Tropical Andean climate variations since the last deglaciation

Proceedings of the National Academy of Sciences, Journal Year: 2024, Volume and Issue: 121(34)

Published: Aug. 12, 2024

Global warming during the Last Glacial Termination was interrupted by millennial-scale cool intervals such as Younger Dryas and Antarctic Cold Reversal (ACR). Although these events are well characterized at high latitudes, their impacts low latitudes less known. We present high-resolution temperature hydroclimate records from tropical Andes spanning past ~16,800 y using organic geochemical proxies applied to a sediment core Laguna Llaviucu, Ecuador. Our record aligns with western Amazon eastern central indicates dominant long-term influence of changing austral summer insolation on intensity South American Summer Monsoon. ~4 °C glacial termination, stable temperatures in early mid-Holocene, slight, gradual since ~6,000 ago. Importantly, we observe ~1.5 cold reversal coincident ACR. These data document change pattern deglaciation that resembles southern which thought be controlled radiative forcing atmospheric greenhouse gases changes ocean heat transport Atlantic meridional overturning circulation.

Language: Английский

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New calibration of terrestrial brGDGT paleothermometer deconvolves distinct temperature responses of two isomer sets

Earth and Planetary Science Letters, Journal Year: 2023, Volume and Issue: 626, P. 118497 - 118497

Published: Dec. 11, 2023

Bacterial branched glycerol dialkyl tetraethers (brGDGTs) are emerging as one of the most promising tools for quantifying past temperatures across a large variety continental settings. However, temperature-independent parameters such ratio 6-methyl vs. 5-methyl brGDGTs and bacterial community composition, might contribute to high uncertainty brGDGT paleothermometer. In this work, we investigated distributions in surface soils surrounding Lake Qinghai, reanalyzed previously published data. The results show that tetramethylated can be produced along with absence brGDGTs. additional production related brGDGTs, contradiction view only correlated potentially bias MBT′5ME Accordingly, were hypothetically separated into sets, temperature responses two sets separately quantified. Based on theoretical calculation, further developed new calibration model effectively mitigates mixing effect likely associated shift. As demonstrated downcore applications, is brGDGT-based growth reconstruction loess lake sediments, especially when relative abundance varies substantially.

Language: Английский

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Branched GDGT-based temperature calibrations from Central European lakes

The Science of The Total Environment, Journal Year: 2023, Volume and Issue: 906, P. 167724 - 167724

Published: Oct. 11, 2023

Language: Английский

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A critical assessment of lacustrine branched glycerol dialkyl glycerol tetraether (brGDGT) temperature calibration models

Geochimica et Cosmochimica Acta, Journal Year: 2023, Volume and Issue: 359, P. 100 - 118

Published: Aug. 25, 2023

Branched glycerol dialkyl tetraethers (brGDGTs) are membrane-spanning lipids produced by bacteria that ubiquitous in natural sedimentary archives and preserved over geologic timescales. The main influence on their distributions the environment appears to be temperature, thus making them a potentially powerful proxy for paleotemperature reconstruction. Application of recent lacustrine brGDGT-based temperature calibration models specific regions results inaccurate reconstructed temperatures suggesting regional or site-specific may necessary. Using an extended data set 692 lake sediment samples from across globe we determined whether brGDGT same sites significantly different one another via hierarchical agglomerative clustering analysis (HAC). Results HAC showed four significant clusters with varying geographic distributions. Cluster 1 mainly located at high latitudes Mean Annual Air Temperature (MAAT) (mean MAAT= 3.10 ± 5.91°C). 2 concentrated Tibetan Plateau MAAT = 1.54 5.91 °C). 3 span temperate-tropical 17.26 8.16 4 Central South America 24.56 4.01 led us develop random forest regression predict (MAAT Months Above Freezing, MAF, air temperature) based within each cluster (cluster-specific models). Model performance was highest (MAF: R2 0.78, RMSE 2.85 °C, n 261; MAAT: 0.76, 4.07 270), followed 0.54, 1.67 °C; 219; 0.62, 3.62 226) 0.58, 2.46, 67; 0.59, 2.52 67). model had lowest 0.42, 4.51, 38; 0.51, 1.74 129). We also developed classification assignment new (cluster prediction overall accuracy 95%), which informs user as cluster-specific model(s) apply samples. Finally, applied our approach (i.e., reconstruction) seven published (paleo)records illustrate pitfalls among reconstructions models. Overall, study defines broad relationships while underscoring limitations reconstruction subsequent interpretation.

Language: Английский

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BrGDGT-based quantitative reconstructions of paleotemperature in lakes: Regional vs. site-specific calibrations

Quaternary Science Reviews, Journal Year: 2023, Volume and Issue: 322, P. 108416 - 108416

Published: Nov. 11, 2023

Language: Английский

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Temperature changes during the last deglaciation and early Holocene in southwest China

Global and Planetary Change, Journal Year: 2023, Volume and Issue: 229, P. 104238 - 104238

Published: Sept. 6, 2023

Language: Английский

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Distribution of branched glycerol dialkyl glycerol tetraether (brGDGT) lipids from soils and sediments from the same watershed are distinct regionally (central Chile) but not globally

