Moderate greenhouse climate and rapid carbonate formation after Marinoan snowball Earth

When the Marinoan snowball Earth deglaciated in response to high atmospheric carbon dioxide (CO₂) concentrations, the planet warmed rapidly. It is commonly hypothesized that the ensuing supergreenhouse climate then declined slowly over hundreds of thousands of years through continental weathering. However, how the ocean affected atmospheric CO₂ in the snowball Earth aftermath has never been quantified. Here we show that the ocean's carbon cycle drives the supergreenhouse climate evolution via a set of different mechanisms, triggering scenarios ranging from a rapid decline to an intensification of the supergreenhouse climate. We further identify the rapid formation of carbonate sediments from pre-existing ocean alkalinity as a possible explanation for the enigmatic origin of Marinoan cap dolostones. This work demonstrates that a moderate and relatively short-lived supergreenhouse climate following the Marinoan snowball Earth is a plausible scenario that is in accordance with geological data, challenging the previous hypothesis.