DOCSLIB.ORG

Tropical Climate and Vegetation Cover During Heinrich Event 1: Simulations with Coupled Climate- Vegetation Models

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read 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 …………………………………………………………………………. 20 3.3 Methods and experimental design ………………………………………………. 22 3.3.1 The UVic ESCM and TRIFFID DGVM …………………………………... 22 3.3.2 Simulation design and boundary conditions …………………………….. 23 3.3.3 Biome analysis from TRIFFID …………………………………………….. 24 3.4 The equilibrium simulations ……………………………………………………... 26 3.4.1 Pre-industrial simulation (PI_CNTRL) ………………………………….. 26 3.4.2 Last Glacial Maximum simulation (LGM) ………………………………. 31 3.5 Heinrich events 1 simulations …………………………………………………… 34 3.5.1 Changes in climate ………………………………………………………….. 34 3.5.2 Changes in vegetation ………………………………………………………. 38 3.5.3 Biome distribution and model-data comparison ………………………... 39 3.6 Discussion …………………………………………………………………………… 41 3.7 Summary and conclusions ………………………………………………………… 45 3.8 Acknowledgements ………………………………………………………………… 47 4 Climate and vegetation changes around the Atlantic Ocean resulting 49 from changes in the meridional overturning circulation during deglaciation 4.1 Abstract ……………………………………………………………………………… 49 4.2 Introduction …………………………………………………………………………. 50 4.3 Model description and experimental designs ………………………………….. 51 4.4 Results ……………………………………………………………………………….. 53 4.4.1 The variability of AMOC and physical ocean properties ………………. 53 4.4.2 Precipitation and vegetation response …………………………………… 59 4.4.3 Comparison between model and paleovegetation data ………………… 62 4.5 Discussion …………………………………………………………………………… 64 4.6 Conclusion …………………………………………………………………………… 69 4.7 Acknowledgements ………………………………………………………………… 70 5 Tropical vegetation response to Heinrich event 1 as simulated with the 71 UVic ESCM and CCSM3 5.1 Abstract ……………………………………………………………………………… 71 5.2 Introduction ………………………………………………………………………… 72 5.3 Models and experimental design ………………………………………………… 73 5.4 Results ……………………………………………………………………………….. 76 5.4.1 Climate changes ……………………………………………………………… 76 5.4.2 The vegetation cover response …………………………………………….. 79 5.4.3 Biomes distribution comparison …………………………………………... 82 5.5 Discussion …………………………………………………………………………… 84 5.6 Conclusion …………………………………………………………………………… 87 5.7 Acknowledgements ………………………………………………………………… 88 6 Summary of the results 89 6.1 The HE1 climate and vegetation in the tropics ……………………………….. 89 6.2 The BA climate and vegetation in the region around the Atlantic Ocean … 91 6.3 A method for estimating a biome distribution from model outputs ………... 92 7 Conclusion and Outlook 93 7.1 Conclusion …………………………………………………………………………… 93 7.2 Outlook ………………………………………………………………………………. 94 Appendix 95 Biomes estimation flow chart ……………………………………………………………….. 95 Bibliography 97 Acknowledgments The first three years of this PhD were financially supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the German contribution to the Integrated Ocean Drilling Program (SPP 527) “Abrupt Climate Change in the African Tropics (ACCAT)” and the DFG Research Center/Excellence Cluster “The Ocean in the Earth System”, and the finishing stage of the study was funded by “The Excellent Scholarship Program by Bureau of Planning and International Cooperation”, Secretary-General of Ministry of Education and Culture, Indonesia. The work itself was carried out at the Geosciences Department of the University of Bremen, in Germany. I would like to thank the Center for Marine Environmental Sciences (MARUM) and the University of Bremen for giving me the opportunities to attend several international courses, workshops and conferences. I would like to express my gratitude to Prof. Michael Schulz and Dr. André Paul for giving me the experience to work in such an inspiring and motivating environment, and my high appreciation to André especially for his daily patient assistance. His guidance in introducing me into the world of paleoclimate modeling enables me to finish this challenging study. I would like to thank to Dr. Lydie Dupont for her guidance through understanding the pollen proxies study and also together with André in helping me to improve my writing skill as well as to direct my research. I would thank to all the co- authors for their inputs and suggestions in writing my research papers. I also thank Xiao Zhang who simulated the HE1 experiment on the CCSM3, which are used and analysed in this study. I would also like to thank Dr. Andreas Manschke for solving quickly all computer problems, as well as Leslie Sütterlin for her great help with all administration-related work. A general thanks to all the Geomod members for their support and valuable suggestions during the group seminars and also for the many entertaining cakes and coffee breaks, especially