New evidence for changes in Plio–Pleistocene deep water circulation from Southern Ocean ODP Leg 177 Site 1090

Venz, Kathryn A; Hodell, David A

doi:10.1016/s0031-0182(01)00496-5

Cited by 147 publications

(195 citation statements)

References 61 publications

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“…This major reorganization in the North Atlantic overturning circulation across the mid-Pleistocene transition is also evident from the significant increase in the glacialinterglacial amplitude of benthic δ 13 C signatures in the North Atlantic (e.g., Venz and Hodell, 2002;Hodell and VenzCurtis, 2006;Lawrence et al, 2010) indicating a change to being dominantly ventilated by NADW during interglacial periods and enhanced advection of SOW during glacial periods. Apparently, the expansion of the West Antarctic ice sheet across the mid-Pleistocene transition promoted the production and export of AABW from the Southern Ocean (e.g., Naish et al, 2009;Lawrence et al, 2010).…”

Section: Resultsmentioning

confidence: 91%

A major change in North Atlantic deep water circulation 1.6 million years ago

Khélifi

2014

Clim. Past

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Abstract. The global ocean-climate system has been highly sensitive to the formation and advection of deep overflow water from the Nordic Seas as integral part of the Atlantic Meridional Overturning Circulation (AMOC) but its evolution over the Pliocene-Pleistocene global cooling is not fully understood. In particular, changes in the sources and mixing of prevailing deep waters that were involved in driving overturning throughout the Pliocene-Pleistocene climate transitions are not well constrained. Here we investigate the evolution of a substantial deep southward return overflow of the AMOC over the last 4 million years. We present new records of the bottom-water radiogenic neodymium isotope (ε Nd ) variability obtained from three sediment cores (DSDP site 610 and ODP sites 980/981 and 900) at water depths between 2170 and 5050 m in the northeast Atlantic. We find that prior to the onset of major Northern Hemisphere glaciation (NHG) ∼ 3 million years ago (Ma), ε Nd values primarily oscillated between −9 and −11 at all sites, consistent with enhanced vertical mixing and weak stratification of the water masses during the warmer-than-today Pliocene period. From 2.7 Ma to ∼ 2.0 Ma, the ε Nd signatures of the water masses gradually became more distinct, which documents a significant advection of Nordic Seas overflow deep water coincident with the intensification of NHG. Most markedly, however, at ∼ 1.6 Ma the interglacial ε Nd signatures at sites 610 (2420 m water depth (w.d.)) and 980/981 (2170 m w.d.) synchronously and permanently shifted by 2 to 3 ε Nd units to less radiogenic values, respectively. Since then the difference between glacial and interglacial ε Nd values has been similar to the Late Quaternary at each site. A decrease of ∼ 2 ε Nd units at 1.6 Ma was also recorded for the deepest water masses by site 900 (∼ 5 050 m w.d.), which thereafter, however, evolved to more radiogenic values again until the present. This major ε Nd change across the 1.6 Ma transition reflects a significant reorganization of the overturning circulation in the northeast Atlantic paving the way for the more stratified water column with distinct water masses prevailing thereafter.

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Section: Resultsmentioning

confidence: 91%

A major change in North Atlantic deep water circulation 1.6 million years ago

Khélifi

2014

Clim. Past

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“…Foram. 0180/AMS 14C Niebler (1995), Frank et al (1996) Diatom Biostratigraphy Frank et al (1996 Venz and Hodell (2002) record from the same location, which only covers the last 80 kyr, back to 250 ka. The Site 1090 record covers the last 1800 kyr and is spliced with the late Quaternary PS2489 record at 408 ka.…”

Section: Methodsmentioning

confidence: 99%

Terrigenous Sediment Supply in the Polar to Temperate South Atlantic: Land-Ocean Links of Environmental Changes during the Late Quaternary

