H. Elderfield

University of Cambridge, Cambridge, England, United Kingdom

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Publications (273)1183.77 Total impact

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    ABSTRACT: The Mg/Ca compositions of benthic foraminifera from the superfamily Miliolacea have been studied to explore the use of these high-Mg foraminifera as a proxy for deep ocean conditions. Taxonomic analyses, relative abundance, and depth distributions of different Miliolacea species were carried out on a collection of core-top samples, covering a depth range of 131 m to 2530 m, along the Australian coast of the Timor Sea. Pyrgo sp., comprised of Pyrgo sarsi and Pyrgo murrhina was found to be the most suitable for proxy studies. Mg/Ca values of this group of foraminifera show a strong correlation with bottom water temperatures and carbonate ion saturation described by the linear relationship: Mg/Ca = 2.53(±0.22) × BWT + 0.129(±0.023) × Δ[CO32-] + 4.63(±0.53), within the -1 °C to 8 °C temperature range. Absolute Mg/Ca values of Pyrgo sp. calcite and their temperature sensitivity are similar to those observed for inorganic calcite, suggesting that Mg composition of Pyrgo sp. calcite is mainly controlled by inorganic processes. The Mg/Ca composition of Pyrgo sp. calcite provides a new tool for reconstructing both water temperature and carbonate ion saturation when combined with other proxies for one of these parameters. A down-core record from the Eastern Equatorial Pacific has been generated to illustrate how Mg/Ca values can be used for palaeoclimate studies. This down-core record shows large changes in Pacific bottom waters [CO32-] across glacial-interglacial transition, implying an increase in [CO32-] during the glacial period.
    Paleoceanography. 09/2014;
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    ABSTRACT: We report a new method for HR-ICP-MS based accurate and precise B/Ca determination from low mass natural carbonates (≤ 5 µg CaCO3), utilizing a mixed acid matrix (0.1 M HNO3 & 0.3 M HF) and accurate matrix matching technique. Our procedural B/Ca blank of 2.0 ± 1.0 µmol/mol, internal precision ≤ 1.0%, average within run external precision ≤ 4.0% (2σ), and rapid sample analysis (60 samples per day) make the method well suited for routine measurements. Established methods of B/Ca determination require ≥ 65 µg CaCO3 to achieve a comparable external precision of 3.5% (2σ). We report a B/Ca detection limit of 2 µmol/mol compared to ≥ 10 µmol/mol for previous methods, a five-fold improvement. The method presented here can determine a wide range of B/Ca (9.0 - 250 µmol/mol) in mass limited samples with considerable tolerance for matrix matching efficiency (≤ ± 30%). The long-term reproducibility of B/Ca measured on Cambridge in-house consistency standards containing < 20, ~85, and ~200 µmol/mol of B/Ca are ± 3.7% (2σ, n = 100), ± 3.9% (2σ, n = 150), and ± 3.2% (2s, n =180) respectively. A host of other trace element to Ca ratios can also be determined at comparable external precision from samples containing ≤ 5 µg CaCO3. This method is suitable for trace element analysis of single foraminifera shells.
    Geochemistry Geophysics Geosystems 01/2014; · 2.94 Impact Factor
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    ABSTRACT: We present an improved method for accurate and precise determination of the boron isotopic composition (11B/10B) of carbonate and water samples using a mineral acid matrix and HR-ICP-MS. Our method for δ11B determination utilizes a micro-distillation based boron purification technique for both carbonate and seawater matrices. The micro-distillation method is characterized by low blank (⩽0.01 ng-B) and 99.8 ± 5.7% boron recovery. We also report a new ICP-MS method, performed in a hydrofluoric acid matrix, using a jet interface fitted Thermo® Element XR that consumes <3.0 ng-B per quintuplicate analyses (±0.5‰, 2σ, n = 5). A comparatively high matrix tolerance limit of ⩽50 ppb Na/K/Mg/Ca characterizes our ICP-MS method. With an extremely low procedural blank (⩽0.05 ± 0.01 ng-B) the present isotope method is optimized for rapid (∼25 samples per session) analysis of small masses of carbonates (foraminifera, corals) with low boron abundance and small volume water samples (seawater, porewater, river water). Our δ11B estimates of seawater (39.8 ± 0.5‰, 2σ, n = 30); SRM AE-120 (−20.2 ± 0.5‰, 2s, n = 33); SRM AE-121 (19.8 ± 0.4‰, 2s, n = 16); SRM AE-122 (39.6 ± 0.5‰, 2s, n = 16) are within analytical uncertainty of published values. We apply this new method to assess the impacts of laboratory handling induced sample contamination and seawater physio-chemical parameters (temperature, pH, and salinity) on marine carbonate bound δ11B by analyzing core-top planktonic foraminifera samples.
