Palimpsest Meltwater Landscape as an Analog for Future Ice Sheet Deglaciation

Understanding the deglaciation of modern ice sheets and glaciers is crucial in the face of global climate change. Meltwater transport through subglacial plumbing is a key component of deglaciation, but direct observation is obscured by the presence of overlying ice. Recently released LiDAR data of the southern Fraser Plateau, British Columbia, which was covered by the Cordilleran Ice Sheet (CIS), reveal a palimpsest landscape of various meltwater-derived landforms associated with glaciolacustrine landforms. Through GIS investigation, four landform assemblages have been identified: 1. Drumlins and ribbed moraine; 2. Subglacial meltwater-derived erosional corridors; 3. Eskers; 4. Proglacial lakes with proglacial channels and perched subaqueous fans. Erosional corridors (2) truncate drumlins and ribbed moraine (1), eskers (3) are present across the landscape, and proglacial landforms (4) truncate all other assemblages. Esker sedimentology and stratigraphy suggests that most eskers were formed by relatively low magnitude drainage events in sub- and supraglacial positions. In contrast, erosional corridors (2) record drainage events orders of magnitude larger. This palimpsest landscape suggests a chronology of deglaciation initiated by large subglacial floods and ending with widespread proglacial lakes. The source of meltwater for the subglacial floods is either: subglacial lakes near the margin of the CIS that drained one to the other, thence to the margin; or ice-dammed proglacial lakes that drained subglacially one to the other. Preliminary observations of shorelines at elevations above some of the highest erosional corridors (2), suggest a subglacially cascading proglacial lake system driving fast-paced deglaciation. Further work is required to assess the presence of subglacial lakes and their cascading drainage.