sea-tac. glacial evidence in what way is a glacier like a water reservoir (other than they are both...

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?

Carbon

6C12.01

• 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?