Arctic warming induced by the Laurentide Ice Sheet topography

It is well known that ice sheet-climate feedbacks are essential for realistically simulating the spatio-temporal evolution of continental ice sheet over glacial-interglacial cycles. However, many of these feedbacks are dependent on the ice sheet thickness, which is poorly constrained by proxy data records. For example, height estimates of the Laurentide Ice Sheet (LIS) topography at the Last Glacial Maximum (LGM; ~ 21,000 years ago) vary by more than 1 km between different ice-sheet reconstructions. In order to better constrain the LIS elevation it is therefore important to understand how the mean climate is influenced by elevation discrepancies of this magnitude. Here we use an atmospheric model coupled to a slab-ocean model to analyze the LGM surface temperature response to a broad range of LIS elevations (from 0 to over 4 km). We find that raising the LIS topography induces a widespread surface warming in the Arctic region, amounting to approximately 1.5 °C per km elevation increase, or about 6.5 °C for the highest LIS. The warming is attributed to an increased northward energy flux by atmospheric stationary waves, reinforced by surface albedo and water vapor feedbacks, which account for about two-thirds of the total temperature response. These results suggest a positive feedback between continental-scale ice sheets and the Arctic temperatures that may help constrain LIS elevation estimates for the LGM and explain differences in ice distribution between the LGM and earlier glacial periods.