Camille Li, Kerim Nisancioglu, Trond Dokken,

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Camille Li, Kerim Nisancioglu, Trond Dokken,
Øyvind Lie Bjerknes Centre for Climate
ResearchDavid Battisti University of
WashingtonLev TarasovMemorial
UniversityOUTLINE1. Background D-O
events2. A conceptual model3. Clues from
climate models
A conceptual model for D-O events
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Dansgaard-Oeschger events
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Dansgaard-Oeschger events

• abrupt warming events in Greenland
• large amplitude in Greenland (7-12C)
• climate signal throughout the Northern Hemisphere
• millennial scale timing
• leading hypothesis ocean thermohaline
  circulation

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What can we learn from models?
AOGCM atmosphere-ocean general circulation model
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What can we learn from models?
EMIC earth model of intermediate complexity
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What can we learn from models?
EMIC earth model of intermediate complexity e.g.
ECBILT-CLIO
Knutti et al. 2004 Nature
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What can we learn from models?
EMIC ice sheet model AGCM (atmosphere land)
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Building a conceptual model
TM Dokken
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Building a conceptual model
TM Dokken
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Clues from climate models
ocean
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Clues from climate models
subsurface ocean warming (EMIC)
Atlantic Ocean temperature change after
freshening of Nordic Seas (C)
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Clues from climate models
atmosphere
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Clues from climate models
sea ice Greenland temperature (AGCM)
Li al. 2005 GRL
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Clues from climate models
jets storminess (AOGCM/AGCM)
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Summary
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A final picture
cold interstadial state strong, steady jet
warm stadial state weak, wobbly jet
artwork courtesy of D. Battisti see also Seager
Battisti 2006
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Dansgaard-Oeschger events
Rahmstorf 2003