23 results on '"Affek, Hagit"'
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2. [formula omitted] in speleothem carbonates in Soreq Cave as an archive for hydro-climatic conditions
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Affek, Hagit P., Vieten, Rolf, Barkan, Eugeni, Levi, Yoav, Ayalon, Avner, Bar-Matthews, Miryam, Fishman, Ekaterina, and Assor, Ahinoam
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- 2023
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3. Climate-forced change in Hudson Bay seawater composition and temperature, Arctic Canada
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Brand, Uwe, Came, Rosemarie E., Affek, Hagit, Azmy, Karem, Mooi, Randy, and Layton, Kara
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- 2014
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4. Clumped isotope signatures in modern brachiopod carbonate
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Came, Rosemarie E., Brand, Uwe, and Affek, Hagit P.
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- 2014
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5. The effect of salinity on water 17O/16O ratios in brines
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Barkan, Eugeni, Fishman, Ekaterina, and Affek, Hagit P.
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- 2022
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6. The end‐Permian mass extinction: A rapid volcanic CO2 and CH4‐climatic catastrophe
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Brand, Uwe, Posenato, Renato, Came, Rosemarie, Affek, Hagit, Angiolini, Lucia, Azmy, Karem, and Farabegoli, Enzo
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- 2012
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7. Shear heating and clumped isotope reordering in carbonate faults
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Siman-Tov, Shalev, Affek, Hagit P., Matthews, Alan, Aharonov, Einat, and Reches, Ze'ev
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- 2016
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8. Devils Hole paleotemperatures and implications for oxygen isotope equilibrium fractionation
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Kluge, Tobias, Affek, Hagit P., Dublyansky, Yuri, and Spötl, Christoph
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- 2014
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9. A revised calibration of the clumped isotope thermometer
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Zaarur, Shikma, Affek, Hagit P., and Brandon, Mark T.
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- 2013
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10. Last glacial-Holocene temperatures and hydrology of the Sea of Galilee and Hula Valley from clumped isotopes in Melanopsis shells.
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Zaarur, Shikma, Affek, Hagit P., and Stein, Mordechai
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HOLOCENE Epoch , *TEMPERATURE effect , *MELANOPSIS , *HYDROLOGY - Abstract
The carbonate clumped isotope (Δ 47 ) thermometer was applied to fresh water snails ( Melanopsis spp.) grown in the waters of the Sea of Galilee and Hula Valley, in the north of Israel. Modern shells, grown at known temperatures agree with the Δ 47 - T calibration of Zaarur et al. (2013). Fossil Melanopsis shells from 2 locations, Gesher Bnot Ya’aqov (at the southern tip of the Hula Valley) and the Sea of Galilee provide a temperature record for the region during the time interval of the past 20 kyrs. Glacial temperatures are ∼5 °C cooler than mid-Holocene and ∼3 °C cooler than modern, similar to other records in the region. These Δ 47 -derived temperatures are combined with δ 18 O of the shell carbonate to calculate the oxygen isotopic composition of the habitat waters. Contrary to global trends and other regional records, reconstructed δ 18 O water values increase from the late glacial through the Holocene. This reversed signal reflects a decrease in the relative contribution of snowmelt to the watershed post-LGM and a transition to a more rain dominated inflow. A fairly constant difference in δ 18 O water values between the Hula Valley and Sea of Galilee waters, suggests that the hydrological relationship of the two water bodies had remained constant, with the temperature changes playing only a minor role in the extent of evaporation of the Sea of Galilee relative to the Hula. [ABSTRACT FROM AUTHOR] more...
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- 2016
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11. Accounting for kinetic isotope effects in Soreq Cave (Israel) speleothems.
