DOCSLIB.ORG

Chinese Stalagmite \Rmdelta 18O Controlled by Changes in the Indian

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chinese Stalagmite \Rmdelta 18O Controlled by Changes in the Indian ARTICLES PUBLISHED ONLINE: 19 JUNE 2011 | DOI: 10.1038/NGEO1169 Chinese stalagmite δ18O controlled by changes in the Indian monsoon during a simulated Heinrich event Francesco S. R. Pausata1,2*(, David S. Battisti2,3, Kerim H. Nisancioglu1,4 and Cecilia M. Bitz3 Carbonate cave deposits in India and China are assumed to record the intensity of monsoon precipitation, because the δ18O of the carbonate tracks the isotopic signature of precipitation. These records show spatially coherent variability throughout the last ice age and suggest that monsoon strength was altered during the millennial-scale climate variations known as Dansgaard–Oeschger events and during the Heinrich cooling events. Here we use a numerical climate model with an embedded oxygen-isotope model to assess what caused the shifts in the oxygen-isotope signature of precipitation during a climate perturbation designed to mimic a Heinrich event. Our simulations show that a sudden increase in North Atlantic sea-ice extent during the last glacial period leads to cooling in the Northern Hemisphere, reduced precipitation over the Indian basin and weakening of the Indian monsoon. The precipitation is isotopically heavier over India and the water vapour exported to China is isotopically enriched. Our model broadly reproduces the enrichment of δ18O over Northern India and East Asia evident in speleothem records during Heinrich events. We therefore conclude that changes in the δ18O of cave carbonates associated with Heinrich events reflect changes in the intensity of Indian rather than East Asian monsoon precipitation. uring the last glacial period (∼110–10 kyr bp), millennial- and the isotopic composition of the source (for example, owing to scale climate variability was characterized by abrupt changes in sea surface temperature (SST) or river runoff17). Dtransitions between cold stadial and warm interstadial states. Oxygen-isotope records in speleothems throughout Asia are Several of these cold stadial periods are interrupted by extreme often interpreted as an index for the `strength' or `intensity' of 1 18 ice-rafting events, the so-called Heinrich events (H-events) . Asian monsoons, because they feature large oscillations in δ Oc H-events, as well as the more recent Younger Dryas (YD, sometimes that are highly correlated with changes in local summer insolation referred to as H0), are large freshwater discharges from the North owing to the precession of the equinoxes (see, for example, American ice sheet into the North Atlantic occurring irregularly refs 11,13). Several studies have suggested that orbital variations 2 18 throughout the ice age, causing long-lived cold states ; seven H-like cause changes in δ Oc by changing local precipitation processes events occurred during the last glacial period3. The climate changes and/or amounts13,15,18,19, including, for example, variations in the coincident with H-events are not restricted to the North Atlantic seasonality of precipitation. Recent studies, however, suggest that basin, but are communicated over large parts of the globe4,5 through it is difficult to explain the influence of orbital variations on changes in atmospheric and ocean circulation in response to rapid isotopes in the Asian cave records through local climate changes (for changes in Nordic Sea sea-ice extent6–8. example refs 20,21) and that the cave records more probably reflect The rapid climate changes associated with the most recent changes in the δ18O of water vapour owing to non-local climate H-event (H1) and the YD are faithfully recorded in the oxygen- processes, including changes in the processing of the vapour en isotopic composition of stalagmites (speleothems) through- route to the caves and changes in the fractionation at the source out South and East Asia (see, for example, refs 9–12). The (land or ocean)20–23. 