Transcript PowerPoint slides from lecture

Sea-Tac
Average Sea-Tac Temperatures as a function of time
55.00
Temperature (deg F)
54.00
53.00
52.00
51.00
50.00
49.00
48.00
47.00
1940
1950
1960
1970
1980
Years
1990
2000
2010
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 wintersummer
• 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?
Carbon
6
C
12.01
• 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?