Weifu Guo

Woods Hole Oceanographic Institution | WHOI · Department of Geology and Geophysics

Traditional bulk stable isotope (δ18O and δ13C) and clumped isotope (Δ47) records from bivalve shells provide invaluable histories of Earth's local and global climate change. However, biologically driven isotopic fractionations (BioDIFs) can overprint primary environmental signals in the shell. Here, we explore how conventional measurements of δ18O...

The stable (δ¹⁸O and δ¹³C) and clumped (Δ47) isotope compositions of coral carbonate are valuable archives for paleoclimate reconstructions. However, the Δ47-temperature relationships of warm and cold-water corals deviate from that of inorganic carbonate precipitated at equilibrium. Dual clumped isotope thermometry of carbonates (i.e., simultaneous...

The Δ47 (paleo)thermometer has opened a new avenue to determine carbonate formation temperatures independent of the oxygen isotopic composition of the fluid from which the carbonate crystallized. A major limitation of this thermometer is related to kinetic effects if homogeneous isotopic equilibrium is not attained during carbonate precipitation. D...

The Δ47 (paleo)thermometer has opened a new avenue to determine carbonate formation temperatures independent of the oxygen isotopic composition of the fluid the carbonate crystallized from. A major limitation of this thermometer is introduced by kinetic effects, i.e if homogeneous isotopic equilibrium is not attained within the precipitated carbona...

Coral resilience to ocean acidification is largely determined by the degree of physiological control corals can exert on their calcifying fluid carbonate chemistry. In this study, the boron isotopic composition (δ11B) of a Porites colony growing on a reef flat on Kiritimati Island in the equatorial central Pacific is examined to quantify the sensit...

Plain Language Summary Measurable anthropogenic‐induced acidification of the oceans (OA) has occurred over the last four decades. But its impact on coral reef ecosystems, such as coral calcification, has yet to be unambiguously demonstrated. This problem with detection and attribution of OA impacts is due, in large part, to the fact that multiple c...

Surface temperature is a fundamental parameter of Earth's climate. Its evolution through time is commonly reconstructed using the oxygen isotope and the clumped isotope compositions of carbonate archives. However, reaction kinetics involved in the precipitation of carbonates can introduce inaccuracies in the derived temperatures. Here, we show that...

High-precision analysis of the excess abundance (relative to the stochastic distribution) of m/z 48 isotopologues in CO2 evolved from acid digestion of carbonates (∆48) has not been possible until recently due to the relatively low natural abundance of 18O. The 253 Plus™ gas source mass spectrometer equipped with Faraday cups and 1013 Ω resistors h...

The carbonate clumped isotope thermometer, is a powerful tool in paleoclimate and paleoceanography research, because it constrains carbonate formation temperature based on the extent of 13C and 18O clumping within the carbonate lattice (Δ47) and thus does not require knowledge of the isotopic composition of the water from which carbonates precipita...

Stable isotope composition of speleothems reflects the physicochemical condition of their formation environment such as the local temperature and the isotope composition of surface precipitation, making them one of the best archives of terrestrial climate. However, quantitative reconstruction of paleo-temperature from speleothem isotope records is...

Scleractinian corals promote the precipitation of their carbonate skeleton by elevating the pH and dissolved inorganic carbon (DIC) concentration of their calcifying fluid above that of seawater. The fact corals actively regulate their calcifying fluid chemistry implies the potential for acclimation to ocean acidification. However, the extent to wh...

Carbonate clumped isotope (Δ47) thermometer constrains carbonate formation temperature based on the abundance anomalies of 13C-18O bonds within carbonate minerals, and represents a major advance over the conventional carbonate-water oxygen isotope thermometer because it does not require knowledge of the isotope composition of the water from which c...

Triple oxygen isotope composition of carbonate minerals reflects the isotope composition of the water from which carbonates precipitate, and is emerging as a promising proxy for constraining past changes in Earth hydroclimate and surface environment. However, quantitative interpretation of this proxy is not straightforward when carbonate minerals d...

Significance Ocean acidification (OA) threatens coral reef futures by reducing the concentration of carbonate ions that corals need to construct their skeletons. However, quantitative predictions of reef futures under OA are confounded by mixed responses of corals to OA in experiments and field observations. We modeled the skeletal growth of a domi...

Elemental composition of benthic foraminifera tests reflects the physicochemical condition of the seawater in which foraminifera live. This forms the basis of many paleoclimate and paleoceanography proxies. Particularly, Mg/Ca and Mg/Li ratios of benthic foraminifera tests (e.g. Uvigerina, C. pachyderma, H. elegans) have shown great potential for r...

