DOCSLIB.ORG

A New Ice Core Paleothermometer for Holocene and Transition Diffusion Processes Quantified by Spectral Methods

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A New Ice Core Paleothermometer for Holocene and Transition Diffusion Processes Quantified by Spectral Methods FACULTY OF SCIENCE UNIVERSITY OF COPENHAGEN Master Thesis in Geophysics A New Ice Core Paleothermometer for Holocene and Transition Di®usion Processes Quanti¯ed by Spectral Methods Sebastian Bjerregaard Simonsen Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen Supervisor: Sigf¶usJ. Johnsen December 2008 II A New Ice Core Paleothermometer Master Thesis Title: A New Ice Core Paleothermometer for Holocene and Transition Subtitle: Di®usion Processes Quanti¯ed by Spectral Methods ECTS-points: 60 Supervisor: Sigfus J. Johnsen Name of department: Centre for Ice and Climate Neils Bohr Institute University of Copenhagen Author: Sebastian Bjerregaard Simonsen Date: December 31th 2008 Abstract Since the early 1950's stable water isotopes have been considered a temper- ature proxy with application in paleoclimatic reconstruction of permanently snow covered areas. In this thesis a new method of reconstructing the pale- oclimatic information preserved in the isotopic records from Arctic ice cores is tested. The method is based on the de¯nition of the di®erential di®usion 2 2 2 length ¢σ = σ18O ¡ σD. An investigation of the processes a®ecting the di®erential di®usion length is undertaken, covering the densi¯cation of ¯rn, ice flow modelling and isotopic di®usivity in the ¯rn and ice matrix. Three numerical power spectra density estimation methods have been used to retrieve the di®erential di®usion length in 22 sections of ice from two Greenlandic ice cores, GRIP and NGRIP. None of the methods are found superior, but both Burg's algorithm and the Autocorrelation methods show promising behaviors. The modelled and measured di®erential di®usion lengths form an estimate of the surface temperature at the origin of the ice core sections. The inves- tigation of the di®erential di®usion length in deep sections from the NGRIP ice core shows that the temperature reconstruction based on the di®erential di®usion length must be limited to ice younger than about 40 kyr for the two cores. This reduces the number of ice core sections available to 12. The low number of sections limits the interpretation of the tested temperature reconstruction. However, the estimated surface temperatures are within un- certainties of paleotemperatures records derived from combined bore hole temperature and isotope pro¯les from the GRIP and NGRIP ice cores. IV A New Ice Core Paleothermometer Preface The presented thesis accounts for the ¯nal exam of a Masters Degree in Geo- physics at the University of Copenhagen and covers 60-ECTS point. The study has been conducted in about a year of full time study. A basic knowledge of mathematics and physics is required to read this the- sis along with knowledge of Glaciology. If necessary terms are explained to clarify the de¯nitions used. The abbreviations used are all summarized in the Nomenclature at the end of the thesis. All plotted time scales start at present and end at a time before present. To ease the comparison between text and plots I write that the transition into the Last Glacial follows the Holocene, despite that it is reversed in real time. All programming has been conducted using Matlab. VI A New Ice Core Paleothermometer Acknowledgment I would like to thank my supervisor Sigfus J. Johnsen for the many hours of productive discussions of the problems at hand along with introducing me to the study subject. Trevor J. Popp is thanked for providing isotopic data from the NGRIP ice core and proof reading. I thank Ph.D student Hans Christian Steen-Larsen for showing interest and support for the work and proof reading, Ghita Hansen for proof reading and Lykke Pedersen for the love and support during the writing of this thesis and also for proof reading. I would also like to thank the Centre for Ice and Climate at the Niels Bohr Institute for supplying an ideal environment for working with this thesis, along with providing the opportunity to go to the NEEM drill site to expe- rience the ¯eld work involved in drilling ice cores. Finally, my o±ce mates deserve thanks for the productive discussions and the needed distractions. Sebastian B. Simonsen Copenhagen, December 2008 Preface for 2nd Edition After handing in this master thesis December 31th 2008 a couple of errors has come to my attention. They have not been corrected in the thesis. However a list will be given here: Page 51 : Equation (5.18) was ¯st described by [Johnsen et al., 2000]. Page 76 : Severinghaus et al. [1998] was not doing measurements on the GRIP ice core, but GISP2. Equation (5.21) : On the right hand side of the equation in the denomi- nator the subscript sam should be sec. If further errors are found in this work I would be glad to hear about it. Send me a mail on [email protected] Sebastian B. Simonsen Copenhagen, February 2009 VIII A New Ice Core Paleothermometer Contents Contents IX 1 Introduction 1 1.1 Dating Ice Cores . 