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Anthropogenic Forcing of Ocean Warming and Its
Effects on the West Antarctic Ice Sheet
Theresa DiehlPhysical Climatology
Fall 2005
Earth’s Energy Imbalance
• Global net energy surplus of 1 W/m2
Q. Where does all this energy go?
A. ~85% in the last 40 years has gone toward warming the Earth’s oceans
Ocean Warming 1960-2000
Barnett et al., 2005
Three Possible Causes
1. Natural variability of the air-ocean system
2. External forcing due to solar or volcanic variability
3. Anthropogenic forcing from global warming (greenhouse gas and aerosol emissions)
Model Results for Natural Variability
Barnett et al., 2005
Model Results for Human Forcing
Barnett et al., 2005
Antarctica
Oppenheimer, 2005
Schematic Cross-section
Oppenheimer, 2005
In 1998, Oppenheimer…
• Noted that the Larsen and Wordie ice shelves were shrinking
• Hypothesized: Due to ice shelf basal melting?
• Rejects: Fast retreat of grounding lines when ice shelf is disrupted
• Predicts: Collapse of WAIS realistically within next 700 years, as early as 200 years, with 60-120cm of sea level rise possible this century just from WAIS
Jan 31, 2002 – March 7, 2002
http://nsidc.org/iceshelves/larsenb2002/animation.html
What about the other ice shelves?
What’s causing the thinning?
Shepherd et al., 2004
Modeling the Observations for PIG
Payne et al., 2004
Will this destabilize the ice sheet?
Lythe et al., 2004
BEDMAP
Thank you