Hagit P. Affek

• Associate professor
• Professor at Hebrew University of Jerusalem

Traditionally, nuclear spin is not considered to affect biological processes. Recently, this has changed as isotopic fractionation that deviates from classical mass dependence was reported both in vitro and in vivo. In these cases, the isotopic effect correlates with the nuclear magnetic spin. Here, we show nuclear spin effects using stable oxygen...

Closed-basin lakes respond strongly to climate related changes in their water balance. Lake water isotopic composition can thus serve as a sensitive indicator of paleo-hydrological conditions. Such lakes are often highly saline, so that the effect of salinity on the isotopic composition of lake water has to be accounted for in analyzing lake water...

A fundamental issue in the interpretation of speleothem calcite δ¹⁸Occ records is the correct partitioning of the effects of temperature and water δ¹⁸O variations. This study explores the paleo-environmental evolution of the Eastern Mediterranean Sea (EMS) region using Soreq Cave speleothems in the last 160 ka, a period covering glacial MIS6 to the...

Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth‐system processes. However, inter‐laboratory discrepancies in quantifying carbonate clumped isotope (Δ₄₇) measurements persist, and their specific sources remain unclear. To address inter‐laboratory differe...

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 ¹⁷Oexcess) has only recently been analyzed in CaCO3. Carbonate ¹⁷Oexcess is expected to reflect the temperature, in...

Carbonate bearing materials, such as foraminifera, mollusks shells, or speleothems, have the potential to preserve geochemical and isotopic signatures reflecting the environmental conditions at the time they formed. Beyond the conventional δ¹⁸O, information from triple oxygen isotopes (reported as ¹⁷Oexcess, which is defined as (ln (δ¹⁷O/1000 + 1)...

Studying the origin of avian thermoregulation is complicated by a lack of reliable methods for measuring body temperatures in extinct dinosaurs. Evidence from bone histology and stableisotopes often relies on uncertain assumptions about the relationship between growth rate and body temperature, or the isotopic composition (δ ¹⁸ O) of body water. Cl...

Carbonates are a common paleoclimate archive in both marine and land settings. Land carbonates record both temperatures and hydrological conditions. Paleo- temperatures derived from clumped isotopes in land carbonates are often combined with d18O to reconstruct parent water d18O. However, the common interpretation of water d18O as rainfall amounts...

Calcium carbonates have the potential to preserve various geochemical signatures reflecting their environmental conditions at the time they formed. They are ideal archives for paleoclimate and paleoenvironmental studies. Recently, it has been shown that, beyond the conventional stable isotopes, the three isotopes of oxygen in carbonates can help us...

Significance Reconstructing the degree of warming during geological periods of elevated CO 2 provides a way of testing our understanding of the Earth system and the accuracy of climate models. We present accurate estimates of tropical sea-surface temperatures (SST) and seawater chemistry during the Eocene (56–34 Ma before present, CO 2 >560 ppm). T...

Clumped isotopes geochemistry measures the thermodynamic preference of two heavy, rare, isotopes to bind with each other. This preference is temperature dependent, and is more pronounced at low temperatures. Carbonate clumped isotope values are independent of the carbonate δ ¹³ C and δ ¹⁸ O, making them independent of the carbon or oxygen compositi...

Clumped isotope measurements aim to quantify some statistical properties of the isotopologue population in a given sample, which requires prior knowledge of the absolute isotopic abundance ratios in reference materials such as VSMOW or VPDB. In the case of CO2, matters are further complicated by the need to define a mass-dependent fractionation law...

The carbonate clumped isotope (Delta(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 Delta(47)-T calibration of Zaarur et al. (2013). Fossil Melanopsis shells from 2 locations, Gesher Bnot...

As we head toward a warmer world, it is increasingly important to understand anticipated changes in temperature and precipitation and consequent shifts in storm trajectory and intensity. One of the best tools we have for predicting future conditions is the study of warm intervals in Earth’s geologic past, such as the Eocene Epoch (56-34 Ma), charac...

