An initial intercomparison of atmospheric and oceanic climatology for the ICE-5G and ICE-4G models of LGM paleotopography

This paper investigates the impact of the new ICE-5G palcotopography dataset for Last Glacial Maximum (LGM) conditions oil a Coupled model Simulation of the thermal and dynamical state of the glacial atmosphere and oil both land surface and sea surface conditions. The study is based upon coupled climate simulations performed with the ocean-atmosphere-sea ice model of intermediate-complexity Climate de Bilt-coupled large-scale ice-ocean (ECBilt-Clio) model. Four simulations focusing Oil the Last Glacial Maximum [21 000 calendar years before present (BP)] have been analyzed: a first simulation (LGM-4G) that employed the original ICE-4G ice sheet topography and albedo, and a second simulation (LGM-5G) that employed the newly constructed ice sheet topography, denoted ICE-5G, and its respective albedo. Intercomparison of the results obtained in these experiments demonstrates that the LGM-5G simulation delivers significantly enhanced cooling over Canada compared to the LGM-4G simulation whereas positive temperature anomalies are simulated over southern North America and the northern Atlantic. Moreover, introduction of the ICE-5G topography is shown to lead to a deceleration of the subtropical westerlies and to the development of all intensified ridge over North America, which has a profound effect upon the hydrological cycle. Additionally, two flat ice sheet experiments Were carried out to investigate the impact of the ice sheet albedo on global climate. By comparing these experiments with the full LGM simulations, it becomes evident that the climate anomalies between LGM-5G and LGM-4G are mainly driven by changes of the earths topography.