Impact of solar forcing on the surface mass balance of northern ice sheets for glacial conditions
Résumé
The climate of the last glacial period has been punctuated by abrupt changes, termed the Dansgaard–Oeschger (DO) events, occurring every 1500–4500 yr. So far, the cause of these events, which involve changes in the thermohaline circulation, remains an open issue. It has been proposed that small changes in the freshwater flux in the North Atlantic, possibly coming from cyclic variations in solar activity, could act as a pacemaker and synchronize the events. Here we use the general circulation model IPSL_CM4 to investigate the impact of changes in the total solar irradiance (TSI) on the freshwater flux coming from ablation of the Northern hemisphere ice sheets. We test four different TSI values between 1360 and 1375 W/m2, and in this range establish a linear relationship between TSI and ablation rates over different sectors of the ice sheets. Our results show that a change in TSI smaller than 1%, that would be undetectable in paleo-records, can trigger changes in the freshwater flux in the North Atlantic at an amplitude similar to the one required to synchronize abrupt events in the climate model of intermediate complexity CLIMBER. Given the uncertainties on the past solar activity, we conclude that the hypothesis of a solar origin of the periodicity of D/O events cannot be ruled out and that the relationship between ice ablation and TSI variations is worth being further investigated.