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Lecture 6 The Greenhouse Earth Last 100 Myr (Chapter 5)

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Title: Earth s Climate Author: ccr Last modified by: Liu Created Date: 8/17/2003 8:59:14 PM Document presentation format: On-screen Show (4:3) Company – PowerPoint PPT presentation

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Title: Lecture 6 The Greenhouse Earth Last 100 Myr (Chapter 5)


1
Lecture 6 The Greenhouse Earth Last 100
Myr(Chapter 5)
2
Atmospheric CO2 Evolution
Last 100 Myr
3
100 myr ago mid-Cretaceous
Break up of Pangaea Sea level 100-m higher No ice
sheet, even at the S.P. Coral reefs extending 10o
poleward to 40o Why?
4
Warm Arctic
5
Cretaceous Climate and Modeling
Tropical thermostat and latitudinal surface
temperature gradient (?)
Largest warming in the Antarctic due to the
absence of ice sheet (with a height of 3-4km)
Reading material Huber M., 2008, Science, Vol.
321, 353-354
6
Model-data mismatch ?
  • Data problem underestimation of tropical warming
  • Organism adaptation (but, why so many uncorelated
    organism?)
  • Missing interior land data
  • Tropical shell dissolved or recrystallized
    (appearing colder)
  • Model problem not good model yet (but what s
    missing?)

7
The ocean heat transport hypothesis
Increased ocean heat transportgtreduced
pole-equator temperature gradient But does the
atmospheric heat transport compensates the ocean
heat transport? (Bjerkness hypothesis!) coupled
ocean-atmosphere model does not show reduced
temperature gradient either!
Mid-Cretaceous salinity
8
Implication to CO2 and climate change
mid-Cratecous
  • No ice ? less albedo feedback
  • (but, water vapor feedback positive!
  • Which is stronger?)
  • 2. Radiative forcing ln(CO2)

Glacial maximum
9
Two more issues Global sea level
change Asteroid Impact of 65Ma event
10
Global Sea Level Change
11
How to identify Global Sea Level Change
12
Evidence of Sea Level Change
Marine limestone deposits form the coasts of
southern England and northern France
13
100 myr ago mid-Cretaceous
Evidences worldwide indicate sea level change in
global scale or the eustatic sea level
14
Mechanism of sea level change I. change of
volume of ridge (high spreading rate wider ridge)
15
Mechanism of sea level change II. Collision of
continents
Collision squeezes the crust , increases the
ocean area, reduces sea level
16
A check on spreading and colliding mechanism for
sea level
Colliding ?Low sea level
fast
Fast spreading/No colliding gt high sea level
17
Contribution to Sea Level Decrease (100 Ma to 0
Ma)
Cause of sea level change Estimated change (m)
Geological factors
Decrease in ocean ridge volume -50 to -150
Collision of India and Asia -10
Climate factors (related to CO2)
Water stored in ice sheets -50
Thermal expansion of sea water -10
Total -120 to -220
Last glacial maximum 120 m lower sea
level Thermal expansion coefficient 1/7000 /K
deep ocean 10K warming ? 10/7000 5km 7m What
about future global warming?
18
Contribution to Sea Level Change (uncertainty,
version I)
Geological factors
climate factors (related to CO2)
19
65 Ma event Distinction of 70 of species,
including all dinosaurs Why?
20
Evidence of Meteor Impact
Iridium rare on earth, but 10000 times more
abundant in some kinds of meteorites Largest
body every 50 100 myr
21
Site of Meteor Impact Yucatan Peninsula, Mexico
Climatic impact of Meteor
200 km diameter 20km/s speed 11 Richter scale
earth quake 100-1000 times stronger than biggest
earthquake
22
The 55 Ma abrupt warming event
100,000 years long Evidence in d18O and
d13C Possibly increased CO2 and CH4 But NOT
Asteriod impact (too long) Then What is the
triggers for the increase of GHGs?
23
References for Reading
Huber M., 2008, Science, Vol. 321, 353-354
(including SOM)
24
End of Lecture 6
25
Mechanism of sea level change III. Expansion of
volcanic plateau
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