Abstract
Several decades of ground- and air-based geophysical exploration of the subsurface of Earth's ice sheets has resulted in a broad understanding of their thickness, internal structure and the subglacial controls upon ice flow. Radar sounding in particular has proven immensely valuable in illuminating the nature of ice sheets far from ice core sites, and we are presently in the midst of a golden age for radar sounding that includes advances in both technical capabilities and spatial coverage. In this talk I will describe recent examples of novel and anticipated insights into radar-inferred controls upon ice-sheet dynamics. High radar reflectivities suggest that seawater infiltrates upstream of some Antarctic grounding zones and hence that ice-shelf tidal flexure can reverse subglacial water flow there. While radar investigations of subglacial beds often focus on the search for water there, contrasts in small-scale bed roughness are also common and are related to sharp transitions in ice flow. With increasing data coverage, we can expect that similar methods will be applied at regional and continental scales, bridging the present gap between localized radar observations and numerical models of entire ice sheets. For example, we are presently mapping the radiostratigraphy of the whole of the Greenland Ice Sheet. This approach should yield fundamental insights into the evolution of strain in an ice sheet and the subglacial and internal controls upon its flow.