• How can you increase the height of waves?
• The height of the waves increases as:
1.
The wind speed increases
2.
The wind blows for longer times
3.
The distance over which the wind blows the water increases
• What three characteristics do we use to describe waves?
1. Wavelength – The distance between crests
2. Wave height – the vertical distance between the crest and the trough
3. Period – The time it takes for successive waves to pass

• What are the three general forms of ancient Hawaiian surfing? Who surfed?
• body-surfing ( kaha nalu )
• outrigger-canoe-surfing (probably called no ka pakaka ale )
• surfboarding ( he’e nalu )
• Everyone, Men, Women, Children, Chiefs, Commoners – It’s the national sport of Hawaii
• What were the two different types of surfboards used in ancient Hawaii?
Who were allowed to use them?
• olo – a long, narrow board reserved exclusively for chiefs
• alaia – shorter thinner boards for commoners

• Surface Currents – upper 10% of the ocean; upper 400 m
TROPICS
• Pycnocline – the layer between surface and deep waters; where a rapid change in temperature, salinity and density occur
• Deep Current – lower 90% of the ocean

• How they impact ocean currents
• Temperature – remember heat rises!
• Salinity – remember salty water sinks!
• Density – a function of temperature and salinity

http://earth.usc.edu/~stott/Catalina/Oceans.html

• These Start the Water MOVING:
• Sun/solar heating - causes water to expand and move
• Winds - push the water; winds blowing for 10 hrs across ocean will cause the surface water to flow @ ~2% wind speed; wind has the greatest effect on surface currents
• Gravity - pull water downhill or pile against the pressure gradient
(high/low); influences tides
• Coriolis Force/Effect – Rotational effect, pulling to the right in the Northern
Hemisphere and to the left in the
Southern Hemisphere

http://www.bigelow.org/shipmates/hc_currents_lg.gif

• Surface current – with surface circulation is less dense and influenced by winds
1. Warm surface currents: wind and
Earth’s rotation
2. Cold surface currents: flow towards the equator
3. Upwelling current: cold, nutrient rich; result of wind
4. Western Boundary currents : warm
& fast
5. Eastern Boundary currents: broad, slow, cool & shallow, associated with upwelling
• Ex: Gulf Stream = surface current that is the upper 20% of the ocean, western boundary current

• Deep water – cold, dense, salty; move by density forces and gravity; move slower than layers above
• Ex: Global Conveyer Belt = deep current that is the lower 20% of the ocean; takes 1,000 years to complete the cycle.
• Thermohaline Circulation driven by:
• differences in the density of the sea water
• controlled by temperature (thermal) and salinity (haline).
• This slow (~0.1 m/s), but giant circulation has a flow equal to about
100 Amazon Rivers.

• Gyres – large mounds of water; large circular currents in the ocean basin
• Ex: South Pacific Gyre = consists of
4 separate currents – S. Equatorial,
East Australian Current, Peru
Current and the West Wind Drift.

• A Wave is a rhythmic movement that carries energy through matter or space.
• In oceans, waves move through seawater

• Crest – highest point of a wave
• Trough – lowest point of a wave
• Wave Height – vertical distance between the crest and the trough
• Wavelength – horizontal distance between two crests or two troughs

• When a wave passes through the ocean, individual water molecules move up and down
but they do not move forward or backward.

• When a wave breaks against the shore, the crest outruns the trough and the crest collapses.
• Called a breaker.
• In this case, water does move forward and backward.
• Waves Break in the Surf Zone

• Spilling breaker
• Top of wave crest ‘spills over’ wave. Energy released gradually across entire surf zone.
• Plunging breaker
• Crest ‘curls over’ front of wave. Energy dissipates quickly. Common at shorelines with steep slopes
• Surging breaker
• Never breaks as it never attains critical wave steepness. Common along upwardly sloping beach faces or seawalls. Energy released seaward.

• The part of the wave crest closer to shore is in shallower water and moving slower than the part away from the shore in deeper water.
• The wave crest in deeper water catches up so that the wave crest tends to become parallel to the shore.

• Waves come in different shapes and sizes with differences in wave height and wave period.

• Most of the waves present on the ocean’s surface are wind-generated waves.
• Size and type of wind-generated waves are controlled by:
• wind velocity
• wind duration
• Fetch (distance over the sea surface)
• original state of the sea surface.
• As wind velocity increases wavelength, period and height increase, but only if wind duration and fetch are sufficient.
CALM WIND
STORMY WIND

• Fetch is the area of contact between the wind and the water and is where wind-generated waves begin.
• Seas is the term applied to the sea state of the fetch when there is a chaotic jumble of new waves.
• Waves continue to grow until the sea is fully developed or becomes limited by fetch restriction or wind duration.

Chaotic seas inside fetch area.
Swells: wave type found outside the fetch.

• Tidal range is the difference in ocean level between high-tide and lowtide
• The rise and fall in sea level is called a tide .
• Caused by a
.
• One low-tide/high-tide cycle takes about 12 hrs and 25 min.

• Two big bulges of water form on the Earth :
• one directly under the moon
• another on the exact opposite side
• As the Earth spins, the bulges follow the moon.

• Spring Tides
• Earth, Moon, and Sun are lined up
• High Tides are higher and Low Tides are lower than normal
• Neap Tides
• Earth, Moon, and Sun form right angles
• High Tides are lower and Low Tides are higher than normal

• Semidiurnal
• two high and two low tides of approximately equal size every lunar day.
• Diurnal
• one high and one low tide every lunar day.
• Mixed Semidiurnal
• two high and two low tides of different size every lunar day.

• What type of tidal cycle do you see here?
Semi-diurnal?
• The combination of diurnal, semi-diurnal and fortnightly cycles dominates variations in sea level throughout the islands.

• Tidal currents result from tidal variations of sea level, and near shore are often stronger than the large scale circulation.