About half of the CO2 emitted by fossil fuel combustion currently remains in the atmosphere. The other half is removed by CO2 uptake on land and in the ocean. Prediction of future CO2 concentrations relies critically on the understanding of these sources and sinks and their potential variability over time. While such understanding requires quantifi...

Laboratory precipitation experiments provide the basis for the common calibration of both the oxygen isotope and the clumped isotope thermometers. These focus on CaCO3 crystals that form deep in the bulk of the solution, often by the bubbling of N2(g) through a saturated Ca(HCO3)2 solution, following the classic experiments on McCrea (1950). Here w...

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 CO2 degassing from a thin film of water, leading to irreversible 13C enrichment and reversible 18O enrichment and Δ...

Significance Reconstructions of ancient high-latitude climates can help to constrain the amplification of global warming in polar environments. Climate models cannot reproduce the elevated high-latitude temperature estimates in the Eocene epoch, possibly indicating problems in simulating polar climate change. Widely divergent near-Antarctic Eocene...

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 freezin...

The reaction of CO2 hydration/dehydration controls the oxygen isotopic composition in both carbonate minerals and atmospheric CO2 through the exchange of oxygen isotopes with water. The use of delta O-18 as an environmental indicator typically assumes isotopic equilibrium, namely full oxygen isotope exchange between CO2 and water. Clumped isotopes...

The geochemical signature of many speleothems used for reconstruction of past continental climates is af-fected by kinetic isotope fractionation. This limits quanti-tative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clu...

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 (D47) is a novel paleotemperature proxy based on the temperature de...

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 seawate...

The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clump...

Insights into kinetic isotope fractionation in calcite using clumped isotopes in Devils Hole

Fluid inclusion (FI) stable isotopes and clumped isotopes thermometry provide powerful tools for reconstructing paleoclimates using speleothems. Clumped isotopes thermometry is a unique tool for paleotemperature determination using the mass 47 anomaly (Δ47), but its application to speleothems is complicated by the occurrence of a kinetic isotope ef...

Geochemical variations in shallow water corals provide a valuable archive of paleoclimatic information. However, biolog-ical effects can complicate the interpretation of these proxies, forcing their application to rely on empirical calibrations. Car-bonate clumped isotope thermometry (D 47) is a novel paleotemperature proxy based on the temperature...

Clumped isotopes geochemistry measures the thermodynamic preference of two heavy, rare, isotopes to bind with each other. This preference is temperature dependent, and is more pronounced at low temperatures. Carbonate clumped isotope values are independent of the carbonate δ 13 C and δ 18 O, making them independent of the carbon or oxygen compositi...

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 (Delta47) is a novel paleotemperature proxy based on the temperatur...

In many caves, speleothems δ18O deviate from the values expected for cave temperatures and drip water composition. These expected values are based on synthetic CaCO3 precipitation experiments1 that attempted to reflect isotopic equilibrium, although variations among precipitation experiments lead to uncertainties about non-equilibrium effects. Clum...

Accurate records of the distribution of sea surface temperatures (SSTs) during ancient greenhouse climates are critical for understanding global heat transport, global mean temperatures, and polar amplification of warming under elevated atmospheric CO2 concentrations. Recent proxy SST estimates from two Eocene high-latitude southern hemisphere site...

Many coral-based paleothermometers rely on empirical calibrations of aragonite δ18O or Sr/Ca with known sea surface temperature (SST). However, interpreting coral-based paleotemperature records is complicated by kinetic and biologic vital effects that may lead to significantly different empirical calibrations amongst corals of the same species at t...

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 tem-perature of formation of carbonate minerals. It is most powerful as an indicator of environmental paramet...

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 g...

The early Eocene (ca. 55-48 Ma) encompasses one of the warmest intervals of the past 65 m.y. and is characterized by an unusually low equator-to-pole thermal gradient. Recent proxy studies suggest temperatures well in excess of 30 degrees C even at high latitudes, but conflicting interpretations derived from different types of data leave considerab...