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Affek, Hagit P., Matthews, Alan, Ayalon, Avner, Bar-Matthews, Miryam, Burstyn, Yuval, Zaarur, Shikma, and Zilberman, Tami
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KINETIC isotope effects , *SPELEOTHEMS , *THERMOMETERS , *PRECIPITATION (Chemistry) , *CALCITE , *CARBON dioxide - Abstract
There is growing evidence that speleothem calcite grows out of isotopic equilibrium with cave drip water, with clumped isotope analysis providing a sensitive indicator for disequilibrium. This disequilibrium is primarily the result of CO 2 degassing from a thin film of water, leading to irreversible 13 C enrichment and reversible 18 O enrichment and Δ 47 depletion. Here we examine isotopic disequilibrium in Soreq Cave (Israel) using multiple modern-day and late Holocene speleothems. The variability observed in Δ 47 is small, within the analytical uncertainty, but the Δ 47 -derived temperature is offset from the modern cave temperature by ∼4 °C, reflecting degassing related disequilibrium that is fairly constant spatially. δ 18 O is more heterogeneous, reflecting short-term variability in drip water δ 18 O w combined with variability in the speleothem growth rates and related fractionation between dissolved carbonate species and the growing calcite mineral. This complexity, however, is markedly reduced by spatial or temporal averaging, enabling an interpretation of the cave paleoclimate record. We examine the Soreq Cave speleothems through a comparison with 2 types of thermometers: one is based on CaCO 3 precipitation from a bulk solution and is typically used for calibration of the Δ 47 and δ 18 O thermometers; a second that is based on CaCO 3 precipitating at the surface of the solution thus focusing and amplifying the thin film characteristics of speleothem formation. Soreq Cave speleothems are intermediate between these thermometers, providing a cave-specific thermometer calibration. [ABSTRACT FROM AUTHOR] more...
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- 2014
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12. Kinetic isotope effect in CO2 degassing: Insight from clumped and oxygen isotopes in laboratory precipitation experiments.
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Affek, Hagit P. and Zaarur, Shikma
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KINETIC isotope effects , *DEGASSING of metals , *CARBON dioxide , *OXYGEN isotopes , *PRECIPITATION (Chemistry) , *THERMOMETERS - Abstract
Laboratory precipitation experiments provide the basis for the common calibration of both the oxygen isotope and the clumped isotope thermometers. These focus on CaCO 3 crystals that form deep in the bulk of the solution, often by the bubbling of N 2(g) through a saturated Ca(HCO 3 ) 2 solution, following the classic experiments on McCrea (1950). Here we examine oxygen and clumped isotopes in CaCO 3 that was precipitated at the surface of a solution that undergoes passive CO 2 degassing. This CaCO 3 is affected by enhanced disequilibrium that is associated with degassing, and has therefore higher δ 18 O and lower Δ 47 values than those of the accepted thermometer calibrations. These offsets from the common thermometers calibrations increase with decreasing temperature for Δ 47 but decrease with decreasing temperature for δ 18 O. The Δ 47 -δ 18 O co-variance is therefore strongly temperature dependent, in contrast to theoretical predictions. This suggests an influence of additional fractionation in fast growing minerals, between DIC and calcite, that affects δ 18 O and counteracts some of the degassing related enrichment. This effect seems not to influence Δ 47 . The physical setup of CaCO 3 minerals growing at the solution surface is analogous to the degassing and precipitation processes that occur in stalagmites, such that these laboratory experiments may help shed light on the isotopic disequilibrium that is observed in speleothems. [ABSTRACT FROM AUTHOR] more...
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- 2014
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13. Clumped isotope thermometry of cryogenic cave carbonates.
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Kluge, Tobias, Affek, Hagit P., Zhang, Yi Ge, Dublyansky, Yuri, Spötl, Christoph, Immenhauser, Adrian, and Richter, Detlev K.
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THERMOMETRY , *CRYOGENICS , *METEOROLOGICAL precipitation , *SPELEOTHEMS , *CARBON isotopes , *OXYGEN isotopes , *CALCIUM carbonate - Abstract
Abstract: Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCCfine). This leads to rapid physicochemical changes including CO2 degassing and CaCO3 precipitation, resulting in significantly 13C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCCcoarse) yielding strongly 18O-depleted carbonate. This is due to the formation of relatively 18O-enriched ice causing the gradual depletion of 18O in the water from which the CCC precipitates. Cryogenic carbonates from Central European caves were found to have been formed primarily during the last glacial period, specifically during times of permafrost thawing, based on the oxygen isotope ratios and U–Th dating. Information about the precise conditions of CCCcoarse formation, i.e. whether these crystals formed under equilibrium or disequilibrium conditions with the parent fluid, however, is lacking. An improved understanding of CCCcoarse formation will increase the predictive value of this paleo-permafrost archive. Here we apply clumped isotopes to investigate the formation conditions of cryogenic carbonates using well-studied CCCcoarse from five different cave systems in western Germany. Carbonate clumped isotope measurements yielded apparent temperatures between 3 and 18°C and thus exhibit clear evidence of isotopic disequilibrium. Although the very negative carbonate δ18O values can only be explained by gradual freezing of pool water accompanied by preferential incorporation of 18O into the ice, clumped isotope-derived temperatures significantly above expected freezing temperatures indicate incomplete isotopic equilibration during precipitation of CCC. [Copyright &y& Elsevier] more...
