GG231 Chapter Notes - Chapter 12: Arctic Ocean, Atmospheric Circulation, Ice Shelf

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Published on 13 Apr 2013
School
WLU
Department
Geography
Course
GG231
Professor
Chapter 12 and 9 Climate Change & Drought and Famine
Brian Kwok 1
Arctic threatened by climate change
o Aboriginal peoples of N. Canada have witnessed marked warming of climate, decrease in Arctic sea-ice
cover, increased permafrost thaw and erosion of coastal villages
o Arctic ocean will be ice free by middle of 21st century if melting rate continues
o Seasonal sea ice averages 2m, used to be 3m
o Melting may contribute to even higher Arctic temperatures in the future
Harmful to some northern animals
o Calving of Canadian, Greenland and Antarctic ice shelves
o Local warming in Canadian Arctic will exceed 3C during this century
If entire ice were to melt, global sea level would rise by 7m
Climate and Weather
o Climate atmospheric characteristics of a region over years or decades
o Weather atmospheric conditions of a region for shorter periods (days or weeks)
o Climate is more than averages of temperature and precipitation
Two locales may have similar temperatures but different climates
Climate has warmed over most of the earth during the past century
Magnitude differed considerably from place to place
o Some areas more wet, some more dry
The Atmosphere
o Atmospheric composition
Comprises of nitrogen, oxygen and smaller amounts of other gases
Permanent gases
o Concentrations do not change
Variable gases
o Proportions of which vary in time and space
Permanent gases
Constitutes about 99% of all atmospheric gases
o Nitrogen, oxygen and argon
Nitrogen plays an important role in climate when combined with other gases
o Forms 78% of atmosphere
o Especially oxygen
Oxygen is second largest component
o Forms 21% of atmosphere
Argon third component
o Last 1% of atmosphere
Contains small amounts of neon, helium, krypton, xenon and hydrogen
Variable gases
Constitute small portion of total mass of the atmosphere
Include carbon dioxide, water vapour, ozone, methane, nitrogen oxides and
halocarbons
Carbon dioxide
o Very small percentage, concentration very low
o Part of the biogeochemical cycle
o Released naturally through volcanic activity, plant/animal respiration,
wildfires and organic material decay
Also through burning fossil fuel
o Removed by plants, chemical weathering and sea water absorption
o Concentration increasing since the Industrial Revolution
Production greater than absorption
Water vapour
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Chapter 12 and 9 Climate Change & Drought and Famine
Brian Kwok 2
Produced by evaporation of water at Earth’s surface
Condenses to form clouds
Temperature primary control of the amount of water vapour in the atmosphere
o Warm air increases evaporation
Holds more vapour than cold air
Ozone
o Forms when oxygen atom bonds with oxygen molecule
o Mostly found in stratosphere
o Shields earth from UV radiation
o Ozone in stratosphere protects us
o Zone in troposphere, produced by smog, irritates lungs and eyes
Methane
o Major component of natural gas
o Forms through bacterial decay in moist places that lack oxygen
Marshes, swamps, bogs, coal mines, oil wells, rice paddies,
landfills, livestock
o Stays in atmosphere for about 12 years
Major contributor to global warming
Nitrogen oxides
o Present in troposphere and stratosphere
o Natural sources include microbiological processes in soils, oceans, wildfires
and lightning strikes
Automobiles, power plants, aircrafts, fertilizers
Average residence time of about 114 years
Contributes to global warming
Halocarbons
o Contain carbon and halogen elements
o Entirely anthropogenic
Used in industrial processes, firefighting, fumigants, refrigerants
and propellants
o 25-100 years in atmosphere
o Contributes to warming in troposphere and ozone depletion
Aerosols
o Not gases, but microscopic liquid and solid particles in atmosphere
o Natural sources include desert dust, wildfires, sea spray, volcanic eruptions
Burning forests, fossil fuel consumption
o Can cause cooling or warming of war
o Structure of the atmosphere
Troposphere much of heat radiating from earth trapped here
Stratosphere dry layer where water vapour occurs as ice crystals
Mesosphere and thermosphere far from earth’s surface, little impact on climate and natural
hazards
o Atmospheric circulation
Warm air rises in troposphere in equatorial areas and moves north or south
Creates regions of high and low pressure near N. and S. poles
Wind produced by movement of air from high to low pressure areas
Climate change
o Evidence that earth is warming is unequivocal
o Most of the warming occurred between 1995-2010
Sea-surface temperatures rose
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Chapter 12 and 9 Climate Change & Drought and Famine
Brian Kwok 3
Glaciers have receded
Permafrost is thawing
o Global warming concluded 90% that humans have contributed to it
o Complex and far-reaching effects on planet’s environment
Changes caused by climate warming too rapid for many organisms to adjust
o Cryosphere frozen part of hydrosphere
Snow, sea and glacier ice, permafrost
Changes can impact climate
o Glaciers forms ice sheet flow from high areas to low areas under their own weight
Have inputs and outputs
Inputs snow turning into ice
Outputs melting, sublimation and calving of ice blocks
Advance when input greater than output
o Alternates between glacial intervals and interglacial intervals
Glacial continental glaciations
Interglatial warmer climate with less ice coverage
o Glaciations
Many glacial intervals, characterized by repeated advances and retreats of ice sheets
Pleistocene Epoch last glaciations period
Covered about 30% of land area
Global sea level 130 m lower than today’s levels
Holocene Epoch interglacial interval we live in today
Began 116000 years ago
10% covered by ice
Causes of glaciations
No single factor can explain glaciations, result of several factors
Positions of continents affect ocean and atmospheric circulation
Milankovitch cycle
o Shape of earth’s orbit around sun
o Tilt or wobble of the earth
o Precession of the equinoxes
o Can be combined to determine net changes in radiation that any point on
earth receives
Correlate well with major advances and retreats
o Greenhouse effect
Surface temperature determined by three factors
Amount of sunlight planet receives
Amount of sunlight reflected
Degree to which atmosphere retains heat
2/3 of radiation passes atmosphere and reaches surface of planet
Absorbed and warms surface and atmosphere
Some radiated back into atmosphere
Earth surface would be much colder than it actually is without the greenhouse effect
Layers of atmosphere act similar to glass in greenhouse
Greenhouse gases carbon dioxide, methane, nitrogen oxide gases
o Increases warming
o Carbon dioxide accounts for 56% of anthropogenic greenhouse effect
Cores of glaciers have been recovered, air bubbles trapped show atmospheric air at the time
of freezing
o Global climate change over the past 800 000 years
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Document Summary

Harmful to some northern animals: calving of canadian, greenland and antarctic ice shelves, local warming in canadian arctic will exceed 3c during this century. If entire ice were to melt, global sea level would rise by 7m. Climate and weather: climate atmospheric characteristics of a region over years or decades, weather atmospheric conditions of a region for shorter periods (days or weeks, climate is more than averages of temperature and precipitation. Two locales may have similar temperatures but different climates. Climate has warmed over most of the earth during the past century. Magnitude differed considerably from place to place: some areas more wet, some more dry. Comprises of nitrogen, oxygen and smaller amounts of other gases. Permanent gases: concentrations do not change. Variable gases: proportions of which vary in time and space. Constitutes about 99% of all atmospheric gases: nitrogen, oxygen and argon.

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