EarthComm Fluids Pages 7-11

Oceans of the World There are 4 large oceans on Earth (Atlantic, Pacific, Indian, Antarctic) All oceans have land borders (continents), but all oceans are connected to each other About 70% of the Earth’s surface is covered by water. Pacific Atlantic Indian Antarctic Pacific Antarctic

Oceans of the World (Continued) The open ocean is very deep: average depth = 4-5 km Near the bottom of the ocean it is dark, cold, and has very high pressure Dark deep ocean floor Ocean floor in shallow waters

Ocean zones and Depths

The Warm and the Cold Ocean The ocean is layered by temperature Upper layer = warmer water – as high as 25 o C (~77 o F) Lower layer = colder water – near 0 o C (near 32 o F)

The Warm and the Cold Ocean Temperature of water decreases sharply between 200m and 1000m below surface

Thermocline – the zone of rapid change from warm water to cold water with increasing depth in the ocean  Similar to temperature difference noticed while treading water (top warmer, near feet colder)

Pycnocline – a layer of water in the ocean characterized by a rapid change of density with depth  Density of ocean water increases as the temperature decreases (toward floor)  Density of ocean water decreases as the temperature increases (toward surface) The thermocline and pycnocline happen to be approximately the same thickness in salt water due to the temperature and density characteristics

The Warm and the Cold Ocean Density changes as depth and temperature of the water changes.

Circulation of Oceans The layer above the thermocline is continuously circulating (moving) The deeper cold part of the ocean is continuously circulating

Circulation of Oceans (Continued) The circulations are different in nature Oceanographers – scientists who study the Earth’s oceans  They have come up with many theories to account for the circulation of the oceans, and they continue to work on the complicated problem

The Wind Stress Upper layer circulation is caused mainly by wind stress Wind Stress – the frictional force exerted on the ocean surface by wind The blowing wind causes waves on the water’s surface Wind direction

The Wind Stress (Continued) As the waves get larger the wind has more effect on them Waves can cause problems a. Shoreline erosion b. Hazards to ships

The Coriolis Effect Water in the ocean moves in straight lines once set in motion Earth rotates underneath the moving water which actually causes the water to move in a curved path  Coriolis force – the apparent force caused by the Earth’s rotation which serves to deflect a moving body on the surface of the Earth The overall circulation of the oceans depends on the Coriolis effect