DOCSLIB.ORG

U.S. Earth System History Science

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
U.S. Earth System History Science PAGES International Project Offi ce Sulgeneckstrasse 38 3007 Bern Switzerland Tel: +41 31 312 31 33 Fax: +41 31 312 31 68 [email protected] Text Editing: Leah Christen News Layout: Christoph Kull Julie Brigham-Grette, Christoph Kull and Circulation: 3700 Thorsten Kiefer, Editors VOL.14, N°2 – AUGUST 2006 U.S. Earth System History Science An unusual debris ladened iceberg photographed off the coast of East Greenland close to the site of JM96- 1205 (see Fig. 1 on page 8). It appears that the iceberg has turned over thus revealing what was probably the basal debris zone of a tidewater outlet glacier (photographer: Anne E. Jennings, Sept. 1996). Contents 2 Announcements www.pages-igbp.org - Editorial: U.S. Earth System History Program - Models and abrupt climate change - Inside PAGES - Late Holocene hydrologic variability in - PAGES-LOTRED-SA meeting in Argentina North American peatlands 3 Program News 29 Science Highlights (open section) - DAYACLIM: A Sahara climate program - San Valentin Glacier ice core (Chile) - Holocene climate change (Yemen) 4 National Page - Climate and human evolution (Africa) - Indonesia - Surface temperatures over the past two millennia 5 ESH Science Highlights - East Pacifi c production during the 37 Workshop Reports last deglaciation - HOLIVAR open science meeting - UK - Holocene IRD in the North Atlantic - PAGES/CLIVAR workshop - Switzerland - Dendrochronology and the Asian Monsoon - ICDP workshop PASADO - Argentina - Tropical Pacifi c climate, solar forcing and - Climate change challenge - Sweden the last millennium - LUCIFS workshop - Germany - The mystery interval 17.5 - 14.5 kyr ago - Ocean-Land INQUA workshop - Spain - South American Monsoon and the LGM - Indonesian throughfl ow - Germany - U.S. lake drilling projects - Post glacial oaks in North America 44 Last Page - Consolidating high and low frequency - Calendar information for climate reconstructions - New on the PAGES bookshelf ISSN 1563–0803 The PAGES International Project Offi ce and its publications are supported by the Swiss and US National Science Foundations and NOAA. 2 Announcements Editorial: U.S. Earth System History Program in Transition A significant portion of paleoclimate science conducted by the United States over the past 14 years has been carried out through proposals to the Earth System History (ESH) Program of the U.S. National Science Founda- tion (NSF). This cross-disciplinary program has been jointly supported under the Directorate for Geosciences with contributions from its divisions, including Earth Sciences, Ocean Sciences and Atmospheric Sciences. Initially developed under the U.S. Global Change Research Program involving a number of federal agencies, NSF acutely acknowledged the need for a program to promote pioneering research on the temporal and spatial scales of natural climate variability, climate proxies, and modeling in order to better understand the forcing mechanisms, systemic sensitivities, and feedbacks responsible for past climate change on regional and global scales. Partnerships for shared support of selected proposals were also fostered in the earlier years with the NSF Office of Polar Programs and the National Oceanic and Atmospheric Administration’s (NOAA) former Paleoclimate element in the Office of Global programs (now known as the Climate Change Data and Detection element in the Climate Program Office). Since its inception, the ESH program has been guided by an adhoc advisory group composed of scientists on rotation from a range of disciplines who periodically sought community input to guide program manag- ers in developing targeted areas of emphasis for annual solicitations as the science evolved. The program has supported a vast range of projects world-wide, primarily but not exclusively, aimed at high-resolution climate records using a variety of sedimentary, geochemical, and biogeochemical paleo-proxies from diverse environments to develop both qualitative and quantitative estimates of past change. The program has par- ticularly encouraged over time the integration of empirical and observational data with a variety of model simulations of regional and global climate change. Recent initiatives of emphasis within the ESH program have focused on topics including Holocene change, abrupt change on a variety of timescales, and regional vs. global scale change. Because the solicitation for the ESH program expires September 30, 2006, NSF and the science commu- nity are now poised to determine how this successful program might evolve in the coming years to address ongoing and future scientific needs (see www.nsf.gov/pubs/2006/nsf06029/nsf06029.jsp). Plans are now be- ing formulated for an official review, during which time the Directorate for Geosciences will continue to seek community input during the decision making process. An initial workshop held in November 2005 focused on a few relevant cross-cutting science questions and the workshop recommendations are available at www. mesh.usc.edu/workshop.htm for community comment. The short articles presented in this issue were volunteered at large from ESH-funded researchers and repre- sent only a small cross-section of the range of science address by the ESH initiative. To learn more about past ESH initiatives, go to the ESH website at www.nsf.gov/funding/pgm_summ.jsp?pims_id=5750&org=ATM. JULIE BRIGHAM-GRETTE PAGES SSC Chair [email protected] Tales from the field Do you have an interesting and humorous story from your paleoenvironmental fieldwork? Send us your tale (max. 500 words) so that we can publish it in PAGES News! ��������������������������������������������������� ������������������ ������ ����� ��� ����� ���������� ���������������� ��� ���� ���������� ��� ���� �������� ������������ ��� ����� ����� ���� ��� ������ ����� ����� �� ���� ������ ��� ����������� ����� ���� ����� ��� ���� �������� ������ ���� ���� ��������� �� ����� ��� ������ ����������� �������� ����� ��� ���� ������ ����� ��� ����� ��� ���� ���� �������� ��������� ���������������������������������������������������������������� PAGES NEWS, VOL.14, N°2, AUGUST 2006 Announcements 3 In early June, the PAGES-CLIVAR tions will close 15 September 2006. workshop on Past Millennia Variabil- We particularly encourage nomina- Inside PAGES ity, organized by the PAGES office, tions of paleoscientists from eastern was held in Wengen, Switzerland. Asia, and from Russia and former This very