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  1. Article ; Online: Reconciling atmospheric CO

    Komar, Nemanja / Zeebe, Richard E

    Science advances

    2021  Volume 7, Issue 4

    Abstract: The Cenozoic era (66 to 0 million years) is marked by long-term aberrations in carbon cycling and large climatic shifts, some of which challenge the current understanding of carbon cycle dynamics. Here, we investigate possible mechanisms responsible for ... ...

    Abstract The Cenozoic era (66 to 0 million years) is marked by long-term aberrations in carbon cycling and large climatic shifts, some of which challenge the current understanding of carbon cycle dynamics. Here, we investigate possible mechanisms responsible for the observed long-term trends by using a novel approach that features a full-fledged ocean carbonate chemistry model. Using a compilation of pCO
    Language English
    Publishing date 2021-01-22
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2810933-8
    ISSN 2375-2548 ; 2375-2548
    ISSN (online) 2375-2548
    ISSN 2375-2548
    DOI 10.1126/sciadv.abd4876
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Solar System chaos and the Paleocene-Eocene boundary age constrained by geology and astronomy.

    Zeebe, Richard E / Lourens, Lucas J

    Science (New York, N.Y.)

    2019  Volume 365, Issue 6456, Page(s) 926–929

    Abstract: Astronomical calculations reveal the Solar System's dynamical evolution, including its chaoticity, and represent the backbone of cyclostratigraphy and astrochronology. An absolute, fully calibrated astronomical time scale has hitherto been hampered ... ...

    Abstract Astronomical calculations reveal the Solar System's dynamical evolution, including its chaoticity, and represent the backbone of cyclostratigraphy and astrochronology. An absolute, fully calibrated astronomical time scale has hitherto been hampered beyond ~50 million years before the present (Ma) because orbital calculations disagree before that age. Here, we present geologic data and a new astronomical solution (ZB18a) showing exceptional agreement from ~58 to 53 Ma. We provide a new absolute astrochronology up to 58 Ma and a new Paleocene-Eocene boundary age (56.01 ± 0.05 Ma). We show that the Paleocene-Eocene Thermal Maximum (PETM) onset occurred near a 405-thousand-year (kyr) eccentricity maximum, suggesting an orbital trigger. We also provide an independent PETM duration (170 ± 30 kyr) from onset to recovery inflection. Our astronomical solution requires a chaotic resonance transition at ~50 Ma in the Solar System's fundamental frequencies.
    Language English
    Publishing date 2019-08-26
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.aax0612
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Time-dependent climate sensitivity and the legacy of anthropogenic greenhouse gas emissions.

    Zeebe, Richard E

    Proceedings of the National Academy of Sciences of the United States of America

    2013  Volume 110, Issue 34, Page(s) 13739–13744

    Abstract: Climate sensitivity measures the response of Earth's surface temperature to changes in forcing. The response depends on various climate processes that feed back on the initial forcing on different timescales. Understanding climate sensitivity is ... ...

    Abstract Climate sensitivity measures the response of Earth's surface temperature to changes in forcing. The response depends on various climate processes that feed back on the initial forcing on different timescales. Understanding climate sensitivity is fundamental to reconstructing Earth's climatic history as well as predicting future climate change. On timescales shorter than centuries, only fast climate feedbacks including water vapor, lapse rate, clouds, and snow/sea ice albedo are usually considered. However, on timescales longer than millennia, the generally higher Earth system sensitivity becomes relevant, including changes in ice sheets, vegetation, ocean circulation, biogeochemical cycling, etc. Here, I introduce the time-dependent climate sensitivity, which unifies fast-feedback and Earth system sensitivity. I show that warming projections, which include a time-dependent climate sensitivity, exhibit an enhanced feedback between surface warming and ocean CO2 solubility, which in turn leads to higher atmospheric CO2 levels and further warming. Compared with earlier studies, my results predict a much longer lifetime of human-induced future warming (23,000-165,000 y), which increases the likelihood of large ice sheet melting and major sea level rise. The main point regarding the legacy of anthropogenic greenhouse gas emissions is that, even if the fast-feedback sensitivity is no more than 3 K per CO2 doubling, there will likely be additional long-term warming from slow climate feedbacks. Time-dependent climate sensitivity also helps explaining intense and prolonged warming in response to massive carbon release as documented for past events such as the Paleocene-Eocene Thermal Maximum.
    MeSH term(s) Atmosphere/chemistry ; Carbon Dioxide/analysis ; Climate ; Feedback ; Global Warming/statistics & numerical data ; Greenhouse Effect/statistics & numerical data ; Models, Theoretical ; Oceans and Seas ; Temperature ; Time Factors
    Chemical Substances Carbon Dioxide (142M471B3J)
    Language English
    Publishing date 2013-08-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.1222843110
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  4. Article ; Online: Journal club. A physicist and biogeochemist gets a kick out of the problem of Brownian motion and diffusion.

