Unit 4

Energy Flow in Global Systems

Systems

• three types depending on their interactions with its surroundings.

•  open system – energy and matter can enter and leave. Ex a tree

• closed system – energy can enter and leave but matter can not. Ex the earth

• isolated system – neither energy or matter may enter or leave. Ex the universe

The Biosphere

•   the layer around the earth in which living organisms are found

•    three parts

•   atmosphere – air

•   lithosphere – land

• hydrosphere – water

Radiation

• is the process by which solar energy reaches Earth

• visible light reaches the Earth’s surface unchanged

•   some of the visible light •    is absorbed – heating the surface•   is reflected • the warmed objects on the surface emit infrared

radiation

Radiation continued

• infrared radiation may be temporarily trapped in the atmosphere but eventually is lost to space

•   Earth maintains an energy and temperature balance by radiating as much energy into space as it absorbs

• dark surfaces absorb more energy and light surfaces reflect energy

Radiation continued

• the reflectivity of a surface is called – albedo

•  the greenhouse gases in the atmosphere absorb infrared radiation keeping the surface warm during the night

• the greenhouse gases include: water vapour, carbon dioxide, methane, nitrous oxide, ozone, CFC’s and HFC’s

Climates and Seasons

• climate is the trend in temperature, atmospheric pressure, humidity and precipitation over many years

• weather is these same factors at a certain time and place

• the tilt of the Earth’s axis and the curvature of the surface result in differing amounts of solar radiation absorbed

Climates and Seasons cont

• tilt of the Earth – angle of inclination – determines the length of day and night at different latitudes

• the Earth travels around the sun in an elliptical orbit

• for ½ the year we are tilted away from the sun and ½ the year we are tilted toward the sun

Climates and Seasons cont

• the three main factors that affect heating at the surface are

• 1. surface conditions - albedo

• 2. tilt - seasons

• 3. latitude – angle of incoming solar radiation

(amount absorbed/reflected)

Specific Heat Capacity

• is the amount of heat required to raise the temperature of 1 g of a substance by 1 ºC 

• Q = mc∆T Q = amount of heat (J)• m = mass in g• c = specific heat capacity

(J/gºC)• ΔT= change in temperature

(°C)

Transfer of Energy

• several mechanism of energy transfer play a role in heating the atmosphere

• 1.   conduction – transfer of energy from one molecule touching another

• energy always moves from the warmer object or molecule to the cooler one

Transfer of Energy cont

• 2.   convection – air circulates and distributes heat

• warm air is lower density than cooler air and so will rise and carry heat with it

• 3.   radiation – the greenhouse gases absorb the long wave radiation given off at Earth’s surface

• all molecules will lose heat by radiation

Phase Changes

• when a phase change occurs energy is gained or lost with not change in temperature

• for example water at 0°C loses energy in order to freeze

• heat of fusion (Hfus)amount of energy

required to melt one mole of a substance

Phase Changes cont

• or the amount of energy lost to freeze 1 m of a substance

•  

• Q = nHfus

Phase Changes cont

• heat of vaporization(H vap) the amount of

energy required to convert one mole of a substance from a liquid to a gas

• the amount of energy lost convert 1 m of a substance from a gas to a liquid 

• Q = n Hvap

Unique Properties of Water

• water has a high specific heat capacity ( 4.19 J/g°C)

• large amounts of heat has to be lost or gained to change the temperature of large bodies of water

• as a result bodies of water have a moderating effect on nearby land

Unique Properties of Water

• water has a high heat of vaporization (40.68 kJ/mol)

• water has a high heat of fusion (6.01 kJ/mol)

• water expands when heated and contracts when cooled reaching its greatest density at 4 °C

Unique Properties of Water

• below 4 °C water begins to expand resulting in ice that has lower density than liquid water

• this explains why ponds and lakes freeze on the surface allowing aquatic organisms to survive the winter below the ice

Hydrologic Cycle

• look at the diagram on page 386 and sketch in your notes

•   

• Work Pg 387 # 1-5

Distributing Heat - Oceans

• oceans are large heat reservoirs• water has low albedo and absorbs more than

90% of the solar energy striking it• oceans cover 70% of the Earths surface• ocean currents carry warm water to different

latitudes affecting coastal areas and influencing worldwide climate – Gulf Stream which becomes the North Atlantic Drift

