Nina DavtianNov 6

RE: https://mastodon.world/@nina_davtian/114502798389880294

Let's give a try to the new #QuotePost functionality, so that I can remind the names of the lead authors of my new co-authored #review paper published in the @EuroGeosciences #journal #Biogeosciences, as well as which team and research center I represent in this #synthesis!
https://doi.org/10.5194/bg-22-6465-2025
#Science
#ScienceMastodon
#AcademicMastodon
#Consensus #Scientific #Publication
#isoGDGTs #brGDGTs #TeamArchaea #TeamBacteria
#archaeal #bacterial #tetraether #lipids
#Paleotemperature #Biogeoscience

Nina DavtianNov 6
My first co-authored #review #article « #Reviews and #syntheses: Best practices for the application of #marine #GDGTs as proxy for #paleotemperatures: #sampling, #processing, #analyses, #interpretation, and #archiving protocols » is now published in the @EuroGeosciences journal #Biogeosciences!
https://doi.org/10.5194/bg-22-6465-2025
#Science
#ScienceMastodon
#AcademicMastodon
#Consensus #Synthesis #Analysis
#isoGDGTs #brGDGTs #TeamArchaea #TeamBacteria
#archaeal #bacterial #tetraether #lipids
#Paleotemperature
Nina DavtianMar 8, 2025
On this #InternationalWomensDay, let me highlight two #WomenInSTEM.
First, Amy Cromartie, who leads the following @EuroGeosciences #preprint:
https://egusphere.copernicus.org/preprints/2025/egusphere-2025-526/
Second, Devika Varma, who recently defended her #PhD #thesis. Her PhD work at @NIOZnieuws aimed to investigate #paleotemperature indicators based on #archaeal hydroxylated #tetraether #lipids (OH-isoGDGTs):
https://www.nioz.nl/en/news/investigating-paleotemperature-proxies-based-on-archaeal-hydroxylated-tetraether-lipids
#IWD #IWD25 #IWD2025
#Science #ScienceMastodon #AcademicMastodon
#GDGTs #brGDGTs #isoGDGTs
(1/3)
Utilizing Probability Estimates from Machine Learning and Pollen to Understand the Depositional Influences on Branched GDGT in Wetlands, Peatlands, and Lakes

Abstract. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) serve as critical molecular biomarkers for the quantitative reconstruction of past environments, ambient temperature and pH across various archives. Despite their success, numerous issues persist that limit their application. The distribution of brGDGTs varies significantly based on provenance, resulting in biases in environmental reconstructions that rely on fractional abundances and derived indices, such as the MBT’5ME. This issue is especially significant in shallow lakes, wetlands, and peatlands within semi-arid and arid regions, where ecosystems are sensitive to diverse environmental and climatic factors. Recent advancements, such as machine learning techniques, have been developed to identify changes in sources; however, these techniques are insufficient for detecting mixed source environments. The probability estimates derived from five machine learning algorithms are employed here to detect provenance changes in brGDGT downcore records and to identify periods of mixed provenance. A new global modern database (n=2301) was compiled to train, validate, test, and apply these algorithms to two sedimentary records. Our findings are corroborated by pollen and non-pollen palynomorphs obtained from the identical records. These microfossil proxies are utilized to discuss changes in provenance, hydrology, and ecology that influence the distribution of brGDGTs. Probability estimates derived from Random Forest with a sigmoid calibration are most effective in detecting changes in brGDGT distribution. Minor changes in the relative contributions of brGDGTs provenance can significantly influence the distribution of brGDGTs, especially regarding the MBT'5ME index. This study introduces a novel brGDGT wetland index aimed at monitoring potential biases arising from wetland development.

Nina DavtianFeb 11, 2025

On this #InternationalDayOfWomenAndGirlsInScience, here is a great story presented in two papers led by a #WomanInScience (Jingjing Guo) and last authored by another #WomanInScience (Francien Peterse).

#Scientific #publication #1: https://doi.org/10.5194/cp-21-343-2025
Scientific publication #2: https://doi.org/10.1016/j.orggeochem.2025.104947

#Science
#ScienceMastodon
#AcademicMastodon
#PaleoClimate
#PaleoHydrology
#EastAsianMonsoon
#PaleoTemperature
#OrganicGeochemistry
#GDGTs #brGDGTs
#ClimateProxies #Loess
#IDWGS #IDWGS2025

Towards quantitative reconstruction of past monsoon precipitation based on tetraether membrane lipids in Chinese loess

Abstract. Variations in the oxygen isotope composition (δ18O) of cave speleothems and numerous proxy records from loess–paleosol sequences have revealed past variations in East Asian monsoon (EAM) intensity. However, challenges persist in reconstructing precipitation changes quantitatively. Here, we use the positive relationship between the degree of cyclization (DC) of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in modern surface soils from the Chinese Loess Plateau (CLP) and mean annual precipitation (MAP) to quantify past monsoon precipitation changes on the CLP. We present a new ∼ 130 000-year-long DC-based MAP record for the Yuanbao section on the western edge of the CLP, which closely tracks the orbital- and millennial-scale variations in available records of both speleothem δ18O and the hydrogen isotope composition of plant waxes (δ2Hwax) from the same section. Combing our new data with existing brGDGT records from other CLP sites reveals a spatial gradient in MAP that is most pronounced during glacials, when the western CLP experiences more arid conditions and receives up to ∼ 250 mm less precipitation than in the southeast, whereas MAP is ∼ 850 mm across the CLP during the Holocene optimum. Furthermore, the DC records show that precipitation amount on the CLP varies at both the precession scale and the obliquity scale, as opposed to the primarily precession-scale variations in speleothem δ18O and δ2Hwax at Yuanbao and the 100 kyr cycle in other loess proxies, such as magnetic susceptibility, which rather indicates the relative intensity of the EAM. At the precession scale, the DC record is in phase with δ2Hwax from the same section and the speleothem δ18O record, which supports the hypothesis that monsoon precipitation is driven by Northern Hemisphere summer insolation.