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- 2014
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14. Carbonate clumped isotope variability in shallow water corals: Temperature dependence and growth-related vital effects
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Saenger, Casey, Affek, Hagit P., Felis, Thomas, Thiagarajan, Nivedita, Lough, Janice M., and Holcomb, Michael
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CARBONATES , *WATER depth , *CORALS , *WATER temperature , *GEOCHEMISTRY , *PALEOCLIMATOLOGY , *EMPIRICAL research , *TEMPERATURE measurements - Abstract
Abstract: Geochemical variations in shallow water corals provide a valuable archive of paleoclimatic information. However, biological effects can complicate the interpretation of these proxies, forcing their application to rely on empirical calibrations. Carbonate clumped isotope thermometry (Δ47) is a novel paleotemperature proxy based on the temperature dependent “clumping” of 13C–18O bonds. Similar Δ47-temperature relationships in inorganically precipitated calcite and a suite of biogenic carbonates provide evidence that carbonate clumped isotope variability may record absolute temperature without a biological influence. However, large departures from expected values in the winter growth of a hermatypic coral provided early evidence for possible Δ47 vital effects. Here, we present the first systematic survey of Δ47 in shallow water corals. Sub-annual Red Sea Δ47 in two Porites corals shows a temperature dependence similar to inorganic precipitation experiments, but with a systematic offset toward higher Δ47 values that consistently underestimate temperature by ∼8°C. Additional analyses of Porites, Siderastrea, Astrangia and Caryophyllia corals argue against a number of potential mechanisms as the leading cause for this apparent Δ47 vital effect including: salinity, organic matter contamination, alteration during sampling, the presence or absence of symbionts, and interlaboratory differences in analytical protocols. However, intra- and inter-coral comparisons suggest that the deviation from expected Δ47 increases with calcification rate. Theoretical calculations suggest this apparent link with calcification rate is inconsistent with pH-dependent changes in dissolved inorganic carbon speciation and with kinetic effects associated with CO2 diffusion into the calcifying space. However, the link with calcification rate may be related to fractionation during the hydration/hydroxylation of CO2 within the calcifying space. Although the vital effects we describe will complicate the interpretation of Δ47 as a paleothermometer in shallow water corals, it may still be a valuable paleoclimate proxy, particularly when applied as part of a multi-proxy approach. [Copyright &y& Elsevier] more...
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- 2012
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15. Quantifying kinetic fractionation in Bunker Cave speleothems using Δ47
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Kluge, Tobias and Affek, Hagit P.
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SPELEOTHEMS , *KINETIC isotope effects , *PALEOCLIMATOLOGY , *LAND use , *QUANTITATIVE research , *CARBON isotopes , *OXYGEN isotopes , *CAVES - Abstract
Abstract: Isotopic signals in speleothems are used for investigating paleoclimate variability on land and are useful to constrain the dating of prominent climate events. A quantitative use, however, is limited by an incomplete understanding of parameters contributing to the carbon and oxygen isotope signals. These include external and environmental parameters such as δ18O of cave drip waters as well as internal parameters associated with speleothem formation, such as the presence of non-equilibrium effects and especially the magnitude of their isotopic shifts. We explore the use of clumped isotopes as a new tool for investigating the kinetic isotope effect in speleothems. Holocene and modern speleothems from Bunker Cave (Germany) as well as modern material from the adjacent Dechen Cave are all offset from the equilibrium relationship due to kinetic fractionation. This kinetic offset in clumped isotopes is observed in a stalagmite despite mostly negative Hendy tests, providing a sensitive indicator for kinetic fractionation in cave carbonates. The temperature dependence of the clumped isotope values (0.005‰ per °C) is low compared to the observed magnitude of kinetic offsets (between −0.021 and −0.075‰), so that the mean offsets in apparent temperatures due to kinetic isotope effects are on the order of 10 °C. As a result clumped isotopes are useful in identifying temporal variations in the kinetic fractionation in a stalagmite, when the temperatures during the speleothem growth period are either relatively constant (variations <2 °C) or can be independently constrained. The variations in the kinetic isotope fractionation in Bunker Cave are associated with changing drip water super saturation with periods of stronger prior calcite precipitation associated with lower kinetic offsets in the speleothem calcite. In contrast, stalagmite growth rates show no direct correlation with the degree of kinetic fractionation in the investigated range (13–1500 μm/a). [Copyright &y& Elsevier] more...