Vidya, Ute, Heather, Claudia, Takasumi, Gerlinde, Nilima, Huadong and others. Special thanks to my officemates, Thejna, Xiao and Amanda, who have been supportive in every way. I definitely will miss you guys! A special thank to Rima, her beloved husband (Ayi) and “little” Khansa, who sincerely were willing to share their home, during my time in Bremen. General thanks to all Indonesian friends in Bremen, foremost Family Vidjaja for allowing me being part of their family and they have become my second family during my study. I want to deeply thank my long distance Indonesian friends, “Mba” Annastasia, Ulfah, Vigi, Winda, Al-azhar, Aradea and also my teacher back in Indonesia, Dr. Nining Sari Ningsih for their encouragement, endless support and friendship. Despite the distance, they were always there for me and it means a lot. Finally, I would like to express my entire gratitude to my family, who were always my best supporters through my whole life, especially my mom within these recent years, her tremendous support and faith in me were the driving forces behind everything I did. i ii Summary This study focuses on the climate and vegetation responses to abrupt climate change in the Northern Hemisphere during the last glacial period. Two abrupt climate events are explored: the abrupt cooling of the Heinrich event 1 (HE1), followed by the abrupt warming of the Bølling-Allerød interstadial (BA). These two events are simulated by perturbing the freshwater balance of the Atlantic Ocean, with the intention of altering the Atlantic Meridional Overturning Circulation (AMOC) and also of influencing the Intertropical Convergence Zone (ITCZ) and its associated rainbelt. The University of Victoria Earth System-Climate Model (UVic ESCM) is applied in these experiments. The plant-functional types and the temperature from the model output are used for calculating the biome distribution, which is then compared to the available pollen records. In addition, an inter-model comparison for the HE1 is carried out by comparing the UVic ESCM with the Community Climate System Model version 3 (CCSM3). In the UVic ESCM, the HE1 climate is imitated by adding freshwater to the St. Lawrence River where it runs into the North Atlantic Ocean, which causes a slowdown of the AMOC. The weakening of the AMOC is followed by a cooler climate in the North Atlantic Ocean and a warmer climate in the South Atlantic Ocean. This surface temperature see-saw between the Northern and Southern Hemispheres causes a southward shift of the tropical rainbelt. The simulated drier climate north of the Equator during the HE1 event causes an increase of desertification and the retreat of broadleaf forests in West Africa and northern South America. On one hand, the model results for the HE1 event can be shown to be in agreement with the pollen records from tropical Africa and northern South America. On the other hand, the model fails to predict savannah and grassland in
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]
  • 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]
  • Hudson Strait'' Heinrich Events in the Eastern North Atlantic at The
    PALEOCEANOGRAPHY, VOL. 23, PA4218, doi:10.1029/2008PA001591, 2008 Click Here for Full Article Onset of ‘‘Hudson Strait’’ Heinrich events in the eastern North Atlantic at the end of the middle Pleistocene transition (640 ka)? David A. Hodell,1,2 James E. T. Channell,1 Jason H. Curtis,1 Oscar E. Romero,3 and Ursula Ro¨hl4 Received 15 January 2008; revised 28 July 2008; accepted 10 September 2008; published 27 December 2008. [1] Heinrich events are well documented for the last glaciation, but little is known about their occurrence in older glacial periods of the Pleistocene. Here we report scanning XRF and bulk carbonate d18O results from Integrated Ocean Drilling Program Site U1308 (reoccupation of Deep Sea Drilling Project Site 609) that are used to develop proxy records of ice-rafted detritus (IRD) for the last 1.4 Ma. Ca/Sr is used as an indicator of IRD layers that are rich in detrital carbonate (i.e., Heinrich layers), whereas Si/Sr reflects layers that are poor in biogenic carbonate and relatively rich in detrital silicate minerals. A pronounced change occurred in the composition and frequency of IRD at 640 ka during marine isotope stage (MIS) 16, coinciding with the end of the middle Pleistocene transition. At this time, ‘‘Hudson Strait’’ Heinrich layers suddenly appeared in the sedimentary record of Site U1308, and the dominant period of the Si/Sr proxy shifted from 41 ka prior to 640 ka to 100 ka afterward. The onset of Heinrich layers during MIS 16 represents either the initiation of surging of the Laurentide Ice Sheet (LIS) off Hudson Strait or the first time icebergs produced by this process survived the transport to Site U1308.
    [Show full text]