Evolution of millennial‐scale climate variability during the mid‐Pleistocene

Abstract

[1] We use the oxygen isotopic composition of planktonic foraminifera Globigerinoides ruber (white) from Ocean Drilling Program Site 1058 in the subtropical northwestern Atlantic to construct a high-resolution ($ 800 year) climate record spanning the mid-Pleistocene climate transition ($410 ka to 1350 ka). We investigate whether or not millennial-scale instabilities in the proxy record are associated with the extent of continental glaciation. G. ruber d 18 O values display high-frequency fluctuations throughout the record, but the amplitude about mean glacial and interglacial d 18 O values increases at marine isotope stage (MIS) 22 (880 ka) and is highest during MIS 12. These observations support that millennial-scale climate instabilities are associated with ice sheet size. Time series analysis illustrates that these variations have significant concentration of spectral power centered on periods of $10-12 ka and $5 ka. The timing of these fluctuations agrees well, or coincides with, the periodicities of the second and fourth harmonics, respectively, of precessional forcing at the equator. An insolation-based origin of the millennial-scale instabilities would be independent of ice volume and explains the presence of these fluctuations before the mid-Pleistocene climate transition as well as during interglacial intervals (e.g., MIS 37 and 17). Because the amplitude of the millennial-scale variations increases during the mid-Pleistocene transition, feedback mechanisms associated with the growth of large, 100-ka-paced, polar ice sheets may be important amplifiers of regional surface water hydrographic changes.

A 0.6 million year record of millennial‐scale climate variability in the tropics

“…Due to less certainty in the age model prior to MIS 13, caution is exercised in interpretation of patterns in MIS 14 and 15. Upon examination of the full Mo record, the most apparent observations are that there is a clear correlation to local summer insolation and that the entire ~600 kyr is dominated by suborbital‐scale variability, consistent with previous observations from records in the high latitudes [ Oppo et al ., ; McManus et al ., ; Weirauch et al ., ; Bolton et al ., ]. Out of the four additional glacial periods captured in the Mo record, however, MIS 10 is the only interval that appears to follow the pattern of variability observed during the last glacial, with intervals of prolonged oxygenation (i.e., stability) at the onset and maximum of each interval bracketing a period of rapidly changing ventilation (instability) (Figure ).…”

Late Pliocene to early Pleistocene changes in the North Atlantic Current and suborbital‐scale sea‐surface temperature variability

“…[] and Weirauch et al . []). It is an unlikely coincidence that we find no change in both the amplitude of midlatitude North Atlantic suborbital surface ocean temperature variability and the position of the NAC and Arctic Front on glacial‐interglacial time scales across the iNHG, implying that the two observations are likely linked.…”

North Atlantic Upper‐Ocean Hydrography During the Mid‐Pleistocene Transition Evidenced by Globorotalia truncatulinoides Coiling Ratios

“…All bulk sediments from this study have been previously processed and size fractioned as described by Diester‐Haass et al () for Sites 607, 552, and 925 and Weirauch et al () for Site 1058. Because of high sedimentation rates at Site 1058, we subsampled the cores at a rate of 30–40 cm in order to achieve the same ~3‐kyr time step as at Sites 607, 552, and 925 (Diester‐Haass et al, ).…”