| Popis: |
Ice cores collected on dynamic ice sheets cannot be correctly interpreted without accounting for how the ice-sheet shape and flow have changed. By being the last ice sheet of the type occupying primarily a marine basin, the West Antarctic ice sheet has a highly variable behavior. For the past quarter century, researchers have sought a quantitative prediction of its future behavior, including its potential for collapse, and the corresponding effect on sea level. Observations confirm changes on timescales from the Quaternary to less than a minute. The dynamics of the ice sheet involve the complex interaction of kilometers-thick ice that is warm at its base and cold along the margins of ice streams, subglacial till reaches a level where it is composed of a combination of marine sediment and eroded sedimentary rocks, and water that moves primarily between the ice and bed, but whose direction can differ from the direction of ice motion. The pressure of the water system is often sufficient to float the ice sheet locally and small changes in the amount of water in the till can cause it to rapidly switch from very weak to very stiff. |
