DOCSLIB.ORG

Tree Ring Effects and Ice Core Acidities Clarify the Volcanic Record of the First Millennium

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tree Ring Effects and Ice Core Acidities Clarify the Volcanic Record of the First Millennium Clim. Past, 11, 105–114, 2015 www.clim-past.net/11/105/2015/ doi:10.5194/cp-11-105-2015 © Author(s) 2015. CC Attribution 3.0 License. Tree ring effects and ice core acidities clarify the volcanic record of the first millennium M. G. L. Baillie1 and J. McAneney2 1School of Geography, Archaeology and Palaeoecology, Elmwood Avenue, Queen’s University, Belfast, Belfast BT7 1NN, Northern Ireland, UK 2Independent Researcher, Bangor, Northern Ireland, UK Correspondence to: M. G. L. Baillie ([email protected]) Received: 28 February 2014 – Published in Clim. Past Discuss.: 15 April 2014 Revised: 8 December 2014 – Accepted: 12 December 2014 – Published: 16 January 2015 Abstract. In 2012 Plummer et al., in presenting the volcanic 1 Background chronology of the Antarctic Law Dome ice core, chose to list connections to acid layers in other ice cores and also Large explosive volcanic eruptions can induce hemispheric, possible chronological coincidences between ice acid dates and occasionally global, environmental effects through the and the precise dates of frost damage, and/or reduced growth injection of sulfate aerosols into the stratosphere altering the in North American bristlecone pines. We disagree with the absorption and reflection of solar radiation within the atmo- chronological links indicated by Plummer et al. for the period sphere, producing an overall cooling effect on global climate before AD 700, and in this paper we show that a case can be (Rampino and Self, 1982). Attempts to trace the areal ex- made that better linkages between ice acid and tree ring ef- tent of such environmental effects rely mostly on evidence fects occur for this period if the ice chronologies are system- of tree growth response to climate derived from precisely atically moved forward by around 7 years, consistent with a dated tree ring chronologies. For example, Briffa et al.(1998) hypothesis published by Baillie in 2008. In the paper we seek investigated the relationship between maximum latewood to explore the proposition that frost damage rings in North density (MXD) in high-latitude and high-elevation conifers American bristlecone pines are a very useful indicator of the from around the Northern Hemisphere and historical erup- dates of certain large explosive volcanic eruptions; the dating tions, while Scuderi(1990) assessed growth minima in fox- of major eruptions being critical for any clear understanding tail pines from the Sierra Nevada against volcanic records of volcanic forcing. This paper cannot prove that there is an back to 1000 BC. error in the Greenland Ice Core Chronology 2005 (GICC05), In 1984 LaMarche and Hirschboeck postulated a rela- and in equivalent ice chronologies from the Antarctic, how- tionship between frost rings (damage caused by unseasonal ever, it does provide a coherent argument for an apparent ice frost during the growing season) in high-elevation bristle- dating offset. If the suggested offset were to prove correct it cone pines from the western United States and explosive vol- would be necessary to locate where the error occurs in the ice canism. They suggested that climatic dislocation caused by chronologies and in this regard the dating of the increasingly high-altitude volcanic aerosols could cause unseasonal cold controversial Icelandic Eldgjá eruption in the AD 930s, and air to move down the Rockies freezing still growing trees, the China/Korean Millennium eruption which occurs some 7 leaving visible scarring. Although they were able to show years after Eldgjá, may well be critical. In addition, if the off- reasonable linkages between frost rings and volcanoes in re- set were to be substantiated it would have implications for the cent times (for example they noted frost rings in 1912 the alleged identification of tephra at 429.3 m in the Greenland year of the Katmai eruption in Alaska, and in the years 1884, GRIP core, currently attributed to the Italian volcano Vesu- 1837, 1817, 1680, 1640 and 1601, each within 1 or 2 years vius and used as a critical zero error point in the GICC05 of known eruptions), this relationship tended to break down chronology. further back in time when comparisons were made with vol- canic evidence deduced from ice cores, in the absence of his- Published by Copernicus Publications on behalf of the European Geosciences Union. 