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- 2012
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16. Defining an absolute reference frame for ‘clumped’ isotope studies of CO2
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Dennis, Kate J., Affek, Hagit P., Passey, Benjamin H., Schrag, Daniel P., and Eiler, John M.
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CARBON dioxide , *THERMODYNAMIC equilibrium , *BIOGEOCHEMISTRY , *CARBONATES , *MASS spectrometry , *STABLE isotopes , *TEMPERATURE measurements , *MASS transfer - Abstract
Abstract: We present a revised approach for standardizing and reporting analyses of multiply substituted isotopologues of CO2 (i.e., ‘clumped’ isotopic species, especially the mass-47 isotopologues). Our approach standardizes such data to an absolute reference frame based on theoretical predictions of the abundances of multiply-substituted isotopologues in gaseous CO2 at thermodynamic equilibrium. This reference frame is preferred over an inter-laboratory calibration of carbonates because it enables all laboratories measuring mass 47 CO2 to use a common scale that is tied directly to theoretical predictions of clumping in CO2, regardless of the laboratory’s primary research field (carbonate thermometry or CO2 biogeochemistry); it explicitly accounts for mass spectrometric artifacts rather than convolving (and potentially confusing) them with chemical fractionations associated with sample preparation; and it is based on a thermodynamic equilibrium that can be experimentally established in any suitably equipped laboratory using commonly available materials. By analyzing CO2 gases that have been subjected to established laboratory procedures known to promote isotopic equilibrium (i.e., heated gases and water-equilibrated CO2), and by reference to thermodynamic predictions of equilibrium isotopic distributions, it is possible to construct an empirical transfer function that is applicable to data with unknown clumped isotope signatures. This transfer function empirically accounts for the fragmentation and recombination reactions that occur in electron impact ionization sources and other mass spectrometric artifacts. We describe the protocol necessary to construct such a reference frame, the method for converting gases with unknown clumped isotope compositions to this reference frame, and suggest a protocol for ensuring that all reported isotopic compositions (e.g., Δ47 values; ) can be compared among different laboratories and instruments, independent of laboratory-specific analytical or methodological differences. We then discuss the use of intra-laboratory secondary reference frames (e.g., based on carbonate standards) that can be more easily used to track the evolution of each laboratory’s empirical transfer function. Finally, we show inter-laboratory reproducibility on the order of ±0.010 (1σ) for four carbonate standards, and present revised paleotemperature scales that should be used to convert carbonate clumped isotope signatures to temperature when using the absolute reference frame described here. Even when using the reference frame, small discrepancies remain between two previously published synthetic carbonate calibrations. We discuss possible reasons for these discrepancies, and highlight the need for additional low temperature (<15°C) synthetic carbonate experiments. [Copyright &y& Elsevier] more...
- Published
- 2011
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17. Glacial/interglacial temperature variations in Soreq cave speleothems as recorded by ‘clumped isotope’ thermometry
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Affek, Hagit P., Bar-Matthews, Miryam, Ayalon, Avner, Matthews, Alan, and Eiler, John M.