3 2 Ice Cores as a Paleothermometer 5 2.1 Stable Water Isotopes . 5 2.1.1 Temperature Proxy from Water Isotopes . 8 2.2 Other Methods . 11 2.2.1 Borehole Inversion . 11 2.2.2 Melt Layer Analysis . 11 2.2.3 Accumulation Change . 11 2.2.4 Gas Isotopes . 12 2.3 Outline of a New Palaeothermometer . 12 3 Densi¯cation of Firn 13 3.1 Densi¯cation by the Arnaud-model . 14 3.2 Densi¯cation by the Herron-Langway-model . 15 3.3 Comparison of the Two Models . 16 4 Models of Ice Flow 19 4.1 Flow in Firn . 19 4.2 Flow in Ice . 20 4.2.1 Coordinate System . 20 4.2.2 Derivation of Normal Strain Rates . 21 4.3 The Dansgaard-Johnsen Flow Model . 22 4.3.1 De¯nition of the Shape Function . 24 4.4 Modelling the Ice Flow . 24 X A New Ice Core Paleothermometer 4.5 Parametrization of the Flow Equation . 25 4.6 Forward Modelling of Particle Paths . 29 4.7 Formulation of the Inverse Problem . 32 4.7.1 A Priori Information . 32 4.7.2 Occam's Inversion . 33 4.7.3 Probability Density of Data and Likelihood Function . 34 4.7.4 Metropolis Algorithm for Monte Carlo Simulations . 34 4.7.5 Burn-in and Model Sampling . 35 4.7.6 Model Parameter Estimation After Sampling . 36 4.8 NGRIP A Priori Information . 37 4.8.1 Estimation of Lagrange Multipliers . 38 4.9 Results of the Monte Carlo Simulations . 39 4.10 Comparison with the ss09sea . 41 5 Isotopic Di®usion in Firn and Ice 45 5.1 Di®usion in Firn . 46 5.1.1 Analytical Solution of the Di®usion Length . 47 5.1.2 Numerical Solution of the Di®usion Length . 47 5.1.3 Temperature Dependency of the Di®usion length . 48 5.2 Di®usion in Ice . 50 5.3 Di®erential Di®usion Length . 51 5.4 Modelled Di®usion Length . 52 6 Spectral Analysis of Isotopic Data 55 6.1 Depositional Spectra of Snow . 55 6.2 Power Spectral Properties of Di®usion . 56 6.2.1 The Fourier Transformed Isotopic Di®usion . 56 6.2.2 Sampling E®ects . 57 6.2.3 Measuring Noise and Cut-O® . 59 6.2.4 Climate Variability Correction . 59 6.3 Data Processing . 60 6.3.1 Fast Fourier Transform . 60 6.3.2 Autocorrelation Method . 63 6.3.3 Burg's Algorithm . 65 7 Results and Discussion 69 7.1 Spectral Estimates of Di®erential Di®usion . 69 7.2 Ice Di®usivity in the NGRIP Core . 72 7.3 Paleoclimatic Record from Di®erential Di®usion . 73 7.3.1 GRIP Record . 73 7.3.2 NGRIP Record . 76 7.4 Processing Long Records . 76 7.5 Bias in the Presented Paleothermometer . 78 7.5.1 Firn Depth . 78 CONTENTS XI 7.5.2 Flow Model Induced Uncertainties . 79 7.5.3 Ice Sheet Evolution . 79 7.5.4 Sample Size of the Measured Water Isotopes . 80 7.5.5 Cut-o® . 80 8 Conclusion 83 9 Outlook 85 10 Danish Summery - Dansk Resume 87 Appendices 91 A Analysis and Data for the Flow model 91 A.1 Testing the Forward Algorithm . 91 A.2 Inverse modelling with out Occam . 93 A.3 NGRIP and NEEM Depth vs. Age Data . 94 B Di®usion lengths 95 Bibliography 97 List of Figures 105 List of Tables 107 Nomenclature 109 XII A New Ice Core Paleothermometer 1 Introduction In the past couple of years the climate has caught a lot of attention in the broad media picture. The global warming is on everybody's lips. Suddenly, the present warming has become a global issue. Big organizations such as the UN have turned there focus on it through the Intergovernmental Panel on Climate Change (IPCC, [IPCC, 2007]). The reason that we are talking about a global warming is due to our ability to determine the past climate, past the time scale of manmade temperature measurements. A whole sci- ence has developed around this called paleoclimatology, covering a broad range of study disciplines, e.g. tree rings, sedimentary, corals, speleotherms and ice cores. All are able to determine past climate on di®erent time scales and time resolution. One of the most successful methods to determine the past climate for the last couple of hundred thousand years has proven to be ice cores. Depending on the site, ice cores have a climate record of di®erent lengths; Greenland about 115 to 250 kyr1 back in time [Dansgaard et al., 1993], and Antarctica at least 800 kyr back in time [EPICA Members, 2004].