    Zeebe, Richard E

    Nature

    2010  Volume 466, Issue 7310, Page(s) 1025

    Language English
    Publishing date 2010-08-26
    Publishing country England
    Document type Comment ; Journal Article
    ZDB-ID 120714-3
    ISSN 1476-4687 ; 0028-0836
    ISSN (online) 1476-4687
    ISSN 0028-0836
    DOI 10.1038/4661025e
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  5. Article: Long-term legacy of massive carbon input to the Earth system: Anthropocene versus Eocene.

    Zeebe, Richard E / Zachos, James C

    Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

    2013  Volume 371, Issue 2001, Page(s) 20120006

    Abstract: Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO2), a total of 5000 Pg C may enter the atmosphere, causing CO2 concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8(°)C and ... ...

    Abstract Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO2), a total of 5000 Pg C may enter the atmosphere, causing CO2 concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8(°)C and surface ocean pH to decline by approximately 0.7 units. A carbon release of this magnitude is unprecedented during the past 56 million years-and the outcome accordingly difficult to predict. In this regard, the geological record may provide foresight to how the Earth system will respond in the future. Here, we discuss the long-term legacy of massive carbon release into the Earth's surface reservoirs, comparing the Anthropocene with a past analogue, the Palaeocene-Eocene Thermal Maximum (PETM, approx. 56 Ma). We examine the natural processes and time scales of CO2 neutralization that determine the atmospheric lifetime of CO2 in response to carbon release. We compare the duration of carbon release during the Anthropocene versus PETM and the ensuing effects on ocean acidification and marine calcifying organisms. We also discuss the conundrum that the observed duration of the PETM appears to be much longer than predicted by models that use first-order assumptions. Finally, we comment on past and future mass extinctions and recovery times of biotic diversity.
    Language English
    Publishing date 2013-10-28
    Publishing country England
    Document type Journal Article
    ZDB-ID 208381-4
    ISSN 1471-2962 ; 1364-503X ; 0080-4614 ; 0264-3820 ; 0264-3952
    ISSN (online) 1471-2962
    ISSN 1364-503X ; 0080-4614 ; 0264-3820 ; 0264-3952
    DOI 10.1098/rsta.2012.0006
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  6. Article: On the molecular diffusion coefficients of dissolved CO₂,HCO₃ ⁻, and CO₃ ²⁻ and their dependence on isotopic mass

    Zeebe, Richard E

    Geochimica et cosmochimica acta. 2011 May 1, v. 75, no. 9

    2011  

    Abstract: The molecular diffusion coefficients of dissolved carbon dioxide (CO₂), bicarbonate ion (HCO₃ ⁻), and carbonate ion (CO₃ ²⁻) are fundamental physico-chemical constants and are of practical significance in various disciplines including geochemistry, ... ...

