Investigating oxygen and carbon isotopic relationships in speleothem records over the last millennium using multiple isotope-enabled climate models

Abstract. The incorporation of water isotopologues into the hydrology of general circulation models (GCMs) facilitates the comparison between modelled and measured proxy data in paleoclimate archives. However, the variability and drivers of measured and modelled water isotopologues, and indeed the diversity of their representation in different models are not well constrained. Improving our understanding of this variability in past and present climates will help to better constrain future climate change projections and decrease their range of uncertainty. Speleothems are a precisely datable paleoclimate archive and provide well preserved (semi-)continuous multivariate isotope time series in the lower and mid-latitudes, and are, therefore, well suited to assess climate and isotope variability on decadal and longer timescales. However, the relationship between speleothem oxygen and carbon isotopes to climate variables also depends on site-specific parameters, and their comparison to GCMs is not always straightforward. Here we compare speleothem oxygen and carbon isotopic signatures from the Speleothem Isotopes Synthesis and AnaLysis database version 2 (SISALv2) to the output of five different water-isotope-enabled GCMs (ECHAM5-wiso, GISS-E2-R, iCESM, iHadCM3, and isoGSM) over the last millennium (850–1850 common era, CE). We systematically evaluate differences and commonalities between the standardized model simulation outputs. The goal is to distinguish climatic drivers of variability for both modelled and measured isotopes. We find strong regional differences in the oxygen isotope signatures between models that can partly be attributed to differences in modelled temperatures. At low latitudes, precipitation amount is the dominant driver for water isotope variability, however, at cave locations the agreement between modelled temperature variability is higher than for precipitation variability. While modelled isotopic signatures at cave locations exhibited extreme events coinciding with changes in volcanic and solar forcing, such fingerprints are not apparent in the speleothem isotopes, and may be attributed to the lower temporal resolution of speleothem records compared to the events that are to be detected. Using spectral analysis, we can show that all models underestimate decadal and longer variability compared to speleothems, although to varying extent. We found that no model excels in all analyzed comparisons, although some perform better than the others in either mean or variability. Therefore, we advise a multi-model approach, whenever comparing proxy data to modelled data. Considering karst and cave internal processes through e.g. isotope-enabled karst models may alter the variability in speleothem isotopes and play an important role in determining the most appropriate model. By exploring new ways of analyzing the relationship between the oxygen and carbon isotopes, their variability, and co-variability across timescales, we provide methods that may serve as a baseline for future studies with different models using e.g. different isotopes, different climate archives, or time periods.

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How Does Diet Influence Our Lives? Evaluating the Relationship between Isotopic Signatures and Mortality Patterns in Italian Roman Imperial and Medieval Periods

Molecules ◽

10.3390/molecules26133895 ◽

2021 ◽

Vol 26 (13) ◽

pp. 3895

Author(s):

Marica Baldoni ◽

Alessandra Nardi ◽

Flavio De Angelis ◽

Olga Rickards ◽

Cristina Martínez-Labarga

Keyword(s):

Middle Ages ◽

Dietary Habits ◽

Roman Period ◽

Survivorship Analysis ◽

Linear Effect ◽

Isotopic Signatures ◽

Carbon Isotopic ◽

Religious Aspects ◽

The Relationship ◽

Source Of Information

The present research investigates the relationship between dietary habits and mortality patterns in the Roman Imperial and Medieval periods. The reconstructions of population dynamics and subsistence strategies provide a fascinating source of information for understanding our history. This is particularly true given that the changes in social, economic, political, and religious aspects related to the transition from the Roman period to the Middle Ages have been widely discussed. We analyzed the isotopic and mortality patterns of 616 individuals from 18 archeological sites (the Medieval Latium sites of Colonna, Santa Severa, Allumiere, Cencelle, and 14 Medieval and Imperial funerary contexts from Rome) to compile a survivorship analysis. A semi-parametric approach was applied, suggesting variations in mortality patterns between sexes in the Roman period. Nitrogen isotopic signatures influenced mortality in both periods, showing a quadratic and a linear effect for Roman Imperial and Medieval populations, respectively. No influence of carbon isotopic signatures has been detected for Roman Imperial populations. Conversely, increased mortality risk for rising carbon isotopic values was observed in Medieval samples.