Frontiers in Earth Science, Journal Year: 2024, Volume and Issue: 12

Published: April 17, 2024

Quantitative reconstructions of past continental climates are vital for understanding contemporary and climate change. Branched glycerol dialkyl tetraethers (brGDGTs) unique bacterial lipids that have been proposed as universal paleothermometers due to their correlation with temperature in modern settings. Thus, brGDGTs may serve a crucial paleotemperature proxy variations improving regional projections, especially critical but under constrained regions. That said, complications can arise application varying source contributions (e.g., soils vs. peats lacustrine). As such, this study investigates brGDGT distributions Chilean lake surface sediments corresponding watershed determine the sediments. Global datasets were additionally compiled comparison. Distinct lakes indicate minimal bias from soil inputs lacustrine well situ production brGDGTs, which supports use reliable proxies region. The ΣIIIa/ΣIIa ratio, initially promising indicator marine settings, shows global complexities challenging establishment thresholds apportionment. we show ratio be successfully applied Direct comparisons further research discerning sources on scales moving forward. Overall, contributes valuable insights into variability, essential accurate paleoreconstructions.

Language: Английский

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Environmental controls on the distribution of brGDGTs and brGMGTs across the Seine River basin (NW France): implications for bacterial tetraethers as a proxy for riverine runoff

Biogeosciences, Journal Year: 2024, Volume and Issue: 21(9), P. 2227 - 2252

Published: May 7, 2024

Abstract. Branched glycerol dialkyl tetraethers (brGDGTs) are bacterial lipids that have been widely used as environmental proxies in continental paleorecords. Another group of related lipids, branched monoalkyl (brGMGTs), has recently proposed a potential paleotemperature proxy. Nevertheless, the sources and dependencies both brGDGTs brGMGTs along river–sea continuum still poorly understood, complicating their application paleoenvironmental some aquatic settings. In this study, factors controlling distributions explored across Seine River basin (NW France), which encompasses freshwater-to-seawater continuum. BrGDGTs were analyzed soils, suspended particulate matter (SPM), sediments (n=237) collected land–sea basin. Both types compounds (i.e., brGMGTs) shown to be produced situ, freshwater saltwater, based on high concentrations distinct settings (SPM sediments) vs. soils. Redundancy analysis further shows salinity nitrogen dominantly control brGDGT distributions. Furthermore, relative abundance 6-methyl 5-methyl (the IR6Me ratio), total (TN), δ15N, chlorophyll concentration co-vary specific geographical zone with low salinity, suggesting preferentially under low-salinity high-productivity conditions. contrast brGDGTs, brGMGT distribution appears primarily regulated by influence individual homologues. Salinity is positively correlated homologues H1020a H1020b negatively H1020c H1034b SPM. This suggests bacteria living produce H1034b, whereas grow saltwater appear predominantly responsible for production H1020b. Based ratio freshwater-derived (H1020c H1034b) saltwater-derived (H1020a H1020b), novel proxy, Riverine IndeX (RIX), trace riverine organic inputs, values (>0.5) indicating higher contribution. We successfully applied RIX Godavari (India) paleorecord upper Paleocene lower Eocene from Arctic Coring Expedition at Lomonosov Ridge, showing its applicability modern samples

Language: Английский

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Tracing Holocene temperatures and human impact in a Greenlandic Lake: Novel insights from hyperspectral imaging and lipid biomarkers

Quaternary Science Reviews, Journal Year: 2024, Volume and Issue: 339, P. 108851 - 108851

Published: July 25, 2024

Global warming particularly impacts terrestrial and aquatic ecosystems in the Arctic. To constrain sensitivity of Arctic lakes make meaningful predictions about future change under global warming, we need to examine their response previous warm phases. Lake sediments from Greenland's deglaciated area offer valuable archives investigate past climate variability associated lake changes. Here, applied hyperspectral imaging lipid biomarker thermometry a Holocene-length sediment record 578 Eastern Settlement Norse (61.08° N, 45.62° W; ∼155 m a.s.l) local temperature, productivity, anoxia histories. We calibrated branched glycerol dialkyl tetraethers (brGDGTs) with summer mean water temperatures (SMWT) using previously published site-specific calibration analyzed pigment fluxes based on imaging. Notably, reconstructions were corroborated two independent proxies (GDGT-0/Crenarchaeol bacterio pheophytins). investigated lake's environmental history identified periods significant by employing generalized additive models (GAMs). Our results reveal transitions driven both natural shifts anthropogenic impacts. During early Holocene, low SMWT productivity coupled high suggest strong seasonality prolonged inverted thermal stratification, possibly enhanced extended ice cover. The mid-Holocene showed higher along anoxia, indicating dimictic system. Holocene temperature rise lagged that Northern Hemisphere, but closely followed Atlantic-Fennoscandian stack. Thermal Maximum (7.5–4.5 cal ka BP) aligns other regional reconstructions. After 3 BP, observed Neoglacial cooling characterized increased reduced due stratification. At around 1.0 saw surge which attribute land use damming Norse. Despite post-Norse decline disappearance never reverted its pre-Norse state, modern sheep farming further intensifying recent decades. While resulted cold during period was anthropogenically induced. This research underscores value integrating biomarkers for detailed changes within lakes. It provides crucial insights anticipating ecologic climatic resilience ongoing influence.

Language: Английский

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Decoupled terrestrial temperature and hydroclimate during the Plio-Pleistocene in the East Asian monsoonal region

Quaternary Science Reviews, Journal Year: 2024, Volume and Issue: 344, P. 108955 - 108955

Published: Sept. 11, 2024

Language: Английский

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