Modeling the Eocene: A Paleoclimate Study

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Modeling the Eocene A Paleoclimate Study

• Student Mario Lopez
• Advisor Dennis Hartmann

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Eocene Thermal Maximum (55 Mya)

• Exceptionally warm time in Earth history
• High greenhouse gas levels
• Small equator to pole temperature gradients

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Motivation

• Greenhouse Climate
• Anthropogenic CO2 emissions since
  industrialization (past 250 yrs)
• Future climate on Earth could be like Eocene

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Cenozoic Era
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Long Term CO2 Trend
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Very Recent CO2 Trend
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Proxy Evidence of Past Warm Climates

• Fossil Evidence
• Sea Floor Sediments

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Fossil Evidence
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Flora and Fauna
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Ancient Surface Dwelling Planktonic Foraminifera

• Provide paleoclimate records in sea floor
  sedimentary layers

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Previous Modeling Attempts

• General Circulation Models (GCMs)
• Produced globally higher surface temperatures
• Underestimated high latitude temperatures
• Overestimated tropical Sea Surface Temperatures
  (SSTs)

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Huber Sloan (2001)
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Modeling the Eocene

• Goal Get model to agree with proxy data
• Warm-up the poles
• Maintain near modern tropical SSTs

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Methodology

• CAM 3.0 with SLAB ocean model
• Very High CO2 levels
• Change model parameters to best simulate Eocene

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Comparing CAM Runs
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Comparing CAM Runs
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CAM Control Run

• Present day results compared with observations

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CAM with 10xCO2

• Raised global temperatures
• Wintertime freezing at poles
• Very warm tropical SSTs

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DJF Zonal Temperature Averages
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JJA Zonal Temperature Averages
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10xCO2 with New Land Surface

• All land tropical rainforest
• Warms atmosphere
• Similar results to 10xCO2 with original land
  surface, but warmer poles

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DJF Zonal Temperature Averages
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JJA Zonal Temperature Averages
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Some Ideas

• Lower Land Surface
• Polar Stratospheric Clouds
• Tropical Cyclones

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Tropical Cyclones

• Assumption Tropical Cyclones more prevalent at
  high SSTs
• Transfer heat from ocean surface to atmosphere
• Could help cool tropics in a greenhouse world

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Benefit of Tropcial Cyclones

• Transport heat poleward in the ocean mixed layer
• Presumed cooling affect in tropics and warming
  affect at high latitudes

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Summary

• Interesting climate regime in Earth history
• Difficult to model
• Tweaking CAM 3.0 to best represent the Eocene

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Acknowledgements

• Dennis Hartmann
• Marc Michelsen