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TEMPERATURE measurements , *PHYSICAL measurements , *SPELEOLOGY , *GEOMORPHOLOGY - Abstract
Abstract: ‘Clumped isotope’ thermometry is based on analyzing mass 47 in CO2 extracted from carbonates and uses the tracer mass 47 anomaly (Δ47). Δ47 is defined as the deviation of R 47 from that expected for a random distribution of isotopologues and reflects a temperature dependent preference of 13C and 18O to create a bond with each other in CO2 or in the carbonate lattice. Being an internal characteristic of the carbonate mineral, it is independent of the isotopic composition of the water in which equilibrium precipitation of the carbonate occurs and can therefore be used to independently determine carbonate growth temperatures. This work provides a first examination of the applicability of ‘clumped isotopes’ thermometry to reconstructing the growth temperatures of speleothems, by examining the glacial/interglacial variations of the Δ47 values of speleothem carbonates from Soreq cave, Israel. The results indicate that the last glacial maximum temperatures were 6–7°C colder than modern day temperature and a sample at 56Ky BP was 3°C colder than the modern. Early Holocene temperatures were slightly above modern day, and late Holocene temperatures were slightly below modern day. These temperature variations are similar to those previously estimated for Eastern Mediterranean sea surface water. Cave water was 18O depleted in the Holocene compared to modern day (by 0.6–1‰) and 1.1‰ more enriched in the last glacial maximum. Comparison of these cave water δ18O values with fluid inclusion δD values indicated a late Holocene d-excess value within the range of modern rainfall, implying ∼45% relative humidity. Last glacial maximum and early Holocene d-excess values were significantly lower, suggesting relative humidity of ∼60% and ∼70%, respectively. The temperatures reported in this study were empirically corrected for a non-equilibrium artifact observed in a modern speleothem. The similarity of the temperature variations obtained here to other, independent, records in the region suggests that the Δ47–temperature calibration slope observed in inorganic synthetic calcite and marine organisms may also be applied in speleothems. But the offset observed in modern temperature suggests that the intercept is different so that a separate calibration is needed for accurate absolute temperature reconstruction using speleothem ‘clumped isotopes’. Similar examination of additional caves would be necessary to determine whether such empirical correction can be generally applied or is it a unique characteristic of Soreq cave. [Copyright &y& Elsevier] more...
- Published
- 2008
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18. Seasonal and diurnal variations of 13C18O16O in air: Initial observations from Pasadena, CA
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Affek, Hagit P., Xu, Xiaomei, and Eiler, John M.
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BUDGET , *RESPIRATION , *TIME series analysis , *ENERGY minerals - Abstract
Abstract: The budget of atmospheric CO2 is widely studied using records of temporal and spatial variations of concentrations, δ13C and δ18O values. However, the number and diversity of sources and sinks prevents these alone from fully constraining the budget. Molecules containing two rare isotopes can serve as additional tracers and potentially provide additional, independent, constraints. We present data documenting seasonal and diurnal variations of CO2 having a mass of 47 u (mostly 13C18O16O) in air from Pasadena, CA. We report these data using the ‘mass 47 anomaly’ (Δ47), which is defined as the deviation of R 47(=[47]/[44]) from that expected for a random distribution of isotopologues. Between February 2004 and December 2005, Δ47 showed a seasonal pattern that differed significantly from that expected based on thermodynamic equilibrium. During the year 2004 Δ47 was 0.76‰ in winter, increased to 0.87‰ in summer and gradually decreased through the autumn to 0.81‰ at the end of the year. Δ47 then increased again through the winter and spring of 2005 to 0.97‰ in summer followed by a decrease to 0.88‰ at the end of 2005. The seasonal variations cannot be accounted for by variations in the relative contribution of local fossil fuel sources. Diurnal variations were the combined effect of both fuel combustion and respiration having Δ47 values of 0.41‰ and ca. 0.77‰, respectively. The seasonal cycle may be interpreted as a competition between low Δ47 values in respiration and higher Δ47 values resulting from CO2-water exchange in photosynthesis. [Copyright &y& Elsevier] more...
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- 2007
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19. Abundance of mass 47 CO2 in urban air, car exhaust, and human breath
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Affek, Hagit P. and Eiler, John M.
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ATMOSPHERIC carbon dioxide , *LOW temperatures , *CARBON dioxide , *CARBON compounds - Abstract
Abstract: Atmospheric carbon dioxide is widely studied using records of CO2 mixing ratio, δ 13C and δ 18O. However, the number and variability of sources and sinks prevents these alone from uniquely defining the budget. Carbon dioxide having a mass of 47u (principally 13C18O16O) provides an additional constraint. In particular, the mass 47 anomaly (Δ47) can distinguish between CO2 produced by high temperature combustion processes vs. low temperature respiratory processes. Δ47 is defined as the abundance of mass 47 isotopologues in excess of that expected for a random distribution of isotopes, where random distribution means that the abundance of an isotopologue is the product of abundances of the isotopes it is composed of and is calculated based on the measured 13C and 18O values. In this study, we estimate the δ 13C (vs. VPDB), δ 18O (vs. VSMOW), δ47, and Δ47 values of CO2 from car exhaust and from human breath, by constructing ‘Keeling plots’ using samples that are mixtures of ambient air and CO2 from these sources. δ47 is defined as , where is the R 47 value for a hypothetical CO2 whose δ 13CVPDB =0, δ 18OVSMOW =0, and Δ47 =0. Ambient air in Pasadena, CA, where this study was conducted, varied in [CO2] from 383 to 404μmolmol−1, in δ 13C and δ 18O from −9.2 to −10.2‰ and from 40.6 to 41.9‰, respectively, in δ47 from 32.5 to 33.9‰, and in Δ47 from 0.73 to 0.96‰. Air sampled at varying distances from a car exhaust pipe was enriched in a combustion source having a composition, as determined by a ‘Keeling plot’ intercept, of −24.4±0.2‰ for δ 13C (similar to the δ 13C of local gasoline), δ 18O of 29.9±0.4‰, δ47 of 6.6±0.6‰, and Δ47 of 0.41±0.03‰. Both δ 18O and Δ47 values of the car exhaust end-member are consistent with that expected for thermodynamic equilibrium at∼200°C between CO2 and water generated by combustion of gasoline–air mixtures. Samples of CO2 from human breath were found to have δ 13C and δ 18O values broadly similar to those of car exhaust–air mixtures, −22.3±0.2 and 34.3±0.3‰, respectively, and δ47 of 13.4±0.4‰. Δ47 in human breath was 0.76 ±0.03‰, similar to that of ambient Pasadena air and higher than that of the car exhaust signature. [Copyright &y& Elsevier] more...