    Abstract The molecular diffusion coefficients of dissolved carbon dioxide (CO₂), bicarbonate ion (HCO₃ ⁻), and carbonate ion (CO₃ ²⁻) are fundamental physico-chemical constants and are of practical significance in various disciplines including geochemistry, biology, and medicine. Yet, very little experimental data is available, for instance, on the bicarbonate and carbonate ion diffusion coefficient. Furthermore, it appears that no information was hitherto available on the mass-dependence of the diffusion coefficients of the ionic carbonate species in water. Here I use molecular dynamics simulations to study the diffusion of the dissolved carbonate species in water, including their dependence on temperature and isotopic mass. Based on the simulations, I provide equations to calculate the diffusion coefficients of dissolved CO₂,HCO₃ ⁻, and CO₃ ²⁻ over the temperature range from 0° to 100°C. The results indicate a mass-dependence of CO₂ diffusion that is consistent with the observed ¹²CO₂/¹³CO₂ diffusion ratio at 25°C. No significant isotope fractionation appears to be associated with the diffusion of the naturally occurring isotopologues of HCO₃ ⁻ and CO₃ ²⁻ at 25°C.
    Keywords Biological Sciences ; bicarbonates ; carbon dioxide ; diffusivity ; dissolved carbon dioxide ; equations ; geochemistry ; isotope fractionation ; medicine ; molecular dynamics ; temperature
    Language English
    Dates of publication 2011-0501
    Size p. 2483-2498.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 300305-x
    ISSN 0016-7037
    ISSN 0016-7037
    DOI 10.1016/j.gca.2011.02.010
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  7. Article: No discernible effect of Mg²⁺ ions on the equilibrium oxygen isotope fractionation in the CO₂–H₂O system

    Uchikawa, Joji / Zeebe, Richard E

    Chemical geology. 2013 Apr. 8, v. 343

    2013  

    Abstract: Equilibrium oxygen isotope fractionation factors ( [Formula: see text] , [Formula: see text] and [Formula: see text] ) are fundamental geochemical parameters that characterize ¹⁸O partitioning in the CO₂–H₂O system. These constants were established in ... ...

    Abstract Equilibrium oxygen isotope fractionation factors ( [Formula: see text] , [Formula: see text] and [Formula: see text] ) are fundamental geochemical parameters that characterize ¹⁸O partitioning in the CO₂–H₂O system. These constants were established in laboratory experiments using deionized H₂O (e.g., Beck et al. (2005) and references therein). The applicability of these constants in environmental waters, including natural seawater, appears questionable due to potentially strong ionic interactions in such aqueous media. For instance, considerable portions of carbonate ions in seawater exist as cation–CO₃ ²⁻ ion complexes such as MgCO₃ ⁰. In this study, quantitative BaCO₃ precipitation experiments were performed to examine the effect of Mg²⁺ concentrations on the oxygen isotope equilibrium between dissolved inorganic carbon (DIC) species and H₂O. Our results from Mg²⁺-free control experiments in which BaCO₃ samples were precipitated from simple NaHCO₃ solutions were in good agreement with empirical results from three independent studies and with theoretical calculations. BaCO₃ precipitations from solutions with Mg²⁺ concentrations higher than 2.5mM caused intolerable quantities of Mg(OH)₂ co-precipitation, which interfered with δ¹⁸O measurements. Within the limit of 2.5mM of [Mg²⁺], the MgCO₃ ⁰ abundance in the total carbonate ions ([CO₃ ²⁻]T) and [DIC] was varied over approximately 0 to 40% and 0 to 36%, respectively, by manipulating solution chemistry. Despite such chemical treatment, there was no effect of Mg²⁺-addition on [Formula: see text] . These results suggest that the presence of Mg²⁺ in solutions has a negligible effect on the oxygen isotope equilibrium in the CO₂–H₂O system. In seawater, Mg²⁺ is the most important cation that forms complexes with CO₃ ²⁻. Hence, if our results also hold at higher [Mg²⁺] and higher ionic strength, they imply that the applicability of freshwater-based equilibrium fractionation factors is not compromised by ionic interactions in seawater.
    Keywords carbon ; chemical treatment ; ionic strength ; ions ; isotope fractionation ; isotopes ; laboratory experimentation ; magnesium ; oxygen ; seawater
    Language English
    Dates of publication 2013-0408
    Size p. 1-11.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 2179-9
    ISSN 0009-2541
    ISSN 0009-2541
    DOI 10.1016/j.chemgeo.2013.02.002
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  8. Article: The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO₂–H₂O system: Implications for δ¹⁸O vital effects in biogenic carbonates

    Uchikawa, Joji / Zeebe, Richard E

    Geochimica et cosmochimica acta. 2012 Oct. 15, v. 95

    2012  

    Abstract: Interpretations of the primary paleoceanographic information recorded in stable oxygen isotope values (δ¹⁸O) of biogenic CaCO₃ can be obscured by disequilibrium effects. CaCO₃ is often depleted in ¹⁸O relative to the δ¹⁸O values expected for ... ...

