Lecture 6 - Marina Isotope Record

Question 1

isotopes

stable isotopes of carbon

Answer 1

12C and 13C
- do not break down in any other way
- useful because they behave differently in ecosystems

Question 2

isotopes

stable isotopes of oxygen

Answer 2

16O - common, light (8P, 8N)
18O - rare, heavy (8P, 10N)

Question 3

microorganisms & chemical clues

how do microorganisms give chemical clues

Answer 3

skeletons made using CaCO3, in shallow oceans limestone sedimentary rocks deposited from skeletons of these organims
- chemical sed rock = long term tombs for microorganisms

Question 4

microorganisms & chemical clues

steps of hydrolgic cycle

Answer 4

during non-glacial periods
- water evaporates and makes clouds
- some rain, all the water rains back down into the ocean
- complete cycle

during glacial periods
- water evaporates and makes clouds
- rain over land, snow over glaciers
- glacier snow never makes it back to ocean
- sea level goes down
- ice becomes light isotope rich and leaves 18O enriched sea water

Question 5

microorganisms & chemical clues

why does 16O get carried into clouds and leave 18O behind

Answer 5

takes more heat energy to melt heavy oxygen

Question 6

massive international effort

deep sea drilling project

Answer 6

1968-1983
- ocean drilling program: 1985-present
- drills in deep sea come up with sedimentary cores
- can get precise recordof O2 records in the sea

Question 7

cyclical changes in solar energy

Answer 7

differences in how much solar energy hits the earth at given periods

Question 8

obliquity - axial tilt

what is it, why is it important

Answer 8

Earth does not spin vertical, but on tilted axis
- also wobbles back and forth (btwn 22.1 and 24.5 degrees)
- gives cause to season, part of earth tilted towards sun = summer
- more extreme tilts means more extreme winters/summers

Question 9

obliquity - axial tilt

pattern of obliquity

Answer 9

increase obliquity affects poles
- increases seasonal differences
- 41k year cycle btwn relative min and max, cycles don’t always go to the extremes

Question 10

axial precession

axial precession

Answer 10

earth spins on axis at tilt, and wobbles
- wobble results in “The Precession of Equinoxes”

Question 11

axial precession

what are equinoxes

Answer 11

equal illumination on N and S hemispheres
- autumn and spring

Question 12

axial precession

what are solstices

Answer 12

Earth’s axis pointed toward or away from Sun
- summer, pointed directly for N hem
- winter, pointed away for N hem
- as axis wobbles, changes point of orbit during which pole pointed towards sun

Question 13

axial precession

occurence of precession

Answer 13

periodicites of 23k and 100k
- increases and decreases seasonality, currently N Hem seasonality reduced

Question 14

what is eccentricity

Answer 14

how much of a circle vs oval the orbit is
- season in elongated part of the orbit lasts longer
- can amplify effects of precession
- periods of 100k and 413k

Question 15

Miankovitch Cycles

Answer 15

eccentricity, axial precession, obliquity
- all are mathematically defined through analysis of orbit
- periodicity is very regular
- have profound effects on cycles in Earth’s climate