The Water Cycle 11.2 Ocean Currents

A large amount of ocean water that moves (like a river) in a particular and unchanging pattern More than 20 major currents in the world that transport huge quantities of dissolved minerals, solar energy, oxygen and carbon dioxide as well as fish and plankton

Surface Currents Direction and speed of surface currents is directly connected to the direction and speed of the wind blowing over the water and hot and cold air rising and falling   Spinning of the Earth on its axis affects both winds and ocean current Spins west to east so the winds and currents get deflected right (east) in the northern hemisphere Called the Coriolis effect Continent shape and placement affects how and where surface currents will move

Deep Currents Dense, cold water tends to sink beneath warmer water and then move along the ocean floor Called a density current Three different layers to ocean water: the surface (Sun’s energy heats the water), the thermocline (water temperature drops rapidly here), and deep water

Deep Currents Cont. The amount of salt in ocean water also contributes to the movement of density currents High salinity is denser than water with low salinity Areas near melting ice or near huge rivers are less saline Increased salinity results from evaporation and freezing The saltiest, coldest and densest waters are found at the North and South Poles

Eventually the dense, cold water will be warmed enough to rise or pushed up by colder, denser water from below Called upwelling which brings nutrient-rich waters to the surface

Ocean Waves and How they Shape the Land Large, rolling waves that form in open oceans are called swells and as they reach shallow water, they become “breakers” Huge waves called tsunamis are created by underwater earthquakes

Waves can erode even the rockiest cost and deposit huge amounts of sediment on shores Softer rock erodes more readily from waves and the sediment carried in them Headlands are sections of the coastline that extend out into the ocean (harder rock) Can create interesting features like sea stacks Bays are indented areas where more deposition occurs

Tides The daily cycle of rising and falling ocean water is called the tide and they are caused by the gravitational attraction between the Earth and the Moon

the difference between high tide and low tide is called the tidal range if the Sun and Moon are both lined up then you get an extra high tide called a spring tide (occurs twice a month) if the Sun and Moon are not lined up then you get less extreme tides called neap tides