Coupled ocean–land millennial-scale changes 1.26 million years ago, recorded at Site U1385 off Portugal

P.C Tzedakis,V Margari,D.A Hodell

doi:10.1016/j.gloplacha.2015.10.008

P.C Tzedakis, V Margari + Show 1 more

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https://doi.org/10.1016/j.gloplacha.2015.10.008

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Abstract

While a growing body of evidence indicates that North Atlantic millennial-scale climate variability extends to the Early Pleistocene, its impact on terrestrial ecosystems has not been established. Here we present ultra-high resolution (70–140year) joint foraminiferal isotopic and pollen analyses from IODP Site U1385 off Portugal, focusing on a short glacial section of Marine Isotope Stage 38, ~1.26millionyears ago. Our records reveal the presence of millennial-scale variability in the coupled ocean–atmosphere–land system in the North Atlantic and provide the first direct evidence for the response of western Iberian vegetation to abrupt climate changes in the Early Pleistocene. The magnitude and pacing of changes bear significant similarities to Dansgaard–Oeschger variability of the last two glacials.

Highlights

The recognition of the extreme and widespread nature of millennialscale climate variability in the North Atlantic region during the last glacial (e.g. Dansgaard et al, 1993; Bond et al, 1993) raised important questions about the geographical extent of such changes and their impact on terrestrial ecosystems
More recent evidence has shown that millennial-scale variability extends to the Early Pleistocene (e.g. Raymo et al, 1998), a period characterized by 41-kyr glacial–interglacial cycles and maximum ice volumes ranging between one- and two-thirds of the Last Glacial Maximum value (e.g. Ruddiman et al, 1986; Shackleton, 1995; Elderfield et al, 2012)
The aim of this study is to provide the first unequivocal evidence for a direct link between North Atlantic climate variability and vegetation response during an Early Pleistocene glacial

Summary

Introduction

The recognition of the extreme and widespread nature of millennialscale climate variability in the North Atlantic region during the last glacial (e.g. Dansgaard et al, 1993; Bond et al, 1993) raised important questions about the geographical extent of such changes and their impact on terrestrial ecosystems. High-frequency oscillations in pollen values had been known from southern European sequences extending to the last glacial, but a close temporal link with North Atlantic changes was only established after comparing pollen and marine proxies within the same deep-sea sequences off Portugal (Sánchez Goñi et al, 2000; Roucoux et al, 2001). More recent evidence has shown that millennial-scale variability extends to the Early Pleistocene Records from the North Atlantic document the presence of icerafted detritus (IRD) and attendant changes in the meridional overturning circulation (MOC) on millennial timescales during the Early Pleistocene Hodell et al (2008) suggested that major iceberg discharges from the Laurentide Ice Sheet via the Hudson Strait (Heinrich events) were initiated from Marine Isotope Stage (MIS) 16 onwards, possibly representing the crossing of a threshold in ice thickness, leading to ice instability; prior to MIS 16, IRD events are of lower amplitude, higher frequency and different lithology compared to classic Heinrich events. The question that arises is whether small differences in the character of ice discharges and mean climate state could lead to differences in the extent of their downstream impact, including the vegetation response

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