Diekmann

Fütterer

Grobe

et al. 2003

The South Atlantic in the Late Quaternary

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Terrigenous sediment parameters in modem sea-bottom samples and sediment cores of the South Atlantic are used to infer variations in detrital sources and modes of terrigenous sediment supply in response to environmental changes through the late Quaternary climate cycles. Massaccumulation rates of terrigenous sediment and fluxes of ice-rafted detritus are discussed in terms of temporal variations in detrital sediment input from land to sea. Grain-size parameters ofterrigenous mud document the intensity of bottom-water circulation, whereas clay-mineral assemblages constrain the sources and marine transport routes of suspended fine-grained particulates, controlled by the modes of sediment input and patterns of ocean circulation. The results suggest low-frequency East Antarctic ice dynamics with dominant lOO-kyr cycles and high rates of Antarctic Bottom Water formation and iceberg discharge during interglacial times. In contrast, the more subpolar ice masses of the Antarctic Peninsula also respond to short-term climate variability with maximum iceberg discharges during glacial terminations related to the rapid disintegration of advanced ice masses. In the northern Scotia Sea, increased sediment supply from southern South America points to extended ice masses in Patagonia during glacial times. In the southeastern South Atlantic, changes in regional ocean circulation are linked to global thermohaline ocean circulation and are in phase with northern-hemispheric processes of ice build-up and associated formation of North Atlantic Deep Water, which decreased during glacial times and permitted a wider extension of southern-source water masses in the study area.

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“…We argue that the lower abundance of N. pachyderma sx in both the eastern and the western Mediterranean Sea after the MPT is paradoxical, since colder conditions and a much thicker ice accumulation in Greenland and Antarctica sheets are documented (Lisiecki and Raymo, 2005). Even the oceanographic process that leads to the entrance of N. pachyderma sx into the Gibraltar Strait during the cold spells of the Late Quaternary is not suitable as an analogue for the MPT, since the whole North Atlantic shows high δ 13 C values, with very low glacial/ interglacial variability that testifies to intense and persistent NADW formation (Raymo et al, 1990;Venz and Hodell, 2002;Kleiven et al, 2003;Clark et al, 2006). Further high-resolution studies would be needed to clarify the climatic/oceanographic forcing that controls the distribution and the dispersal of N. pachyderma sx in the Mediterranean basin during the middle-late Quaternary.…”

Section: The Distribution Of N Pachyderma Sxmentioning

confidence: 99%

“…Researchers have documented a series of phenomena associated to the MPT: an increase in ice sheet volume, sea surface temperature (SST) cooling in the oceans, variations in the Atlantic Meridional Overturning Circulation (AMOC), a significant drop in the CO 2 atmospheric levels, stronger African and Asian monsoon activity and increased dust deposition in the Southern Ocean (e.g. Ruddimann et al, 1989;Mix et al, 1995;Venz and Hodell, 2002;Hodell et al, 2003;Schefus et al, 2004;Lisiecki and Raymo, 2005;McClymont and Rosell-Melè, 2005;Clark et al, 2006;Sun et al, 2006;Martínez-Garcia et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Orbital variations in planktonic foraminifera assemblages from the Ionian Sea during the Middle Pleistocene Transition

Incarbona

Dinarès-Turell

Stefano

et al. 2013

Palaeogeography, Palaeoclimatology, Palaeoecology

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The Middle Pleistocene Transition (1.2-0.7 Ma) is the most recent re-organization of the global climate system which includes variations in the frequency and amplitude of glacial/interglacial cycles, increased ice sheet volume, sea surface temperature cooling and a significant drop in the CO 2 atmospheric levels. Here we present high-resolution planktonic foraminifera data (mean sampling resolution of about 780 years) from core LC10 recovered in the Ionian Sea (eastern Mediterranean), between 1.2 and 0.9 Ma. Selected taxa, among them G. ruber, T. quinqueloba and G. bulloides, show significant periodicities that can be associated to orbital cycles, mainly precession and obliquity. The planktonic foraminifera based paleoclimatic curve exhibits a cooling linear trend that can be associated to similar phenomena observed in the North Atlantic. On the other hand, we refer to the influence of the North African Monsoon the occurrence of two peaks of the low-salinity tolerant species G. quadrilobatus that fall in coincidence of sapropel layers. Finally, we discuss the distribution pattern of N. pachyderma sinistral coiling, with peaks up to about 20% between MIS 30 and 28, and compare it to middle-late Quaternary records of the Sicily Channel and western Mediterranean.

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New evidence for changes in Plio–Pleistocene deep water circulation from Southern Ocean ODP Leg 177 Site 1090

Cited by 147 publications

References 61 publications

A major change in North Atlantic deep water circulation 1.6 million years ago

A major change in North Atlantic deep water circulation 1.6 million years ago

Terrigenous Sediment Supply in the Polar to Temperate South Atlantic: Land-Ocean Links of Environmental Changes during the Late Quaternary

Orbital variations in planktonic foraminifera assemblages from the Ionian Sea during the Middle Pleistocene Transition

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