Reviewer comments: A Late Quaternary climate record based on long chain diol proxies from the Chilean margin"

Abstract. In this study we have applied different indices based on long-chain diols, i.e., the long-chain diol index (LDI) as a proxy for past SST, the diol index as an indicator of past upwelling conditions, and the nutrient diol index (NDI) as a proxy for nitrate and phosphate concentrations in seawater. The proxies were analyzed in marine sediments recovered at ODP Site 1234, located within the Peru–Chile upwelling system, with a ∼2 kyr resolution covering the last 150 kyr. We also generated TEX86H and U37K′ temperature and planktonic δ18O records, as well as total organic carbon (TOC) and accumulation rates (ARs) of TOC and lipid biomarkers (i.e., C37 alkenones, GDGTs, dinosterol, and loliolide) to reconstruct past phytoplankton production. The LDI-derived SST record covaries with TEX86H- and U37K′-derived SST records as well as with the planktonic δ18O record, implying that the LDI reflects past SST variations at this site. TOC and phytoplankton AR records indicate increased export production during the last interglacial (MIS 5), simultaneous with a peak in the abundance of preserved Chaetoceros diatoms, suggesting intensified upwelling during this period. The diol index is relatively low during the upwelling period, but peaks before and after this period, suggesting that Proboscia diatoms were more abundant before and after the period of upwelling. The NDI reveals the same trends as the diol index, suggesting that the input of nitrate and phosphate was minimal during upwelling, which is unrealistic. We suggest that the diol index and NDI should perhaps be considered as indicators for Proboscia productivity instead of upwelling conditions or nutrient concentrations.

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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 Science Journal ◽

10.5194/egqsj-66-91-2017 ◽

2017 ◽

Vol 66 (2) ◽

pp. 91-100

Author(s):

Lorenz Wüthrich ◽

Marcel Bliedtner ◽

Imke Kathrin Schäfer ◽

Jana Zech ◽

Fatemeh Shajari ◽

...

Keyword(s):

Radiocarbon Dating ◽

Late Quaternary ◽

Marine Isotope Stage ◽

Environmental Reconstruction ◽

Moisture Source ◽

Leaf Wax ◽

Mis 3 ◽

Quaternary Climate ◽

Leaf Waxes ◽

Long Chain

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 δ2Hwax 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.

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A Late Quaternary climate record based on long chain diol proxies from the Chilean margin

10.5194/cp-2018-88 ◽

2018 ◽

Cited By ~ 1

Author(s):

Marijke W. de Bar ◽

Dave J. Stolwijk ◽

Jerry F. McManus ◽

Jaap S. Sinninghe Damste ◽

Stefan Schouten

Keyword(s):

Late Quaternary ◽

Phytoplankton Production ◽

Last Interglacial ◽

Quaternary Climate ◽

Before And After ◽

Primary Focus ◽

Multiple Species ◽

Species Productivity ◽

Mis 5 ◽

Long Chain

Abstract. The primary focus of this study is to test the applicability of different paleoenvironmental proxies based on long chain diols, i.e., the LDI as proxy for past SST, the Diol Index as indicator of past upwelling conditions and the NDI as quantitative proxy for nitrate and phosphate concentrations in seawater. The proxies were analyzed in marine sediments recovered at ODP Site 1234, located within the Peru-Chile upwelling system, with a ~ 2 kyr resolution, covering the last 150 kyrs, i.e., encompassing several glacial and interglacial periods. We also generated TEXH86 and UK´37 temperature and planktonic δ18O records, as well as TOC and accumulation rates (ARs) of TOC and lipid biomarkers (i.e., C37 alkenones, GDGTs, dinosterol and loliolide) to reconstruct past phytoplankton production. The LDI-derived SST record co-varies with TEXH86- and UK´37-derived SST records as well as with the planktonic δ18O record, implying that the LDI reflects past SST variations at this site. TOC and phytoplankton AR records indicate increased export production during the Last Interglacial (MIS 5), simultaneous with a peak in the abundance of preserved Chaetoceros diatoms, suggesting intensified upwelling during this period. The Diol Index is relatively low during the upwelling period, but peaks before and after this period, suggesting that Proboscia diatoms were more dominant before and after the period of upwelling. The NDI reveals the same variations as the Diol Index suggesting that the input of nitrate and phosphate was minimal during upwelling, which is unrealistic. We suggest that the Diol Index should perhaps be considered as an indicator for Proboscia (multiple species) productivity instead of upwelling per se, whereas the NDI likely reflects Proboscia alata productivity, and might therefore not be suitable as a more general paleonutrient proxy.

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A Late Quaternary Climate Record Based on Multi-Proxies Analysis from the Jiaochang Loess Section in the Eastern Tibetan Plateau, China

Acta Geologica Sinica - English Edition ◽

10.1111/j.1755-6724.2007.tb01030.x ◽

2007 ◽

Vol 81 (6) ◽

pp. 1087-1096 ◽

Cited By ~ 5

Author(s):

BAI Song ◽

TANG Ya ◽

WANG Chengshan ◽

HUANG Chengmin

Keyword(s):

Tibetan Plateau ◽

Late Quaternary ◽

Eastern Tibetan Plateau ◽

Climate Record ◽

Quaternary Climate

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Climate-Volcanism Feedback and the Toba Eruption of ∼74,000 Years Ago

Quaternary Research ◽

10.1006/qres.1993.1081 ◽

1993 ◽

Vol 40 (3) ◽

pp. 269-280 ◽

Cited By ~ 106

Author(s):

Michael R. Rampino ◽

Stephen Self

Keyword(s):

Late Quaternary ◽

Sea Ice Extent ◽

Volcanic Event ◽

Climate Record ◽

Quaternary Climate ◽

Northern Latitudes ◽

Global Cooling ◽

Hemisphere Surface ◽

Global Sea Level ◽

Stratospheric Dust

AbstractA general feedback between volcanism and climate at times of transition in the Quaternary climate record is suggested, exemplified by events accompanying the Toba eruption (∼74,000 yr ago), the largest known late Quaternary explosive volcanic eruption. The Toba paroxysm occurred during the δ18O stage 5a-4 transition, a period of rapid ice growth and falling global sea level, which may have been a factor in creating stresses that triggered the volcanic event. Toba is estimated to have produced between 1015 and 1016 g of fine ash and sulfur gases lofted in co-ignimbrite ash clouds to heights of at least 32 ± 5 km, which may have led to dense stratospheric dust and sulfuric acid aerosol clouds. These conditions could have created a brief, dramatic cooling or "volcanic winter," followed by estimated annual Northern Hemisphere surface-temperature decreases of ∼3° to 5°C caused by the longer-lived aerosols. Summer temperature decreases of ⩾10°C at high northern latitudes, adjacent to regions already covered by snow and ice, might have increased snow cover and sea-ice extent, accelerating the global cooling already in progress. Evidence for such climate-volcanic feedback, following Milankovitch periodicities, is found at several climatic transitions.

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