    Geochimica et Cosmochimica Acta 01/2014; 140:531–552. · 3.88 Impact Factor
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    ABSTRACT: A record of deep sea calcite saturation (Δ[CO32-]), derived from X-ray Computed Tomography based foraminifer dissolution index, XDX, was constructed for the past 150 ka for a core from the deep (4,157 m) tropical western Indian Ocean. G. sacculifer and N. dutertrei recorded a similar dissolution history, consistent with the process of calcite compensation. Peaks in calcite saturation (~15 µmol/kg higher than the present day value) occurred during deglaciations and early in MIS 3. Dissolution maxima coincided with transitions to colder stages. The mass record of G. sacculifer better indicated preservation than did that of N. dutertrei or G. ruber. Dissolution-corrected Mg/Ca-derived SST records, like other SST records from marginal Indian Ocean sites, showed coolest temperatures of the last 150 ka in early MIS 3, when mixed layer temperatures were ~4 oC lower than present SST. Temperatures recorded by N. dutertrei showed the thermocline to be ~4 oC colder in MIS 3 compared to the Holocene (8 ka BP).
    Geochemistry Geophysics Geosystems 01/2014; · 2.94 Impact Factor
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    ABSTRACT: Changes in the Sr to Ca ratio of sea water have important implications for the interpretation of past climate. It has proven difficult to interpret Sr/Ca of foraminiferal calcite as a measure of seawater Sr/Ca or as reflecting the influence of deep water carbonate ion saturation (Δ[CO32−]) on the incorporation of Sr into benthic foraminiferal carbonate. Here, we address this issue by measurements of paired benthic foraminiferal Sr/Ca and B/Ca (a proxy for deep water Δ[CO32−]) for core-tops from the global ocean and three down cores at different settings during the Last Glacial–interglacial cycle. These new data suggest a significant control of deep water Δ[CO32−] on benthic foraminiferal Sr/Ca, and that down-core shell Sr/Ca variations can be largely accounted for by past deep water Δ[CO32−] changes. We conclude that seawater Sr/Ca has likely remained near-constant on glacial–interglacial timescales during the late Pleistocene, in agreement with model results. With due caution, benthic Sr/Ca may be used as an auxiliary proxy for deep water Δ[CO32−] if seawater Sr/Ca is constant.
    Quaternary Science Reviews 01/2014; 98:1–6. · 4.57 Impact Factor
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    ABSTRACT: The Mg/Ca ratio of foraminiferal calcite is a widely accepted and applied empirical proxy for ocean temperature. The analysis of foraminifera preserved in ocean sediments has been instrumental in developing our understanding of global climate, but the mechanisms behind the proxy are largely unknown. Analogies have been drawn to the inorganic precipitation of calcite, where the endothermic substitution of Mg for Ca is favoured at higher temperatures. However, evidence suggests that foraminiferal Mg incorporation may be more complex: foraminiferal magnesium is highly heterogeneous at the sub-micron scale, and high Mg areas coincide with elevated concentrations of organic molecules, Na, S and other trace elements. Fundamentally, the incorporation mode of Mg in foraminifera is unknown. Here we show that Mg is uniformly substituted for Ca within the calcite mineral lattice. The consistency of Mg-specific X-ray spectra gathered from nano-scale regions across the shell ('test') reveals that the coordination of Mg is uniform. The similarity of these spectra to that produced by dolomite shows that Mg is present in an octahedral coordination, ideally substituted for Ca in a calcite crystal structure. This demonstrates that Mg is heterogeneous in concentration, but not in structure. The degree of this uniformity implies the action of a continuous Mg incorporation mechanism, and therefore calcification mechanism, across these compositional bands in foraminifera. This constitutes a fundamental step towards a mechanistic understanding of foraminiferal calcification processes and the incorporation of calcite-bound palaeoenvironment proxies, such as Mg.
