Basically – why and how the ocean and atmosphere MOVE! There are many scales of motion: From BIG to very small Susan Howard Earth & Space Research Today – I will just cover the basic large scale, GLOBAL circulation. www.ametsoc.org The Ocean and Atmosphere are in CONSTANT motion NASA Movie: Perpetual Ocean Model of ocean currents based on data from satellites and other measurements. NASA/Goddard Space Flight Center Scientific Visualization Studio There are 2 main things that form the Global Ocean and Atmospheric circulation patterns • Energy from the Sun Warming from the sun Sets it in Motion • Rotation of the earth The rotation directs the motion set up the climate system we know it. Energy and the Sun The Sun is constantly emitting energy, in the form of “electrogmagnetic radiation”. What is ELECTROMAGNETIC RADIATION? • • • • • Light Infrared (Heat) Xrays Microwaves Ultraviolet radiation (sunburns!) Solar radiation travels through space and hits the earth and warms it. The Heating of the Earth is Not Even! UNEVEN HEATING: The daily amount of warming at a point on the Earth depends on 3 things Short length of day Small angle of incidence/ low intensity Large amounts of Ice cover Noon in Antarctica May 23rd, 2001 The Heating of the Earth is Not Even! • Length of Day - How much sunlight a point receives in a day • Angle of Incidence (Intensity) – the angle of the sunlight that reaches the earth • Albedo – how much of this light is reflected. Length of Day NH Summer NH Winter Source: Wikipedia • • Earth is tilted with respect to Sun Length of day changes throughout the year Length of Day Source: Wikipedia Angle of Incidence The angle the incoming light makes with respect to the Earth A beam of light shining straight down is more intense that a beam of light shining at an angle Angle of incidence Wikipedia Intensity of Radiation Varies with Latitude The further you get from equator, the less radiation reaches the earth per area Source: http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/solarradiationalevel.html Because the Polar regions receive less radiation, they are cooler. Because they are cooler – ice forms. What does Sea Ice do? It reflects the solar radiation High albedo – high reflection Low albedo – high absorption Radiation reflected Radiation absorbed Warms water Ice cover – reflects radiation So Ice makes the polar regions even cooler! So, because of angle of incidence, length of day, & ice: The Equator gets more heat than the Poles ... a lot more! E q u a t o r Warmer Cooler P o l e Average Annual Heating by Sun Source: Wikipedia Ocean temperature movie From NOAA, Based on satellite measurements What does this Uneven Heating do? • Hot air and cold air behave differently Hot air rises Cold air will sink. • And this causes MOTION How Wind Forms Wind Warm air rises Cold air sinks Convection Cell Wind Low Pressure High Pressure ****Air likes to go from areas of High pressure to Low pressure The GLOBAL Air Circulation is controlled by these convection cells Figure 7.5 in The Atmosphere, 8th edition, Lutgens and Tarbuck, 8th edition, 2001. So, we know: 1) The SUN heats the earth UNEVENLY – And this is going to cause motion. a. The uneven heating causes the rising and sinking of air b. And this rising and sinking causes WIND. c. The sun has set the atmosphere in motion 2) What going to now DIRECT this motion ? ROTATION of the Earth 2) Rotation of the Earth it helps DIRECT the circulation. Coriolis Force It works at right angles to motion and makes the motion curve Coriolis Force Right in Northern Hemisphere Equator Left in Southern Hemisphere Global Wind Patterns With Rotation No Rotation http://www.srh.noaa.gov/jetstream/global/circ.htm Global wind patterns based on Solar heating and Rotation Early Explorers relied on the global wind patterns to sail around the world Summary Movie – Air circulation Movie : Global Atmospheric Circulation By Keith Meldahl, YouTube video Sun’s Heating and Earth’s rotation create wind circulation patterns creates Global Surface Currents in Ocean Wind motion creates Surface Currents in Ocean Map of basic surface currents http://oceanmotion.org/html/background/wind-driven-surface.htm Wind AND ocean currents http://staff.orecity.k12.or.us/steve.tebor/atm%20currents/current/images/world_circulation.jpg The Wind drives large scale surface currents but that isn’t all. Because of uneven heating, just like the Atmosphere, the ocean also has Convection Cells which drives DEEP circulation Basic facts Warm air rises Warm WATER rises Cold air sinks Cold WATER sinks Ocean Conveyer Belt Ocean circulation – major currents Movie : GFDL Ocean current move Questions?