OCEAN CURRENTS

OCEAN CIRCULATION Of the four systems on earth, the hydrosphere is what separates us from the other planets. Earth’s vast quantities of water make life as we know it possible About 70% of Earth’s surface is covered in water - most of which is found in the oceans

SURFACE CURRENTS The ocean is not still, like a pond - it moves in distinct patterns called currents. Some currents flow nearer to the surface Surface Currents These currents are driven by several different forces Solar radiation Wind patterns Coriolis effect

SOLAR RADIATION As energy from the sun hits earth, it is dispersed unevenly across the latitudes This uneven heating causes air to rise and fall over the surface of the earth in distinct patterns

SOLAR RADIATION More direct energy from the sun hits the equator. This air warms up and rises and is deflected either eastward or westward due to the Coriolis effect

CORIOLIS EFFECT The Coriolis Effect is an apparent deflection of an object moving in a rotational motion

SURFACE CURRENTS The way in which the air moves across the surface of the earth, directly influences how surface ocean currents move Ocean currents develop due to friction between ocean water and the winds that blow across the surface. Ocean currents move in a pattern consistent with the pattern of winds that blow across the surface of the earth.

Ocean Circulation

DEEP WATER CURRENTS Some currents flow from the bottom of the ocean upwards Deep water currents These currents are caused mainly by density driven forces and gravity

DENSITY Density is mass per unit volume (D=M/V) In Seawater density depends on two factors Temperature of the water  Volume Salinity of the water  Mass Changes in density cause water to rise and fall Less dense  water rises More dense  water falls These changes are what drives deep water current

SALINITY An increase in dissolved substances increases the density Salinity tends to be highest at the poles and near the equator. Near the poles, water is trapped in glaciers - increasing the amount of salt in the water Near the equator, evaporation is high - increasing the amount of salt in the water

TEMPERATURE A decrease in temperature causes an increase in density - the molecules are moving slower and packed closer together Density is greatest in polar regions - high salinity and low temperature Temperature is the most important factor in density

THERMOCLINE The layer of ocean water between 330m - 1000m , where there is a rapid change of temperature with depth. The thermocline is essentially non-existent in high latitudes (polar regions)

DEEP OCEAN CURRENTS Density Currents Dense water sinks and slowly spreads out across the bottom of the ocean Most deep ocean currents begin in high latitudes (poles) where temperature is low and salinity is high. As the water becomes dense, it sinks and spreads out over the floor of the ocean

DEEP OCEAN CURRENTS Evaporation Deep water currents can also exist as a result of evaporation Evaporation of surface waters increases salinity and thus the density of the water. This is evident in the Mediterranean Sea. A dense water mass forms on the surface, sinks and flows into the Atlantic

CONVEYER BELT

CLIMATE The conveyer belt system of currents moves around the globe, influencing global climate

CLIMATE Heat Transfer Currents transfer heat as they move across the ocean When currents from low-latitude regions move to higher regions, they move warmer water to cooler areas on earth.

Gulf Stream The Gulf Stream is a warm water current that brings warm water from the equator up to the North Atlantic. This allows regions in northwestern Europe, like Great Britian, to experience milder winters - despite their latitude

CLIMATE Warm water currents tend to create milder climates in normally cooler regions - Great Britian Cool water currents tend to create cooler than normal climates - California coast is an example. - Polar currents bring cool waters which create cooler climates, including extensive fox and cool ocean waters.