Currents Currents

Driven by forces of wind, tides, and gravity, currents keep the ocean in constant motion. 7 Major Currents West Wind Drift (AKA=Antarctic Circumpolar Current East Wind Drift North and South Equatorial Currents Peru Current Kuroshio 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

Waves Ch 9

Wave Anatomy

Wave Anatomy

Wave period: is the time (in seconds) between successive waves. *Ideal surfing conditions are when long period swells (more than about 12 seconds between waves) hit the coastline at a time when there are light winds locally (and therefore small windsea).

Wave Speed If the crest of an ocean wave moves a distance of 20 meters in 10 seconds, then the speed of the ocean wave is 2 m/s. On the other hand, if the crest of an ocean wave moves a distance of 25 meters in 10 seconds (the same amount of time), then the speed of this ocean wave is 2.5 m/s. The faster wave travels a greater distance in the same amount of time.

Progressive wave motion http://earthguide.ucsd.edu/earthguide/diagrams/waves/swf/wave_wind.html This diagram shows how the wave base is deeper with longer wavelengths.

Seiche or Standing wave motion http://earthguide.ucsd.edu/earthguide/diagrams/waves/swf/wave_seiche.html These waves go up and down or “rock” and are found in semi-enclosed areas, basins, bays, harbors, or your bathtub!

How Tsunamis form http://news.bbc.co.uk/1/hi/world/asia-pacific/4136289.stm

Types of Coastlines Sea Cliff

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.