Evolving Pliocene-Pleistocene climate: A North Pacific perspective

Abstract

Siliceous microfauna in sediments from North Pacific Deep Sea Drilling Project sites record the response of the regional surface and near-surface waters to global climate change over the past 3.0 Ma. During the Late Pliocene (2.7–3.0 Ma), the northern subtropical and subpolar Pacific experienced warmer climate conditions than those of today. The first predominant polar assemblage maximum occurs in the North Pacific at ∼2.45 Ma signifying this region's response to the initiation of significant northern hemisphere glaciation. North Pacific faunal data show that Late Pliocene (1.8–2.5 Ma) glacial maxima were only about half to two-thirds as severe as those which occurred during the Late Pleistocene. Low faunal assemblage variability during a 200 ka interval in the latest Pliocene (1.6–1.82 Ma) in the North Pacific indicates minimal variations in the surface water properties and climate conditions most like those which existed just prior to 2.5 Ma. A distinct change in faunal assemblage registered in sediments from Site 580 between 1.2 and 1.2 Ma marks the first cooling in the North Pacific comparable in intensity to those of the Late Pleistocene. Since ∼1.26 Ma, high amplitude, high frequency variations in the North Pacific polar assemblage have continued to occur, providing further evidence that the interglacial/glacial extremes that characterize the Late Pleistocene have persisted since this time. The frequency distribution of North Pacific winter sea-surface temperature time series for the Late Pliocene and Early Pleistocene includes major concentrations of variance (power) centered at a frequency corresponding to a 41 ka period, with variance dominance of the temperature time series for the last 800 ka shifting to lower frequencies (∼110 ka period).