18 18 oxygen-isotopic composition of the stalagmite calcite (δ Oc; see The millennial-scale variations in δ Oc captured in cave records equation (1) in Methods) reflects the temperature of the cave throughout southern and eastern Asia and associated with abrupt 18 18 and the precipitation-weighted δ O of precipitation (δ Op; see climate changes, such as H-events, are about one-third of the 18 13 equation (2) in Methods) at the cave site. A change in δ Op may amplitude of the precessional changes . This is remarkable because result from a change in several local and non-local processes, it indicates that variability in the `monsoon strength' on millennial including: the ratio of summer-to-spring precipitation (season- timescales, which is owing to dynamics internal to the Earth's 18 ality of precipitation affects δ Op because summer rainfall has climate system, is of the same order as that associated with the lighter—that is, more negative—δ18O values compared with spring orbitally forced changes. In this study, we shall use models to precipitation13–15); the intensity of precipitation falling at a given lo- examine the changes in climate and in the isotopic composition of cation (amount effect16) owing to changes in the strength of the con- precipitation that result from a sudden change in sea-ice extent in vection; the origin of the water vapour delivered to the site owing to the northern North Atlantic, which is thought to be the causal agent changes in circulation; the isotopic composition (not the amount) of global climate changes associated with H-events. Our particular of water vapour that is arriving from one or more regions owing to goal is to understand the climatological significance of the signals 18 changes in the processing of water vapour en route from the source recorded in the δ Oc of Asian speleothems. 1Bjerknes Centre for Climate Research, NO-5007 Bergen, Norway, 2Geophysical Institute, University of Bergen, NO-5007 Bergen, Norway, 3Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195-1640, USA, 4UNI Research, NO-5007 Bergen, Norway. (Present address: Joint Research Center, Institute for Environment and Sustainability, I-21027 Ispra (VA), Italy. *e-mail: [email protected]. 474 NATURE GEOSCIENCE j VOL 4 j JULY 2011 j www.nature.com/naturegeoscience © 2011 Macmillan Publishers Limited. All rights reserved. NATURE GEOSCIENCE DOI: 10.1038/NGEO1169 ARTICLES a 90° N 75° N 60° N 45° N Latitude 30° N 15° N 0° 180° 150° W 120° W90° W60° W30° W0° 30° E60° E90° E 120° E 150° E 180° Longitude ¬16 ¬10 ¬7 ¬5 ¬3 ¬2 ¬1 ¬0.5 0 0.5 1 2 Temperature difference (H1¬LGM) (˚C) b 90° N 75° N 60° N 45° N Latitude 30° N 15° N 0° 180° 150° W 120° W90° W60° W30° W0° 30° E60° E90° E 120° E 150° E 180° Longitude ¬100 ¬80 ¬60 ¬40 ¬20 0 20 40 60 80 100 Precipitation difference (H1¬LGM) (%) Figure 1 j Annual averaged temperature and precipitation difference between the H1 and LGM. a, Surface temperature difference (◦C). b, Precipitation difference (%). Markers indicate the locations of the following caves: Hulu (circle), Songjia (square), Dongge (star) and Timta (diamond). The lines in a indicate the annual climatological 50% sea-ice extent for H1 (white) and LGM (red) in the North Atlantic sector. Simulated isotopic change owing to an archetypal H-event of sea ice over the northern North Atlantic, causing a strong cooling We take as a starting point the climate of the Last Glacial extending throughout the Northern Hemisphere, as also shown in Maximum (LGM) as simulated by a fully coupled climate model previous studies (for example refs 5,7,29; the simulated warming (Community Climate System Model version 3, CCSM3) using over northeast India