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