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- 2006
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20. Paleo-environmental implication of clumped isotopes in land snail shells
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Zaarur, Shikma, Olack, Gerard, and Affek, Hagit P.
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PALEOCLIMATOLOGY , *ISOTOPE geology , *OXYGEN isotopes , *CARBONATE rocks , *TEMPERATURE measurements , *GEOLOGICAL formations , *CALCIFICATION , *METEOROLOGICAL precipitation - Abstract
Abstract: Clumped isotopes analyses in modern land snail shells are reported and used to interpret shell oxygen isotopes within the context of terrestrial paleo-climatology. Carbonate clumped isotopes thermometry is a new technique for estimating the temperature of formation of carbonate minerals. It is most powerful as an indicator of environmental parameters in combination with δ18O, allowing the partitioning of the δ18O signal into its temperature and water components. Results indicate that snail shell calcification temperatures are typically higher than either the mean annual or the snail activity season ambient temperatures. Small inter- and intra-snail variability suggests that shell aragonite forms at isotopic equilibrium so that the derived temperatures are an eco-physiological parameter reflecting snail body temperature at the time of calcification. We attribute these higher body temperatures to snail eco-physiological adaptations through shell color, morphology, and behavior. In combination with shell oxygen isotope composition, these temperatures allow us to calculate snail body water composition, which is in turn interpreted as a paleo-hydrological indicator, reflecting isotopic composition of local precipitation modified by local evaporation. [Copyright &y& Elsevier] more...
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- 2011
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21. 13C–18O bonds in carbonate minerals: A new kind of paleothermometer
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Ghosh, Prosenjit, Adkins, Jess, Affek, Hagit, Balta, Brian, Guo, Weifu, Schauble, Edwin A., Schrag, Dan, and Eiler, John M.
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CHEMICAL bonds , *CARBONATE minerals , *PALEOTHERMOMETRY , *TEMPERATURE measurements - Abstract
Abstract: The abundance of the doubly substituted CO2 isotopologue, 13C18O16O, in CO2 produced by phosphoric acid digestion of synthetic, inorganic calcite and natural, biogenic aragonite is proportional to the concentration of 13C–18O bonds in reactant carbonate, and the concentration of these bonds is a function of the temperature of carbonate growth. This proportionality can be described between 1 and 50°C by the function: Δ 47 =0.0592·106 · T −2 −0.02, where Δ 47 is the enrichment, in per mil, of 13C18O16O in CO2 relative to the amount expected for a stochastic (random) distribution of isotopes among all CO2 isotopologues, and T is the temperature in Kelvin. This relationship can be used for a new kind of carbonate paleothermometry, where the temperature-dependent property of interest is the state of ordering of 13C and 18O in the carbonate lattice (i.e., bound together vs. separated into different CO3 2− units), and not the bulk δ18O or δ13C values. Current analytical methods limit precision of this thermometer to ca. ±2°C, 1σ. A key feature of this thermometer is that it is thermodynamically based, like the traditional carbonate–water paleothermometer, and so is suitable for interpolation and even modest extrapolation, yet is rigorously independent of the δ18O of water and δ13C of DIC from which carbonate grew. Thus, this technique can be applied to parts of the geological record where the stable isotope compositions of waters are unknown. Moreover, simultaneous determinations of Δ 47 and δ18O for carbonates will constrain the δ18O of water from which they grew. [Copyright &y& Elsevier] more...
