sea-tac. glacial evidence in what way is a glacier like a water reservoir (other than they are both...
TRANSCRIPT
Sea-TacAverage Sea-Tac Temperatures as a function of time
47.00
48.00
49.00
50.00
51.00
52.00
53.00
54.00
55.00
1940 1950 1960 1970 1980 1990 2000 2010
Years
Tem
per
atu
re (
deg
F)
Glacial evidence
• In what way is a glacier like a water reservoir (other than they are both water)?
Advancing/Retreating
• If a glacier has a positive budget, we say that it is advancing
• If a glacier has a negative budget , we say that the it is retreating
• Winter= snowfall• Summer = summer
melting• Net is winter-
summer• If the Net is positive,
it means?• If the Net is
negative, it means?• Is the South
Cascade Glacier advancing or retreating?
Atom/Molecule
• What is an atom?
• What is a molecule?
• Link to ice core oxygen isotope data
• Link to deep sea oxygen-isotope data
Seasons vs. climate change
• Seasons– Temperature variation
annually
• Climate change
Seasons vs. climate change
• Seasons– Temperature variation
annually
• Climate change– Longer term variation
in temperature
Seasons vs. climate change
• Seasons– Temperature variation
annually– Less effect at the
equator; greater effect at the poles
• Climate change– Longer term variation
in temperature– Less effect at the
equator; greater effect at the poles
Seasons vs. climate change
• Seasons– Temperature variation
annually– Less effect at the
equator; greater effect at the poles
– Caused by the tilt of the earth’s axis
• Climate change– Longer term variation
in temperature– Less effect at the
equator; greater effect at the poles
Seasons vs. climate change• Seasons
– Temperature variation annually
– Less effect at the equator; greater effect at the poles
– Caused by the tilt of the earth’s axis
• Climate change– Longer term variation
in temperature– Less effect at the
equator; greater effect at the poles
– Caused by multiple factors: variations in Earth’s orbit, “greenhouse effect, albedo, plate tectonics, ocean circulation
Multin Milankovitch
• 1879-1958• Serbian astrophysist
Basic principles
• What happens to the intensity of light as we increase the distance to the sun?
Basic principles
• What happens to the intensity of light as we increase the distance to the sun?
• What happens when the angle of sunlight striking the Earth is less perpendicular?
Earth’s Orbit is not circular
• Aphelion- the point in the planet’s orbit farthest from the sun.
• Perihelion- the point in the planet’s orbit closest to the sun.
Present day orbit
• Closest to the sun during northern hemisphere winter
• Farthest from the sun during the northern hemisphere summer
Other basic ideas:
• Glaciations tend to happen when the winters are longer than the summers.
• The Earth’s orbit varies in distance from the sun.
• What would happen if we were farthest from the sun in the northern hemisphere winter?
Other basic ideas:
We are more likely to have glaciations if the winters are more intense, even if the summers are more intense.
Milankovitch cycles- Eccentricity
• Earth’s orbit changes from nearly circular to more elliptical.
• The present difference in light intensity between summer and winter is about 6%. During very elliptical orbit, can be as much as 30% different.
• Cycle is ~95,000 years
Milankovitch cycles- Eccentricity
• Predicted variations in eccentricity through time
Milankovitch cycles-Obliquity
• If the axis of the Earth is more vertical to the plane of the ecliptic, are there seasons?
• Earth varies from 21.8 deg to 24.4 deg over 41,000 years
Milankovitch cycles- Obliquity
• Predicted obliquity through time
Milankovitch cycles-Precession
• One cycle of precession occurs about every 21,700 years
Milankovitch cycles- Precession
• Predicted precession cycles through time
Milankovitch cycles
• What happens when we combine all of these cycles together?