106 M. G. L. Baillie and J. McAneney: Tree rings and ice cores clarify the volcanic record torically dated volcanoes. This early attempt at linking tree bristlecone pines (LaMarche and Hirschboeck, 1984; Salzer ring effects and ice core acidities was elaborated further by and Hughes, 2007) while only 1838 is singled out as a nar- Salzer and Hughes(2007) who provided lists of frost ring row ring event (Salzer and Hughes, 2007). Unfortunately by and narrow ring dates back to 5000 years ago, while high- raising the issue of narrow rings Salzer and Hughes allowed lighting tree effects that occurred within 5 years of ice core researchers to pick tree ring phenomena – either frost rings or acidity dates. narrow rings – that occurred proximate to volcanic acid sig- From such work certain dates for explosive volcanism nals dated within the ice core chronologies, these links sug- stand out, for example, AD 1640, AD 1601 and AD 1257 gesting support for the dating of the ice cores (Plummer et al., are represented as acid layers in the Greenland Crête and the 2012). Before analysing the deficiencies in this approach it is Greenland Ice Core Project (GRIP) ice cores (Hammer et al., necessary to provide background on the issue of the ice core 1980; Clausen et al., 1997), they show up in the Greenland chronologies. Ice Sheet project (GISP2) core at 1603 ± 2, 1642 ± 2 and Long ice cores mostly exhibit clear annual layering. Vi- 1259 ± 2 (Zielinski, 1995), in the North Greenland Eemian sual inspection is supplemented by study of annually fluc- Ice Drilling “NEEM-2011-S1” (hereafter NEEM S1) and tuating chemical and isotopic signals that allow unequivo- West Antarctic Ice Sheet Divide (WDC06A) cores (Sigl cal identification of most annual layers. However, ice cores et al., 2013) and in the Antarctic Law Dome (Plummer et al., do suffer from periodic “problem layers” where uncertainty 2012), Dronning Maud Land (DML) (Traufetter et al., 2004), creeps into the layer counting. This is handled by adding and South Pole (Ferris et al., 2011) cores. This implies that 0.5 ± 0.5 years for each problem layer (Vinther et al., 2006) these eruptions were equatorial. However, while trees regis- and by accumulating these problem layers an error figure is ter the effects of the 1640 and 1601 eruptions widely (Briffa obtained for ancient dates. This procedure is short-circuited et al., 1998; Scuderi, 1990; Salzer and Hughes, 2007), the by attempts to identify traces of known volcanoes such massive eruption, now believed to have taken place in AD as Öraefajökull (1362), Hekla 1 (1104) and Vesuvius (AD 1257 and attributed to the Salamas volcano in Indonesia 79) in the ice. Indeed it is claimed that acid and tephra at (Lavigne et al., 2013), shows up patchily in trees (Jones et al., 429:1=429:3 m in the GRIP ice core derived specifically from 2013; D’Arrigo et al., 2013) with perhaps the clearest evi- Vesuvius and provide a zero-error point in the ice chronolo- dence for upset being provided by bristlecone pine frost rings gies (Barbante et al., 2013). While this sounds coherent, one in 1257 and 1259 (Salzer and Hughes, 2007). key issue relates to independent replication of the ice acid- What emerges from this background is that bristlecone ity dates in Dye3, GRIP and NGRIP. Vinther et al.(2006) pine frost rings in high-elevation bristlecone pines from the state that “The three ice core records have been synchronized western United States can be, as originally postulated by using volcanic reference horizons”. This involved identify- LaMarche and Hirschboeck(1984), used as sensitive indi- ing significant ECM signals and then independently count- cators of explosive volcanism. Obviously the relationship is ing the layers between the ECM signals. In our view this not one-to-one; not every volcano automatically produces was a flawed procedure. True dating replication could only frost damage in bristlecone pines, while some frost rings ap- be achieved by counting the whole of each core indepen- pear not to be related to volcanism. However, a case exists dently. For comparison, in dendrochronology replication is that numbers of key large volcanic events are associated with often provided by comparing chronologies produced by in- bristlecone pine frost rings (see Supplement). When these oc- dependent workers in independent laboratories. This appar- cur, the precise dating provided by dendrochronology makes ent lack of completely independent replication of the Dye3, frost ring dates important in any attempts to link to histor- GRIP and NGRIP cores makes the identification of Vesuvius ical records of how human populations were affected. Un- tephra in the ice absolutely critical for the chronology of the fortunately, the introduction of narrow ring dates by Salzer European ice cores. That overall chronology, the Greenland and Hughes(2007) served to complicate the relationship be- Ice Core Chronology 2005 (GICC05), has been regarded as tween volcanoes and tree ring effects. Narrow ring occur- definitive since 2006 (Vinther et al., 2006). rences have the disadvantage that they can have a number The reason for rehearsing this history lies in the conclusion of possible causes, in contrast to frost rings which appear un- of the Vesuvius dating paper by Barbante et al.(2013). They equivocally to be caused by anomalous, unseasonal extreme state: “We identified volcanic glass fragments at 429.3 m cold. depth where the elemental analysis strongly suggests that For example, if we look at a recent paper by Jones et al.