    Abstract Interpretations of the primary paleoceanographic information recorded in stable oxygen isotope values (δ¹⁸O) of biogenic CaCO₃ can be obscured by disequilibrium effects. CaCO₃ is often depleted in ¹⁸O relative to the δ¹⁸O values expected for precipitation in thermodynamic equilibrium with ambient seawater as a result of vital effects. Vital effects in δ¹⁸O have been explained in terms of the influence of fluid pH on the overall δ¹⁸O of the sum of dissolved inorganic carbon (DIC) species (often referred to as “pH model”) and in terms of ¹⁸O depletion as a result of the kinetic effects associated with CO₂ hydration (CO₂+H₂O↔H₂CO₃↔HCO₃ ⁻+H⁺) and CO₂ hydroxylation (CO₂+OH⁻↔HCO₃ ⁻) in the calcification sites (so-called “kinetic model”). This study addresses the potential role of an enzyme, carbonic anhydrase (CA), that catalyzes inter-conversion of CO₂ and HCO₃ ⁻ in relation to the underlying mechanism of vital effects. We performed quantitative inorganic carbonate precipitation experiments in order to examine the changes in ¹⁸O equilibration rate as a function of CA concentration. Experiments were performed at pH 8.3 and 8.9. These pH values are comparable to the average surface ocean pH and elevated pH levels observed in the calcification sites of some coral and foraminiferal species, respectively. The rate of uncatalyzed ¹⁸O exchange in the CO₂–H₂O system is governed by the pH-dependent DIC speciation and the kinetic rate constant for CO₂ hydration and hydroxylation, which can be summarized by a simple mathematical expression. The results from control experiments (no CA addition) are in agreement with this expression. The results from control experiments also suggest that the most recently published kinetic rate constant for CO₂ hydroxylation has been overestimated. When CA is present, the ¹⁸O equilibration process is greatly enhanced at both pH levels due to the catalysis of CO₂ hydration by the enzyme. For example, the time required for ¹⁸O equilibrium is nearly halved by the presence of 3.7×10⁻⁹M of CA used for the experiments. Despite its significant influence on the oxygen isotope exchange kinetics, the equilibrium oxygen isotope fractionation between individual DIC species and H₂O is unaffected by CA. Because many CaCO₃-secreting organisms possess active CA, our findings imply that ¹⁸O equilibration of the CO₂–H₂O system is possible within realistic timescales of biogenic calcification.
    Keywords calcification ; calcium carbonate ; carbon ; carbon dioxide ; carbonate dehydratase ; catalytic activity ; corals ; hydroxylation ; isotope fractionation ; isotopes ; models ; oxygen ; pH ; seawater ; thermodynamics
    Language English
    Dates of publication 2012-1015
    Size p. 15-34.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 300305-x
    ISSN 0016-7037
    ISSN 0016-7037
    DOI 10.1016/j.gca.2012.07.022
    Database NAL-Catalogue (AGRICOLA)

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  9. Book ; Online: Drivers of future seasonal cycle changes of oceanic pCO2

    Gallego, M. Angeles / Timmermann, Axel / Friedrich, Tobias / Zeebe, Richard E.

    eISSN: 1726-4189

    2018  

    Abstract: Recent observations show that the seasonal amplitude of surface ocean partial pressure of CO 2 (pCO 2 ) has been increasing on average at a rate of 2–3 μatm per year (Landschützer et al., 2018). Future increases of pCO 2 seasonality are expected, as ... ...

