Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> We introduce a newly developed global ice sheet model coupled to the Globally Resolved Energy Balance (GREB) climate model for the simulation of global ice sheet evolution on timescales of 100â<span class="inline-formula">kyr</span> or longer (GREB-ISM v1.0). Ice sheets and ice shelves are simulated on a global grid, fully interacting with the climate simulation of surface temperature, precipitation, albedo, landâsea mask, topography and sea level. Thus, it is a fully coupled atmosphere, ocean, land and ice sheet model. We test the model in ice sheet stand-alone and fully coupled simulations. The ice sheet model dynamics behave similarly to other hybrid SIA (shallow ice approximation) and SSA (shallow shelf approximation) models, but the West Antarctic Ice Sheet accumulates too much ice using present-day boundary conditions. The coupled model simulations produce global equilibrium ice sheet volumes and calving rates like those observed for present-day boundary conditions. We designed a series of idealized experiments driven by oscillating solar radiation forcing on periods of 20, 50 and 100â<span class="inline-formula">kyr</span> in the Northern Hemisphere. These simulations show clear interactions between the climate system and ice sheets, resulting in slow buildup and fast decay of ice-covered areas and global ice volume. The results also show that Northern Hemisphere ice sheets respond more strongly to timescales longer than 100â<span class="inline-formula">kyr</span>. The coupling to the atmosphere and sea level leads to climate interactions between the Northern and Southern Hemispheres. The model can run global simulations of 100â<span class="inline-formula">kyrâd<sup>â1</sup></span> on a desktop computer, allowing the simulation of the whole Quaternary period (2.6â<span class="inline-formula">Myr</span>) within 1Â month.
Highlights
Understanding ice-age cycles in the Quaternary period requires an interdisciplinary research approach including the fields of astronomy, geology, physical geography, oceanography and atmospheric science
We introduce a newly developed global ice sheet model coupled to the Globally Resolved Energy Balance (GREB) climate model for the simulation of global ice sheet evolution on time scales of 100 kyr or longer (GREB-ISM v0.3)
It is beyond this study to fully explore these deviations, but 470 the results indicate that the GREB-ISM ice sheet model does have realistic responses to time varying boundary conditions
Summary
Understanding ice-age cycles in the Quaternary period requires an interdisciplinary research approach including the fields of astronomy, geology, physical geography, oceanography and atmospheric science. Geological proxy data show that sea level and surface temperature significantly oscillated with a preferred time scale of about 100 kyr during the last one million years, 25 indicating that large ice sheets and glaciers formed and retreated many times over this period (Imbrie et al, 1984; Shackelton, 2000; Short et al, 1991). These oscillations in the late Quaternary are known as the ice-age cycles. The simulation of one year of global climate with the GREB model can be done about 1sec (about 100,000 simulated 110 years per day on a desktop computer)
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