Lec 2 Flashcards
Topography of the North
Northern areas vary vastly in elevation
Northern conditions are worse at higher elevations
Large areas of flat terrain with several mountains
The Lomonosov ridge
Divides the arctic ocean into two major basins
Influences water circulation, marine life, and ice movement
Geology importance
Biologically important in structuring drainage, soil, materials etc
Territorial claims
Franklin Expedition
Trying to find a passage through the North, failed and left minerals
Most sought after mineral
Diamonds
Precambrian includes
Archean
Proterozoic
Precambrian
Refers to 4.5 billion-543 million years
75 percent of Canada is Precambrian
Canadian Shield
300-600 meter elevation
Can be 1070 meter elevation in Quebec and Labrador
Igneous rocks
Rock of volcanic origin
Sedimentary rock
Rock formed at or near Earth’s surface by the accumulation and lithification of sediments or by precipitation from solution at normal surface temp
Metamorphic rock
Rocks that have been altered by a change of conditions
Forests in the Arctic
Forests have been preserved due to mummification of litter, stumps, boles, roots, seeds, soils
Milankovitch Cycles and Glaciation
Episodic glacial and interglacial periods within the present Ice Age (last couple of million years) have been caused primarily by cyclical changes in the Earth’s circumnavigation of the Sun
3 components of the Milankovitch cycle
Eccentricity
Axial tilt
Precession
Eccentricity
Shape of the Earth’s orbit around the sun
Prime importance to glaciation in that it alters the distance from the Earth and Sun
Axial tilt
Today at about 23.5 degrees
Less axial tilt result in solar radiation more evenly distributed between winter and summer
Less tilt would promote glaciation
Precession
Earth’s slow wobble as it spins on its axis
What triggers an ice age
The amount of summer sunshine on northern continents is crucial
If it drops below a critical value, snow from the past winter does not melt away in the summer
Milankovitch cycles and global warming
Have tremendous value as a theory to explain long term changes in climate
Unlikely to have much impact on the decade-century timescale
Measured over several centuries
For predicting climate change in the 21st century, they will be far less important than radiative forcing from greenhouse gases
Nature geosciences
At the current atmospheric CO2, models show glaciation should not occur
Based on current orbital configuration, for glacial inception to occur CO2 would have to be less than the preindustrial levels
Exact CO2 threshold isn’t clear
Greenhouse gases
CO2
Methane
N2O
SF6
Water
Solar energy absorbed by Earth’s surface is emitted as
Weaker radiation with longer wavelengths (infrared range)
What happens to infrared radiation
Some of it passes through the atmosphere, but a majority is absorbed by GHGs and then reemitted in all directions