    Abstract Recent observations show that the seasonal amplitude of surface ocean partial pressure of CO 2 (pCO 2 ) has been increasing on average at a rate of 2–3 μatm per year (Landschützer et al., 2018). Future increases of pCO 2 seasonality are expected, as marine CO 2 will increase in response to increasing anthropogenic carbon emissions (McNeil et al., 2016). Here we use 7 different global coupled atmosphere/ocean/carbon cycle/ecosystem model simulations, conducted as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), to study future projections of the pCO 2 annual cycle amplitude and to elucidate the causes of its amplification. We find, that for the RCP8.5 emission scenario the seasonal amplitude (climatological maximum-minus-minimum) of upper ocean pCO 2 will increase by a factor of 1.5 to 3 times over the next 60–80 years. To understand the drivers and mechanisms that control the pCO 2 seasonal amplification we develop a complete analytical Taylor expansion of pCO 2 seasonality in terms of its four drivers: dissolved inorganic carbon (DIC), total alkalinity (TA), temperature (T) and salinity (S). Using this linear approximation we show that the DIC and T terms are the dominant contributors to the total change in pCO 2 seasonality. At first order, their future intensification can be traced back to a doubling of the annual mean pCO 2 , which enhances DIC and alters the ocean carbonate chemistry. Regional differences in the projected seasonal cycle amplitude are generated by spatially varying sensitivity terms. The subtropical and equatorial regions (40° S–40° N), will experience a ≈ 30–80 μatm increase in seasonal cycle amplitude almost exclusively due a larger CO 2 concentration that amplifies the T seasonal effect on solubility. This mechanism is further reinforced by an overall increase in the seasonal cycle of T, as a result of stronger ocean stratification and a projected shoaling of mean mixed layer depths. The Southern Ocean will experience a seasonal cycle amplification of ≈ 90–120 μatm in response to the mean pCO 2 -driven change of the DIC contribution and to a lesser extent to the T contribution. However, a decrease of the DIC seasonal cycle amplitude somewhat counteracts this regional amplification mechanism.
    Subject code 550 ; 551
    Language English
    Publishing date 2018-05-02
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Book ; Online: Drivers of future seasonal cycle changes in oceanic pCO2

    Gallego, M. Angeles / Timmermann, Axel / Friedrich, Tobias / Zeebe, Richard E.

    eISSN: 1726-4189

    2018  

    Abstract: Recent observation-based results show that the seasonal amplitude of surface ocean partial pressure of CO 2 ( p CO 2 ) has been increasing on average at a rate of 2–3 µatm per decade (Landschützer et al. 2018). Future increases in p CO 2 seasonality are ... ...

    Abstract Recent observation-based results show that the seasonal amplitude of surface ocean partial pressure of CO 2 ( p CO 2 ) has been increasing on average at a rate of 2–3 µatm per decade (Landschützer et al. 2018). Future increases in p CO 2 seasonality are expected, as marine CO 2 concentration ([CO 2 ]) will increase in response to increasing anthropogenic carbon emissions (McNeil and Sasse 2016). Here we use seven different global coupled atmosphere–ocean–carbon cycle–ecosystem model simulations conducted as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5) to study future projections of the p CO 2 annual cycle amplitude and to elucidate the causes of its amplification. We find that for the RCP8.5 emission scenario the seasonal amplitude (climatological maximum minus minimum) of upper ocean p CO 2 will increase by a factor of 1.5 to 3 over the next 60–80 years. To understand the drivers and mechanisms that control the p CO 2 seasonal amplification we develop a complete analytical Taylor expansion of p CO 2 seasonality in terms of its four drivers: dissolved inorganic carbon (DIC), total alkalinity (TA), temperature ( T ), and salinity ( S ). Using this linear approximation we show that the DIC and T terms are the dominant contributors to the total change in p CO 2 seasonality. To first order, their future intensification can be traced back to a doubling of the annual mean p CO 2 , which enhances DIC and alters the ocean carbonate chemistry. Regional differences in the projected seasonal cycle amplitude are generated by spatially varying sensitivity terms. The subtropical and equatorial regions (40° S–40° N) will experience a ≈ 30–80 µatm increase in seasonal cycle amplitude almost exclusively due to a larger background CO 2 concentration that amplifies the T seasonal effect on solubility. This mechanism is further reinforced by an overall increase in the seasonal cycle of T as a result of stronger ocean stratification and a projected shoaling of mean mixed layer depths. The Southern Ocean will experience a seasonal cycle amplification of ≈ 90–120 µatm in response to the mean p CO 2 -driven change in the mean DIC contribution and to a lesser extent to the T contribution. However, a decrease in the DIC seasonal cycle amplitude somewhat counteracts this regional amplification mechanism.
    Subject code 551
    Language English
    Publishing date 2018-09-03
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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