 Susan Howard  Earth & Space Research Basically – why and how the ocean and atmosphere MOVE! There are many scales of motion: From BIG to very small Today – I will just cover the basic large scale, GLOBAL circulation.

The Ocean and Atmosphere are in CONSTANT motion NASA/Goddard Space Flight Center Scientific Visualization Studio NASA Movie: Perpetual Ocean Model of ocean currents based on data from satellites and other measurements.

There are 2 main things that form the Global Ocean and Atmospheric circulation patterns  set up the climate system we know it. Energy from the Sun Rotation of the earth Warming from the sun Sets it in Motion The rotation directs the motion

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!

Short length of day Small angle of incidence/ low intensity Large amounts of Ice cover Noon in Antarctica May 23 rd, 2001 May 23 rd, 2001 UNEVEN HEATING: The daily amount of warming at a point on the Earth depends on 3 things

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 Earth is tilted with respect to Sun Length of day changes throughout the year Source: Wikipedia NH Summer NH Winter

Length of Day Source: Wikipedia

Angle of Incidence A beam of light shining straight down is more intense that a beam of light shining at an angle The angle the incoming light makes with respect to the Earth

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:

Because the Polar regions receive less radiation, they are cooler. Because they are cooler – ice forms. It reflects the solar radiation What does Sea Ice do? High albedo – high reflection Low albedo – high absorption

Ice cover – reflects radiation Radiation reflected Radiation absorbed Warms water So Ice makes the polar regions even cooler!

So, because of angle of incidence, length of day, & ice: EquatorEquator PolePole The Equator gets more heat than the Poles... a lot more! WarmerCooler

Average Annual Heating by Sun Source: PhysicalGeography.net

Average Annual Heating by Sun Source: Wikipedia

Ocean temperature movietemperature 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

Warm air rises Cold air sinks How Wind Forms Low Pressure High Pressure Wind Convection Cell ****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. It works at right angles to motion and makes the motion curve Coriolis Force

Equator Right in Northern Hemisphere Left in Southern Hemisphere Coriolis Force

Global Wind Patterns No Rotation With Rotation

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 MovieMovie : 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

Wind AND ocean currents

Because of uneven heating, just like the Atmosphere, the ocean also has Convection Cells which drives DEEP circulation The Wind drives large scale surface currents but that isn’t all.

Basic facts Warm WATER risesCold WATER sinks Warm air rises Cold air sinks

Ocean Conveyer Belt

Ocean circulation – major currents MovieMovie : GFDL Ocean current move

Questions?