Factors that relate to the stability of the West Antarctic ice sheet are of global importance because of its potential impact on sea level. The Ross sea sector of the ice shelf is currently growing,but suggestions that the Holocene retreat of the ice sheet has ended may be premature. New data from remote sensing and on-site measurements show that the crucial drainage system of the Ross sea ice is changing - for instance,an ice stream that flowed north less than 300 years ago is now flowing south.The rapidly changing drainage patterns cuase short-term changes in ice balance that may mask or accentuate long-term trends.