The climate-ice sheet interactions at the Late Ordovician glaciation onset revealed by numerical simulations

Abstract. The Late Ordovician marks the first major continental ice sheet event in the Phanerozoic Eon, coinciding with a dramatic global temperature drop and one of the largest mass extinctions. However, the critical role of ice sheet-climate feedbacks in driving the Late Ordovician glaciation remains poorly understood. Using an asynchronous coupling approach, we systematically analyze the feedback processes between the ice sheets and the climate system. The coupled simulations reveal a key positive feedback loop: ice sheet growth triggers katabatic winds, which in turn promote further ice sheet expansion. Results show a 1.5 °C decrease in global mean surface temperature caused by ice sheet onset, with significant cooling over mid- to high-latitude continents while warming over global oceans. The ocean warming is driven by the atmospheric stationary wave triggered by the massive ice sheet on the Gondwana continent. Our findings provide new insights into the mechanisms underlying the “Early Palaeozoic Ice Age” paradigm and highlight the complex interactions between ice sheet dynamics, atmospheric and ocean circulation, emphasizing the importance of incorporating coupled ice sheet-climate feedbacks in palaeoclimate simulations.