Holocene seasonal temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) records from different regions in China

The Holocene, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 28, 2024

The patterns of Holocene temperature change can provide important insight for understanding the recent global warming and assessing future climate change. However, mismatch in mean annual between proxy records models remains controversial, which is likely caused by potential seasonal bias from geological records. Here, 64 surface sediment samples are analyzed to examine brGDGTs reconstruction. Subsequently, we compile 23 brGDGT-based different regions China compare them with TraCE-21 ka simulation results same geographical location. linearly analysis shows a higher correlation MBT′ 5me MAF (mean months above freezing) than that MAT air temperatures), suggesting reconstructed based on aquatic sources may be biased toward MAF. regionally stacked indicate Qinghai-Tibet Plateau Northern warmed ~12 7 BP then cooled thereafter, while an overall trend occurred Southern China. These well reproduced model simulations. summer autumn during primarily driven local insolation modulated ice sheets greenhouse gas concentrations. retreat early middle Holocene, coupled increase gases, considered main driving factor long-term southern China, whereas orbital-induced might major Plateau. Our suggest basically matched Holocene.

Language: Английский

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Discrepancies in lacustrine bacterial lipid temperature reconstructions explained by microbial ecology

Communications Earth & Environment, Journal Year: 2024, Volume and Issue: 5(1)

Published: Dec. 5, 2024

Abstract Bacterial lipid branched glycerol dialkyl tetraethers (brGDGTs) are a valuable tool for reconstructing past temperatures. However, gap remains regarding the influence of bacterial communities on brGDGT profiles. Here, we identified two distinct patterns brGDGTs from surface sediments 38 Tibetan Plateau lakes using an unsupervised clustering technique. Further investigation revealed that salinity and pH significantly change community composition, affecting profiles causing brGDGT-based temperatures to be overestimated by up 2.7 ± 0.7 °C in haloalkaline environments. We subsequently used trained model examine assemblages global lacustrine dataset, confirming applicability our approach. finally applied approach Holocene records Plateau, showing shifts clusters amplified temperature variations over timescales. Our findings demonstrate microbial ecology can robustly diagnose constrain site-specific discrepancies reconstruction.

Language: Английский

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Branched GDGT source shift identification allows improved reconstruction of an 8,000-year warming trend on Sumatra

Organic Geochemistry, Journal Year: 2023, Volume and Issue: 186, P. 104702 - 104702

Published: Nov. 3, 2023

Branched Glycerol Dialkyl Tetraethers (brGDGTs) in sedimentary archives are increasingly used for paleotemperature reconstructions due to their strong correlation with mean annual air temperature. However, environmental factors can influence the brGDGT producing bacterial community, potentially affecting brGDGT-temperature relationship and introducing fundamental errors reconstructions. Here we assess reliability of methylation index brGDGTs (MBT′5ME) sediments as a proxy by tracking provenance differences based on fractional abundances short lake core, two peat cores surface soils Sumatra (n=333 total). Then, attempt reconstruct Holocene paleotemperatures using cores. Our results indicated distinct H-shaped (H-GDGT) compositions soil, environments, suggesting production different communities. We introduce new index, isomerization H-GDGTs (IRH) that distinguish between these environments. In an 11,000-year long core from Diatas, find composition changes dominated community shifts rather than temperature changes. contrast, nearby Padang peatland be robustly brGDGT-based reconstruction since there no signs past or source shifts. The indicate gradual warming trend over 8,000 years, consistent climate model simulations. current MBT′5ME calibrations yielded larger trends compared simulations other studies, need tropical and/or peat-specific calibrations. findings demonstrate importance assessing when employing paleothermometry. methodological framework outlined this study future research reliable down-core years offers novel insights into evolution region low seasonality.

Language: Английский

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Reconstructing 15 000 years of southern France temperatures from coupled pollen and molecular (branched glycerol dialkyl glycerol tetraether) markers (Canroute, Massif Central)

Climate of the past, Journal Year: 2023, Volume and Issue: 19(11), P. 2127 - 2156

Published: Nov. 1, 2023

Abstract. Climatic changes in southern Europe during the Holocene are characterized by a strong spatial and temporal heterogeneity whose patterns still poorly understood, notably presence or not of thermal maximum (HTM; 10 000–6000 cal BP). The climatic also differ according to proxies used (e.g. pollen, chironomid) latitude record. Here, multi-proxy approach combining pollen lipid biomarkers (branched glycerol dialkyl tetraethers, brGDGTs) is applied Canroute sedimentological sequence (Massif Central, France) reconstruct variation over last 15 000 years Europe. This area documented terms vegetation climate change. To provide reliable reconstructions, we have (1) performed multi-method (modern analogue technique, MAT; weighted averaging partial least squares regression, WA-PLS; boosted regression trees, BRT; random forest, RF) molecular brGDGTs (five calibrations) (2) investigated role modern databases calibrations reconstructions. Three different were tested for data: one global database based on Eurasian two regional corresponding Mediterranean–Temperate Temperate Europe–Scandinavian respectively. Five including four soil peat. Results show that use highlights importance considering environmental ecological constraints when using transfer functions sequences. Pollen- brGDGT-inferred trends consistent, Late Glacial Early Holocene. However, reconstructions concerning with MAT pollen-based method, but no difference apparent BRT method nor brGDGT. temperature estimated from independent then compared signals (chironomids, biomarkers) better understand Altogether, our results those already available reveal Holocene, consistent between sites proxies, supporting reliability their despite some discrepancies. During signal does indicate clear pronounced HTM, rather stable temperatures.

Language: Английский

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An adaptive strategy for current afforestation in the forest-steppe ecotone, north China, inferred from the Holocene geo-ecology dynamics

CATENA, Journal Year: 2024, Volume and Issue: 247, P. 108533 - 108533

Published: Nov. 16, 2024

Language: Английский

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