    Earth and Planetary Science Letters 12/2013; · 4.72 Impact Factor
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    ABSTRACT: The El Niño-Southern Oscillation (ENSO) is one of the most important components of the global climate system, but its potential response to an anthropogenic increase in atmospheric CO2 remains largely unknown. One of the major limitations in ENSO prediction is our poor understanding of the relationship between ENSO variability and long-term changes in Tropical Pacific oceanography. Here we investigate this relationship using palaeorecords derived from the geochemistry of planktonic foraminifera. Our results indicate a strong negative correlation between ENSO variability and zonal gradient of sea-surface temperatures across the Tropical Pacific during the last 22 ky. This strong correlation implies a mechanistic link that tightly couples zonal sea-surface temperature gradient and ENSO variability during large climate changes and provides a unique insight into potential ENSO evolution in the future by suggesting enhanced ENSO variability under a global warming scenario.
    Nature Communications 11/2013; 4:2692. · 10.02 Impact Factor
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    ABSTRACT: This Discussion Meeting Issue of the Philosophical Transactions A had its genesis in a Discussion Meeting of the Royal Society which took place on 10-11 October 2011. The Discussion Meeting, entitled 'Warm climates of the past: a lesson for the future?', brought together 16 eminent international speakers from the field of palaeoclimate, and was attended by over 280 scientists and members of the public. Many of the speakers have contributed to the papers compiled in this Discussion Meeting Issue. The papers summarize the talks at the meeting, and present further or related work. This Discussion Meeting Issue asks to what extent information gleaned from the study of past climates can aid our understanding of future climate change. Climate change is currently an issue at the forefront of environmental science, and also has important sociological and political implications. Most future predictions are carried out by complex numerical models; however, these models cannot be rigorously tested for scenarios outside of the modern, without making use of past climate data. Furthermore, past climate data can inform our understanding of how the Earth system operates, and can provide important contextual information related to environmental change. All past time periods can be useful in this context; here, we focus on past climates that were warmer than the modern climate, as these are likely to be the most similar to the future. This introductory paper is not meant as a comprehensive overview of all work in this field. Instead, it gives an introduction to the important issues therein, using the papers in this Discussion Meeting Issue, and other works from all the Discussion Meeting speakers, as exemplars of the various ways in which past climates can inform projections of future climate. Furthermore, we present new work that uses a palaeo constraint to quantitatively inform projections of future equilibrium ice sheet change.
    Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 10/2013; 371(2001):20130146. · 2.89 Impact Factor
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    ABSTRACT: 1] An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for the perturbed AMOC, possibly aiding its return to full strength. Our finding points to the Indian-to-Atlantic salt transport as a potentially important modulator of the AMOC during the abrupt climate changes of the Late Pleistocene.
    Paleoceanography 09/2013; · 3.30 Impact Factor
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    ABSTRACT: 1] An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for the perturbed AMOC, possibly aiding its return to full strength. Our finding points to the Indian-to-Atlantic salt transport as a potentially important modulator of the AMOC during the abrupt climate changes of the Late Pleistocene.
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    ABSTRACT: 1] An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for the perturbed AMOC, possibly aiding its return to full strength. Our finding points to the Indian-to-Atlantic salt transport as a potentially important modulator of the AMOC during the abrupt climate changes of the Late Pleistocene. (2013), Agulhas salt-leakage oscillations during abrupt climate changes of the Late Pleistocene, Paleoceanography, 28, doi:10.1002/ palo.20038.