Load more

Recommended publications
  • ARTICLE in PRESS + MODEL EPSL-08806; No of Pages 16
    ARTICLE IN PRESS + MODEL EPSL-08806; No of Pages 16 Earth and Planetary Science Letters xx (2007) xxx–xxx www.elsevier.com/locate/epsl Sr/Ca and Mg/Ca vital effects correlated with skeletal architecture in a scleractinian deep-sea coral and the role of Rayleigh fractionation ⁎ Alexander C. Gagnon a, , Jess F. Adkins b, Diego P. Fernandez b,1, Laura F. Robinson c a Division of Chemistry, California Institute of Technology, MC 114-96, Pasadena, CA 91125, USA b Division of Geological and Planetary Sciences, California Institute of Technology, MC 100-23, Pasadena, CA 91125, USA c Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA Received 29 November 2006; received in revised form 15 May 2007; accepted 3 July 2007 Editor: H. Elderfield Abstract Deep-sea corals are a new tool in paleoceanography with the potential to provide century long records of deep ocean change at sub- decadal resolution. Complicating the reconstruction of past deep-sea temperatures, Mg/Ca and Sr/Ca paleothermometers in corals are also influenced by non-environmental factors, termed vital effects. To determine the magnitude, pattern and mechanism of vital effects we measure detailed collocated Sr/Ca and Mg/Ca ratios, using a combination of micromilling and isotope-dilution ICP-MS across skeletal features in recent samples of Desmophyllum dianthus, a scleractinian coral that grows in the near constant environment of the deep-sea. Sr/Ca variability across skeletal features is less than 5% (2σ relative standard deviation) and variability of Sr/Ca within the optically dense central band, composed of small and irregular aragonite crystals, is significantly less than the surrounding skeleton.
    [Show full text]
  • Marine Isotopic Stage 5E in the Southwest Pacific: Similarities With
    GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 23, 2185, doi:10.1029/2003GL018191, 2003 Marine Isotopic Stage 5e in the Southwest Pacific: Similarities with Antarctica and ENSO inferences Carles Pelejero1 and Eva Calvo1 Research School of Earth Sciences, The Australian National University, Canberra, Australia Graham A. Logan Petroleum and Marine Division, Geoscience Australia, Canberra, Australia Patrick De Deckker Department of Geology, The Australian National University, Canberra, Australia Received 17 July 2003; revised 15 September 2003; accepted 8 October 2003; published 3 December 2003. [1] A detailed record of alkenone-derived sea-surface matic importance such as El Nin˜o-Southern Oscillation temperatures (SSTs) offshore western New Zealand has (ENSO). Key controls on these oscillations are sea-surface been generated for the penultimate deglaciation and last temperature (SST) gradients [Rind, 1998]. interglacial. SSTs were 3.5 to 4.5°C warmer than present, [3] This study focuses on the penultimate deglaciation peaking 4.5 thousand years ahead of ice volume minima. and the subsequent Marine Isotope Stage 5e/5d shift. New The short duration of Marine Isotopic Stage 5e off New insights are presented on the peculiar characteristics of Zealand exhibits a striking parallelism to the record of air Stage 5e as recorded off New Zealand, a period often temperatures at Vostok, Antarctica. Changes in latitudinal considered analogous to the present interglacial stage. SST gradients for the Southwest Pacific from New Zealand Comparison between SSTs off New Zealand and at the to the equator are also assessed, showing values consistently equator allows the reconstruction of meridional thermal lower than today. In this region, this situation usually occurs gradients in the Southwest Pacific.
