Sea ice changes in the greater PAL LTER study region are occurring 29% faster than the fastest sea ice changes in the Arctic. Over 1979-2006, the sea ice season has become 83 days shorter in the greater PAL LTER area versus 59 days shorter in the greater Chukchi Sea area in the Arctic (though the latter includes twice the area effected). We review the physical processes and potential feedbacks contributing to these polar sea ice changes to better reveal high latitude climate sensitivity and its implications for polar marine ecosystems. The trends toward earlier spring sea ice retreat and later autumn sea ice advance (thus shorter sea ice season) are causing related changes in seasonal food supplies and habitat availability, with both bottom-up and top-down effects (see Ducklow and other PAL LTER posters). Though the magnitude and area of change differ between polar regions, the comparison nevertheless underscores that amplification of climate change is happening in both polar regions with alarming rapidity.