Distributing Heat - Oceans

• Gulf Stream is part of a global ocean current called the thermohaline circulation or Great Ocean Conveyor Belt

• El Nino – Southern Oscillation (ENSO) – is a disruption of the ocean-atmosphere system

• occurs every 3 to 7 years

Distributing Heat - Oceans

• during El Nino the wind direction over the south Pacific reverses

• read pg 389-390

• La Nina – causes an increase in strength of the normal patterns of westward moving winds

Patterns of Wind Movements

• low pressure occurs as warm air expands becoming less dense and rises

• high pressure occurs as cold air contracts, becomes denser, and descends

• a convection current is created when warm air rises at one location cools and contracts sinking to the surface at another location

Patterns of Wind Movements

• there are actually three separate convection currents in each hemisphere

• warm air rises at the equator and sinks at 30° (N and S)

• warm air rises at 60° (N and S) and sinks at the poles

Patterns of Wind Movements

• convection currents veer sideways from their original path due to the rotation of the Earth on its axis – this is called the Coriolis Effect

• this creates • 1. Polar Easterlies• 2. Prevailing Westerlies• 3. Northeast Trade Winds• 4. Doldrums – quiet area of little winds

Jet Streams

• are currents of extremely fast-moving air about 10-15 km above the Earth’s surface

• flow from west to east

• form at boundaries of warm and cold air

• intense winds in the jet stream influence precipitation and thunderstorms

Oceans and Mountains

• sea breezes are formed when in the morning the sun warms the land before the water and the air over the land rises and over the water the cool air sinks creating a convection current

Oceans and Mountains

• land breezes are formed in the evening when the water stays warmer longer so now the warm air rises over the water and sinks over the cooling land again creating a convection current

• Prevailing Westerlies bring warm moist air onshore in BC, as this air is forced to rise higher to get over the mountains the air cools, the moisture condenses and falls as precipitation – orographic precipitation

Oceans and Mountains

• the cool dry air moves down the eastern side of the mountains warming up due to the increase pressure

• little rain occurs here in the rain shadow

• in the winter this warm westerly wind is called a Chinook (snow eater) as it melts and evaporates or sublimates the snow as it goes

Climate

• temperature is a critical element in defining climate

• altitude is also important – temperature drops 4.5 ºC for every kilometre increase in altitude

• humidity is the amount of water vapour in the air

Climate continued

• at higher temperatures more water molecules have enough kinetic energy to exist as a vapour

• if the humidity is low organisms dry out

• the temperature at which water condenses and begins to fall as rain or snow is called the dew point

Climatograph

• is a graphical representation of climate data for a specific region and time period

• includes average monthly temperature and total monthly precipitation

• do investigation 11-A page 405

Biomes

• can be defined as a major geographic region with similar environmental conditions and life forms

• freshwater and ocean or aquatic biomes dominate the biosphere

• 6 distinct terrestrial biomes will be examined

• look at page 407

Adaptations and Biomes

• an adaptation is any characteristic that enables an organism to better survive and reproduce in an environment

• 1. physiological adaptations – occur inside an organism, eg the changes when animals hibernate

• 2. structural adaptations – physical features of an organism, eg fur for warmth

Adaptations and Biomes

• 3. behavioural adaptations – things the organism does to survive, eg migration

 

• Using your text book make notes on the 6 terrestrial biomes

Paleoclimate

• is the study of past climates

• Geological Survey of Canada has completed reconstructing Canada’s Paleoclimate from 6000 years ago

• they discovered the vegetation zones

Paleoclimate

• causes of natural climate change• o  Earth’s tilt • o  Earth’s orbit• o   continental drift• o   weathering (breaks rocks into smaller pieces)• o   catastrophic events – meteors, volcanoes• feedback

Paleoclimate

• rapid climatic changes sometimes resulted in “mass extinctions”

• slower climatic changes may explain animal migrations, evolution of physical characteristics, changes in diet, decreases in populations and forests moving north and south