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  • Gaojun Li, Henry Elderfield
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    ABSTRACT: It is generally accepted that progressive cooling of global climate since the Late Cretaceous results from decreasing partial pressure of atmospheric CO2 (pCO2). However, details on how and why the carbon cycle evolved and how it would affect pCO2 have not been fully resolved. While the long-term decline of pCO2 might be caused by the decrease of volcanic degassing through the negative feedback between pCO2 and silicate weathering, seafloor spreading, the major control of CO2 degassing, seems to have remained relatively constant. Alternative explanation, known as ‘uplift driven climate change’ hypothesis, proposes that tectonic uplift may have enhanced the sink of atmospheric CO2 by silicate weathering, and thus produced the decline of pCO2. However, increasing weathering sink of CO2 could deplete atmosphere all of its CO2 within several million years while holding volcanic outgassing constant. In this work, major fluxes of long-term carbon cycle are calculated based on a reverse model constrained by marine C, Sr and Os isotopic records and the spreading rate of sea floor. Weathering of island basalt and continental silicate rocks are separated in the new model. The results indicate a long-term decline of island basalt weathering in consistent with the global cooling trend over the past 100 million years. Dramatic changes of the CO2 fluxes associated continental silicate weathering, reverse weathering, volcanic degassing and the growth of organic carbon reservoir have been observed. Disturbance of atmospheric CO2 cycle by these fluxes seems to be maintained by the concomitant adjustments of island basalt weathering that were sensitive to the pCO2 controlled environment factors such as temperature and runoff. The negative feedbacks between pCO2 and weathering of island basalt might have played a significant role in stabilizing the long-term carbon cycle.
    Geochimica et Cosmochimica Acta 02/2013; 103:11–25. · 3.88 Impact Factor
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    ABSTRACT: Ocean acidification due to rising atmospheric CO2 is expected to affect the physiology of important calcifying marine organisms, but the nature and magnitude of change is yet to be established. In coccolithophores, different species and strains display varying calcification responses to ocean acidification, but the underlying biochemical properties remain unknown. We employed an approach combining tandem mass-spectrometry with isobaric tagging (iTRAQ) and multiple database searching to identify proteins that were differentially expressed in cells of the marine coccolithophore species Emiliania huxleyi (strain NZEH) between two CO2 conditions: 395 (∼current day) and ∼1340 p.p.m.v. CO2. Cells exposed to the higher CO2 condition contained more cellular particulate inorganic carbon (CaCO3) and particulate organic nitrogen and carbon than those maintained in present-day conditions. These results are linked with the observation that cells grew slower under elevated CO2, indicating cell cycle disruption. Under high CO2 conditions, coccospheres were larger and cells possessed bigger coccoliths that did not show any signs of malformation compared to those from cells grown under present-day CO2 levels. No differences in calcification rate, particulate organic carbon production or cellular organic carbon: nitrogen ratios were observed. Results were not related to nutrient limitation or acclimation status of cells. At least 46 homologous protein groups from a variety of functional processes were quantified in these experiments, of which four (histones H2A, H3, H4 and a chloroplastic 30S ribosomal protein S7) showed down-regulation in all replicates exposed to high CO2, perhaps reflecting the decrease in growth rate. We present evidence of cellular stress responses but proteins associated with many key metabolic processes remained unaltered. Our results therefore suggest that this E. huxleyi strain possesses some acclimation mechanisms to tolerate future CO2 scenarios, although the observed decline in growth rate may be an overriding factor affecting the success of this ecotype in future oceans.
    PLoS ONE 01/2013; 8(4):e61868. · 3.73 Impact Factor
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    ABSTRACT: The Mg/Ca ratio in foraminiferal calcite is one of the principal proxies used for paleoceanographic temperature recon-structions, but recent core-top sediment observations suggest that salinity may exert a significant secondary control on plank-tic foraminifers. This study compiles new and published laboratory culture experiment data from the planktic foraminifers Orbulina universa, Globigerinoides sacculifer and Globigerinoides ruber, in which salinity was varied but temperature, pH and light were held constant. Combining new data with results from previous culture studies yields a Mg/Ca-sensitivity to salinity of 4.4 ± 2.3%, 4.7 ± 1.2%, and 3.3 ± 1.7% per salinity unit (95% confidence), respectively, for the three foraminifer species studied here. Comparison of these sensitivities with core-top data suggests that the much larger sensitivity (27 ± 4% per salinity unit) derived from Atlantic core-top sediments in previous studies is not a direct effect of salinity. Rather, we suggest that the dissolution correction often applied to Mg/Ca data can lead to significant overestimation of tem-peratures. We are able to reconcile culture calibrations with core-top observations by combining evidence for seasonal occur-rence and latitude-specific habitat depth preferences with corresponding variations in physico-chemical environmental parameters. Although both Mg/Ca and d 18 O yield temperature estimates that fall within the bounds of hydrographic obser-vations, discrepancies between the two proxies highlight unresolved challenges with the use of paired Mg/Ca and d 18 O anal-yses to reconstruct paleo-salinity patterns across ocean basins. The first step towards resolving these challenges requires a better spatially and seasonally resolved d 18 O sw archive than is currently available. Nonetheless, site-specific reconstructions of salinity change through time may be valid.