Load more

Recommended publications
  • Conversion of GISP2-Based Sediment Core Age Models to the GICC05 Extended Chronology
    Quaternary Geochronology 20 (2014) 1e7 Contents lists available at ScienceDirect Quaternary Geochronology journal homepage: www.elsevier.com/locate/quageo Short communication Conversion of GISP2-based sediment core age models to the GICC05 extended chronology Stephen P. Obrochta a, *, Yusuke Yokoyama a, Jan Morén b, Thomas J. Crowley c a University of Tokyo Atmosphere and Ocean Research Institute, 227-8564, Japan b Neural Computation Unit, Okinawa Institute of Science and Technology, 904-0495, Japan c Braeheads Institute, Maryfield, Braeheads, East Linton, East Lothian, Scotland EH40 3DH, UK article info abstract Article history: Marine and lacustrine sediment-based paleoclimate records are often not comparable within the early to Received 14 March 2013 middle portion of the last glacial cycle. This is due in part to significant revisions over the past 15 years to Received in revised form the Greenland ice core chronologies commonly used to assign ages outside of the range of radiocarbon 29 August 2013 dating. Therefore, creation of a compatible chronology is required prior to analysis of the spatial and Accepted 1 September 2013 temporal nature of climate variability at multiple locations. Here we present an automated mathematical Available online 19 September 2013 function that updates GISP2-based chronologies to the newer, NGRIP GICC05 age scale between 8.24 and 103.74 ka b2k. The script uses, to the extent currently available, climate-independent volcanic syn- Keywords: Chronology chronization of these two ice cores, supplemented by oxygen isotope alignment. The modular design of Ice core the script allows substitution for a more comprehensive volcanic matching, once it becomes available. Sediment core Usage of this function highlights on the GICC05 chronology, for the first time for the entire last glaciation, GICC05 the proposed global climate relationships during the series of large and rapid millennial stadial- interstadial events.
    [Show full text]
  • Ice Core Science 21
    Science Highlights: Ice Core Science 21 Dating ice cores JAKOB SCHWANDER Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland; [email protected] Introduction 200 [ppb An accurate chronology is the ba- NO 100 3 ] sis for a meaningful interpretation - 80 ] of any climate archive, including ice 2 0 O 2 40 [ppb cores. Until now, the oldest ice re- H 0 200 Dust covered from a continuous core is [ppb 100 that from Dome Concordia, Antarc- 2 ] ] tica, with an estimated age of over -1 1.6 0 Sm 1.2 µ 800,000 years (EPICA Community [ Conduct. 0.8 160 [ppb Members, 2004). But the recently SO 80 4 2 recovered cores from near bedrock ] 60 - ] at Kohnen Station (Dronning Maud + 40 0 Na Land, Antarctica) and Dome Fuji [ppb 20 40 [ 0 Ca (Antarctica) compete for the longest ppb 2 20 + climatic record. With the recovery of ] 80 0 + more and more ice cores, the task of ] 4 establishing a good common chro- 40 [ppb NH nology has become increasingly im- 0 portant for linking the fi ndings from 1425 1425 .5 1426 1426 .5 1427 the different records. Moreover, in Depth [m] order to create a comprehensive Fig. 1: Seasonal variations of impurities in early Holocene ice from the North GRIP ice core. picture of past climate dynamics, it Summer layers are indicated by grey lines. is crucial to aim at a common chro- al., 1993, Rasmussen et al., 2006). is assessed with such a model, then nology for all paleo-records. Here Ideally the counting uncertainty is one can construct a chronology of the different methods for dating ice on the order of 1%.