is discussed in Supplementary Information). insolation, carbon dioxide, ice sheets and continental geometry Precipitation is greatly reduced throughout the North Atlantic from 21 kyr bp (ref. 24). A second set of experiments (H1) was and northern Indian Ocean in the H1 experiment. Note that carried out in which freshwater is abruptly added to the North there are no significant changes in the annual average or seasonal Atlantic to mimic an H-event (see Methods), causing an extensive distribution of precipitation at the location of the Chinese caves expansion of sea ice in the northern North Atlantic25. We call these (Fig. 1, Table 1). The atmospheric circulation and the spatial and experiments `H1' because they feature an extension of sea ice in the seasonal changes in surface temperature and precipitation in the North Atlantic that is consistent with the extension of ice-covered uncoupled experiments are very similar to those from the coupled area in a typical H-event1 and because the sedimentary chronology experiments (compare Fig. 1 and Supplementary Fig. S1). This is unambiguously tied to the cave chronologies for the H1 event26. enables us to use the uncoupled LGM and H1 experiments to The coupled climate model used in the LGM and H1 experiments determine changes in the isotopic composition of precipitation does not contain an isotope module. Hence, to examine the isotopic associated with abrupt changes in the North Atlantic sea ice. 18 changes associated with the sudden expansion of sea ice in the The simulated change (H1 minus LGM) in δ Op over south 18 North Atlantic, we ran two further off-line experiments using the Asia is shown in Fig. 2. The increase in δ Op in southern and same atmospheric model (Community Atmosphere Model version eastern Asia is primarily owing to changes in the δ18O and 3, CAM3; ref. 27) as is used in CCSM3, but with an embedded amount of precipitation during the monsoon season—May to module for stable water isotopes28. These experiments use the same August (MJJA; Supplementary Fig. S2). The cooler H1 climate 18 (21 kyr bp) boundary conditions as the coupled experiments. The features an increase in δ Op throughout southern and eastern annual cycle in SST and sea-ice concentration is prescribed to be Asia, including all cave sites, ranging from C0:9 at Hulu to identical to that from the coupled LGM experiment and from the C1:7 at Timta.
Load more

Recommended publications
  • Neanderthal Extinction by Competitive Exclusion William E
    Neanderthal Extinction by Competitive Exclusion William E. Banks, Francesco d’Errico, A. Townsend Peterson, M. Kageyama, Sima Adriana, M. F. Sánchez Goñi To cite this version: William E. Banks, Francesco d’Errico, A. Townsend Peterson, M. Kageyama, Sima Adriana, et al.. Neanderthal Extinction by Competitive Exclusion. PLoS ONE, Public Library of Science, 2008, 3 (12), pp.e3972. 10.1371/journal.pone.0003972. halshs-00453393 HAL Id: halshs-00453393 https://halshs.archives-ouvertes.fr/halshs-00453393 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. Neanderthal Extinction by Competitive Exclusion William E. Banks1*, Francesco d’Errico1,2, A. Townsend Peterson3, Masa Kageyama4, Adriana Sima4, Maria-Fernanda Sa´nchez-Gon˜ i5 1 Institut de Pre´histoire et de Ge´ologie du Quaternaire, UMR 5199-PACEA, Universite´ Bordeaux 1, CNRS, Talence, France, 2 Institute for Human Evolution, University of Witwatersrand, Johannesburg, South Africa, 3 Natural History Museum and Biodiversity Research Center, The University of Kansas, Lawrence, Kansas, United States of America, 4 Laboratoire des Sciences du Climat et de l’Environnement/IPSL, UMR 1572, CEA/CNRS/UVSQ, CE Saclay, L’Orme des Merisiers, Gif-sur-Yvette, France, 5 EPHE, UMR5805-EPOC, Universite´ Bordeaux 1, CNRS, Talence, France Abstract Background: Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH).
