The Dynamic Ocean

Currents Ocean current is the mass of ocean water that flows from one place to another. Surface currents are movements of water that flow horizontally in the upper part of the ocean’s surface.  Surface currents develop from friction between the ocean and the wind that blows across its surface.

Gyres Gyres are huge circular-moving current systems that dominate the surfaces of the oceans. There are 5 major gyres  North Pacific  South Pacific  North Atlantic  South Atlantic  Indian

Wait a minute What do you notice about the currents in the Northern and Southern Hemispheres???? Because of Earth’s rotation currents are deflected to the right in the Northern Hemisphere and to the left in the Southern

Coriolis Effect The deflection of currents away from their original course as a result of Earth’s rotation.

Ocean Currents and Climate When currents from low-latitude regions move into higher latitudes, they transfer heat from warmer to cooler areas on Earth. As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas.

Lets look at Currents Read the short article on Page 454. Think about the old message in a bottle trick!!!!

Waves and Tides

Wave Characteristics Most ocean waves obtain their energy and motion from the wind.

Wave characteristic Wave height Wavelength Wave period Fetch

How big a wave gets depends on three factors:  (1) wind speed,  (2) length of time the wind has blown,  (3) fetch.

Eventually waves will hit a max height based on the previous three factors. This is known as being fully developed. White Caps- occur then the excess energy of a wave is given off.

Breaking Waves As the waves move into shallow water they slow down. As the waves slow they begin to “crowd up” so the wavelength will decrease but their height will increase. Eventually the waves become to steep and break causing surf.

Tides Tides are daily changes in the elevation of the ocean surfac e. Ocean tides result from the gravitational attraction exerted upon Earth by the moon and, to a lesser extent, by the sun. The two forces that produces tides are gravity and inertia.

During one day there are 2 high tides and 2 low tides

A beach is the accumulation of sediment found along the shore of a lake or ocean. Waves along the shoreline are constantly eroding, transporting, and depositing sediment.

When swimming in the ocean, have you ever wondered why you tend to be carried down the beach, away from your towel in an undertow?

Longshore Transport A longshore current is a near-shore current that flows parallel to the shore. It is the primary method of sediment transport along the beach. The key to notice is that waves do not hit the shore straight on the they come at an angle.

Longshore Currents

Features caused by longshore drift A spit is an elongated ridge of sand that projects from the land into the mouth of an adjacent bay. A baymouth bar is a sandbar that completely crosses a bay. A tombolo is a ridge of sand that connects an island to the mainland or to another island.

Barrier Islands Barrier islands are long, narrow, offshore deposits of sand or sediments that parallel the coast line.

Protecting our beaches Groins, breakwaters, and seawalls are some structures built to protect a coast from erosion or to prevent the movement of sand along a beach.

Beach Nourishment Beach nourishment is the addition of large quantities of sand to the beach system.