Alkenone and boron-based Pliocene pCO2 records

Seki, Osamu; Foster, Gavin L.; Schmidt, Daniela N.; Mackensen, Andreas; Kawamura, Kimitaka; Pancost, Richard D.

doi:10.1016/j.epsl.2010.01.037

Cited by 499 publications

(631 citation statements)

References 64 publications

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“…The enhanced global ocean biological pump may have increased the quantity of carbon dioxide (CO 2 ) sequestered in the abyssal basins and thus overprinted the apparently absent ventilation signature in the Atlantic δ 13 C data. This is fully consistent with the relatively rapid decline in atmospheric CO 2 that was observed during the severe deterioration of global climate over the intensification of the NHG (Seki et al, 2010). Most markedly, after interglacial MIS 71/59 (1.89-1.68 Ma) a pronounced shift of 2 to 3 ε Nd units towards less radiogenic values occurred resulting in values of −11.5 at site 980/981 and −13 at site 610 near glacial-interglacial MIS 45/44 (∼ 1.4 Ma).…”

Section: Resultssupporting

confidence: 71%

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: Resultssupporting

confidence: 71%

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

Khélifi

2014

Clim. Past

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“…Compound specific δ 13 C values for the long-chain even numbered n-alkan-1-ols were then corrected for the derivatization process following Rieley (1994). Compound specific δ 13 C values were not corrected for variations in δ 13 C of atmospheric CO 2 over time, because these were assumed to be small for the time scale used in this study (e.g., Seki et al, 2010). δ 13 C values are reported relative to the Vienna Pee Dee Belemnite (VPDB)-scale, calculated by comparison against a calibrated reference CO 2 gas.…”

Section: Analytical Techniquesmentioning

confidence: 99%

Strengthening of North American dust sources during the late Pliocene (2.7 Ma)

Naafs

Hefter

Acton

et al. 2012

Earth and Planetary Science Letters

129

156

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a b s t r a c t a r t i c l e i n f oHere we present orbitally-resolved records of terrestrial higher plant leaf wax input to the North Atlantic over the last 3.5 Ma, based on the accumulation of long-chain n-alkanes and n-alkanl-1-ols at IODP Site U1313. These lipids are a major component of dust, even in remote ocean areas, and have a predominantly aeolian origin in distal marine sediments. Our results demonstrate that around 2.7 million years ago (Ma), coinciding with the intensification of the Northern Hemisphere glaciation (NHG), the aeolian input of terrestrial material to the North Atlantic increased drastically. Since then, during every glacial the aeolian input of higher plant material was up to 30 times higher than during interglacials. The close correspondence between aeolian input to the North Atlantic and other dust records indicates a globally uniform response of dust sources to Quaternary climate variability, although the amplitude of variation differs among areas. We argue that the increased aeolian input at Site U1313 during glacials is predominantly related to the episodic appearance of continental ice sheets in North America and the associated strengthening of glaciogenic dust sources. Evolutional spectral analyses of the n-alkane records were therefore used to determine the dominant astronomical forcing in North American ice sheet advances. These results demonstrate that during the early Pleistocene North American ice sheet dynamics responded predominantly to variations in obliquity (41 ka), which argues against previous suggestions of precession-related variations in Northern Hemisphere ice sheets during the early Pleistocene.

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“…Pagani et al, 2010;Seki et al, 2010). Past CO 2 -concentrations close to or even higher than modern values along with a near-modern palaeogeography, ocean bathymetry and palaeobiology, suggest that the warm Pliocene climates may provide plausible comparative scenarios for interpreting the path of future climate warming during the 21 st century (e.g.…”

Section: Introductionmentioning

confidence: 99%

Climate and environment of a Pliocene warm world

Salzmann

Williams

Haywood

et al. 2011

Palaeogeography, Palaeoclimatology, Palaeoecology

161

105

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The Pliocene Epoch, 5.33 -2.58 million years ago (Ma), was a generally warmer and wetter interval with atmospheric CO 2 -concentrations at or slightly above modern levels. This paper provides an overview of Pliocene vegetation, sea surface temperatures and climate modelling outcomes.. Most prominent changes in Pliocene biome distribution compared to today include a northwards shift of temperate and boreal vegetation zones in response to a warmer and wetter climate as well as an expansion of tropical savannas and forests at the expense of deserts. Modelling experiments using the Hadley Centre climate model identified significantly higher Pliocene sea surface temperatures at the high-latitudes with only minor warming predicted in the tropics. Global mean annual surface temperatures (MAT) are estimated to have been 2 to 3ºC higher during the Piacenzian (3.6-2.58 Ma) than today with a reduced equator to pole gradient. The marine realm during the Pliocene was characterised by a reconfiguration of ocean gateways, particularly the narrowing of the Indonesian Seaway and closure of the Central American Isthmus, which produced essentially a modern pattern of ocean circulation. In the Southern Ocean a warm early Pliocene gave way to late Piacenzian cooling. Proxy data indicate a reduced east to west sea surface temperature gradient in the tropical Pacific during the Pliocene warmth. The Pliocene is one of the most intensively studied geological intervals of the pre-Quaternary. No other warm period in the geological past yields such a unique combination of near modern atmospheric CO 2 -concentrations, palaeogeography and palaeobiology. However, this paper also identifies data gaps and shortcomings in the reconstruction of Pliocene environments using proxy data and climate models on which future research should focus.

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Alkenone and boron-based Pliocene pCO2 records

Cited by 499 publications

References 64 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

Strengthening of North American dust sources during the late Pliocene (2.7 Ma)

Climate and environment of a Pliocene warm world

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