    [Show full text]
  • Tropical Climate and Vegetation Cover During Heinrich Event 1: Simulations with Coupled Climate- Vegetation Models
    Tropical climate and vegetation cover during Heinrich event 1: Simulations with coupled climate- vegetation models Dissertation zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften Dr. rer. nat. im Fachbereich 5 (Geowissenschaften) der Universität Bremen vorgelegt von Dian Noor Handiani Bremen, Oktober 2012 Erklärung Name: Dian Noor Handiani Anschrift: Woltmershauser straße 464, 28197 Bremen, Deutschland Hiermit versichere ich, dass ich 1. die Arbeit ohne unerlaubte fremde Hilfe angefertigt habe, 2. keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt habe und 3. die den benutzten Werken wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich gemacht habe. Bremen, Oktober 2012 (Unterschrift) Gutachter Prof. Dr. Michael Schulz Prof. Dr. Michal Kucera Promotionskolloquium: 20.12.2012 Mitglieder der Kommission: Herr Prof. Dr. Michael Schulz Herr Prof. Dr. Michal Kucera Herr Prof. Dr. Gerold Wefer Frau Prof. Dr. Gesine Mollenhauer Frau Dr. Lydie Dupont Frau Annegret Krandick Table of Content Acknowledgements i Summary iii Zusammenfassung v 1 Introduction 1 1.1 Motivation of study ………………………………………………………………… 1 1.2 Tropical climate and vegetation in the Heinrich events ……………….......... 3 1.3 Atlantic Meridional Overturning Circulation (AMOC) ………………………. 6 1.4 Research objectives ………………………………………………………………… 9 1.5 Research approach and chapter outline ………………………………………… 10 2 Methodology 11 2.1 The UVic ESCM ……………………………………………………………………. 11 2.1.1 The atmospheric model …………………………………………………….. 11 2.1.2 The ocean and sea-ice model ……………………………………………… 13 2.1.3 The land surface and dynamic vegetation models …………………….. 14 2.2 Plant functional types and biomes ………………………………………………. 15 2.3 A scheme of biome distribution estimation …………………………………….. 16 2.4 Experimental design ………………………………………………………………. 17 3 Tropical climate and vegetation changes during Heinrich event 1: 19 a model-data comparison 3.1 Abstract ……………………………………………………………………………… 19 3.2 Introduction ………………………………………………………………………….
    [Show full text]
  • The Last Glacial Maximum and Heinrich Event I on the Iberian Peninsula: a Regional Climate Modelling Study for Understanding Human Settlement Patterns
    Geophysical Research Abstracts Vol. 20, EGU2018-7848, 2018 EGU General Assembly 2018 © Author(s) 2018. CC Attribution 4.0 license. The Last Glacial Maximum and Heinrich Event I on the Iberian Peninsula: A regional climate modelling study for understanding human settlement patterns Patrick Ludwig (1,2), Yaping Shao (2), Martin Kehl (3), and Gerd-Christian Weniger (4) (1) Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Department Troposphere Research, Karlsruhe, Germany ([email protected]), (2) Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany, (3) Institute of Geography, University of Cologne, Cologne, Germany, (4) Neanderthal Museum, Mettmann, Germany The dating and spatial distribution of archaeological sites on the Iberian Peninsula (IP) suggest a poor occupation of the Southern IP by hunter-gatherers after the Last Glacial Maximum (LGM) and during Heinrich event 1 (H1) compared to Northern Iberia. The H1 was a period of cold and arid climate conditions and is assumed to have played an important role in the population dynamics in Europe at the end of the Pleistocene. In this study, the potential influence of climate change on the human settlement patterns on the IP is analysed based on regional paleoclimate modelling. The WRF model is used to simulate continuous time slices of 30 years of climate con- ditions representative for both the LGM and H1 at high spatial resolution (12.5 km). The model results indicate that, apart from a general decrease in temperature, a considerable decrease in precipitation over the southern IP occurred during the H1, that agrees with the available climate proxy data.
