Improving the Incorporation of Ice Streams in North American Ice Sheets by Combining Datasets of Subglacial Geology, Landform Evidence and a Revised Model of Subglacial Hydrology

The aim of this study is to improve model simulation of North American paleo ice sheets, ensuring that ice streams form in appropriate locations, influencing the ice sheet spatial extent and volume. We highlight the diverse range of ice stream types of the North American Ice Sheet (NAIS) complex (Cordilleran, Laurentide and Innuitian) that formed during the Last Glacial Maximum (LGM, 26-21ka) and assess their influence on ice sheet geometry. Topographically controlled marine-terminating ice streams dominated the northern and eastern margins, such as the Hudson Strait and Lancaster Sound, and strongly controlled the ice sheet volume and shape. In contrast, land-terminating, geologically controlled ice streams dominated the low-relief southern margin. We show progress towards reconciling ice stream discharges and ice sheet volume with empirical estimates and note that previous modelling studies overestimated ice sheet volume, likely because of inadequate incorporation of ice streaming. In this study we use a higher-order ice sheet model (Community Ice Sheet Model v2.1), run at 16 km and 4 km and forced with climatology from two 1° simulations using the CESM2.1 (Community Earth System Model), to simulate the NAIS complex during the LGM. We aim to increase the realism of ice sheet geometry and history by simulating ice streams in known locations. We achieve this using geological information of the ice sheet bed (e.g., sediment properties affecting basal sliding) and geomorphological landform information about known ice stream tracks. Also, we have added a steady-state subglacial hydrology routing scheme to the ice sheet model. Using this approach, we investigate the controls on ice stream formation, suggest methods for ensuring appropriate ice stream formation, and estimate ice stream discharge during the LGM. We apply a new streamline routing algorithm to track flow geometry and drainage basin evolution