Analysis of multiply substituted isotopologues of molecules (‘clumped isotope geochemistry’) presents special challenges to both precision and accuracy. Previous discussions have focused on mass spectrometric precision for these rare species and intralaboratory reference frames. This discipline has spread, demanding interlaboratory standardization....

Carbonate clumped isotopes is a new paleothermometer based on the relative abundance of 13C-18O bonds in CaCO3 (Δ47). Being an internal property of the carbonate lattice, it provides a temperature estimate that is independent of the isotopic composition of the water in which the carbonate was formed. As such it is most relevant on land where the co...

Carbonate `clumped isotopes' reflect the formation temperatures of carbonates that are formed at thermodynamic equilibrium. However, kinetic isotope effects (KIE) are recognized in carbonates formed by CO2 degassing out of bicarbonate solution and are associated with the competition between the rate of degassing and the rate at which isotope equili...

The carbonate `clumped isotope' (Delta47) thermometer is based on the dependence of the abundance of 13C-18O bonds in carbonates on the carbonate formation temperature. We repeated at higher analytical precision the original thermometer calibration experiments of Ghosh et al., (2006) using carbonates precipitated synthetically by slow degassing of...

The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form the basis of carbonate clumped-isotope thermomet...

The stratospheric CO_2 oxygen isotope budget is thought to be governed primarily by the O(1D)+CO_2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO_2 isotopologue ^...

The stratospheric CO(2) oxygen isotope budget is thought to be governed primarily by the O((1)D)+CO(2) isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO(2) isotopolo...

The stable isotope composition of stratospheric CO_2 is a long-lived tracer of stratospheric photochemical processing. Although the stratospheric CO_2 isotopologue budget is thought to be governed primarily by the O(^1D)+CO_2 isotope exchange reaction, there is increasing evidence that other important physical processes may be occurring that standa...

The early Eocene climatic optimum (EECO, ~53 Ma) is the warmest interval of the Cenozoic. Recent studies suggest tropical sea surface temperatures (SSTs) well in excess of 30°C, even warmer than previous datasets had implied. If correct, these estimates carry implications for Earth's current warming trend. Conflicting interpretations of data from p...

Atmospheric CO2 mixing ratios and C and O isotopic compositions are reported for the Los Angeles basin in southern California, a region renowned for its air pollution. Air samples collected midday on the Caltech campus in Pasadena, California, contained ∼30 ppm more CO2 in 1998–2003 than in 1972–1973 (averaging 397 ppm in 1998–2003 and 366 ppm in 1...

The stable isotope composition of Stratospheric CO2 is a long-lived tracer of Stratospheric photochemical processing. Measurements of its composition constrain a variety of problems associated with the atmospheric budget of CO2, such as Stratosphere-Troposphere exchange and transport. We report a strong meridional variation in the proportion of 13C...

‘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 R47 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 clumped isotope thermometry is based on a homogeneous thermodynamic equilibrium that orders ^(13)C and ^(18)O into bonds with each other within the carbonate lattice. To improve understanding of this new geothermometer and advance its application to natural environments, we present here theoretical predictions of the equilibrium and kinet...

‘Clumped isotopes’ data (Δ_(47)) are based on abundance of ^(13)C-^(18)O bonds in the carbonate lattice or CO_2 molecules and reflects the temperature dependent thermodynamic preference of two heavy isotopes to create a chemical bond with each other.

Assuming that a given speleothem precipitates near thermodynamic equilibrium, quantitative interpretation of its ^(18)O record in terms of physical parameters is generally hampered by the lack of robust methods for separating isotopic variations due to paleo-temperatures and those reflecting source water composition. Moreover, in many settings it a...

