Numerical 3-d model experiments on global climate sensitivity to solar constant variations

Abstract

The aim of the study is to show an important role of the solar radiation flux in positive feedback “temperature - surface albedo” during the transition to glaciation regimes observed in the history of the Earth. The study is based on a three-dimensional hydrodynamic global climate coupled model, including ocean model with real depths and continents configuration, sea ice evolution model and energy - moisture balance atmosphere model. A series of numerical experiments were carried out to assess the impact of changes in solar radiation flux on the global climate. It is assumed that the solar constant gradually decreases discretely compared to the current value and in each case is determined the steady climatic mode. Simulation period is about 2000 years. Gradual increase in the sea ice area and a catastrophic increase at the end of stage 3, when the oceans are completely covered with ice (so called “snow ball Earth”) are get. These results are naturally explained by the presence of the “temperature decrease - glaciation” positive feedback. The stage 3 maximum surface air temperature is -30° C, the minimum -80°C. Strong temperature and ice cover changes lead to significant changes in the horizontal and vertical thermohaline ocean circulation. The vertical thermohaline circulation has the weakened horizontal velocities in the north direction in the ocean upper layers and increased in the direction of the equator in the deep layers (in contrast to the present situation). The author was supported by the Russian Foundation for Basic Research (project no. №17-01-00693).