successful event will al- Soviet Union countries, since these This spring, the PAGES office was so have some follow-up activities. geographic regions will be under- busy keeping different PAGES proj- Read more in the workshop report represented when current members ects on track: on page 38. leave at the end of this year. For de- Several guest scientists spent Finally, the PAGES office has tails, please go to: www.pages-igbp. a few days to a few weeks at the been engaged in organizing several org/people/sscleaders/nominations. PAGES office. Bert Rein compiled an upcoming fall activities. The IGBP- html. extensive National PAGES Germany SCOR Fast Track Initiative on Ocean website and Sri Yudawati Cahyarini Acidification will hold its first work- Next issue of PAGES News: set up the Indonesian PAGES (page shop at the end of September in the The next issue of the PAGES news- 5, this issue). All 18 of the currently USA (http://igbp-scor.pages.unibe. letter will be published in December. available national PAGES websites ch/firstworkshop.html). Regional It will contain an open section on are online at: www.pages-igbp.org/ Variability workshops will be held general paleoscience themes and a about/national/. A few more Nation- for the Mediterranean area, together special section on radiocarbon chro- al PAGES are in the pipeline and will with the MEDCLIVAR program, in nometry. Please send your contribu- be ready in autumn this year. Spain in November, and for South tions of science highlights, program In May, the IPO, with the help America, alongside the annual news, workshop reports and humor- of Isabelle Larocque, organized the PAGES SSC meeting, in Argentina ous tales from the field to Christoph second Databoard meeting, at the in October. Information is available Kull ([email protected]) by 31 Oc- PAGES office in Bern. This project, on our calendar webpage (www. tober 2006. Guidelines can be found which aims to develop a better da- pages-igbp.org/calendar/). at www.pages-igbp.org/products/ ta network in the near future, will newsletters/instructions.html. be of special benefit to the paleo- SSC nominations community. Further information is At the upcoming SSC meeting, two available at www.pages-igbp.org/ new SSC members will be elected. services/data/. The related Open Call for Nomina- Regional Climate Variations in South America over the late Holocene October 4-7, 2006; Malargüe, Mendoza, Argentina The aim of this meeting is to deepen the academic interactions among paleoclimatologists of South America, without neglecting the presence of notable investigators from outside the region. During the four day meeting, the conference will be organized around 8 thematic sessions related to climatic, high-resolution paleoclimatic and numerical modeling studies in South America. The preliminary sessions are related to: - Documentary data and early instrumental data - Tree rings - Lake and marine sediments - Ice cores - Glaciers - Pollen and vegetation records - Multi-proxy reconstruction methods - Climate and modeling Abstract Deadline: 8 September, 2006 Further Infromation: www.pages-igbp.org/science/initiatives/lotred-sa Claudia
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]
  • Chapter 2. Ocean Observations
    Chapter 2. Ocean observations 2.1 Observational methods Before we introduce the observational instruments and methods, we will first introduce some definitions related to observations. Accuracy: The difference between a result obtained and the true value. Precision: Ability to measure consistently within a given data set (variance in the measurement itself due to instrument noise). Generally the precision of oceanographic measurements is better than the accuracy. 2.1.1 Measurements of depth. Each oceanographic variable, such as temperature (T), salinity (S), density , and current , is a function of space and time, and therefore a function of depth. In order to determine to which depth an instrument has been lowered, we need to measure ``depth''. Meter wheel. The wire is passed over a meter wheel, which is simply a pulley of known circumference with a counter attached to the pulley to count the number of turns, thus giving the depth the instrument is lowered. This method is accurate when the sea is calm with negligible currents. In reality, ship is moving and currents are strong, the wire is not straight. The real depth is shorter than the distance the wire paid out. Measure pressure. Derive depth from hydrostatic relation: where g=9.8m/s2 is acceleration of gravity and is depth. (i) Protected and unprotected reversing thermometer developed especially for oceanographic use. They are mercury- in-glass thermometers which are attached to a water sampling bottle. The pressure was measured using the pair of reversing thermometers - one protected from seawater pressure by a vacuum and the other open to the seawater pressure.
    [Show full text]
  • Response of Biological Productivity to North Atlantic Marine Front Migration During the Holocene
    Clim. Past, 17, 379–396, 2021 https://doi.org/10.5194/cp-17-379-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Response of biological productivity to North Atlantic marine front migration during the Holocene David J. Harning1,2,3, Anne E. Jennings2,3, Denizcan Köseoglu˘ 4, Simon T. Belt4, Áslaug Geirsdóttir1, and Julio Sepúlveda2,3 1Faculty of Earth Sciences, University of Iceland, Reykjavík, Iceland 2Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA 3Department of Geological Sciences, University of Colorado, Boulder, USA 4Biogeochemistry Research Centre, Plymouth University, Plymouth, UK Correspondence: David J. Harning ([email protected]) Received: 9 September 2020 – Discussion started: 18 September 2020 Revised: 22 December 2020 – Accepted: 4 January 2021 – Published: 8 February 2021 Abstract. Marine fronts delineate the boundary between dis- 1 Introduction tinct water masses and, through the advection of nutrients, are important facilitators of regional productivity and bio- diversity. As the modern climate continues to change, the Marine fronts are the boundary that separates different water migration of frontal zones is evident, but a lack of infor- masses and are a globally ubiquitous feature in the oceans mation about their status prior to instrumental records hin- (Belkin et al., 2009). By nature, marine fronts are charac- ders future projections. Here, we combine data from lipid terized by strong horizontal gradients of typically correlated
    [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]