    [Show full text]
  • Weakening and Strengthening of the Indian Monsoon During Heinrich
    PUBLICATIONS Paleoceanography RESEARCH ARTICLE Weakening and strengthening of the Indian 10.1002/2013PA002509 monsoon during Heinrich events Key Points: and Dansgaard-Oeschger oscillations • Intensity of Indian monsoon is traced with geochemical and grain size Gaudenz Deplazes1, Andreas Lückge2, Jan-Berend W. Stuut3,4, Jürgen Pätzold3, Holger Kuhlmann3, analyses of sediments 3 3 1,5 • Fluvial versus aeolian sediment input Dorothée Husson , Mara Fant , and Gerald H. Haug to Arabian Sea mimics DO oscillations 1 2 • During Heinrich events the Indian Geological Institute, Department of Earth Sciences, ETH Zürich, Zürich, Switzerland, Bundesanstalt für Geowissenschaften monsoon weakened distinctly und Rohstoffe, Hannover, Germany, 3MARUM-Center for Marine Environmental Sciences, Bremen University, Bremen, Germany, 4NIOZ-Royal Netherlands Institute for Sea Research, Texel, The Netherlands, 5DFG-Leibniz Center for Earth Surface Process and Climate Studies, Institute for Geosciences, Potsdam University, Potsdam, Germany Supporting Information: • Readme • Figure S1 • Figure S2 Abstract The Dansgaard-Oeschger oscillations and Heinrich events described in North Atlantic sediments • Figure S3 and Greenland ice are expressed in the climate of the tropics, for example, as documented in Arabian Sea • Figure S4 sediments. Given the strength of this teleconnection, we seek to reconstruct its range of environmental • Figure S5 • Figure S6 impacts. We present geochemical and sedimentological data from core SO130-289KL from the Indus submarine slope spanning the last ~ 80 kyr. Elemental and grain size analyses consistently indicate that Correspondence to: interstadials are characterized by an increased contribution of fluvial suspension from the Indus River. In G. Deplazes, contrast, stadials are characterized by an increased contribution of aeolian dust from the Arabian Peninsula.
    [Show full text]
  • H4 Abrupt Event and Late Neanderthal Presence in Iberia
    Earth and Planetary Science Letters 258 (2007) 283–292 www.elsevier.com/locate/epsl H4 abrupt event and late Neanderthal presence in Iberia ⁎ Pierre Sepulchre a, , Gilles Ramstein a, Masa Kageyama a, Marian Vanhaeren b, Gerhard Krinner c, María-Fernanda Sánchez-Goñi d, Francesco d'Errico e,f a Laboratoire des Sciences du Climat et de l'Environnement/IPSL, UMR CNRS-CEA-UVSQ 1572, CE Saclay, L'Orme des Merisiers Bât. 701, 91191 Gif sur Yvette Cedex, France b Ethnologie Préhistorique, UMR 7041 CNRS-ArScAn, 92023 Nanterre, France c Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS-UJF Grenoble, BP 96, F-38402, Saint Martin d'Hères, France d Ecole Pratique des Hautes Etudes, Département de Géologie et Océanographie, UMR 5805 CNRS-EPOC, Université Bordeaux1, 33405 Talence, France e Institut de Préhistoire et de Géologie du Quaternaire, UMR 5199 CNRS-PACEA, Université Bordeaux1, 33405 Talence, France f Department of Anthropology, George Washington University, 2110 G Street, NW Washington, DC 20052, United States Received 15 November 2006; received in revised form 23 March 2007; accepted 23 March 2007 Available online 31 March 2007 Editor: M.L. Delaney Abstract Heinrich event 4 (H4) is well documented in the North Atlantic Ocean and the adjacent continents as a cooling event 39,000 yr before present (BP). To quantify the impact of this event with respect to climate and vegetation over the Iberian Peninsula, we perform numerical experiments using a high-resolution general circulation model forced by sea surface temperatures before and during H4. Our model simulates an expansion of aridity over the peninsula during H4, a desertification of the south, and a replacement of arboreal by herbaceous plants in the north, all of which are in agreement with contemporaneous pollen sequences from marine cores located off the Iberian Peninsula.