We present theoretical calculations for all three isotope ratios of sulfur (33S/32S, 34S/32S, 36S/32S) at the B3LYP/6-31+G(d,p) level of theory for aqueous sulfur compounds modeled in 30-40 H2O clusters spanning the range of sulfur oxidation state (Sn, n = -2 to +6) for estimating equilibrium fractionation factors in aqueous systems. Computed 34β v...

Carbonate formation at hyperalkaline springs is typical of serpentinization in peridotite massifs worldwide. These travertines have long been known to exhibit large variations in their carbon and oxygen isotope compositions, extending from apparent equilibrium values to highly depleted values. However, the exact causes of these variations are not w...

The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonat...

Significance We provide biogeochemical, micropaleontological, and petrological constraints on a subseafloor habitat at the passive Iberia Margin, where mixing of reduced hydrothermal serpentinization fluids with oxic seawater provided the energy and substrates for metabolic reactions. This mixing zone was inhabited by bacteria and archaea and is co...

Changes in the formation of dense water in the Arctic Ocean and Nordic Seas [the "Arctic Mediterranean" (AM)] probably contributed to the altered climate of the last glacial period. We examined past changes in AM circulation by reconstructing radiocarbon ventilation ages of the deep Nordic Seas over the past 30,000 years. Our results show that the...

Stable isotopes record the evolution of planetary systems, beginning with stars coalescing from molecular clouds, followed by the nucleosynthesis of elements in stars, and proceeding to the accretion and differentiation of planets. Current stable isotope measurements range in scale from isotopic mapping of the Milky Way Galaxy with spectrographs on...

Volatile methylated sulfur compounds emitted from terrestrial and aquatic ecosystems play a significant role in the global sulfur cycle, yet no satisfactory methods are available to trace their source and transformation in natural systems. Here we present a method for quantification and multiple sulfur isotopic analysis of a variety of volatile sul...

Coupled fractionations of N and O isotopes during biological nitrate reduction provide important constraints on the marine nitrogen cycle at present and in the geologic past. Recent laboratory experiments with mono-cultures of nitrate-assimilative algae and plankton, and denitrifying bacteria demonstrate that N and O isotopic compositions of the re...

Phosphoric acid digestion has been used for oxygen- and carbon-isotope analysis of carbonate minerals since 1950, and was recently established as a method for carbonate ‘clumped isotope’ analysis. The CO_2 recovered from this reaction has an oxygen isotope composition substantially different from reactant carbonate, by an amount that varies with te...

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...

Deep-sea corals are a unique archive in paleoceanography. They have large banded skeletons that allow for high resolution records and have a high uranium content allowing for accurate calendar ages independent of radiocarbon age measurements. However, their use as a paleoceanographic archive is complicated by the fact that the bulk isotope and trac...

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...

Many biogenic carbonates exhibit correlated depletions in δ18O and δ13C relative to the compositions expected for isotopic equilibrium with ambient waters and dissolved inorganic carbon (DIC). Such ‘vital effects’ complicate the use of biogenic carbonates in paleoclimate studies, particularly efforts to quantify carbonate growth temperature using c...

'Clumped isotope' thermometry of carbonates in the carbonaceous chondrites (CM, CI, CR and Tagish Lake) demonstrates that aqueous alteration of their parent bodies occurred from -31 to 71°C and involved reaction with fluids having δ¹⁸O_VSMOW values of -29.7‰ to 11.8‰ and δ¹⁷O_VSMOW of -14.9‰ to 7.6‰. Estima...

Several disciplines of geochemistry demand ppm-level precision in isotope ratio measurements (e.g., ^(142)Nd excesses in ancient terrestrial rocks; δ^(15)N in air from ice cores). ‘Clumped isotope’ geochemistry (the study of molecules containing more than one rare isotope) is one such field that presents several unusual analytical challenges, the s...

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...

Aqueous alteration of primitive meteorites was among the earliest geological processes during the evolution of our solar system. ‘Clumped-isotope’ thermometry of carbonates in the CM chondrites, Cold Bokkeveld, Murray, and Murchison, demonstrates that they underwent aqueous alteration at 20–71 °C from a fluid with δ18OVSMOW of 2.0‰ to 8.1‰ and δ17O...

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...

Despite its low average mixing ratio (70-100 ppbv), carbon monoxide plays an important role in atmospheric chemistry. It is the major sink of OH radicals, and thus strongly influences the oxidizing capacity of the atmosphere, and the lifetimes of many other atmospheric trace gases (e.g., methane, NHMCs and HCFCs). At present, the budget of atmosphe...