Sensitivity of ice-atmosphere interactions since the Last Glacial Maximum

The understanding of ice sheet-climate interactions is critical to the simulation of past and future climates using General Circulation Models (GCM). Ice sheet evolution has previously been modeled using prescribed temperature and precipitation fields derived from proxy data, field observations, or GCM experiments. This approach ignores important climate feedbacks involving the changes in ice sheet topography and surface albedo that occur as ice sheets grow and decay. Here, we use a relatively new two-way coupling scheme between climate and ice sheet models that allows surface boundary conditions to be exchanged between the models during the simulations and thus simulates ice-atmosphere interactions. This study explores the sensitivity of the deglaciation of the last glacial maximum (LGM, ~20 kyr BP) Laurentide Ice Sheet to the coupling interval between the NCAR Community Atmospheric Model (CAM) and a three-dimensional thermo-mechanically coupled ice sheet model. The effects on the ice sheet deglaciation timescale under constant atmospheric forcing of ice-atmosphere interactions simulated with no coupling, and 500- and 1000-year coupling intervals are investigated. Greenhouse gas concentrations (CO2, CH4, NO2) were fixed to their LGM minimum values, while orbital parameters were set to 10 kyr BP values. Sensitivity experiments lead to the determination of deglaciation timescales associated to each coupling interval. Insights are used to identify and quantify the role of ice-atmosphere feedbacks and their effects on the deglaciation of the Laurentide Ice Sheet.