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atmosphere > System Earth Ch 12 > Flashcards

System Earth Ch 12 Flashcards

1
Q

What is the young sun paradox?

A

the fact that the earth must have been warm enough for liquid water to exist throughout its history but that the sun used to be 30% less bright

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2
Q

why has the sun’s brightness changed over time?

A

luminosity increase is due to a change in density caused by the conversion of hydrogen into helium.

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3
Q

what does it mean that luminosity change for the sun is a robust model?

A

does not depend sensitively on the details of the model - the specifics may be different but the core of the issue will not go away.

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4
Q

How well do we understand the sun?

A

turns out, pretty well. We have found out that it emits neutrinos in a type that went unmeasured for a very long time. This is how the sun produces energy.

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5
Q

how does teh sun loose mass?

A

solar wind - outflow of charged particles from the sun’s corona. There us also a rapid rotation which with the magnetic field heats up the star’s corona, driving a stellar wind.

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6
Q

Can we calculate the faint young sun paradox mathematically?

A

yes, you can look at 30% decrease in luminosity -> 22 degrees temperature change and do your maths from there, while including feedback loops.

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7
Q

what are the three possible solutions to the faint young sun paradox?

A
  1. planetary albedo was lower in the past.
  2. larger GHE
  3. additional heat sources present.
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8
Q

geothermal heat?

A

heat produced by the decay of radioactive elements in the Earth’s crust and mantle.

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9
Q

what is the problem with the geothermal heat flux?

A

it is not enough. It would have been enough to keep deep ocean warm but not the top from freezing.

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10
Q

why is albedo not a solution to the faint sun paradox?

A

the albedo would have had to be near 0 which is impossible.

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11
Q

what is probably the solution to the faint young sun paradox and which options are wrong?

A

enhanced GHE but it could not have been water vapour alone. Ammonia is also not an option

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12
Q

Why were there more reduced gases in the atmosphere prior to 2.4 By ago?

A

This was before an oxygenated atmosphere. So ammonia could have been present were it not for ultraviolet radiation.

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13
Q

is CO2 an option for the faint sun paradox?

A

with the silicate, carbon cycle, it is definitley a possibility. We would have needed 1000 times current levels, but this is quite possible.

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14
Q

serpentinization

A

serpentine minerals are formed in a reaction with watera nd iron and magnesium- rich basalts. If CO2 is in the water, methane is formed.

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15
Q

early form of bacteria?

A

methanogenic bacteria

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16
Q

why is the sky blue

A

scattering of sunlight by N2 and O2 molecules - Rayleigh scattering

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17
Q

What is Rayleigh scattering

A

when the shorter wavelengths are scattered preferentially to long wave. So we see a blue sky

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18
Q

Mie scattering

A

scattering particles that are close in size to the wavelength.

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19
Q

thermophile

A

organisms with optimum temp between 40 and 80

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20
Q

hyperthermophile

A

organisms with optimum temp above 80 degrees

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21
Q

organic haze effect

A

the temperature decreases due to the anti greenhouse effect.

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22
Q

deep sea cores

A

go back 200 My

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23
Q

oxygen isotopes

A

look at carbonate rocks. but may have been influenced by other processes such as a change in seawater compositon.

24
Q

tillites

A

mixtures of cobbles, pebbles, and and mud that have been packed together to form rocks.

25
Q

moraines

A

terminal point or flank of a glacier

26
Q

dropstones

A

misplaced chunks of rocks that you find in laminated areas

27
Q

Huronian glaciation

A

2.3 By ago
radiometiric age dating
glacial deposits
uranite deposits
HIGH O2

28
Q

warm period after huronian glaciation

A

probably due to weathering

29
Q

Late protozoic glaciation

A

Australia at the equator and covered in ice.
high incoming radiation
enhanced weathering, reduced CO2
all continents at the equator
fewer glaciers - more weathering.
potential snowball earth

30
Q

snowball earth graph

A

you have stability points you have to force to get there.

31
Q

Phanerozoic eon

A

permo carboniferous
sufficient O2 to prevent CH4 accumulation
carbon burial rate doubled - formation of coal beds
atmospheric CO2 based on paleosol data -> decreased CO2 - ice ago triggered.

32
Q

vascular plants

A

can help enhanced weathering but would not have occured in carboniferous - there were no vascular plants at that point.

33
Q

warm mesozoic era

A

dinosaurs!
deep ocean was 12 K warmer than today.
higher CO2
look at 12C ratio
reversed thermohaline circulation with upwelling at poles.
more efficient hadley cell circulation

34
Q

paleomagnetic data

A

efficient seafloor spreading - faster spreading - enhanced CO2 production.

35
Q

12-C and 13-C

A

plants and plankton take up 12-C more than 13-C. low 13/12 shows photosynthesis produced OM under elevated CO2
more 13-C => less 12-C in atm.

36
Q

paleo-eocene

A

isotopic info
low 13C
Thermal Maximum
55My ago
25 degrees at poles
aerosol cloud mechanisms
methane aerosol forcing

37
Q

Cenozoic climate

A

india collides with asia
weathering increases and high albedo
very active but quite slow
first formation of ice sheet 35 My ago
delta 18O => cooling conditions

38
Q

Last 1.8M y

A

are there different mechanisms or do we have much more data? resolution has increased by factor of 10

39
Q

Pleistocene glaciation

A

land/sea distribution similar
long term trend - we are heading towards a glaciation

40
Q

positive delta 18 O

A

cold conditions

41
Q

how has peiodicity changed in the last 100kyr?

A

it has become in line with Milankovitch cycles

41
Q

eccentricity

A

oval or circular orbit - 100kyr

42
Q

obliquity

A

tilt - 40 kyr

43
Q

precession

A

spinning top - 26 kyr

44
Q

Q1. why does the sun get brighter with time?

A

luminosity increases with density change

45
Q

Q2. how migh tcarbon silicate cycle helped save the faint young sun paradox?

A

the negative feedback loop kept the global temperature in check.

46
Q

Q3. methan in Archaen era?

A

kept the planet warm and methanogenic bacteria

47
Q

Q4. What triggered the Huronian glaciation?

A

Great Oxygenation Event

48
Q

Q5. Types of geologic evidence used to infer past glaciation?

A

deep sea ice cores and oxygen isotopes

49
Q

Q6. How many separate periods of glaciation have occurred in Earth’s history?

A

5

50
Q

Q7. What types of geologic evidence support snowball earth model?

A

location of continents and evidence on Australia

51
Q

Q8. carbon isotopes?

A

13C is high in plants - lower 12C in atmosphere.
Plants take up12 more easily

52
Q

Q9. atmospheric CO2 and plants

A

photo and respiration

53
Q

Q10. What mechanisms explain warm climate of mesozoic era?

A

thermohaline circulation. high CO2 ratio and efficient hadley cell circulation.

54
Q

Q11. Why has the climate cooled in the last 40M y?

A

India collided with Asia and then weathering.

atmosphere (12 decks)

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