• More recently, the widely accepted mechanism is that Earth passed through a CO2 threshold (DeConto and Pollard, 2003; Pearson et al., 2009; Pagani et al., 2011). Yet recent and emerging work is suggesting that the ocean circulation system did fundamentally shift around this time (Via and Thomas, 2006; Abelson and Erez, 2017).
  • To what extent did this help to precondition the Earth system for its major glaciation? How did this reorganisation impact the global carbon cycle? Perhaps gateways played a role in this climate transition after all (Lear and Lunt, 2016).