Millennial-scale oceanic climate variability off the Western Iberian margin during the last two glacial periods

Abreu, Lucia de; Shackleton, Nicholas J; Schönfeld, Joachim; Hall, Michael A; Chapman, Mark R

doi:10.1016/s0025-3227(03)00046-x

Cited by 271 publications

(278 citation statements)

References 74 publications

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“…The configuration of long-term variations in δ 18 O calcite is similar to that recorded in Greenland ice cores (NGRIP Members 2004), by planktic foraminifera from the western Portuguese margin (de Abreu et al 2003), the Alborán Sea (Cacho et al 1999), the Ionian Sea (Allen et al 1999) and by speleothems from Israel (Bar-Matthews et al 1999) (Fig. 7).…”

Section: Oxygen Isotope Composition Of Calcite From Lake Banyolessupporting

confidence: 69%

“…24 In Lake Banyoles, millennial-scale δ 18 O calcite and δ 13 C calcite shifts through MIS 3 (Fig. 3) may be analogous to enhanced variability observed across the North Atlantic and western Mediterranean (Fig. 7;Cacho et al 1999;de Abreu et al 2003). Although the chronology could be better constrained, a response to abrupt HE has been suggested from previous reconstructions from the lake (Valero-Garcés et al 1998;Höbig et al 2012) and in the surrounding region (González-Sampériz et al 2006).…”

Section: Isotope Covariance and Facies Variabilitymentioning

confidence: 71%

“…One of the most distinct δ 18 O calcite excursions in Lake Banyoles is through the Late Glacial to Holocene transition, with a maximum change of -2‰ (-4.7‰ at 11.9 m, -6.7‰ at 8.5 m). A shift to lower δ 18 O calcite is a prominent feature that is common across most Mediterranean lakes during that time (Roberts et al 2008), and is comparable in magnitude to the changes in the composition of western Iberian margin and Alborán Sea planktic foraminifera (Cacho et al 1999;de Abreu et al 2003). The subsequent excursion to higher δ 18 O calcite at 9.3 m may correspond to the 8.2 ka event, which is constrained by a U/Th date at 10.8 m (9.7 ka), assuming a 5.8-m offset between the BAN II and La Draga cores.…”

Section: Isotope Covariance and Facies Variabilitymentioning

confidence: 81%

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Western Mediterranean climate and environment since Marine Isotope Stage 3: a 50,000-year record from Lake Banyoles, Spain

et al. 2015

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We present new stable isotope (δ 18 O calcite and δ 13 C calcite ) and diatom data from a 67-m sediment core (BAN II) from Lake Banyoles, northeastern Spain. We reassessed the chronology of the sequence by correlating stable isotope data with a shorter U-series-dated record from the lake, confirming a sedimentological offset between the two cores and demonstrating that BAN II spans Marine Isotope Stages (MIS) 3 to 1. Through comparison with previous records, the multi-proxy data are used to improve understanding of palaeolimnological dynamics and, by inference, western Mediterranean climate and environmental change during the past ca. 50,000 years. Three main zones, defined by isotope and diatom data, correspond to the MIS. The basal zone (MIS 3) is characterised by fluctuating δ 18 O calcite and benthic diatom abundance, indicating a high degree of environmental and climate variability, concomitant with large lake-level changes. During the full glacial (MIS 2), relatively constant δ 18 O calcite and a poorly preserved planktonicdominated diatom assemblage suggest stability, and intermittently, unusually high lake level.In MIS 1, δ 18 O calcite and δ 13 C calcite initially transition to lower values, recording a pattern of Late Glacial to Holocene change that is similar to other Mediterranean records. This study suggests that Lake Banyoles responds limnologically to changes in the North Atlantic oceanatmosphere system and provides an important dataset from the Iberian Peninsula, a region in need of longer-term records that can be used to correlate between marine and terrestrial archives, and between the western and eastern Mediterranean.4

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Section: Oxygen Isotope Composition Of Calcite From Lake Banyolessupporting

confidence: 69%

Section: Isotope Covariance and Facies Variabilitymentioning

confidence: 71%

Section: Isotope Covariance and Facies Variabilitymentioning

confidence: 81%

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Western Mediterranean climate and environment since Marine Isotope Stage 3: a 50,000-year record from Lake Banyoles, Spain

et al. 2015

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“…If the AMOC was to collapse it would have severe impacts on the climate in this region, causing reductions in surface air temperatures of up to 10°C in the North Atlantic according to modelling studies (Manabe and Stouffer, 1988;Vellinga and Wood, 2002;Jackson et al, 2015). Past evidence of temperature changes of these magnitudes has been observed in paleo-proxy records (Dansgaard et al, 1993;Blunier and Brook, 2001;de Abreu et al, 2003), and was originally linked to the possibility of a bi-stable AMOC by Broecker et al (1990). Projecting present day climate change into the future through the representative concentration pathways, models from the Coupled Model Inter-Comparison Project 5 (CMIP5) show evidence for a weakening of the AMOC circulation of 11-34% by 2100, while a complete collapse is deemed unlikely (Collins et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability

Mecking¹,

Drijfhout²,

Jackson³

et al. 2017

Tellus A: Dynamic Meteorology and Oceanography

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Evidence from paleo-proxy records suggests that the Atlantic Meridional Overturning Circulation (AMOC) can be in both an AMOC on state, the AMOC as we observe it today, and an AMOC off state, where the AMOC becomes extremely weak or even collapses. The freshwater transport due to the AMOC (M ov ) at 34°S in the Atlantic has often been used as an indicator for bi-stability, with a positive M ov suggesting a monostable AMOC and a negative M ov suggesting a bi-stable AMOC. Often studies have shown that the sign of the divergence of the M ov might be a good indicator of AMOC bi-stability. In this study we investigate how model bias affects the sign of M ov across all latitudes in the Atlantic basin, through a detailed analysis of the Coupled Model Inter-Comparison Project 5 (CMIP5) model ensemble. M ov , in the CMIP5 models is generally too positive in the southern Atlantic due to a salinity bias, while in the subtropical North Atlantic the values of M ov are influenced by a combination of velocity and salinity biases. We compare these results to observations, reanalysis products and Hadley Centre Global Environmental Model version 3 global configuration version 2, a current generation coupled model which exhibits a stable AMOC off state, and discuss the differences that can lead to the possibility of a bi-stable AMOC as opposed to a monostable AMOC.

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“…Luetscher et al (2015) presented a δ 18 O record from a northern Alpine speleothem, but it overlaps only slightly with ours and shows very little variation from 30 to 15 ka (∼ 1 ‰ δ 18 O, which is equivalent to ∼ 8 ‰ δ 2 H). The only long continuous isotope records spanning the last 40 to 60 kyr currently come from an LPS in Crvenka, Serbia (R. , which shows not much more than 10 ‰ variability, and from marine cores offshore Portugal (Abreu et al, 2003) and in the Mediterranean Sea (Frigola et al, 2008). The marine δ 18 O records (measured on foraminifera) show a minor trend towards more enriched values (corresponding to a δ 2 H trend < 10 ‰) from ∼ 60 to 20 ka.…”

Section: Paleoclimatologymentioning

confidence: 99%

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

Wüthrich

Bliedtner

Schäfer

et al. 2017

E&G Quaternary Sci. J.

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Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland, E&G Quaternary Sci. J., 66, 91-100, https://doi.org/10.5194/egqsj-66-91-2017, 2017. Abstract:We present the results of leaf wax analyses (long-chain n-alkanes) from the 6.8 m deep loess sequence of Möhlin, Switzerland, spanning the last ∼ 70 kyr. Leaf waxes are well preserved and occur in sufficient amounts only down to 0.4 m and below 1.8 m depth, so no paleoenvironmental reconstructions can be done for marine isotope stage (MIS) 2.Compound-specific δ 2 H wax analyses yielded similar values for late MIS 3 compared to the uppermost samples, indicating that various effects (e.g., more negative values due to lower temperatures, more positive values due to an enriched moisture source) cancel each other out. A pronounced ∼ 30 ‰ shift towards more negative values probably reflects more humid conditions before ∼ 32 ka. Radiocarbon dating of the n-alkanes corroborates the stratigraphic integrity of leaf waxes and their potential for dating loess-paleosol sequences (LPS) back to ∼ 30 ka. Kurzfassung:Wir präsentieren die Ergebnisse von Blattwachsanalysen (langkettige n-Alkane) aus einer 6.8 m mächtigen Löss-Sequenz bei Möhlin, Schweiz, welche bis etwa 70 ka zurückreicht. Nur bis 0.4 m Tiefe und unterhalb von 1.8 m sind die Blattwachse gut und in ausreichender Menge erhalten, so dass Aussagen bezüglich der Umweltbedingungen während der marinen Isotopenstufe (MIS) 2 nicht gemacht werden können. Die Muster der n-Alkane zeigen für alle Proben einen dominanten Input von Gras-Alkanen, jedoch ist es nur anhand der n-Alkane nicht möglich,

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Millennial-scale oceanic climate variability off the Western Iberian margin during the last two glacial periods

Cited by 271 publications

References 74 publications

Western Mediterranean climate and environment since Marine Isotope Stage 3: a 50,000-year record from Lake Banyoles, Spain

Western Mediterranean climate and environment since Marine Isotope Stage 3: a 50,000-year record from Lake Banyoles, Spain

The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

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