    [Show full text]
  • The Connected Isotopic Water Cycle in the Community Earth System Model Version 1
    RESEARCH ARTICLE The Connected Isotopic Water Cycle in the Community 10.1029/2019MS001663 Earth System Model Version 1 Key Points: E. Brady1 , S. Stevenson2 , D. Bailey1 , Z. Liu3, D. Noone4 , J. Nusbaumer5 , • An isotope‐enabled version of the 1 6 1 7 8 9 Community Earth System Model B. L. Otto‐Bliesner , C. Tabor , R. Tomas , T. Wong , J. Zhang , and J. Zhu (iCESM1) is now publicly available 1 2 • iCESM1 simulates the major Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA, Bren School observed features of δ18O and δD of Environmental Science & Management, University of California, Santa Barbara, CA, USA, 3Department of Geography, over the late twentieth century The Ohio State University, Columbus, OH, USA, 4College of Earth, Ocean, & Atmospheric Sciences, Oregon State • iCESM1 is useful for both modern University, Corvallis, OR, USA, 5NASA Goddard Institute for Space Studies and Center for Climate Systems Research, climate and paleoclimate 6 applications Columbia University, New York, NY, USA, Department of Geosciences, University of Connecticut, Storrs, CT, USA, 7Department of Computer Science, University of Colorado Boulder, Boulder, CO, USA, 8Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM, USA, 9Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA Correspondence to: S. Stevenson, [email protected] Abstract Because of the pervasive role of water in the Earth system, the relative abundances of stable isotopologues of water are valuable for understanding atmospheric, oceanic, and biospheric processes, Citation: and for interpreting paleoclimate proxy reconstructions. Isotopologues are transported by both large‐scale Brady, E., Stevenson, S., Bailey, D., Liu, and turbulent flows, and the ratio of heavy to light isotopologues changes due to fractionation that can Z., Noone, D., Nusbaumer, J., et al (2019).
    [Show full text]
  • Millennial‐Scale Sea Surface Temperature Changes in the Eastern Mediterranean (Nile River Delta Region) Over the Last 27,000 Years Isla S
    PALEOCEANOGRAPHY, VOL. 25, PA1208, doi:10.1029/2009PA001740, 2010 Click Here for Full Article Millennial‐scale sea surface temperature changes in the eastern Mediterranean (Nile River Delta region) over the last 27,000 years Isla S. Castañeda,1 Enno Schefuß,2 Jürgen Pätzold,2,3 Jaap S. Sinninghe Damsté,1 Syee Weldeab,4 and Stefan Schouten1 Received 28 January 2009; revised 17 August 2009; accepted 7 October 2009; published 10 March 2010. k′ [1] In this study we utilize two organic geochemical proxies, the U37 index and TEX86,toexaminepastsea surface temperatures (SST) from a site located near the Nile River Delta in the eastern Mediterranean (EM) k′ Sea. The U37 and TEX86 records generally are in agreement and indicate SST ranges of 14°C–26°C and 14°C–28°C, respectively, during the last 27 cal ka. During the Holocene, TEX86‐based SST estimates are k′ usually higher than U37‐based SST estimates, which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the EM and is related to the onset of the modern flow regime of the Nile River. Both records show that SST varied on centennial to millennial timescales in response to global climate events, i.e., cooling during the Last Glacial Maximum (LGM), Heinrich event 1 (H1), and the Younger Dryas (YD) and warming during the Bølling‐Allerød and in the early Holocene during deposition of sapropel S1. The H1 cooling was particularly severe and is marked by a drop in SST of ∼4.5°C in comparison to pre‐H1 SST, with temperatures >1°C cooler than during the LGM.
    [Show full text]
  • Heinrich Events Show Two-Stage Climate Response in Transient Glacial Simulations
    Clim. Past, 15, 153–168, 2019 https://doi.org/10.5194/cp-15-153-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Heinrich events show two-stage climate response in transient glacial simulations Florian Andreas Ziemen, Marie-Luise Kapsch, Marlene Klockmann, and Uwe Mikolajewicz Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany Correspondence: Florian Andreas Ziemen (fl[email protected]) Received: 23 February 2018 – Discussion started: 21 March 2018 Revised: 14 December 2018 – Accepted: 22 December 2018 – Published: 24 January 2019 Abstract. Heinrich events are among the dominant modes 1 Introduction of glacial climate variability. During these events, massive iceberg armadas were released by the Laurentide Ice Sheet Heinrich events (Heinrich, 1988), one of the two dominant and sailed across the Atlantic where they melted and re- modes of glacial climate variability, are associated with a leased freshwater, as well as detritus, that formed character- reorganization of the North Atlantic Ocean circulation (see istic layers on the seafloor. Heinrich events are known for Clement and Peterson, 2008, for a review). They are quasi- cold climates in the North Atlantic region and global climate periodic with a recurrence period of about 7 kyr and fall into changes. We study these events in a fully coupled complex the Dansgaard–Oeschger cold periods (stadials). In Hein- ice sheet–climate model with synchronous coupling between rich events, iceberg armadas released from the Laurentide Ice ice sheets and oceans. The ice discharges occur as an inter- Sheet spread a characteristic trace of detritus from the Hud- nal variability of the model with a recurrence period of 5 kyr, son Strait area across the North Atlantic seafloor.
