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Question for Thought

Question: What could have caused such extreme warming in the Arctic Circle during the PETM?

Think back to Lesson 4 in which you explored the delicate radiation balance of the earth. What variables of the global climate system could be manipulated to create warming of the magnitude that occurred in the PETM?

Recall the effect on surface temperature if you increase the concentration of greenhouse gases. It is believed that during the PETM there was a massive release of greenhouse gases. This release may have been caused by the destabilization of methane clathrate hydrates .

During the PETM, it is believed that the movement of Earth's tectonic plates disrupted ocean circulation patterns, creating a warming of Arctic waters by about 1.0-2.5°C. This was enough warming to destabilize the arctic store of methane clathrate hydrates (pictured at the right), freeing methane molecules from their icy cages. Once in the atmosphere, these greenhouse gases acted to increase the earth's surface temperature by about 6°C over a period of 20,000 years.