Currents

Currents

Driven by forces of wind, tides, and gravity, currents keep the ocean in constant motion.

7 Major CurrentsWest Wind Drift (AKA=Antarctic Circumpolar CurrentEast Wind DriftNorth and South Equatorial CurrentsPeru CurrentKuroshio Current-near Japan’s coast, travels up to 75 miles a day at 3 mi/hr.Gulf Stream

These currents flow in large rotating loops called GYRES(Clockwise in N. Hemi. and counterclockwise in S. Hemi.) WHY?

Due to the Coriolus Effect

The Coriolis effect is most apparent in the path of an object moving longitudinally. On the Earth an object that moves along a north-south path, or longitudinal line, will undergo apparent deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

COASTAL CURRENTS

Some currents occur along the coast and only affect limited areas.

LONGSHORE Current-caused by waves striking a beach at an angle front and part of the wave hits the shallow water first and slows down. The rest of the wave bends and comes onto the shore creating a current that parallels the beach. Longshore currents often form sandbars.

RIP Currents- are dangerous effects of Longshore currents. This Rip current or Rip tide can carry swimmers out to sea. Swimmers should swim parallel to the shore until the rip current is no longer felt and they can swim safely to shore.

Rip Currents

Fridtjof Nansen

• Special made boat named the Fram

• Froze it in ice to drift to North Pole

• Never made it, always 30-50 degrees to the right

• Why? Coriolus effect

Ekman Spiral

High Energy Beach

Low Energy Beach

TIDES

Tides are the alternating rise and fall of sea level with respect to land, as influenced by the gravitational attraction of the moon and sun.

Other factors influence tides; coastline configuration, local water depth, seafloor topography, winds, and weather alter the arrival times of tides, their range, and the interval between high and low water.

The Sun does influence our tides to some degree (the effect of the Sun on Earth tides is less than half that of the Moon).

Proxigean Spring Tide

• When the moon, sun, and earth are all at their closest point, they are said to be at the Proxigee.

• This occurs roughly every 1 ½ years.

• Mass release of eggs and mating occurs during this strong tide

• Our last one was just last Sunday, May 6, 2012.