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Foraminifera abundance and stable isotope records from ODP Site 984 (61.25°N, 24.04°W, 1648 m) in the North Atlantic are used to reconstruct surface circulation variations and the relative strength of the North Atlantic Deep Water (NADW) formation over the period spanning the peak warmth of Marine Interglacial Stage (MIS) 9e (~324-336 ka). This interval includes the preceding deglaciation, Termination 4 (T4), and the subsequent glacial inception of MIS 9d. The records indicate a greatly reduced contribution of NADW during T4, as observed in more recent deglaciations. In contrast with the most recent deglaciation, the lack of a significant NADW signal extended from T4 well into the peak interglacial MIS 9e and persisted nearly until the transition to the subsequent glacial stage MIS 9d. Although NADW formation resumed during MIS 9e, only depths greater than 2000 m appear to have been ventilated. The poorly ventilated intermediate depth of Site 984 (<2000 m) may have resulted on one hand from a general reduction of deep water ventilation by NADW during the study interval or, on the other hand, from different pathways of the spread of newly formed NADW that bypassed the study location. The intermediate depths may have also been invaded by southern-sourced waters as the formation of intermediate depth NADW weakened. The absence of any significant NADW signal at the water depth of Site 984 during the climatic optimum contrasts sharply with subsequent interglacial peaks (MIS 5e and the Holocene). Despite the perturbed intermediate depth circulation, oceanic heat transport northeastward was not interrupted and may have contributed to the relatively mild interglacial conditions of MIS 9e. [ABSTRACT FROM AUTHOR]

The last interglacial interval was terminated by the inception of a long, progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth. However, the feedbacks, internal dynamics, and global teleconnections associated with declining northern summer insolation remain incompletely understood. Here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre (SPG) circulation of the North Atlantic Ocean. Detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from Ocean Drilling Program site 984 south of Iceland reveal repeated, progressive cold water-mass expansions into subpolar latitudes during the last peak interglacial interval, marine isotope substage 5e. These movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydro-graphic boundary that may have been analogous to the modern Arctic front, and associated with rapid changes in the strength of the SPG. This persistent millennial-scale oceanographic oscillation accompanied a long-term cooling trend at a time of slowly declining northern summer insolation, providing an early link in the propagation of those insolation changes globally, and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent ∼100 ka. [ABSTRACT FROM AUTHOR]

Abstract: Over the last 20,000yr, Loch Sunart has accumulated an important record of Late Pleistocene and Holocene sedimentation characteristic of sea lochs on the western coast of Scotland. A seismic survey conducted using a Seistec Boomer system has demonstrated five distinct sediment-acoustic facies in the loch. These facies have been correlated with sediment sequences identified in a long Calypso core (12m) acquired from the RV Marion Dufresne. Grain-size and pollen analyses, accompanied with three 14C dates, have yielded information on the patterns of sedimentation since the Late Glacial Maximum. In addition, these data have identified three significant cooling events since the Younger Dryas: 8200, 5500 and 3500 cal.yrBP and the Little Ice Age. [Copyright &y& Elsevier]

The Bay of Quiberon (NW France), which is protected by the Quiberon Peninsula, provides well-preserved sedimentary archives for high-resolution reconstruction of Holocene climate variability. Very-high-resolution seismic profiles were obtained from two Seistec boomer seismic campaigns conducted in the bay. The seismic surveys reveal the deposition of five distinct sedimentary units. This succession is correlated with radiocarbon-dated sediments sampled in a long CASQ core (MD08-3204CQ). The analysis of the sediments shows significant changes in grain size, indicating a complex series of palaeo-climate events dated at 8800, 8600, 4270, 3860, 2470 and 1060 cal. yr BP. These may be correlated with millennial timescale climate variability corresponding to the phases of Holocene rapid climate changes (RCCs), associated with negative North Atlantic Oscillation (NAO) index and usually characterized by weaker winter storms. On the contrary, periods between RCCs are characterized by the predominance of westerly winds and stormy conditions for Brittany (i.e. positive NAO). However, only storm events occurring during the RCCs have been preserved in the Bay of Quiberon. This paper aims to reconstruct the Holocene sedimentary infill of the bay, highlighting the role of episodic acceleration phases of the sea-level rise on the preservation of sedimentary archives. Thus, the Bay of Quiberon provides substantially a complete sedimentation record of the last 10,000 years characterized by a series of complex palaeo-environmental changes. [ABSTRACT FROM AUTHOR]

