Northern Hemisphere Glaciation during the Globally Warm Early Late Pliocene

Abstract

The early Late Pliocene (3.6 to ∼3.0 million years ago) is the last extended interval in Earth's history when atmospheric CO2 concentrations were comparable to today's and global climate was warmer. Yet a severe global glaciation during marine isotope stage (MIS) M2 interrupted this phase of global warmth ∼3.30 million years ago, and is seen as a premature attempt of the climate system to establish an ice-age world. Here we propose a conceptual model for the glaciation and deglaciation of MIS M2 based on geochemical and palynological records from five marine sediment cores along a Caribbean to eastern North Atlantic transect. Our records show that increased Pacific-to-Atlantic flow via the Central American Seaway weakened the North Atlantic Current and attendant northward heat transport prior to MIS M2. The consequent cooling of the northern high latitude oceans permitted expansion of the continental ice sheets during MIS M2, despite near-modern atmospheric CO2 concentrations. Sea level drop during this glaciation halted the inflow of Pacific water to the Atlantic via the Central American Seaway, allowing the build-up of a Caribbean Warm Pool. Once this warm pool was large enough, the Gulf Stream–North Atlantic Current system was reinvigorated, leading to significant northward heat transport that terminated the glaciation. Before and after MIS M2, heat transport via the North Atlantic Current was crucial in maintaining warm climates comparable to those predicted for the end of this century.

Late Pliocene and Early Pleistocene vegetation history of northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

“…The existing terrestrial and marine records also provide consistent evidence for the intensification of continental glaciations in the Northern Hemisphere during the middle Pliocene (e.g., Matthiessen et al, 2009;de Schepper et al, 2013, and references therein). Therefore, we suggest dry and cold environments reconstructed from PZ-8 pollen assemblages to be simultaneous with the coldest stage(s) of the Zhuravlinean glaciation traced in eastern Chukotka.…”

“…The relatively numerous remains of Botryococcus and Pediastrum colonies imply that green algae started to colonize the initial lake, which was rather shallow during this interval. It is known that their abundance is greater in sediments deposited in shallow water, especially in small lakes and in the littoral environments of larger lakes (e.g., Guy-Ohlson, 1992;Clausing, 1999;van Geel, 2001). …”

Climate variability and long-term expansion of peatlands in Arctic Norway during the late Pliocene (ODP Site 642, Norwegian Sea)

“…A re-establishment of the NAC at 3.285 Ma, following the glacial maximum of MIS M2, is also seen in the alkenone-and Mg / Ca-derived SSTs as well as dinoflagellate assemblage changes at IODP Site U1308 (50 • N, 24 • W) and Deep Sea Drilling Project (DSDP) Site 610 (53 • N, 19 • W) further north (De Schepper et al, 2013). The warming documented at these sites is in agreement with this study.…”

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

“…Dinocyst distribution in marine surface sediments has shown to reflect changes in the sea surface water properties, mostly responding to temperature (e.g., Rochon et al, 1999;Zonneveld et al, 2013). Down-core changes in dinocyst assemblages are widely used in reconstructing past environmental changes in the Quaternary (e.g., de Vernal et al, 2009), but also in the Neogene and Paleogene (e.g., Versteegh and Zonneveld, 1994;Head et al, 2004;Pross and Brinkhuis, 2005;Sluijs et al, 2005;Schreck et al, 2013;De Schepper et al, 2011, 2013Hennissen et al, 2017).…”