    Geochimica et Cosmochimica Acta 01/2013; 121:196-213. · 3.88 Impact Factor
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    ABSTRACT: Salinity increase in the subtropical gyre system may have pre-conditioned the North Atlantic Ocean for a rapid return to stronger overturning circulation and high-latitude warming following meltwater events during the Last Glacial period. Here we investigate the Gulf Stream – subtropical gyre system properties over Dansgaard–Oeschger (DO) cycles 14 to 12, including Heinrich ice-rafting event 5. During the Holocene and Last Glacial Maximum a positive gradient in surface dwelling planktonic foraminifera δ18O (Globigerinoides ruber) can be observed between the Gulf Stream and subtropical gyre, due to decreasing temperature, increasing salinity, and a change from summer to year-round occurrence of G. ruber. We assess whether this gradient was a common feature during stadial-interstadial climate oscillations of Marine Isotope Stage 3, by comparing existing G. ruber δ18O from ODP Site 1060 (subtropical gyre location) and new data from ODP Site 1056 (Gulf Stream location) between 54 and 46 ka. Our results suggest that this gradient was largely absent during the period studied. During the major warm DO interstadials 14 and 12 we infer a more zonal and wider Gulf Stream, influencing both ODP Sites 1056 and 1060. A Gulf Stream presence during these major interstadials is also suggested by the large vertical δ18O gradient between shallow dwelling planktonic foraminifera species, especially G. ruber, and the deep dwelling species Globorotalia inflata at site 1056, which we associate with strong summer stratification and Gulf Stream presence. A major reduction in this vertical δ18O gradient from 51 ka until the end of Heinrich event 5 at 48.5 ka suggests site 1056 was situated within the subtropical gyre in this mainly cold period, from which we infer a migration of the Gulf Stream to a position nearer to the continental shelf, indicative of a narrower Gulf Stream with possibly reduced transport.
    Quaternary Science Reviews 01/2013; 81:105–113. · 4.57 Impact Factor
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    ABSTRACT: Neodymium isotopes are becoming widely used as a palaeoceanographic tool for reconstructing the source and flow direction of water masses. A new method using planktonic foraminifera which have not been chemically cleaned has proven to be a promising means of avoiding contamination of the deep ocean palaeoceanographic signal by detrital material. However, the exact mechanism by which the Nd isotope signal from bottom waters becomes associated with planktonic foraminifera, the spatial distribution of rare earth element (REE) concentrations within the shell, and the possible mobility of REE ions during changing redox conditions, have not been fully investigated. Here we present REE concentration and Nd isotope data from mixed species of planktonic foraminifera taken from plankton tows, sediment traps and a sediment core from the NW Atlantic. We used multiple geochemical techniques to evaluate how, where and when REEs become associated with planktonic foraminifera as they settle through the water column, reside at the surface and are buried in the sediment.Analyses of foraminifera shells from plankton tows and sediment traps between 200 and 2938 m water depth indicate that only ∼20% of their associated Nd is biogenically incorporated into the calcite structure. The remaining 80% is associated with authigenic metal oxides and organic matter, which form in the water column, and remain extraneous to the carbonate structure. Remineralisation of these organic and authigenic phases releases ions back into solution and creates new binding sites, allowing the Nd isotope ratio to undergo partial equilibration with the ambient seawater, as the foraminifera fall through the water column.Analyses of fossil foraminifera shells from sediment cores show that their REE concentrations increase by up to 10-fold at the sediment–water interface, and acquire an isotopic signature of bottom water. Adsorption and complexation of REE3+ ions between the inner layers of calcite contributes significantly to elevated REE concentrations in foraminifera. The most likely source of REE ions at this stage of enrichment is from bottom waters and from the remineralisation of oxide phases which are in chemical equilibrium with the bottom waters.As planktonic foraminifera are buried below the sediment–water interface redox-sensitive ion concentrations are adjusted within the shells depending on the pore-water oxygen concentration. The concentration of ions which are passively redox sensitive, such as REE3+ ions, is also controlled to some extent by this process. We infer that (a) the Nd isotope signature of bottom water is preserved in planktonic foraminifera and (b) that it relies on the limited mobility of particle reactive REE3+ ions, aided in some environments by micron-scale precipitation of MnCO3.This study indicates that there may be sedimentary environments under which the bottom water Nd isotope signature is not preserved by planktonic foraminifera. Tests to validate other core sites must be carried out before downcore records can be used to interpret palaeoceanographic changes.