Abstract In this study we use bulk sediment organic matter stable isotopes (δ13C org and δ15N) to examine the nature and timing of preserved organic matter in borehole PRGL1-4 from Northwestern Mediterranean Sea. This region is known as a transitional zone between the North Atlantic atmospheric circulation and the North African monsoon system. In the Gulf of Lion (SE France), increased inputs of organic matter from sediment-laden rivers occurred during warm substages of the last 200 kyr (MIS 5e, 5c, and 5a; MIS 6d, and 6b). Increased terrestrial organic matter are inferred from organic carbon isotopic composition (δ13C org), and are interpreted as resulting from enhanced rainfall over the Rhone river catchment area. Such increase in terrestrial organic carbon induced enhancement of the primary productivity leading to the formation of local oxygen minimum zone as demonstrated by ∼3‰ values in δ15N. Comparison with regional paleohydrological records from the northern Mediterranean borderlands reveals the regional character of these pluvial events. Taking advantage of the location of PRGL1-4 borehole, out of Mediterranean cyclogenesis area, we suggest that the pluvial events recorded during warm substages of the last 200 kyr occurred in response to enhanced passage of North Atlantic atmospheric perturbation over the Gulf of Lion catchment area (especially over Rhone river watershed which represent 80% of the GoL catchment area), a scenario possibly similar to that encountered today during negative- NAO like conditions. At a regional scale, our data suggests that high rainfall events over the Gulf of Lion catchement area and the Rhone watershed occurred at the time of North African summer monsoon and the sapropel deposition in the Mediterranean basin, thus highlighting a close coupling between mid- (North Atlantic) and low-latitudes (monsoon) climate systems. Importantly, our geochemical evidence from the Gulf of Lion support an extra-Mediterranean source for the regional pluvial events described in many paleoclimatic records from the northern Mediterrean borderlands during warm substages of the last climate cycles. Consequently, we suggest that this region as a whole could provide, in addition to the river runoff from the North African sector, the necessary conditions for the sapropel deposition. Highlights • We examine the nature/timing of preserved organic matter in PRGL1-4 from the Gulf of Lion, NW Med. • GoL experienced increase terrestrial OM during warm periods of the last 200 kyr (MIS 5 and MIS 6). • Increased terrestrial OM led to local OMZ are infered from OM stable isotopes (δ13C org and δ15N). • High runoff from Rhone river point for addition of extra-Mediterranean (Atlantic) into the GoL. • Extra-Mediterranean runoff from the N Med may act as a possible forcing for sapropel deposition. [ABSTRACT FROM AUTHOR]

This study proposes to combine seismic stratigraphic interpretation of very high-resolution sub-bottom chirp profiles acquired along the Santos Basin slope on the Southern Brazilian Margin during the SANBA project to recently published results from five continuous long cores acquired in the Santos Basin (sampling sediments as old as 772 ka with detailed biostratigraphic and chronostratigraphic data). The seismic-core correlation is consistent over the area and shows that 100,000 years cycles' terminations (G/IG transitions, identified on long sediment cores) do correlate to strong seismic reflectors identified regionally on chirp profiles. In particular, the last eight 100,000 years cycles (down to MIS19) are well-identified throughout the area. Additional higher-resolution sea-level drops or cooling events (e.g., MIS4, MIS7b, MIS9b) can sometimes be distinguished on the chirp profiles but only in areas with sufficiently high sedimentation rates (around 10 cm/ka). At MIS12, we observe a change in seismic architecture with more numerous, more closely spaced seismic reflectors but with smaller amplitudes. According to the available data, this change also corresponds to a change in sedimentation rates (smaller rates before MIS12), which may be related to the mid-Brunhes Transition (at 430 ka) and/or the imprint of 400 ka Milankovitch cycles. Two cores show a specific Nanno Foram Ooze at this transition towards the following Super-interglacial MIS11. This study demonstrates the ability and the reliability of very high-resolution chirp profiles to record continuously the stacking of G/IG climatic cycles on the slope of the Santos Basin despite relatively low subsidence rates on this old passive margin and small direct input from rivers. Therefore, the study points to the continuous feeding of the margin by sediment brought up laterally by currents, most probably mainly Brazilian Current (BC) that follows the shelfbreak down to the South. • Sub-bottom profiles from the slope of Santos Basin record Glacial/Interglacial transitions as prominent reflectors. • Reflectors correspond to change from silty clay and sand layers (during glacials) to Marl deposition during interglacial. • The last eight 100,000 years cycles (down to MIS19) are well identified on profiles and cores. • At MIS12, we observe a change in seismic architecture and sedimentation rates corresponding to the mid-Brunhes Event. [ABSTRACT FROM AUTHOR]