    [Show full text]
  • Orbital and Millennial-Scale Precipitation Changes in Brazil from Speleothem Records
    Chapter 2 Orbital and Millennial-Scale Precipitation Changes in Brazil from Speleothem Records Francisco W. Cruz, Xianfeng Wang, Augusto Auler, Mathias Vuille, Stephen J. Burns, Lawrence R. Edwards, Ivo Karmann, and Hai Cheng Abstract Paleorainfall variability on orbital and millennial time scales is discussed for the last glacial period and the Holocene, based on a multi-proxy study of speleothem records from Brazil. Oxygen isotope (δ18O) records from Botuverá and Santana caves, precisely dated by U-series methods, indicate stronger summer monsoon circulation in subtropical Brazil during periods of high summer insola- tion in the southern hemisphere. In addition, variations in Mg/Ca and Sr/Ca ratios from speleothems confirm that this monsoon intensification led to an increase in the long-term mean rainfall during insolation maxima. However, they also suggest that glacial boundary conditions, especially ice volume buildup in the northern hemi- sphere, promoted an additional displacement of the monsoon system to the south, which produced rather wet conditions during the period from approximately 70 to 17 ka B.P., in particular at the height of the Last Glacial Maximum (LGM). These δ18O records, together with speleothem growth intervals from northeastern Brazil, have also revealed new insights into the influence of the northern hemi- sphere millennial-scale events on the tropical hydrological cycle in South America. This teleconnection pattern is expressed by an out-of-phase relationship between precipitation changes inferred from speleothem records in Brazil and China, partic- ularly during Heinrich events and the Younger Dryas. We argue that the pronounced hemispheric asymmetry of moisture is a reflection of the impact of meridional overturning circulation conditions on the position and intensity of the intertropical convergence zone (ITCZ).
    [Show full text]
  • Abrupt Shifts of the Sahara-Sahel Boundary During Heinrich Stadials J
    Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Clim. Past Discuss., 9, 119–142, 2013 www.clim-past-discuss.net/9/119/2013/ Climate doi:10.5194/cpd-9-119-2013 of the Past © Author(s) 2013. CC Attribution 3.0 License. Discussions This discussion paper is/has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP if available. Abrupt shifts of the Sahara-Sahel boundary during Heinrich Stadials J. A. Collins1, A. Govin1, S. Mulitza1, D. Heslop2, M. Zabel1, J. Hartmann3, U. Rohl¨ 1, and G. Wefer1 1MARUM – Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, 28359 Bremen, Germany 2Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia 3Institute for Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany Received: 14 December 2012 – Accepted: 20 December 2012 – Published: 4 January 2013 Correspondence to: J. A. Collins ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 119 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract Relict dune fields that are found at 14◦ N in the modern-day African Sahel are tes- tament to equatorward expansions of the Sahara desert during the late Pleistocene. However, difficulties of dating dune formation mean that abrupt millennial-scale climate 5 events are not always resolved in these records. High-resolution marine core studies have identified Heinrich Stadials as the dustiest periods of the last glacial, although no studies have mapped the spatio-temporal evolution of dust export from West Africa.
