Pliocene palaeoceanography of the Arctic Ocean and subarctic seas

Abstract

The Pliocene is important in the geological evolution of the high northern latitudes. It marks the transition from restricted local-to extensive regional-scale glaciations on the circum-Arctic continents between 3.6 and 2.4 Ma. Since the Arctic Ocean is an almost land-locked basin, tectonic activity and sea-level fluctuations controlled the geometry of ocean gateways and continental drainage systems, and exerted a major influence on the formation of continental ice sheets, the distribution of river run-off, and the circulation and water mass characteristics in the Arctic Ocean. The effect of a water mass exchange restricted to the Bering and Fram Straits on the oceanography is unknown, but modelling experiments suggest that this must have influenced the Atlantic meridional overturning circulation. Cold conditions associated with perennial sea-ice cover might have prevailed in the central Arctic Ocean throughout the Pliocene, whereas colder periods alternated with warmer seasonally ice-free periods in the marginal areas. The most pronounced oceanographic change occurred in the Mid-Pliocene when the circulation through the Bering Strait reversed and low-salinity waters increasingly flowed from the North Pacific into the Arctic Ocean. The excess freshwater supply might have facilitated sea-ice formation and contributed to a decrease in the Atlantic overturning circulation.

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 PZ-16 interval coincides well with MIS G16. Generally, the revealed deterioration of climate conditions is simultaneous with the onset of an intensified Northern Hemisphere glaciation during the Late Pliocene, which is dated between 3.0 and 2.9 Myr BP (Matthiessen et al, 2009, and references therein).…”

The emergence of modern sea ice cover in the Arctic Ocean

“…At this time, the Arctic Ocean was partly isolated, with restricted AAG through-flow 21 , and the Bering Strait still in the initial opening phase [38][39][40][41] . The prevalence of an estuarine circulation in the Arctic Ocean 42,43 , together with a high continental mean annual temperature (MAT) would have restricted the occurrence of sea ice in the Arctic interior. As such, the marginal seas (including the study location here) would have been ice-free or covered by first-year winter sea ice only ( late Miocene-early Pliocene, including mountainous uplift 44 and open/closing gateways (AAG, Bering Strait, Central American Seaways (CAS)) 21,45,46 , triggered the expansion of the Arctic sea ice coverage, reaching the modern summer limit (Fig.…”

Pliocene Model Intercomparison Project (PlioMIP): experimental design and boundary conditions (Experiment 1)

“…However, extreme warmth documented in marine and terrestrial sequences in the Arctic argues for at least seasonally ice-free conditions (Brouwers, 1994;Cronin et al, 1993;Robinson 2009;Matthiessen et al, 2009). In a fashion similar to the method used in the Southern Hemisphere, modern seasonal growth patterns of sea-ice were used to expand and contract the ice margin from its midPliocene maximum extent (=modern summer extent) to a summer ice-free condition.…”