Abstract
Abstract. We present a new high-resolution marine pollen record from NW Iberian margin sediments (core MD03-2697) covering the interval between 340 000 and 270 000 years ago, a time period centred on Marine Isotope Stage (MIS) 9 and characterized by particular baseline climate states. This study enables the documentation of vegetation changes in the north-western Iberian Peninsula and therefore the terrestrial climatic variability at orbital and in particular at millennial scales during MIS 9, directly on a marine stratigraphy. Suborbital vegetation changes in NW Iberia in response to cool/cold events are detected throughout the studied interval even during MIS 9e ice volume minimum. However, they appear more frequent and of higher amplitude during the 30 000 years following the MIS 9e interglacial period and during the MIS 9a-8 transition, which correspond to intervals of an intermediate to high ice volume and mainly periods of ice growth. Each suborbital cold event detected in NW Iberia has a counterpart in the Southern Iberian margin SST record. High to moderate amplitude cold episodes detected on land and in the ocean appear to be related to changes in deep water circulation and probably to iceberg discharges at least during MIS 9d, the mid-MIS 9c cold event and MIS 9b. This work provides therefore additional evidence of pervasive millennial-scale climatic variability in the North Atlantic borderlands throughout past climatic cycles of the Late Pleistocene, regardless of glacial state. However, ice volume might have an indirect influence on the amplitude of the millennial climatic changes in Southern Europe.
Highlights
We examined sediments from the Marine Isotope Stage (MIS) 9 interval of core MD03-2697 which is located on the NW Iberian margin, at ∼100 km off the Galician coast (42◦09.6 N, 09◦42.1 W, 2164 m)
The new marine pollen record MD03-2697 retrieved from the NW Iberian margin provides a detailed reconstruction of the vegetation changes during MIS 9 in the adjacent landmass
As shown by the other long European pollen records, the vegetation response in NW Iberia to orbital-scale climatic variability is represented by three forest stages of different extent, indicating a short-lived climatic optimum on land coeval with sea surface temperatures (SST) maximum in the mid-latitudes of the eastern North Atlantic ocean during the MIS 9e ice volume minimum, and a second forested interval of moderate warming
Summary
An increasing number of studies on previous climatic cycles shows that millennial-scale variability is an inherent pattern of the Late Pleistocene climate affecting glacial periods (Bond et al, 1993; Bond and Lotti, 1995; Dansgaard et al, 1993; Grootes et al, 1993; Grimm et al, 2006; Allen et al, 1999; Sanchez Goni et al, 2000) and intervals of reduced ice volume such as the current or the last interglacial (Bond et al, 1997; Delmotte et al, 2004, EPICA community members, 2004; Martrat et al, 2004, 2007; McManus et al, 1999; Oppo and Lehman, 1995; Oppo et al, 1998, 2001, 2007). Few studies have focused on the climatic variability of the interval between 340 000 and 270 000 years ago, encompassing the Marine Isotope Stage (MIS) 9 interglacial complex. The Antarctica ice cores record during the MIS 9 peak interglacial the highest greenhouse gas concentrations of the past 650 000 years, excluding the Holocene industrial period (Petit et al, 1999; Siegenthaler et al, 2005; Spahni et al, 2005). From the Southern Iberian margin core MD01-2443, revealed a suborbital vegetation change during the MIS 9e ice volume minimum bringing to an end the interglacial forest stage (Tzedakis et al, 2004b; Roucoux et al, 2006).
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