    Geochimica et Cosmochimica Acta 10/2012; 94:57–71. · 3.88 Impact Factor
  • Rene Boiteau, Mervyn Greaves, Henry Elderfield
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    ABSTRACT: The rate of uranium accumulation in oceanic sediments from seawater is controlled by bottom water oxygen concentrations and organic carbon fluxes—two parameters that are linked to deep ocean storage of CO2. To investigate glacial-interglacial changes in what is known as authigenic U, we have developed a rapid method for its determination as a simple addition to a procedure for foraminiferal trace element analysis. Foraminiferal calcite acts as a low U substrate (U/Ca < 15 nmol/mol) upon which authigenic U accumulates in reducing sediments. We measured a downcore record of foraminiferal U/Ca from ODP Site 1090 in the South Atlantic and found that U/Ca ratios increase by 70-320 nmol/mol during glacial intervals. There is a significant correlation between U/Ca records of benthic and planktonic foraminiferal species and between U/Ca and bulk sediment authigenic U. These results indicate that elevated U/Ca ratios are attributable to the accumulation of authigenic U coatings in sediments. Foraminiferal Mn/Ca ratios were lower during the glacial intervals, suggesting that the observed U accumulation on the shells is not directly linked to U incorporation into secondary manganese phases. Thus, foraminiferal U/Ca ratios may provide useful information on past changes in sediment redox conditions.
    Paleoceanography 09/2012; 27(3):3227-. · 3.30 Impact Factor
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    ABSTRACT: Earth's climate underwent a fundamental change between 1250 and 700 thousand years ago, the mid-Pleistocene transition (MPT), when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing. Over this time, an increase occurred in the amplitude of change of deep-ocean foraminiferal oxygen isotopic ratios, traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep-ocean temperature. We have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios. Our results suggest that the MPT was initiated by an abrupt increase in Antarctic ice volume 900 thousand years ago. We see no evidence of a pattern of gradual cooling, but near-freezing temperatures occur at every glacial maximum.
    Science 08/2012; 337(6095):704-9. · 31.20 Impact Factor

Publication Stats

9k Citations
1,183.77 Total Impact Points

Institutions

  • 1985–2014
    • University of Cambridge
      • Department of Earth Sciences
      Cambridge, England, United Kingdom
  • 1987–2006
    • Woods Hole Oceanographic Institution
      • Department of Marine Chemistry and Geochemistry
      Falmouth, MA, United States
  • 2003
    • Cardiff University
      • School of Earth and Ocean Sciences
      Cardiff, Wales, United Kingdom
  • 2002
    • Universität Bremen
      • MARUM - Center for Marine Environmental Sciences
      Bremen, Bremen, Germany
  • 1996
    • Hebrew University of Jerusalem
      Yerushalayim, Jerusalem District, Israel
  • 1995
    • University of Southampton
      Southampton, England, United Kingdom
  • 1992
    • University of the Ryukyus
      Okinawa, Okinawa, Japan
  • 1984
    • Dalhousie University
      Halifax, Nova Scotia, Canada
  • 1978–1982
    • University of Leeds
      Leeds, England, United Kingdom