A global synthesis of the marine and terrestrial evidence for glaciation during the Pliocene Epoch

The Pliocene climate is globally warm and characterised by high atmospheric carbon dioxide concentrations, yet the terrestrial and marine scientific communities have gathered considerable evidence for substantial glaciation events in both the Northern and Southern Hemisphere prior to the Quaternary. Evidence on land is fragmentary, but marine records of glaciation present a more complete history of Pliocene glaciation. Here we present a global compilation of the terrestrial and marine glacial evidence for the Pliocene and demonstrate four glaciation events that can be identified in the Southern and/or Northern Hemisphere prior to the latest Pliocene intensification of Northern Hemisphere glaciation. There are two globally recognisable glacial events in the early Pliocene (c. 4.9–4.8 Ma and c. 4.0 Ma), one event around the early/late Pliocene transition (c. 3.6 Ma), and one event during Marine Isotope Stage M2 (c. 3.3 Ma). Long-term climate cooling, decreasing carbon dioxide concentrations in the atmosphere and high climate sensitivity in the Pliocene probably facilitated each glaciation event, however the mechanisms behind the early Pliocene glacial events are unclear. The global glaciation at c. 3.3 Ma may be caused by changes in ocean gateways, whereas the decline in carbon dioxide concentrations is important for the latest Pliocene intensification of Northern Hemisphere glaciation.