    [Show full text]
  • Bayesian Calibration of the Mg/Ca Paleothermometer in Planktic Foraminifera”
    “Bayesian calibration of the Mg/Ca paleothermometer in planktic foraminifera” Jessica E. Tierney1, Steven B. Malevich1, William Gray2, Lael Vetter1 & Kaustubh Thirumalai1 1University of Arizona, Department of Geosciences, 1040 4th St. Tucson, AZ 85721. 2Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL), Gif-sur-Yvette, France This is a post print of a paper published in the journal Paleoceanography and Paleoclimatology, doi: 10.1029/2019PA003744 https://doi.org/10.1029/2019PA003744 manuscript submitted to Paleoceanography and Paleoclimatology 1 Bayesian calibration of the Mg/Ca paleothermometer 2 in planktic foraminifera 1 1 2 1 3 Jessica E. Tierney , Steven B. Malevich , William Gray , Lael Vetter & 1 4 Kaustubh Thirumalai 1 5 University of Arizona Department of Geosciences, 1040 E 4th St Tucson AZ 85721 2 6 Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL), Gif-sur-Yvette, France 7 Key Points: 8 • We introduce Mg/Ca Bayesian calibrations for planktic foraminifera 9 • Hierarchical modeling is used to constrain multivariate Mg/Ca sensitivities 10 • For deep-time applications, we incorporate estimates of Mg/Ca of seawater Corresponding author: Jessica Tierney, [email protected] –1– manuscript submitted to Paleoceanography and Paleoclimatology 11 Abstract 12 The Mg/Ca ratio of planktic foraminifera is a widely-used proxy for sea-surface temper- 13 ature, but is also sensitive to other environmental factors. Previous work has relied on 14 correcting Mg/Ca for non-thermal influences. Here, we develop a set of Bayesian mod- 15 els for Mg/Ca in four major planktic groups – Globigerinoides ruber (including both pink 16 and white chromotypes), Trilobatus sacculifer, Globigerina bulloides, and Neogloboquad- 17 rina pachyderma (including N.
    [Show full text]
  • 95. Lea D. W., Elemental and Isotopic Proxies of Past Ocean
    This article was originally published in Treatise on Geochemistry, Second Edition published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non- commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial Lea D.W. (2014) Elemental and Isotopic Proxies of Past Ocean Temperatures. In: Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, vol. 8, pp. 373-397. Oxford: Elsevier. © 2014 Elsevier Ltd. All rights reserved. Author's personal copy 8.14 Elemental and Isotopic Proxies of Past Ocean Temperatures DW Lea, University of California, Santa Barbara, CA, USA ã 2014 Elsevier Ltd. All rights reserved. 8.14.1 Introduction 373 8.14.2 A Brief History of Early Research on Geochemical Proxies of Temperature 374 8.14.3 Oxygen Isotopes as a PaleotemperatureProxy in Foraminifera 375 8.14.3.1 Background 375 8.14.3.2 Paleotemperature Equations 376 8.14.3.3 Secondary Effects and Diagenesis 376 8.14.3.4 Results
    [Show full text]
  • Geologic Constraints on Earth System Sensitivity to CO Table 2
    Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Earth Syst. Dynam. Discuss., 2, 211–240, 2011 www.earth-syst-dynam-discuss.net/2/211/2011/ Earth System Dynamics ESDD doi:10.5194/esdd-2-211-2011 Discussions 2, 211–240, 2011 © Author(s) 2011. CC Attribution 3.0 License. Geologic constraints This discussion paper is/has been under review for the journal Earth System on earth system Dynamics (ESD). Please refer to the corresponding final paper in ESD if available. sensitivity to CO2 D. L. Royer et al. Geologic constraints on earth system Title Page sensitivity to CO2 during the Cretaceous Abstract Introduction and early Paleogene Conclusions References Tables Figures D. L. Royer1, M. Pagani2, and D. J. Beerling3 1Department of Earth and Environmental Sciences and College of the Environment, J I Wesleyan University, Middletown, Connecticut, 06459, USA J I 2Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520, USA Back Close 3Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK Full Screen / Esc Received: 27 February 2011 – Accepted: 28 February 2011 – Published: 3 March 2011 Correspondence to: D. L. Royer ([email protected]) Printer-friendly Version Published by Copernicus Publications on behalf of the European Geosciences Union. Interactive Discussion 211 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract ESDD Earth system sensitivity (ESS) is the long-term (>103 yr) equilibrium temperature re- 2, 211–240, 2011 sponse to doubled CO2. ESS has climate policy implications because global tem- peratures are not expected to decline appreciably for at least 103 yr, even if anthro- 5 pogenic greenhouse-gas emissions drop to zero.
