Local sea-level changes are not simply a function of global ocean volumes but also the interactions between the solid Earth, the Earth’s gravitational field and the loading and unloading of ice sheets. These processes lead to variability in relative sea-levels across the globe. The most complex interactions are found in regions beneath the former ice sheets themselves. Efforts to better understand these interactions have brought new insights into the behavior and history of the ice sheets but also left us with many remaining questions. In this presentation I review some of these interactions, or glacial-isostatic adjustment, with field examples from the Antarctica Peninsula and northwest Scotland.
Along the Antarctica Peninsula, small advances and retreats in the ice sheets result in measurable changes in relative sea levels that include increases in the rate of rebound or uplift and periods of transgression during the fall in sea levels. These changes can be used to track the behavior of the former ice sheets at a relatively fine scale. In Scotland, we investigate the rate of relative sea-level change accompanying the retreat of a large ice stream that once drained a portion of the northwestern British-Irish-Ice Sheet at the last glacial maximum. Contrasting behaviors between Antarctica and Scotland highlight how important the geologic structure beneath the former ice sheets is in determining the interactions between ice sheets and relative sea levels.