Nina DavtianNov 7, 2024
My co-authored #scientific #publication by De Jonge et al. (2024) G³ just got cited in this new #paper with a multi-#biomarker paleo-sequence:
https://doi.org/10.1016/j.gloplacha.2024.104620
Also featuring a novel (OH-)isoGDGT-based #paleotemperature #ClimateProxy!
Disclaimer: I am not a co-author and I was not a reviewer either.
#Science
#ScienceMastodon #AcademicMastodon
#PaleoClimate #SeaTemperature #SeaSurfaceTemperature #SST
#Biomarkers #Alkenones #Diols #LongChainDiols #GDGTs #isoGDGTs
https://mastodon.world/@nina_davtian/113364845688520878
Multi-proxy reconstructions of paleotemperature in the southern South China Sea since the last deglaciation

The accuracy of paleothermometers is a prerequisite for understanding the past sea surface temperature (SST) changes in the tropical seas. Here, we an…

Nina DavtianOct 25, 2024
I am honored to co-author the new #scientific #publication first-authored by Petter Hällberg! This time, it is the use of #levoglucosan rather than #GDGTs—as #paleohydrology rather than #paleotemperature #ClimateProxies this time!—which granted me this #collaboration and co-authorship!
https://doi.org/10.1016/j.quascirev.2024.108948
More information in the following thread: 👇🏻 (1/6)
#Science
#ScienceMastodon #AcademicMastodon
#Paper #OpenAccess #OpenAccessWeek #OpenAccessWeek24 #OpenAccessWeek2024
#isoGDGTs #brGDGTs
Disentangling seasonal and annual precipitation signals in the tropics over the Holocene: Insights from δD, alkanes and GDGTs

Rainfall seasonality in the tropics has a substantial impact on both ecosystems and human livelihoods. Yet, reconstructions of past rainfall variabili…

Dr. Or M. BialikAug 15, 2024
A lot of times, when I discuss #marine #paleotemperature or #ocean #FutureTemperatures, I use the #Mediterranean as a reference for what those temperatures mean for things like plankton, deep water generation, or mineral preference.
Every year, that reference is getting warmer, and now it hit a new record.
Nina DavtianNov 11, 2023

Unlike #TEX86, another #GDGT-based #paleotemperature #ClimateProxy named the #Ring #Index of hydroxylated tetraethers (RI-OH) behaves as an #SST proxy despite the terrigenous #inputs.
This #place too deserves a #thread about my related #PhD #research #publication in #Paleoceanography and #Paleoclimatology:
https://doi.org/10.1029/2018PA003452 (1/5)

#Science #ScienceMastodon #Paper
#PaleoClimate #PaleoClimates
#ClimateChange #ClimateChanges #AbruptClimateChange
#SeaSurfaceTemperature
#MediterraneanSea

@gdgt

Nina DavtianOct 31, 2023

Two #basic #things to #know for #GDGT #lovers like me:
- These #nerdy #membrane-spanning #lipids are #ubiquitous in the #environment
- #GDGTs may have #multiple and #mixed #sources

If like a younger me* you apply #TEX86 in (#paleo)prodelta #deposits, be prepared to obtain #spooky #results from this #GDGT-based #paleotemperature #ClimateProxy!
#Links to the related #research #publication and #source #data in my auto-reply 👇🏻

*Me when I was a #PhDStudent

#HappyHalloween2024

@gdgt

💧🌏 Greg CocksJul 24, 2023
Past And Future Warming – Direct Comparison On Multi-Century Timescales
--
https://doi.org/10.5194/cp-18-911-2022 <-- shared paper / technical note
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#GIS #spatial #mapping #anthropogenic #climatechange #humanimpact #global #temperature #millenia #centuries #model #modeling #spatialanalysis #IPCC #globalmeantemperatures #paleotemperature #reconstruction #warming #impacts #multicentury #greenhousegasemissions #emissions #holocene #spatiotemporal #variability
Technical Note: Past and future warming – direct comparison on multi-century timescales

Abstract. In 2013, the Intergovernmental Panel on Climate Change concluded that Northern Hemisphere temperatures had reached levels unprecedented in at least 1400 years. The 2021 report now sees global mean temperatures rising to levels unprecedented in over 100 000 years. This Technical Note briefly explains the reasons behind this major change. Namely, the new assessment reflects additional global warming that occurred between the two reports and improved paleotemperature reconstructions that extend further back in time. In addition to past and recent warming, the conclusion also considers multi-century future warming, which thereby enables a direct comparison with paleotemperature reconstructions on multi-century time scales.