    [Show full text]
  • Bayesian Calibration of the Mg/Ca Paleothermometer in Planktic Foraminifera
    manuscript submitted to Paleoceanography and Paleoclimatology 1 Bayesian calibration of the Mg/Ca paleothermometer 2 in planktic foraminifera 1 1 2 1 3 Jessica E. Tierney , Steven B. Malevich , William Gray , Lael Vetter & 1 4 Kaustubh Thirumalai 1 5 University of Arizona Department of Geosciences, 1040 E 4th St Tucson AZ 85721 2 6 Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), Gif-sur-Yvette, France 7 Key Points: 8 • We introduce Mg/Ca Bayesian calibrations for planktic foraminifera 9 • Hierarchical modeling is used to constrain multivariate Mg/Ca sensitivities 10 • For deep-time applications, we incorporate estimates of Mg/Ca of seawater Corresponding author: Jessica Tierney, [email protected] {1{ manuscript submitted to Paleoceanography and Paleoclimatology 11 Abstract 12 The Mg/Ca ratio of planktic foraminifera is a widely-used proxy for sea-surface temper- 13 ature, but is also sensitive to other environmental factors. Previous work has relied on 14 correcting Mg/Ca for non-thermal influences. Here, we develop a set of Bayesian mod- 15 els for Mg/Ca in planktic foraminifera that account for the multivariate influences on 16 this proxy in an integrated framework. We use a hierarchical model design that lever- 17 ages information from both laboratory culture studies and globally-distributed core top 18 data, allowing us to include environmental sensitivities that are poorly constrained by 19 core top observations alone. For applications over longer geological timescales, we de- 20 velop a version of the model that incorporates changes in the Mg/Ca ratio of seawater. 21 We test our models { collectively referred to as BAYMAG { on sediment trap data and 22 on representative paleoclimate time series and demonstrate good agreement with obser- 23 vations and independent SST proxies.
    [Show full text]
  • Sea Surface Temperature Calculations in the Equatorial East Atlantic From
    PALEOCEANOGRAPHY, VOL. 15, NO. 1,PAGES 124-134, FEBRUARY 2000 Paleo-seasurface temperature calculationsin the equatorial east Atlantic from Mg/Ca ratios in planktic foraminifera- A comparisonto seasurface temperature estimates from U37 ', oxygen isotopes,and foraminiferal transfer function D. Niirnberg and A. Miiller GEOMAR ResearchCenter, Kiel, Germany R. R. Schneider FachbereichGeowissenschaften, University of Bremen, Bremen, Germany Abstract. We presenttwo -270 kyr paleo-seasurface temperature (SST) recordsfrom the EquatorialDivergence and the SouthEquatorial Current derived from Mg/Ca ratiosin the plankticforaminifer Globigerinoides sacculifer. The presentstudy suggests that the magnesiumsignature of G. sacculiferprovides a seasonalSST estimatefrom the upper -50 m of the watercolumn generated during upwelling in australlow-latitude fall/winter. Common to both down-core recordsis a glacial-interglacialamplitude of-3ø-3.5øC for the last climaticchanges and lower Holoceneand glacial oxygenisotope stage 2 temperaturescompared with interglacial stage 5.5 andglacial stage 6 temperatures,respectively. The comparisonto publishedSST estimatesfrom alkenones,oxygen isotopes, and foraminiferal transfer function from the samecore material pinpoints discrepancies and conformities between methods. 1. Introduction 1.2. Foraminiferal Mg/Ca Ratios as Paleotemperature Indicators 1.1. Paleo-Sea Surface Temperature Estimations Althoughvarious SSTu•7' approaches were developed to Becauseof the incompatibilityof methodsand their reconstructsea surface SSTu•'
