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#isotope

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Niels de Winter

Exploring macroevolutionary links in multi-species #planktonic #foraminifera Mg∕Ca and stable #oxygen #isotope from 15 Ma to recent @EGU_BioGeo bg.copernicus.org/articles/22/

bg.copernicus.orgExploring macroevolutionary links in multi-species planktonic foraminiferal Mg∕Ca and δ18O from 15 Ma to recentAbstract. The ratio of the trace element Mg over Ca (Mg/Ca) and the oxygen isotopic composition (δ18O) of foraminiferal calcite are widely employed for reconstructing past ocean temperatures, although geochemical signals are also influenced by several other factors that vary temporally and spatially. Here, we analyse a global dataset of Mg/Ca and δ18O data of 59 middle Miocene to recent species of planktonic foraminifera from a wide range of depth habitats, many of which have never been analysed before for Mg/Ca. We investigate the extent to which Mg/Ca and δ18O covary through time and space and identify several sources of mismatch between the two proxies. Once the data are adjusted for long-term non-thermal factors, Mg/Ca and δ18O are overall positively correlated in a way consistent with temperature being the dominant controller through both space and time and across many different species, including deep dwellers. However, we identify several species with systematic offsets in Mg/Ca values, to which multispecies calibrations should be applied with caution. We can track the appearance of such offsets through ancestor-descendent species over the last 15 Myr and propose that the emergence of these offsets may be the geochemical expression of evolutionary innovations. We find that virtually all of the Mg/Ca- and δ18O-derived temperatures from the commonly used genera Globigerinoides and Trilobatus are within uncertainty of each other, highlighting the utility of these species for paleoceanographic reconstructions. Our results highlight the potential of leveraging information from species lineages to improve sea surface temperature reconstruction from planktonic foraminifera over the Cenozoic.
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Crazy-to-Bike

@mpweiher@mastodon.social

Zur IEA:
"Sie gilt als traditionell atomfreundlich."
https://de.m.wikipedia.org/wiki/Internationale_Energieagentur

Ups. Eigentor.
Ich wollte unabhängige, nicht lobbyismusgesteuerte Quellen. Kannst du nicht liefern.

Und zur geologischen Stabilität ohne Wassereinbruch usw. für Jahrtausende:
Gorleben macht vor, wie gut das funktioniert.
Garantieren kann das eh keiner.

Insofern bei deinen "Quellen': Traue keiner Statistik, die du nicht selbst gefälscht hast.

Zum "an Uran lecken":
In der Zerfallsreihe entsteht mitnichten nur leicht abschirmbare #Alphastrahlung. Auch die #Spaltprodukte zerfallen auch mitunter mit Betazerfällen, also #Betastrahlung.
#Gammastrahlung tritt als Begleiterscheinung auf.

In den #Zerfallsreihen entstehen auch #Plutonium #Isotope

Also ganz ungefährlich das #Uran und seine Spalt- und Zerfallsprodukte.

Und Paracelsus: Ja. Nutzt denen in der Nähe aber dann nix, wenn, wahrscheinlich lange Zeit unbemerkt, massiv radioaktive Stoffe aus dem Atommülllager in deren Trinkwasser eingetragen werden.

Du bist schlicht Atomlobbyist, vermutlich sogar beruflich in einer Interessensbranche tätig, der, so wie #Klimawandelleugner auch, tatsächlich glaubt, er sitzt in einem anderen Boot, wenn es zum #GAU kommt.

#Energiewende #Energiegewinnung #Atomkraftwerk #Kernkraftwerk #AKW #KKW #Atomkraft #Kernenergie #erneuerbareEnergien #regenerativeEnergien

de.m.wikipedia.orgInternationale Energieagentur – Wikipedia
Public
Niels de Winter

A clumped #isotope calibration of #coccoliths at well-constrained culture temperatures for marine #temperature #reconstructions

cp.copernicus.org/articles/20/

cp.copernicus.orgA clumped isotope calibration of coccoliths at well-constrained culture temperatures for marine temperature reconstructionsAbstract. Numerous recent studies have tested the clumped isotope (Δ47) thermometer on a variety of biogenic carbonates such as foraminifera and bivalves and showed that most follow a common calibration. However, there may be a difference between biogenic-carbonate-based calibrations and the most recent inorganic carbonate calibrations that are assumed to have formed close to isotopic equilibrium. Biogenic calibrations such as those based on foraminifera from seafloor sediments suffer from uncertainties in the determination of the calcification temperatures. Therefore, well-constrained laboratory cultures without temperature uncertainty can help resolve these discrepancies. Although the sample size requirements for a reliable Δ47 measurement have decreased over the years, the availability and preservation of many biogenic carbonates are still limited and/or require substantial time to be extracted from sediments in sufficient amounts. Coccoliths, on the other hand, are abundant and often well-preserved in sediments, and they are a potential interesting target for palaeoceanography. We thus determined the Δ47–temperature relationship for coccoliths due to their relative ease of growth in the laboratory. The carbon and oxygen isotopic compositions of coccolith calcite have limited use in palaeoenvironmental reconstructions due to physiological effects that cause variability in the carbon and oxygen isotopic fractionation during mineralization. However, the relatively limited data available suggest that clumped isotopes may not be significantly influenced by these effects. We cultured three species of coccolithophores under controlled carbonate system conditions with CO2(aq) concentrations between 5 and 45 µM, pH between 7.9 and 8.6 units, and temperatures between 6 and 27 °C. Our well-constrained results agree with a previous culture study that there are no apparent species- or genus-specific vital effects on the Δ47–temperature relationship in coccolithophores despite significant deviations from equilibrium in the C and O isotopic composition. We find that while varying environmental parameters other than temperature does not have a significant effect on Δ47, changing the parameters yields coccolith Δ47–temperature calibrations that agree within 1.2 ppm. Our coccolith-specific Δ47–temperature calibration with well-constrained temperatures shows a consistent, positive offset of 2–3 °C to the inorganic carbonate calibrations, which point to as yet unknown coccolith-specific disequilibrium effects. Thus, we suggest the use of our coccolith-specific calibration for further coccolith palaeoceanographic studies and that calibrations derived from laboratory-grown biogenic carbonates are desirable to reinforce the confidence of clumped-isotope-based temperature reconstructions in palaeoceanography.
Public
Jens Notroff

Original study:

Amy K. Styring et al., Carbon #isotope values of #hazelnut shells: a new proxy for canopy density, Front. Environ. Archaeol. 3, 2024. 🔓

frontiersin.org/articles/10.33

FrontiersCarbon isotope values of hazelnut shells: a new proxy for canopy densityHazel (Corylus avellana) has been abundant in the vegetation of northern and central Europe since the early Holocene and has provided food and materials for humans ever since. Here we use stable carbon isotope (δ13C) values of hazelnut shells to infer woodland openness based on the premise of the “canopy effect”. It is well established that plants growing in dense, shaded forests have lower carbon isotope (δ13C) values than plants growing in open areas. By measuring δ13C values in hazelnuts collected from trees growing in different levels of light intensity, we show that the canopy effect is preserved in hazelnuts and that their δ13C values can be used to infer woodland openness in the past. We apply the method to hazelnuts recovered from sites dated to between the Mesolithic and Iron Age (c. 7000 BCE−1000 CE) in southern Sweden. Our results show that the nuts dated to the Mesolithic were harvested from hazels growing in a range of closed to open settings while nuts from subsequent periods were harvested from progressively more open environments. Given the abundance of hazelnuts recovered from many archaeological contexts, this method has the potential to reconstruct the microhabitats exploited by humans in the past and explore the impact of humans on their environment.
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