Ocean Motion

Wave They obtain their energy and motion from wind. Crest The tops of the waves Trough The bottom of the waves

Anatomy of a Wave Picture

Wave Characteristics Wave height The vertical distance between the trough and crest Wavelength The horizontal distance between two successive crests OR two successive troughs Wave period The time it takes one full wave (wavelength) to pass a fixed position

Wave characteristics are dependent on three factors: Wind speed Length of time wind has blown Fetch Distance the wind traveled across open water

Wave Motion The water does not travel the entire distance, but the wave does. Consider the following: a floating object on the water such as a rubber duck What motion does the duck exhibit? (Forward motion or up and down or both – Explain)

Particle Motion Circular orbital motion allows energy to travel forward yet the individual water particles only move in a circle

Breaking Waves As the original wave advances toward shore: It begins to “feel bottom” at a water depth = ½ of its wavelength

Tides Daily change in the elevation of the ocean surface. Ocean tides result from the change in the gravitational attraction exerted upon Earth by the moon and the sun.

Ocean Tides The moon is the primary body influencing ocean tides It takes the moon 29 ½ days to make one revolution around the Earth The sun is farther away so it has a much smaller affect on ocean tides.

Gravitational force The moon pulls the ocean water creating a bulge on the side closest to the moon Therefore, the side farthest from the moon has less pull

Tidal Cycle The sun has some influence on tidal bulges Its influence is most noticed at full and new moons as they sun and moon are aligned Alignment = combined forces pulling on the Earth’s water Larger tidal bulges (higher hide tides) are created as are larger tidal troughs (lower low tides)

Tidal range Difference in height between successive high and low tides Spring tides Tides having the greatest tidal range due to the alignment of the Earth, moon & sun Experienced during full and new moons 2 per month Neap tides When the daily tidal range is the least Experienced at the first and third quarters of the moon (when the moon and sun act on Earth at right angles)

Tidal Cycle

Tidal Patterns Three main tidal patterns: Diurnal tides Semidiurnal tides Mixed tides

Diurnal tides A single high tide & a single low tide each day Gulf of Mexico Semidiurnal tides each day Two high and two low tides Both high or low tides are at the same height Atlantic coast of U. S. Mixed tides (Diurnal and semidiurnal each day) Large inequality in high water heights and/or low water heights Pacific Coast of U. S.