A Positive Cooling Feedback for the Neoproterozoic Snowball Earth Initiation Due To Weakening of Ocean Ventilation

Abstract

Ocean ventilation describes the process that water of ocean interior affects and is affected by the atmosphere through exchange within the surface mixed layer (Thiele & Sarmiento, 1990). The rate of ocean ventilation is an important factor in regulating the heat, salinity, and marine elemental cycles in the ocean system. Enhanced ocean ventilation can transport more surface oxidized water into the deep ocean effectively, shaping the oxygen minimum zones, and pump nutrients from the deep into the shallow ocean, affecting life habitats (Yamamoto et al., 2015). Weakened ocean ventilation can reduce atmospheric carbon dioxide level (pCO 2 ) by relocating carbon from the atmosphere to the deep ocean and storing in the deep ocean, which might facilitate glaciation (Anderson et al., 2019;Brovkin et al., 2007;Stephens & Keeling, 2000). Ocean ventilation is affected by climate and continental configuration (Donnadieu et al., 2016). The changes of ocean stratification (Gnanadesikan et al., 2007), strength and location of mid-latitude westerly wind (Russell et al., 2006), and sea-ice cover (Polyakov et al., 2017) associated with climate change all modulate ocean ventilation.Among the factors described above, sea-ice is critically important to ocean ventilation as it directly blocks the sea surface from communicating with the atmosphere. For example, sea-ice expansion during the Last Glacial Maximum (LGM) had a strong isolating effect (Gu et al., 2020), and was probably the dominant contributor to LGM deoxygenation and the enlarged carbon storage in the deep ocean (Cliff et al., 2021;Jaccard et al., 2016). During