Simulation of the Northern Hemisphere Ice sheet throughout ice age cycles: Impact of Mass-Balance-related parameters

One of the challenges of earth system modeling is to confirm the theories of ice age cycle by simulating it using physically based models. Here we simulate the glacial cycle known as saw-tooth shape 100ka cycle time sequence using a three dimensional ice sheet model, IcIES (Saito and Abe-Ouchi, 2004), which includes the thermo-mechanical coupling processes (used for simulations of Antarctica and Greenland ice sheet) with the process of delayed isostatic rebound. We also use an atmospheric GCM (CCSR/NIES) to estimate the climate sensitivity to Milankovitch forcing and atmospheric CO2 as well as mass balance related parameters such as lapse rate, albedo feedback and desertification effect, while we do not force the model by any proxy data such as isotopic temperature derived by ice core data in former studies. We show that the ice age cycles with a saw-tooth shape 100 ka cycle and the major NH ice sheet (Laurentide ice sheet and Fenno-Scandian ice sheet) volume and geographical distribution in the past 400,000 years are successfully simulated in which relatively small (around 5K/km) lapse rate parameter is used. This small lapse rate is consistent with the lapse rate of free atmosphere in summer calculated in the present-day data. It is shown that the temperature related processes such as lapse rate and albedo feedback plays a large role in determining the amplitude and nature of 100ka ice age cycle of Northern Hemisphere Ice sheet.