ABSTRACT
Studies of ice and sediment core archives demonstrate that Earth's Polar Regions are capable of large climatic shifts triggered by relatively small changes in external forcings. Ice cores capture seasonal variations in snowfall, which is eventually buried by further snowfall and becomes compressed and forms ice. Sediment cores collected from southern Greenland indicate glacial erosion was active in Greenland during the Eemian, and therefore a significantly sized ice sheet must have persisted through this time. Where the ice sheet has advanced across the continental shelf, sediment types recovered in drill cores provide absolute constraints of past expansion and retreat of marine-based ice sheets through time. Closer to the Polar Regions, direct indications of cryospheric change can be identified by shifts in terrigenous sediment supply to the ocean. The abundance of gravel in marine sediment cores adjacent to the continental margin of a polar ice sheet generally reflects the proximity of a glacier calving into the ocean.