    [Show full text]
  • A Brief History of Ice Core Science Over the Last 50 Yr
    Clim. Past, 9, 2525–2547, 2013 Open Access www.clim-past.net/9/2525/2013/ Climate doi:10.5194/cp-9-2525-2013 © Author(s) 2013. CC Attribution 3.0 License. of the Past A brief history of ice core science over the last 50 yr J. Jouzel1 1Laboratoire des Sciences de Climat et de l’Environnement/Institut Pierre Simon Laplace, CEA-CNRS-UVSQ – UMR8212, CEA Saclay, L’Orme des Merisiers, Bt. 701, 91191 Gif/Yvette, Cedex, France *Invited contribution by J. Jouzel, recipient of the EGS Milutin Milankovic Medal 1997. Correspondence to: J. Jouzel ([email protected]) Received: 30 April 2013 – Published in Clim. Past Discuss.: 3 July 2013 Revised: 24 September 2013 – Accepted: 30 September 2013 – Published: 6 November 2013 Abstract. For about 50 yr, ice cores have provided a about “The history of early polar ice cores” and on many wealth of information about past climatic and environmen- other scientific articles, reports and websites. I was also in- tal changes. Ice cores from Greenland, Antarctica and other terested in looking at how ice core research, which for about glacier-covered regions now encompass a variety of time fifty years has produced such a wealth of information about scales. However, the longer time scales (e.g. at least back past changes in our climate and our environment, is perceived to the Last Glacial period) are covered by deep ice cores, outside our scientific community; one well-documented ex- the number of which is still very limited: seven from Green- ample is given by Spencer Weart, an historian of science, land, with only one providing an undisturbed record of a part who has written a book called “The discovery of global of the last interglacial period, and a dozen from Antarctica, warming” (Weart, 2008, updated in 2013) with a chapter on with the longest record covering the last 800 000 yr.
    [Show full text]
  • Bayesian Calibration of the Mg/Ca Paleothermometer in Planktic Foraminifera Jessica E
    Bayesian Calibration of the Mg/Ca Paleothermometer in Planktic Foraminifera Jessica E. Tierney, Steven B. Malevich, William Gray, Lael Vetter, Kaustubh Thirumalai To cite this version: Jessica E. Tierney, Steven B. Malevich, William Gray, Lael Vetter, Kaustubh Thirumalai. Bayesian Calibration of the Mg/Ca Paleothermometer in Planktic Foraminifera. Paleoceanography and Pale- oclimatology, American Geophysical Union, 2019, 34 (12), pp.2005-2030. 10.1029/2019PA003744. hal-02973694 HAL Id: hal-02973694 https://hal.archives-ouvertes.fr/hal-02973694 Submitted on 28 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. RESEARCH ARTICLE Bayesian Calibration of the Mg/Ca Paleothermometer in 10.1029/2019PA003744 Planktic Foraminifera Key Points: 1 1 2 1 • We introduce Mg/Ca Bayesian Jessica E. Tierney , Steven B. Malevich , William Gray , Lael Vetter , calibrations for planktic foraminifera and Kaustubh Thirumalai1 • Hierarchical modeling is used to constrain multivariate Mg/Ca 1Department of Geosciences, University of Arizona, Tucson, AZ, USA, 2Laboratoire des Sciences du Climat et de sensitivities l'Environnement (LSCE/IPSL), Gif-sur-Yvette, France • For deep-time applications, we incorporate estimates of Mg/Ca of seawater Abstract The Mg/Ca ratio of planktic foraminifera is a widely used proxy for sea-surface temperature but is also sensitive to other environmental factors.
