Currents

Surface currents – Develop from friction between the ocean and the wind that blows across the ocean surface – 2 Types: warm and cold

Gyres Gyre: large circulation of water within an ocean basin (ie. Atlantic, pacific, or indian ocean basin) Wind main force that generates surface currents – Coriolis effect is a factor that influences currents – Coriolis effect: the deflection of currents away from their original course as a result of Earth’s rotation – Northern hemisphere: clockwise – Southern hemisphere: counterclockwise

Currents & Climate Currents moderate temperatures on land by bringing warm water from the equator and cold water from the poles

Upwelling Wind induced vertical water movement Upwelling: the rising of cold water to replace warmer surface water that has been displaced by wind Brings dissolved nutrients, such as nitrates and phosphates, to the ocean surface

Waves

Wave Characteristics Most ocean waves derive their energy from the wind Wave height: the vertical distance between trough and crest Wavelength: horizontal distance between two successive crests or troughs Wave period: the times it takes for one wave to pass a certain point

Wave Characteristics The height, length, and period that are eventually achieved by a wave depend on three factors – Wind speed – Length of time wind is blowing – & fetch; the distance the wind has traveled across open water.

Wave Motion Circular orbital motion allows energy to move forward through the water while the water particles that transmit the wave move around in a circle

Circular orbital motion Water particles move in circle Movement up and down and Back and forth Fig. 8.4

Tides

The regular changes in the elevation of the ocean surface Tides form from the gravitational attraction exerted upon different parts of the Earth’s surface by the moon, and by a lesser extent by the sun.

Tidal Patterns Diurnal: a single high tide and a single low tide each tidal day Semidiurnal: two high tides and two low tides each tidal day Mixed: two unequal high water level heights, low water heights, or both

Shoreline Features and Processes

Shoreline Processes and Features Many shoreline features result from wave erosion, deposition, and transport of sediments Longshore currents: the current that flows parallel to the shore and moves a large amount of sediment along the shore

Erosional Features Sea Cave, Sea arch, and sea stack – Listed in order of increasing erosion

Depositional Features Examples: spits, tombolos, and barrier islands Barrier island – Example: North Carolina outer banks

Stabilizing the Shore Structures are built along beaches to prevent erosion of sediment along the coast – Examples include groins, breakwaters, and seawalls Beach nourishment: the artificial addition of large quantities of sand to the beach system