8 Notes Water by the equator is the hottest. Water by the Poles is the coolest.Ocean currents are caused by Uneven Heating.Ocean Currents are Convection Currents.
9 1. shape of the continents 2. temperature differences CAUSES OF CURRENTS1. shape of the continents2. temperature differences(colder water is denser)3. spinning of the Earth(deflecting currents to right in Northern hemisphere)4. winds
10 1 2 4 Currents are affected by: 1 continents 2 temperature 3 Coriolis spin4 Gulf Stream43Credits: CNMOC, U. S. Navy; CNMOC, U. S. Navy; NASA; U. S. Geological Survey
11 Current Forces Explained Sun/solar heating - causes water to expand and moveWinds - push the water; winds blowing for 10 hrs across ocean will cause the surface water to ~2% wind speed; wind has the greatest effect on surface currentsGravity - pull water downhill or pile against the pressure gradient (high/low); influences tides
13 WindsWinds driven by uneven solar heating & Earth’s spin, drive the movement of the ocean’s surface currents. The prime movers are the powerful westerlies and the persistent trade winds (easterlies).
15 Current Forces (cont’d) Coriolis effect/force - Force due to the Earth's rotation, capable of generating currents. It causes moving bodies to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The "force" is proportional to the speed and latitude of the moving object. It is zero at the equator and maximum at the polescauses the water to move around the mound of water
16 Surface CurrentsSurface current – with surface currents circulation is less dense and influenced by windsWarm surface currents: wind and Earth’s rotationCold surface currents: flow towards the equatorUpwelling current: cold, nutrient rich; result of windWestern Boundary currents: warm & fastEastern Boundary currents: broad, slow, cool & shallow, associated with upwellingEx: Gulf Stream = surface current that is the upper 20% of the ocean, western boundary current
17 Properties of Deep Ocean Currents Deep ocean water characteristics:ColdDenseSaltyMove by density forces and gravityMove slower than layers aboveThermohaline Circulation: is global ocean circulation. It is driven by differences in the density of the sea water which is controlled by temperature (thermal) and salinity (haline).
18 Graphic - http://www.grida.no/climate/vital/32.htm Global Conveyer BeltThermohaline circulation links the Earth's oceans. Cold, dense, salty water from the North Atlantic sinks into the deep and drives the circulation like a giant plunger.Graphic -
19 Ocean Currents & Living Things Currents are important to marine life as they help move food and nutrients making them available for photosynthesis, metabolic requirements and or consumption.