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Water, Water, Everywhere TIDES, CURRENTS, & WAVES
Welcome to the ocean planet.
326,000,000,000,000,000,000 gallons.
Average depth of the ocean is 13,124 feet.
The deepest point in the ocean is The Mariana Trench near the Phillipines.
This trench has a maximum depth of 36,200 feet.
SEAWATER (1kg)
965
35
fresh water
othercomponents
g
g
DISSOLVED GASES % in
ATM
% in
ocean
nitrogen
oxygen
carbon dioxide
78% 48%
21% 36%
.04% 15%
TIDES =>
• LUNAR TIDES -gravitational force between earth & moon
• “bulge” forms on side facing moon
TIDES =>
• “bulge” forms on opposite side
due to inertia
• How many tides/day?
TIDES =>
• “lunar day” is 24 hr. & 50 min.
• orbital plane of moon is inclined 28.5º
TIDES =>
• SOLAR TIDES are caused by the SUN and are 1/2 the height of lunar tides
TIDES =>
• “constructive” interference leads to “SPRING” tides
• “destructive” interference leads to “NEAP” tides
TIDES etc. =>
• TIDAL RANGE is the difference between high to low water
• TIDAL CURRENTS are due to flow of water in or out of a bay or harbor
TIDES etc. =>
FLOOD CURRENT is water flowing in due to rising tide
EBB CURRENT is the outflow due to falling tide
TIDES etc. =>
• SLACK WATER is the still water between tide changes
• tidal currents can reach 3mi/hr
OCEAN CURRENTS
• A combination of 4 things circulates the ocean in the Atlantic, forming “gyres”.
4 forces of current:
• surface winds • the sun’s heat • the Coriolis effect • gravity
The NORTH ATLANTIC gyre
• a series of four interconnecting currents:
• The Gulf Stream
• The North Atlantic Current
• The Canary Current
• The North Equatorial Current
STUDYING CURRENTS
• FLOAT METHOD • depends on movement of a free-floating object
• FLOW METHOD • measure current as it flows past a fixed point
sometimes big big boats sail the ocean blue…
sometimes it gets purrrty windy…
and other times…
ACCIDENTAL DATA?
• May, 1990: • The Hansa Carrier • 21 boxcar-sized cargo containers lost • containing 30,910 pairs of Nike shoes!
ACCIDENTAL DATA?
• pairs were not tied together • beachcombers placed ads, held swap meets, etc… • oceanographers noticed ads
ACCIDENTAL DATA?
• requested where and when information on shoe findings • refined computer models of the North Pacific gyre • some completed a FULL circuit of the gyre!
ACCIDENTAL DATA?
• January 1992, freighter lost 29,000 rubber ducks, etc. in the N. Pacific • recovered from 500mi of Alaskan shoreline
WAVE CLASSIFICATION
• by the DISTURBING FORCE: • wind • storm surges • landslides • seismic activity • volcanic eruptions
WAVELENGTH
A B crest
trough
height
orbital path of individual water molecule at water surface
FREQUENCY: number of wave crests passing point A or point B each second
B A
PERIOD: time required for wave crest at point A to reach point B
B A
• WIND WAVE: 60-150m (200-500ft.)
• SEISMIC SEA WAVE (tsunami): 200km (125mi.)
• TIDE: 1/2 circumference of Earth
TYPICAL WAVELENGTHS
TROPICAL STORM FORMATION
• area of storms moving off African coast… “cape verde” storms • converging winds cause storm to begin rotation • requires WARM water to continue dev. (80ºF)
FORMATION
• water vapor rises quickly • often continues until it hits land in the W. hemisphere • sometimes moves over colder water or is sheared off by easterly winds
FORMATION
• A TROPICAL DISTURBANCE is an organized area of storms for at least 24 hrs.
IF DEVELOPMENT CONTINUES
• A TROPICAL DEPRESSION is an area of low pressure with defined circulation
• A TROPICAL STORM is a strong area of low press. and max. sustained winds 39-73mph.
IF DEVELOPMENT CONTINUES
• A HURRICANE has maximum sustained winds over 73 mph. • usually 200-250 miles in diameter
IF DEVELOPMENT CONTINUES
• EXAMPLES of hurricanes:
• Sept. 2004 – Hurricane Frances approaches Florida…
• Sept. 2004 – Ivan in Texas, Jeanne nearing Bahamas
• Sept. 2004 – Hurricane Jeanne nearing Bahamas with 115mph. winds
• Sept. 2004 – Hurricane Jeanne makes landfall at Port St. Lucie…
http://www.nhc.noaa.gov/
stay in touch…
Can it be the end??
