Ocean Ocean CurrentsCurrents

http://www.att.com/ehs/earth96/current.html

2 Parts to the Ocean2 Parts to the Ocean

• Surface

• Deep Water

Surface LayerSurface Layer

• Layer at the top of the ocean

• Well mixed by waves, tides, and weather events like rain or a hurricane

• Sits on top of the deep water because the surface layer is less dense.

• Depth varies depending on location and season, but the depth is usually a couple hundred meters.

ThermoclineThermocline

• Boundary layer between the surface layer and the deep waters

• Thermocline– Δ in T

• Causes change in density

Water Movement - CurrentsWater Movement - Currents

• Move ocean water horizontally at the ocean's surface.

• Driven mainly by the wind (moving air)

• The Coriolis Effect– The Earth's spin causes the wind to curve.

The wind in the northern hemisphere curves to the right and the wind in the southern hemisphere curves to the left.

http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/tornado/spin.html

Water Movement - CurrentsWater Movement - Currents

• Location of land masses

• This movement of water helps spread energy from the Sun.

Deep WaterDeep Water

• T = about 3 degrees Celsius So, • The biggest source of deep water is

surface water that sinks in the North Atlantic Ocean. – Ocean water is very cold and very salty. – This cold, salty water is dense enough to sink

into the depths of the ocean. • Remember, the saltier and colder water is, the

more dense it is! And more dense material will sink below less dense material!

Deep WaterDeep Water

• Dense ocean surface water in the North Atlantic sinks slowly downward until it sinks slowly downward until it reaches a level of equal densityreaches a level of equal density. – If the water is more dense (colder and/or

saltier) then any other water in the deep ocean, it will sink all the way to the sea floor.

Deep WaterDeep Water

• Once the water reaches a level of equal density, the water spreads out. – The deep ocean is broken into horizontal

layers, with each deeper layer having more dense water in it.

http://www-aviso.cnes.fr:8090/images/information/publication/news/news8/challenor_fig2.jpg

Deep WaterDeep Water

• The water that sinks in the North Atlantic flows all the way past the equator into the Southern Hemisphere.

• The water then flows past Antarctica and into the Pacific and Indian Oceans.

• Some of the deep waters are warmed and so rise again to the surface.

Deep WaterDeep Water

• The cycle of ocean water circulation from the surface to the depths of the ocean back to the surface again is referred to as conveyor belt cycling.

http://www.usgcrp.gov/usgcrp/Library/nationalassessment/LargerImages/SectorGraphics/Coastal/Belt.jpg

http://www.windows.ucar.edu/earth_science/images/ocean_currents1_sm.jpg