CONSTRAINING NORTH AMERICAN GLACIAL CYCLE HISTORIES THROUGH THEIR FOOTPRINT: A COUPLED ICE/ SEDIMENT/HYDROLOGY MODEL APPROACH

What new constraints does the addition of fully coupled subglacial hydrology and sediment production/transport add to data-constrained glacial cycle ice sheet modelling? As a corollary, what are the inferred local erosion/denudation rates and relative contribution from relevant processes? We probe these questions for the context of the last glacial cycle of the North American ice sheet complex.

Currently there are few ice sheet models which implement sediment production/transport and even fewer with a realistic hydrology which modulates these sedimentary processes. To date, models of subglacial hydrology have been designed for either glacier scale (complex description of processes) or continental scale (heavily simplified for basal drag calculation). The model presented here represents a trade off: a parameterized choice of poroelastic and linked-cavity systems for inefficient drainage with a flux switch to efficient (tunnel) drainage. The subglacial sediment model incorporates both abrasion and quarrying with transport via both glacial entrainment and soft sediment deformation.

These sediment and hydrology models have been fully coupled to the Glacial Systems Model (GSM), a 3D ice sheet model with full suite of ice dynamics, solid earth processes, and range of climate representations. GSM ensemble parameters are constrained by comparison of resultant ice histories against a range of geophysical and geological data. An esker-margin density time series is used to constrain the drainage regime, debris trains provide a control on sediment transport, and the present day distribution of sediment over North America is an outcome requirement. Our probe will invoke comparison of a large ensemble of last glacial model runs against the above constraints.