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CARBON ISOTOPES, KEROGEN TYPES AND THE PERMIAN-TRIASSIC BOUNDARY IN AUSTRALIA: IMPLICATIONS FOR EXPLORATION

The APPEA Journal ◽

10.1071/aj96028 ◽

1997 ◽

Vol 37 (1) ◽

pp. 472 ◽

Cited By ~ 27

Author(s):

C.B. Foster ◽

G.A. Logan ◽

R.E. Summons ◽

J.D. Gorter ◽

D.S. Edwards

Keyword(s):

Organic Matter ◽

Carbon Isotopes ◽

Secular Change ◽

Simple Relationship ◽

Predictive Tool ◽

Marine Fauna ◽

Isotopic Signatures ◽

Carbon Isotopic ◽

Eastern Australia ◽

Plant Microfossils

A global stratotype section for the boundary between the Permian and Triassic Systems is yet to be agreed internationally. However, in many parts of the world, there is evidence of massive extinction of marine fauna at or near the P-T boundary. In the absence of marine fauna, as is the case in most of Australia, changes in plant microfossils, in carbon isotopic signatures, and radiometric dates using SHRIMP, have been used to mark the boundary. The leading questions which arise from this are whether these events are synchronous and how they affect exploration.In eastern Australia, the top of the coal measures has been used as the top of the Permian, although presently only plant microfossils can be used to determine if the youngest seam is present. This has important economic consequences for determination of volumes of effective source rock and for estimates of coal-bed methane. It has been suggested that changes in the carbon isotopic signatures (δ13C) of either organic matter (δ13Corg) or carbonates (δ13Ccarb) can be used to delimit the P-T boundary. From studies of (δ13Ccarb data, Scholle (1995) concluded that 'the establishment of a secular variation curve which has enough detail and reliability to be used as a chemostratigraphic tool still lies in the future'. We concur, and demonstrate for organic carbon that, while there is evidence for secular change, the 13C signature is complicated and overprinted by contributions from different parent plant types; wood-dominated organics are typically −24 %o, while non-woody matter is significantly lighter (−30 %o). There is no simple relationship of δ13Corg to geological age. The consistency of our data, from both the east and west of Australia, allows us to construct a model to predict probable depositional and organic facies using either carbon isotopes (from kerogen or oil) or quantitative estimates of organic matter from standard palynlogical slides. This offers a novel and usefl predictive tool for hydrocarbon exploration.

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Biosignatures of ancient microbial life are present across the igneous crust of the Fennoscandian shield

Communications Earth & Environment ◽

10.1038/s43247-021-00170-2 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Henrik Drake ◽

Nick M. W. Roberts ◽

Manuel Reinhardt ◽

Martin Whitehouse ◽

Magnus Ivarsson ◽

...

Keyword(s):

Fennoscandian Shield ◽

Stable Carbon ◽

Deep Biosphere ◽

Isotopic Signatures ◽

Microbial Life ◽

Carbon Isotopic ◽

Terrestrial Life ◽

Vein Mineral ◽

Methyl Branched Fatty Acids

AbstractEarth’s crust contains a substantial proportion of global biomass, hosting microbial life up to several kilometers depth. Yet, knowledge of the evolution and extent of life in this environment remains elusive and patchy. Here we present isotopic, molecular and morphological signatures for deep ancient life in vein mineral specimens from mines distributed across the Precambrian Fennoscandian shield. Stable carbon isotopic signatures of calcite indicate microbial methanogenesis. In addition, sulfur isotope variability in pyrite, supported by stable carbon isotopic signatures of methyl-branched fatty acids, suggest subsequent bacterial sulfate reduction. Carbonate geochronology constrains the timing of these processes to the Cenozoic. We suggest that signatures of an ancient deep biosphere and long-term microbial activity are present throughout this shield. We suggest that microbes may have been active in the continental igneous crust over geological timescales, and that subsurface investigations may be valuable in the search for extra-terrestrial life.

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New equation to decipher the relationship between carbon isotopic composition of methane and maturity of gas source rocks

Science China Earth Sciences ◽

10.1007/s11430-020-9692-1 ◽

2021 ◽

Vol 64 (3) ◽

pp. 470-493 ◽

Cited By ~ 1

Author(s):

Jianping Chen ◽

Xulong Wang ◽

Jianfa Chen ◽

Yunyan Ni ◽

Baoli Xiang ◽

...

