1 / 28

The Greenhouse Climate

The Greenhouse Climate. We Know the Last 100 Myr Pretty Well…. Why? Know Continental Positon Shape of the Ocean Basins Temperature Sea Levels. Cretaceous: “abundance of chalk”. Pangaea was breaking up…. Sea Level was MUCH Higher…. Climate Evidence.

felder
Télécharger la présentation

The Greenhouse Climate

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Greenhouse Climate

  2. We Know the Last 100 Myr Pretty Well… • Why? • Know • Continental Positon • Shape of the Ocean Basins • Temperature • Sea Levels

  3. Cretaceous: “abundance of chalk”

  4. Pangaea was breaking up….

  5. Sea Level was MUCH Higher….

  6. Climate Evidence • Warm-adapted vegetation and critters north of the Arctic circle • Brown-leaf evergreens • Turtles and crocodiles • No continental glaciation • Tropical conditions to 40 • Coral growing at the paleolatitude of New York • NO HARD Freezes in temperate latitudes.

  7. 180 Myr Ago

  8. 160 Myr Ago

  9. 120 Myr Ago

  10. 80 Myr Ago

  11. 60 Myr Ago

  12. Why so much warmer? • Climate models • Geography • CO2 4-6 times current levels • Ocean Circulation • Today the atmosphere transports about double the heat that the oceans transport • In Cretaceous that ratio was probably reversed

  13. CO2 probably drove the warming • Note that CO2 effect is not linear • At low levels snow and ice contribute to positive feedback • They reflect a lot of solar radiation back to space • At high levels there is much weaker effects • Little snow to melt • CO2 Saturation • But water vapor feedback works in the opposite direction

  14. Regression

  15. Transgression

  16. But what causes changes in sea level? • Changes in Climate • Ice vs no ice….about 50 meters of change in Cretaceous • Thermal contraction of water ~ 7 meters • Change in ocean basin volume • Spreading rates (50 to 150 meters) • Continental Collisions (~10 meters)

  17. Fast Spreading

  18. Slow Spreading

  19. Continental Collision • The size of continents effects the size of oceans (duh….) • The collision of India with Asia decreased the continental area by 2 million Km2 (and increased the oceans by that amount) • Net effect was about 10 meters of sea level drop

  20. Effects of Sea Level on Climate • Water has a large heat capacity and moderates regional climates • That’s why maritime (western ends of continents) climates tend to be milder • High stands of sea level extend the reach of maritime climates

  21. Climatic Factors • Ice Sheets • Antarctic ~ 66 meters of sea level rise • Greenland ~ 6 meters • Thermal Expansion/Contraction • The volume of water changes about 1 part in 7000 per degree C • Given ocean cooling since the cretaceous, that works out to about 7 meters of sea level drop.

  22. The 55 Myr Spike • We found this spike in the data….. • Increase in global temperatures of 5-9 C • Major acidification of the oceans • Extinction of about half of the forams • Why? • Major release of carbon • Methane on the seafloor

More Related