    [Show full text]
  • Polar Regions (Arctic and Antarctic)
    16 Polar Regions (Arctic and Antarctic) OLEG ANISIMOV (RUSSIA) AND BLAIR FITZHARRIS (NEW ZEALAND) Lead Authors: J.O. Hagen (Norway), R. Jefferies (Canada), H. Marchant (Australia), F. Nelson (USA), T. Prowse (Canada), D.G. Vaughan (UK) Contributing Authors: I. Borzenkova (Russia), D. Forbes (Canada), K.M. Hinkel (USA), K. Kobak (Russia), H. Loeng (Norway), T. Root (USA), N. Shiklomanov (Russia), B. Sinclair (New Zealand), P. Skvarca (Argentina) Review Editors: Qin Dahe (China) and B. Maxwell (Canada) CONTENTS Executive Summary 80 3 16 . 2 . 6 . Arctic Hydrology 82 1 16 . 2 . 6 . 1 . Changes in Precipitation, Snow 16 . 1 . Po l a r Re g i o n s 80 7 Accumulation, and Spring Melt 82 3 16 . 1 . 1 . Previous Work—Summary of Special Report 16 . 2 . 6 . 2 . Surface Water Budgets on Regional Impacts of Climate Change 80 7 and Wet l a n d s 82 3 16 . 1 . 2 . Distinctive Characteristics of Polar Regions 80 9 16 . 2 . 6 . 3 . Ecological Impact of 16 . 1 . 3 . Climate Change in the 20th Century 81 0 Changing Runoff Regimes 82 3 16 . 1 . 3 . 1 . The Arctic 81 0 16 . 2 . 6 . 4 . Sensitivity of Arctic Ocean 16 . 1 . 3 . 2 . The An t a r c t i c 81 2 to River Flow 82 4 16 . 1 . 4 . Scenarios of Future Change 81 3 16 . 2 . 7 . Changes in Arctic Biota 82 4 16 . 2 . 7 . 1 . Impacts of Climate Change on 16 . 2 . Key Regional Concerns 81 4 Arctic Terrestrial Environments 82 4 16 . 2 . 1 .
    [Show full text]
  • Biogenic Carbonates – Oxygen
    Chapter 6 BIOGENIC CARBONATES – OXYGEN Contents 6.1 Introduction ................................................................................................................... 1 6.2 The Phosphoric Acid Method ....................................................................................... 2 6.2.1 A major breakthrough ............................................................................................ 2 6.2.2 Acid Fractionation Factors ..................................................................................... 3 6.2.3. Applicability ......................................................................................................... 5 6.3 The Oxygen Isotope Paleotemperature Scale ............................................................... 6 6.4 Factors Affecting Oxygen Isotope Paleotemperatures ............................................... 11 6.4.1 Variations in 18O of ocean water in space and time .......................................... 11 6.4.2 Vital effects .......................................................................................................... 13 6.4.3. Diagenesis ........................................................................................................... 14 6.4.4 Ecology of the organism ...................................................................................... 19 6.5 Applications of Oxygen Isotope Paleothermometry ................................................... 19 6.5.1 The Quaternary ...................................................................................................
    [Show full text]
  • Temperature and Atmospheric CO2 Concentration Estimates Through the PETM Using Triple Oxygen Isotope Analysis of Mammalian Bioapatite
    Temperature and atmospheric CO2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite Alexander Gehlera,1, Philip D. Gingerichb,c, and Andreas Packd aGeowissenschaftliches Zentrum, Geowissenschaftliches Museum, Georg-August-Universität, D-37077 Göttingen, Germany; bDepartment of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109; cMuseum of Paleontology, University of Michigan, Ann Arbor, MI 48109; and dGeowissenschaftliches Zentrum, Abteilung Isotopengeologie, Georg-August-Universität, D-37077 Göttingen, Germany Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved May 17, 2016 (received for review September 17, 2015) The Paleocene–Eocene Thermal Maximum (PETM) is a remarkable cli- Substantially different CO2 scenarios have been discussed for the matic and environmental event that occurred 56 Ma ago and has PETM. Mass balance estimates range from an increase in atmo- importance for understanding possible future climate change. The spheric CO2 concentration of less than 100 ppm to an increase of Paleocene–Eocene transition is marked by a rapid temperature rise several 10,000 ppm, depending on the proposed magnitude of the contemporaneous with a large negative carbon isotope excursion (CIE). CIE and the associated carbon source (10, 22, 24, 25, 27, 31–34). Both the temperature and the isotopic excursion are well-documented Existing proxy data for CO2 concentrations in the time interval by terrestrial and marine proxies. The CIE was the result of a massive surrounding the PETM (50–60 Ma) suggest background partial release of carbon into the atmosphere. However, the carbon source pressure of CO2 (pCO2) levels between 100 and 1,900 ppm (ref.
    [Show full text]