Keyword(s):

Isotopic Composition ◽

Carbon Isotopic Composition ◽

Source Rocks ◽

Carbon Isotopic ◽

Gas Source ◽

New Equation ◽

The Relationship

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Did an extensive forest ever develop on the Chinese Loess Plateau during the past 130 ka?: a test using soil carbon isotopic signatures

Applied Geochemistry ◽

10.1016/j.apgeochem.2004.09.007 ◽

2005 ◽

Vol 20 (3) ◽

pp. 519-527 ◽

Cited By ~ 21

Author(s):

Weiguo Liu ◽

Hong Yang ◽

Yunning Cao ◽

Youfeng Ning ◽

Li Li ◽

...

Keyword(s):

Soil Carbon ◽

Loess Plateau ◽

Chinese Loess Plateau ◽

Chinese Loess ◽

Isotopic Signatures ◽

The Past ◽

Carbon Isotopic ◽

The Chinese Loess Plateau

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Stable oxygen and carbon isotopes of carbonate concretions of the Miocene Yeonil Group in the Pohang Basin, Korea: Types of concretions and formation condition

Sedimentary Geology ◽

10.1016/j.sedgeo.2005.09.005 ◽

2006 ◽

Vol 183 (1-2) ◽

pp. 15-30 ◽

Cited By ~ 25

Author(s):

Kyung Sik Woo ◽

Boo-Keun Khim

Keyword(s):

Carbon Isotopes ◽

Formation Condition ◽

Oxygen And Carbon Isotopes ◽

Carbonate Concretions ◽

Pohang Basin ◽

Stable Oxygen

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Evidence from the Changing Carbon Isotopic of Kerogen, Oil, and Gas during Hydrous Pyrolysis from Pinghu Formation, the Xihu Sag, East China Sea Basin

Energies ◽

10.3390/en14248317 ◽

2021 ◽

Vol 14 (24) ◽

pp. 8317

Author(s):

Qiang Cao ◽

Jiaren Ye ◽

Yongchao Lu ◽

Yang Tian ◽

Jinshui Liu ◽

...

Keyword(s):

Carbon Isotopes ◽

Oil And Gas ◽

Thermal Evolution ◽

Vitrinite Reflectance ◽

Heating Time ◽

Source Rocks ◽

Evolution Process ◽

Carbon Isotopic ◽

Hydrous Pyrolysis ◽

Increasing Temperature

Semi-open hydrous pyrolysis experiments on coal-measure source rocks in the Xihu Sag were conducted to investigate the carbon isotope evolution of kerogen, bitumen, generated expelled oil, and gases with increasing thermal maturity. Seven corresponding experiments were conducted at 335 °C, 360 °C, 400 °C, 455 °C, 480 °C, 525 °C, and 575 °C, while other experimental factors, such as the heating time and rate, lithostatic and hydrodynamic pressures, and columnar original samples were kept the same. The results show that the simulated temperatures were positive for the measured vitrinite reflectance (Ro), with a correlation coefficient (R2) of 0.9861. With increasing temperatures, lower maturity, maturity, higher maturity, and post-maturity stages occurred at simulated temperatures (Ts) of 335–360 °C, 360–400 °C, 400–480 °C, and 480–575 °C, respectively. The increasing gas hydrocarbons with increasing temperature reflected the higher gas potential. Moreover, the carbon isotopes of kerogen, bitumen, expelled oil, and gases were associated with increased temperatures; among gases, methane was the most sensitive to maturity. Ignoring the intermediate reaction process, the thermal evolution process can be summarized as kerogen0(original) + bitumen0(original)→kerogenr (residual kerogen) + expelled oil (generated) + bitumenn+r (generated + residual) + C2+(generated + residual) + CH4(generated). Among these, bitumen, expelled oil, and C2-5 acted as reactants and products, whereas kerogen and methane were the reactants and products, respectively. Furthermore, the order of the carbon isotopes during the thermal evolution process was identified as: δ13C1 < 13C2-5 < δ13Cexpelled oil < δ13Cbitumen < δ13Ckerogen. Thus, the reaction and production mechanisms of carbon isotopes can be obtained based on their changing degree and yields in kerogen, bitumen, expelled oil, and gases. Furthermore, combining the analysis of the geochemical characteristics of the Pinghu Formation coal–oil-type gas in actual strata with these pyrolysis experiments, it was identified that this area also had substantial development potential. Therefore, this study provides theoretical support and guidance for the formation mechanism and exploration of oil and gas based on changing carbon isotopes.

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