas normally humid climates. This also prevents the
upwelling of nutrients in the coastal waters of South
America. The N.O.A.A. set buoys in the ocean to help
predict when El Nino will occur.
La Nina – A change in the Pacific waters where there
are colder than normal water temperatures. This also
affects weather patterns and usually follows an
El Nino event.
Waves – Created by the wind and move in a circular
pattern with only the energy of the wave being
directed towards the shore.
Wave Measurements:
1. Wavelength – The distance between two
successive wave crests.
2. Wave Height – The distance between the
trough and crest of a wave.
3. Wave Period – The time between two
successive wave crests.
As a wave approaches the shore, the energy of the wave
interacts with the ocean floor and begins to rise
upwards. Gravity will eventually pull it over to form a
breaker.
Undertow – A subsurface current that forms when the
waves washes up onto the shore and carries sand,
debris, swimmers, etc. back out to the sea.
Longshore Current – A current that runs
parallel to the shoreline.
Whitecaps – White, foaming waves with steep
crests that usually form during storms.
Swells – Long ocean waves that forms a high
wave and can travel long distances.
Tsunamis – Huge waves that are formed when
a large volume of water is suddenly moved up
or down usually by seismic or volcanic events.
Storm Surge – A rise in sea level caused by
strong winds usually associated with a
hurricane.
Tides – The daily change in the ocean level
caused by the gravitational pull of the sun and
especially the moon. Although the sun is larger
and we do orbit it, the moon is much closer
and has a greater gravitational influence. The
Earth rotates once every 24 hours.
Tidal Range – The difference in the level of
the ocean between high and low tides.
High Tide – The bulge in the ocean when
the Earth is facing the moon or opposite of.
Low Tide – The ocean water is drawn
away from the shore by the gravitational pull of
the moon.
Spring Tide – Occurs when the Earth, moon and
sun are in alignment to create the largest tidal
range, longest time between, and occurs twice
a month during the new and full moons.
Neap Tide – When the Earth, moon and sun
form a 90° angle resulting in the smallest tidal
range. Occurs twice every 28 days during the
first and the third quarter moons.
Tidal Bore – A body of water that rushes into a
narrow bay and causes a very sudden tidal rise.
The Bay of Fundy in Canada, has the greatest
tidal range due to its long, narrow, inlet.