West antarctic ice sheet is most susceptible to climate change. West antarctica is warming and ice shelves are collapsing here. Co2 is a greenhouse gas that traps heat. Ice cores record co2 for 800,000 yrs + How are ice sheets like bank accounts: withdrawing ice, ablation. What evidence gives us ice sheet history: deposits left by glaciers. Material left behind when the ice is gone. Sediment and rock, or till, becomes soil. Till allows us to define the extent of ice. Ice advanced into ocean during last ice age. Ocean sonar data gives us: water depth, shape of seafloor, ice flow direction. Flutes on seafloor: tell ice flow direction. Surface air temperature trends in antarctica: wa and peninsular. Warmed ~3 degrees c in 50 years. Global average= 0. 6 degrees celsius: ea. Current trends in antarctica ice from satellites: measure mass change from satellite measurements of gravity, 1 gigaton of ice= 10x10x10 football fields.