Carbonate ‘clumped isotope’ thermometry can determine the growth temperatures of carbonate minerals based on their abundances of ^(13)C-^(18)O bonds, as reflected by the ‘Δ_(47)’ value of CO_2 extracted by phosphoric acid digestion. This method is precise (as good as ±1 °C), thermodynamically based, and independent of the δ^(18)O of water from whic...

The budget of atmospheric CO 2 is widely studied using records of temporal and spatial variations of concentrations, d 13 C and d 18 O 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...

The concentration of CO2 in air and its delta13C and delta18O are widely used to constrain fluxes to and from the atmosphere. However, the large number of sources and sinks prevent these alone from fully constraining the CO2 budget. We develop Delta47 as a new isotopic tracer, reflecting the abundance of mostly 13C18O16O. Delta47 is the deviation o...

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...

Variation in the C18OO content of atmospheric CO2 (delta18Oa) can be used to distinguish photosynthesis from soil respiration, which is based on carbonic anhydrase (CA)-catalyzed 18O exchange between CO2 and 18O-enriched leaf water (delta18Ow). Here we tested the hypothesis that mean leaf delta18Ow and assimilation rates can be used to estimate who...

Atmospheric carbon dioxide is widely studied using records of CO2 mixing ratio, δ13C and δ18O. However, the number and variability of sources and sinks prevents these alone from uniquely defining the budget. Carbon dioxide having a mass of 47 u (principally 13C18O16O) provides an additional constraint. In particular, the mass 47 anomaly (Δ47) can d...

CO2 concentration in air and its delta13C and delta18O values are used to constrain fluxes to and from the atmosphere. However, the large number of sources and sinks prevent these from fully constraining the budget. Molecules containing two rare isotopes potentially carry additional information. We examined CO2 having mass 47, mostly 13C18O16O, in...

Abundances of bonds between 13C and 18O in carbonate minerals are predicted to increase with decreasing temperature due to the isotope exchange equilibrium:13C16O3= + 12C18O16O2= = 13C18O16O2=+ 12C16O3=. We show that the abundance of the doubly substituted CO2 isotopologue, 13C18O16O, in CO2 produced by phosphoric acid digestion of calcite is corre...

Urey’s carbonate oxygen isotope paleothermometer is a milestone of paleoclimate research but constrains temperature only if the oxygen isotope composition of water from which carbonate grew is known. Moreover, difficulty in recognizing diagenetic overprinting has confounded the interpretation of carbonate oxygen isotope compositions for much of the...

Atmospheric CO2 is widely studied using records of concentration, delta 13C and delta 18O, although the number and variability of sources and sinks prevents these alone from uniquely defining the budget. CO2 of mass 47 (mainly 13C18O16O) provides an additional potential tracer, but little is known about its ability to differentiate among various bu...

Isoprene emission from leaves is dynamically coupled to photosynthesis through the use of primary and recent photosynthate in the chloroplast. However, natural abundance carbon isotope composition (delta(13)C) measurements in myrtle (Myrtus communis), buckthorn (Rhamnus alaternus), and velvet bean (Mucuna pruriens) showed that only 72% to 91% of th...

Isoprene (2-methyl-1,3-butadiene) protection against effects of singlet oxygen was investigated in Myrtus communis and Rhamnus alaternus. In M. communis, singlet oxygen produced in the leaves by Rose Bengal (RB) led to a 65% decrease in net assimilation rates within 3 h, whereas isoprene emission rates showed either a 30% decrease at ambient CO2 co...

Isoprene has an important effect on tropospheric chemistry and it constitutes up to several percent of the C fixed in photosynthesis. We present results of two recent studies: In the first, protection of photosynthesis against singlet oxygen was demonstrated. This is done by comparing the effect of singlet oxygen on net assimilation and isoprene em...

CO 2 profiles obtained along a 30-m-thick unsaturated zone under land irrigated with sewage effluents show two production regions: a seasonal one in the root zone and another, at steady state, near the water table (29 m). On an annual basis the CO 2 flux from the deep source toward the atmosphere (6.3 g C m 2 yr 1) is balanced by a similar influx o...