8.8 Energy Transfer within the Climate System
Dec 24, 2015
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