8.8 Energy Transfer within the Climate System

Air and Ocean Circulation

Sun hits earth at different intensities and latitudes Water and land absorb heat differently THEREFORE: Earth is heated unevenly

Heat sinks: reservoir that absorbs and stores thermal energy

e.g. ocean, land and atmosphere

Energy Transfer in the Atmosphere

Convection currents: circular current in air and other fluids caused by rising of warm fluid as cold fluid sinks

Prevailing Winds

Prevailing winds pass over body of water, pick up water vapour, condense as they reach land. Results in more precipitations on this land

8.9 Long and Short Term Climate Changes

Climate change triggered by changes in the Earth’s balance

LONG TERM CHANGES:

Earth’s climate undergoes cyclical changes due to variations in Earth’s orbit

Changes in Earth’s land forms cause changes in ocean currents and wind patterns

Continental drift: theory the Earth’s continents used to be one super continent

Plate Tectonics: theory explaining slow movement of the large plates of the Earth’s crust

Long Term Cycles

Earths last Ice age 20 000 yrs ago

Temps 10ºC lower on average

Ice 3km thick covered Canada

Links we formed between continents because land normally under the ocean was exposed.

Plants and animals migrated across these land bridges, settling in new lands

For the past 800 000 years Earth’s climate has cycled between ice age and interglacial periods-time when earth warms up between ice ages

Why the Cycle?

Eccentricity: (Shape of orbit)-orbit around the sun varies from being nearly circular to elliptical, due to influences of Jupiter and Saturn’s gravities

Tilt: Earth tilts on it’s axis ranging from 22.1° to 24.5° (current axis is 23.5° and is decreasing)

Precession of tilt (wobble): Earth spins on it’s axis and slowly wobbles (cycle of 26 000 yrs)

Short Term Variations in Climate

Volcanic Eruptions: particles shade the earths surface

Air and Ocean Currents

Changes in the Sun’s Radiation

8.10 Feed Back Loops

Feed back loop: process in which the result acts to influence the original process (e.g. water vapour)

Positive feedback loop: effect increases the original cause

Negative feedback loop: effect decreases the original cause

low clouds: trap earths heat

Warmer temps -> more (low) clouds ->even warmer temps (pos. loop)

high clouds: reflect suns heat

Warmer temps -> more (high clouds) -> cooler temps (neg. loop)

Albedo Effect

Albedo: a measure of the amount of Sun’s radiation is reflected off a surface

Ice reflects 75% of the Sun’s radiation (0.75)

Grass reflects 20% (0.20)

Earths average albedo is between 30% and 40% (0.30, 0.40)

Albedo Effect: positive feedback loop in which an increase in Earth’s temp causes ice to melt, causing Earth’s surface to absorb more radiation leading to increase in temperature

or: more ice forms, causing more radiation to be reflected causing earths temperature to decrease

8.11 Studying Past Climates

Proxy record: stores of information in tree rings, ice cores, coral reefs and fossils that can be measured to give clues about past climates

Ice cores: gas bubbles tested which give info on conditions in the atmosphere, past temperatures and amounts of precipitation

Tree Rings: thick in years of good growing conditions (warm, wet), thin for poor growing conditions (cold, dry)

Coral Reefs: layers of growth determine ocean temperatures and growth periods

Rock sediments and caves: consist of plant pollen, fossils, rock formations from minerals

Homework:

Using your text pages 348-361

Pg 353 #’s 2-6

Pg 357 #’s 1-3

Pg 361 # 4