System Earth Ch 12 Flashcards
What is the young sun paradox?
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
why has the sun’s brightness changed over time?
luminosity increase is due to a change in density caused by the conversion of hydrogen into helium.
what does it mean that luminosity change for the sun is a robust model?
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.
How well do we understand the sun?
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.
how does teh sun loose mass?
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.
Can we calculate the faint young sun paradox mathematically?
yes, you can look at 30% decrease in luminosity -> 22 degrees temperature change and do your maths from there, while including feedback loops.
what are the three possible solutions to the faint young sun paradox?
- planetary albedo was lower in the past.
- larger GHE
- additional heat sources present.
geothermal heat?
heat produced by the decay of radioactive elements in the Earth’s crust and mantle.
what is the problem with the geothermal heat flux?
it is not enough. It would have been enough to keep deep ocean warm but not the top from freezing.
why is albedo not a solution to the faint sun paradox?
the albedo would have had to be near 0 which is impossible.
what is probably the solution to the faint young sun paradox and which options are wrong?
enhanced GHE but it could not have been water vapour alone. Ammonia is also not an option
Why were there more reduced gases in the atmosphere prior to 2.4 By ago?
This was before an oxygenated atmosphere. So ammonia could have been present were it not for ultraviolet radiation.
is CO2 an option for the faint sun paradox?
with the silicate, carbon cycle, it is definitley a possibility. We would have needed 1000 times current levels, but this is quite possible.
serpentinization
serpentine minerals are formed in a reaction with watera nd iron and magnesium- rich basalts. If CO2 is in the water, methane is formed.
early form of bacteria?
methanogenic bacteria
why is the sky blue
scattering of sunlight by N2 and O2 molecules - Rayleigh scattering
What is Rayleigh scattering
when the shorter wavelengths are scattered preferentially to long wave. So we see a blue sky
Mie scattering
scattering particles that are close in size to the wavelength.
thermophile
organisms with optimum temp between 40 and 80
hyperthermophile
organisms with optimum temp above 80 degrees
organic haze effect
the temperature decreases due to the anti greenhouse effect.
deep sea cores
go back 200 My
oxygen isotopes
look at carbonate rocks. but may have been influenced by other processes such as a change in seawater compositon.
tillites
mixtures of cobbles, pebbles, and and mud that have been packed together to form rocks.
moraines
terminal point or flank of a glacier
dropstones
misplaced chunks of rocks that you find in laminated areas
Huronian glaciation
2.3 By ago
radiometiric age dating
glacial deposits
uranite deposits
HIGH O2
warm period after huronian glaciation
probably due to weathering
Late protozoic glaciation
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
snowball earth graph
you have stability points you have to force to get there.
Phanerozoic eon
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.
vascular plants
can help enhanced weathering but would not have occured in carboniferous - there were no vascular plants at that point.
warm mesozoic era
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
paleomagnetic data
efficient seafloor spreading - faster spreading - enhanced CO2 production.
12-C and 13-C
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.
paleo-eocene
isotopic info
low 13C
Thermal Maximum
55My ago
25 degrees at poles
aerosol cloud mechanisms
methane aerosol forcing
Cenozoic climate
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
Last 1.8M y
are there different mechanisms or do we have much more data? resolution has increased by factor of 10
Pleistocene glaciation
land/sea distribution similar
long term trend - we are heading towards a glaciation
positive delta 18 O
cold conditions
how has peiodicity changed in the last 100kyr?
it has become in line with Milankovitch cycles
eccentricity
oval or circular orbit - 100kyr
obliquity
tilt - 40 kyr
precession
spinning top - 26 kyr
Q1. why does the sun get brighter with time?
luminosity increases with density change
Q2. how migh tcarbon silicate cycle helped save the faint young sun paradox?
the negative feedback loop kept the global temperature in check.
Q3. methan in Archaen era?
kept the planet warm and methanogenic bacteria
Q4. What triggered the Huronian glaciation?
Great Oxygenation Event
Q5. Types of geologic evidence used to infer past glaciation?
deep sea ice cores and oxygen isotopes
Q6. How many separate periods of glaciation have occurred in Earth’s history?
5
Q7. What types of geologic evidence support snowball earth model?
location of continents and evidence on Australia
Q8. carbon isotopes?
13C is high in plants - lower 12C in atmosphere.
Plants take up12 more easily
Q9. atmospheric CO2 and plants
photo and respiration
Q10. What mechanisms explain warm climate of mesozoic era?
thermohaline circulation. high CO2 ratio and efficient hadley cell circulation.
Q11. Why has the climate cooled in the last 40M y?
India collided with Asia and then weathering.