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- 2006
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22. Carbonate 17Oexcess as a paleo-hydrology proxy: Triple oxygen isotope fractionation between H2O and biogenic aragonite, derived from freshwater mollusks.
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Bergel, Shelly J., Barkan, Eugeni, Stein, Mordechai, and Affek, Hagit P.
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OXYGEN isotopes , *CARBONATE minerals , *CARBONATES , *ISOTOPIC fractionation , *ARAGONITE , *WATER , *COMPOSITION of water , *SEASHELLS - Abstract
Carbonates are common paleoclimate archives in a variety of environments with land carbonates recording both temperatures and hydrological conditions. Whereas δ18O has long been used for that purpose, triple oxygen isotopes (given as 17O excess) has only recently been analyzed in CaCO 3. Carbonate 17O excess is expected to reflect the temperature, in which the carbonate formed, and the triple oxygen isotopic composition of its parent water. The reconstruction of past water 17O excess values from carbonate records requires characterization of the 17O fractionation between water and CaCO 3. Here, we use freshwater mollusk shells grown in well constrained spring environments, at a temperature range of 15–28 °C, to derive the fractionation factor 17α between CO 2 extracted from CaCO 3 and the carbonate habitat water. The spring water temperature and isotopic composition are constant year-round, avoiding uncertainty associated with seasonality. The derived 18α and 17α between CO 2 extracted from mollusk aragonite and spring water are used to calculate the fractionation slope θ (=ln17α/ln18α), resulting in 0.5231 ± 0.0003, with no discernible temperature dependence. Using this value, we evaluated the fractionation slope of the acid digestion of CaCO 3 as 0.5170 ± 0.0004. The minor difference between the fractionation slope between aragonite and parent water and the reference slope of 0.528, implies that 17O excess in carbonates is only weakly temperature dependent. On the other hand, carbonate 17O excess values directly record variability in 17O excess of the parent water, making it a useful paleo-hydrological proxy. [ABSTRACT FROM AUTHOR] more...
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- 2020
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23. The end‐Permian mass extinction: A rapid volcanic CO2 and CH4‐climatic catastrophe
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Brand, Uwe, Posenato, Renato, Came, Rosemarie, Affek, Hagit, Angiolini, Lucia, Azmy, Karem, and Farabegoli, Enzo
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PERMIAN Period , *MASS extinctions , *VOLCANIC ash, tuff, etc. , *CARBON dioxide , *CLIMATE change , *CATASTROPHISM , *GEOCHEMISTRY , *OCEAN temperature - Abstract
Abstract: The end of the Permian was a time of crisis that culminated in the Earth''s greatest mass extinction. There is much speculation as to the cause for this catastrophe. Here we provide a full suite of high-resolution and coeval geochemical results (trace and rare earth elements, carbon, oxygen, strontium and clumped isotopes) reflecting ambient seawater chemistry and water quality parameters leading up to the end‐Permian crisis. Preserved brachiopod low-Mg calcite-based seawater chemistry, supplemented by data from various localities, documents a sequence of interrelated primary events such as coeval flows of Siberian Trap continental flood basalts and emission of carbon dioxide leading to warm and extreme Greenhouse conditions with sea surface temperatures (SST) of ~36°C for the Late Permian. Although anoxia has been advanced as a cause for the mass extinction, most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling, but not a general cause. Instead, we suggest that renewed and increased end‐Permian Siberian Trap volcanic activity, about 2000years prior to the extinction event, released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering. Eventually, these rapidly discharged greenhouse gas emissions, less than 1000years before the event, ushered in a global Hothouse period leading to extreme tropical SSTs of ~39°C and higher. Based on these sea surface temperatures, atmospheric CO2 concentrations were about 1400ppmv and 3000ppmv for the Late and end‐Permian, respectively. Leading up to the mass extinction, there was a brief interruption of the global warming trend when SST dropped, concurrent with a slight, but significant recovery in biodiversity in the western Tethys. It is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the Permian. After aerosol deposition, global warming resumed and the biotic decline proceeded, and was accompanied by suboxia, in places of the surface ocean which culminated in the greatest mass extinction in Earth history. [Copyright &y& Elsevier] more...
- Published
- 2012
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