    [Show full text]
  • Anatomy of Heinrich Layer 1 and Its Role in the Last Deglaciation
    PUBLICATIONS Paleoceanography RESEARCH ARTICLE Anatomy of Heinrich Layer 1 and its role 10.1002/2016PA003028 in the last deglaciation Key Points: David A. Hodell1 , Joseph A. Nicholl1 , Tomaso R. R. Bontognali2, Steffan Danino3 , • Heinrich Layer 1 is represented by a 4 3 1 5 double peak in the central North Javier Dorador , Julian A. Dowdeswell , Joshua Einsle , Holger Kuhlmann , 6 1 4 Atlantic Belen Martrat , Maryline J. Mleneck-Vautravers , Francisco Javier Rodríguez-Tovar , • Best estimates for the ages of the two and Ursula Röhl5 peaks are ~16.1 (H1.1) and ~15 ka (H1.2) 1Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge, UK, • Heinrich Event 1 cannot account for 2 3 cooling and weakened AMOC during Geological Institute and Institute of Geochemistry and Petrology, ETH Zurich, Zurich, Switzerland, Scott Polar Research 4 early Heinrich Stadial 1 (~20–16.1 ka) Institute, Department of Geography, University of Cambridge, Cambridge, UK, Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada, Spain, 5MARUM–Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany, 6Department of Environmental Chemistry, Institute of Environmental Assessment and Water Supporting Information: fi • Supporting Information S1 Research (IDÆA), Spanish Council for Scienti c Research (CSIC), Barcelona, Spain • Movie S1 • Movie S2 • Figure S1 Abstract X-ray fluorescence (XRF) core scanning and X-ray computed tomography data were measured • Figure S2 every 1 mm to study the structure of Heinrich Event 1 during the last deglaciation at International Ocean • Figure S3 Discovery Program Site U1308. Heinrich Layer 1 comprises two distinct layers of ice-rafted detritus (IRD), which are rich in detrital carbonate (DC) and poor in foraminifera.
    [Show full text]
  • Catastrophic Ice Shelf Breakup As the Source of Heinrich Event Icebergs Christina L
    PALEOCEANOGRAPHY, VOL. 19, PA1004, doi:10.1029/2003PA000890, 2004 Catastrophic ice shelf breakup as the source of Heinrich event icebergs Christina L. Hulbe,1 Douglas R. MacAyeal,2 George H. Denton,3 Johan Kleman,4 and Thomas V. Lowell5 Received 31 January 2003; revised 4 August 2003; accepted 8 October 2003; published 22 January 2004. [1] Heinrich layers of the glacial North Atlantic record abrupt widespread iceberg rafting of detrital carbonate and other lithic material at the extreme-cold culminations of Bond climate cycles. Both internal (glaciologic) and external (climate) forcings have been proposed. Here we suggest an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the Antarctic Peninsula: rapid disintegrations of fringing ice shelves induced by climate-controlled meltwater infilling of surface crevasses. We postulate that peripheral ice shelves, formed along the eastern Canadian seaboard during extreme cold conditions, would be vulnerable to sudden climate-driven disintegration during any climate amelioration. Ice shelf disintegration then would be the source of Heinrich event icebergs. INDEX TERMS: 3344 Meteorology and Atmospheric Dynamics: Paleoclimatology; 1827 Hydrology: Glaciology (1863); 4267 Oceanography: General: Paleoceanography; KEYWORDS: Heinrich events, ice shelf disintegration Citation: Hulbe, C. L., D. R. MacAyeal, G. H. Denton, J. Kleman, and T. V. Lowell (2004), Catastrophic ice shelf breakup as the source of Heinrich event icebergs, Paleoceanography, 19, PA1004, doi:10.1029/2003PA000890. 1. Introduction 1.2. Previously Proposed Heinrich Event Mechanisms 1.1. Signature of Heinrich Events [3] The origin of the Heinrich events remains a major [2] Six major pulses of ice-rafted detritus (IRD) mark unsolved problem in Pleistocene climatology.
    [Show full text]