15_Dynamic Ocean Waves and Tides
DYNAMIC OCEAN, WAVES, AND TIDES
ESC1000C - Dr. Jackie Miranda
March 10, 2025
AGENDA
60 Second News Update
Ocean currents and upwelling
Waves
Tides
Ocean Tides Lab 2025
60 SECOND NEWS UPDATE
Delivered by Olivia, March 2025
EVENT ANNOUNCEMENT
Pizza with the professors on Wednesday, March 12 at Noon in ES104
Topic: Red Tides and Marine Plankton
OCEAN CIRCULATION
Definition
Ocean currents: masses of water that flow from one place to another.
Surface currents develop from friction between the ocean and the wind.
Characterized by large, slowly moving gyres (circular currents).
FIVE MAIN GYRES
North Pacific Gyre
South Pacific Gyre
North Atlantic Gyre
South Atlantic Gyre
Indian Ocean Gyre
Factors Influencing Circulation
Initiated by large-scale winds.
Coriolis effect:
Clockwise in the Northern Hemisphere
Counterclockwise in the Southern Hemisphere
Direction influenced by the shape of continents.
GULF STREAM
Mapped by Benjamin Franklin in the 18th century.
Transports warm water northward along the East Coast toward Europe.
Formation of the Sargasso Sea characterized by sargassum algae mats.
OCEAN CURRENTS AND CLIMATE
Effects of Currents
Warm currents from low to high latitudes transfer heat.
Cold currents impact humidity and temperature, especially in tropics and summer months.
Cold currents can increase water acidity.
Impacts
Warm currents help moderate temperatures in regions like England and northern Europe.
Cold currents can contribute to desert-like conditions.
UPWELLING AND DEEP-OCEAN CIRCULATION
Upwelling
Rising of cold water from deeper ocean layers, especially along western coasts.
Nutrient-rich cold water rises to the surface, enhancing marine productivity.
Deep-Ocean Circulation
Driven by thermohaline circulation, influenced by temperature and salinity.
Cold water, denser than warm water, drives deep circulation.
Operates like a conveyor belt through different ocean basins.
THERMOHALINE CIRCULATION
Water density increases with cooling and salinity.
Most deep ocean currents originate at high latitudes and flow towards the equator.
LET'S REVIEW
Circular ocean surface currents are known as gyres.
Surface circulation is primarily driven by wind and modified by the Coriolis effect and land.
Upwelling provides nutrient-rich water and is a mechanism of thermohaline circulation.
WAVES
Definition: Waves transmit energy, primarily from wind.
WAVE SIZE
Parts of a wave: crest (top) and trough (bottom).
Factors determining wave size:
Fetch: distance wind blows
Wind speed
Duration of wind
WAVE CHARACTERISTICS
Wave height: vertical distance between trough and crest.
Wavelength: horizontal distance between crests.
Wave period: time for one wavelength to pass a point.
Wave base: depth below which wave motion is negligible.
CIRCULAR ORBITAL MOTION
Water particles move in circles as waveforms progress through water.
AT THE BEACH
Waves begin to slow down as they feel the bottom at depths < ½ wavelength.
Waves break when they run over themselves, creating surf.
WAVES APPROACHING THE SHORE
Deep water waves have constant wavelength.
As waves touch bottom, wavelength decreases and velocity diminishes, resulting in increased wave height.
LET'S REVIEW
Wave height is the distance from crest to trough.
Major influencing factors of wave height: fetch, wind speed, wind duration (wind direction is not a factor).
TIDES
Definition
Tides: periodic changes in ocean surface elevation, primarily caused by gravitational forces from the Moon and Sun.
Tidal Cycles
Monthly cycles depend on positions of the Sun and Moon.
Spring tides (greater range) occur during full and new moons; neap tides (smaller range) occur during quarter moons.
TIDAL CURRENTS AND PATTERNS
Tidal currents: horizontal flow related to tide changes.
Types of tidal currents:
Flood current: moves into coastal areas.
Ebb current: moves seaward.
Influences: coastline shape, ocean basin configuration, water depth.
TIDAL FLUCTUATIONS
Example of tidal range: Bay of Fundy, Canada (56 ft range).
TIDAL PATTERNS
Diurnal
One high and one low tide per tidal day; typical in Gulf of Mexico.
Semidiurnal
Two high and two low tides per tidal day; common along the Atlantic Coast of the US with equal heights.
Mixed
Two high and two low tides daily with significant height differences; prevalent along the Pacific Coast.
Tidal Graph Example
Mixed tidal pattern shows variance in tidal heights over a daily cycle.
CLEARWATER BEACH TIDES
Example tide chart for Clearwater Beach, FL, March 2025, showing high and low tides.
LET’S REVIEW
Greatest tidal range tides are spring tides.
A tide with one high and one low per day is diurnal.
A tide with two high and two low of differing heights is a mixed tide.
Spring tides occur when the angles among Earth, Sun, and Moon are aligned (180°) or during full/new moons.
OCEAN TIDE LAB
Data to be collected: greatest tidal range, highest high, lowest low, tidal range, moon phase.
OCEANOGRAPHY EXAM NOTICE
Exam scheduled for Wednesday, March 12.
Bonus points for completed review sheet.