    [Show full text]
  • Scientific Dating of Pleistocene Sites: Guidelines for Best Practice Contents
    Consultation Draft Scientific Dating of Pleistocene Sites: Guidelines for Best Practice Contents Foreword............................................................................................................................. 3 PART 1 - OVERVIEW .............................................................................................................. 3 1. Introduction .............................................................................................................. 3 The Quaternary stratigraphical framework ........................................................................ 4 Palaeogeography ........................................................................................................... 6 Fitting the archaeological record into this dynamic landscape .............................................. 6 Shorter-timescale division of the Late Pleistocene .............................................................. 7 2. Scientific Dating methods for the Pleistocene ................................................................. 8 Radiometric methods ..................................................................................................... 8 Trapped Charge Methods................................................................................................ 9 Other scientific dating methods ......................................................................................10 Relative dating methods ................................................................................................10
    [Show full text]
  • A New Mass Spectrometric Tool for Modelling Protein Diagenesis
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Institutional Research Information System University of Turin 114 Abstracts / Quaternary International 279-280 (2012) 9–120 budgets, preferably spanning an entire glacial cycle, remain the most by chiral amino acid analysis. However, this knowledge has not yet been accurate for extrapolating glacial erosion rates to the entire Pleistocene able to produce a model which is fully able to explain the patterns of and for assessing their impact on crustal uplift. In the Carlit massif, where breakdown at low (burial) temperatures. By performing high temperature topographic conditions have allowed the majority of Würmian sediments experiments on a range of biominerals (e.g. corals and marine gastropods) to remain trapped within the catchment, clastic volumes preserved and and comparing the racemisation patterns with those obtained in fossil widespread 10Be nuclide inheritance on ice-scoured bedrock steps in the samples of known age, some of our studies have highlighted a range of path of major iceways reveal that mean catchment-scale glacial denuda- discrepancies in the datasets which we attribute to the interplay of tion depths were low (5 m in w100 ka), non-uniform across the landscape, a network of diagenesis reactions which are not yet fully understood. In and unsteady through time. Extrapolating to the Pleistocene, the trans- particular, an accurate knowledge of the temperature sensitivity of the two formation of Cenozoic landscapes by glaciers has thus been limited, many main observable diagenetic reactions (hydrolysis and racemisation) is still cirques and valleys being pre-glacial landforms merely modified by glacial elusive.
    [Show full text]
  • The WAIS Divide Deep Ice Core WD2014 Chronology – Part 2: Annual-Layer Counting (0–31 Ka BP)
    Clim. Past, 12, 769–786, 2016 www.clim-past.net/12/769/2016/ doi:10.5194/cp-12-769-2016 © Author(s) 2016. CC Attribution 3.0 License. The WAIS Divide deep ice core WD2014 chronology – Part 2: Annual-layer counting (0–31 ka BP) Michael Sigl1,2, Tyler J. Fudge3, Mai Winstrup3,a, Jihong Cole-Dai4, David Ferris5, Joseph R. McConnell1, Ken C. Taylor1, Kees C. Welten6, Thomas E. Woodruff7, Florian Adolphi8, Marion Bisiaux1, Edward J. Brook9, Christo Buizert9, Marc W. Caffee7,10, Nelia W. Dunbar11, Ross Edwards1,b, Lei Geng4,5,12,d, Nels Iverson11, Bess Koffman13, Lawrence Layman1, Olivia J. Maselli1, Kenneth McGwire1, Raimund Muscheler8, Kunihiko Nishiizumi6, Daniel R. Pasteris1, Rachael H. Rhodes9,c, and Todd A. Sowers14 1Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA 2Laboratory for Radiochemistry and Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland 3Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA 4Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA 5Dartmouth College Department of Earth Sciences, Hanover, NH 03755, USA 6Space Science Laboratory, University of California, Berkeley, Berkeley, CA 94720, USA 7Department of Physics and Astronomy, PRIME Laboratory, Purdue University, West Lafayette, IN 47907, USA 8Department of Geology, Lund University, 223 62 Lund, Sweden 9College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA 10Department of Earth, Atmospheric,
    [Show full text]
  • Did Comet HEINRICH-Swift-Tuttle Terminate Roman and Global Civilization? [ROME’S POPULATION CATASTROPHE: G
    1 Did Comet HEINRICH-Swift-Tuttle Terminate Roman and Global Civilization? [ROME’S POPULATION CATASTROPHE: https://it.wikipedia.org/wiki/Demografia_di_Roma] G. Heinsohn, January 2021 In the first millennium CE, the people of ROME built residential quarters, latrines, water pipes, sewage systems, streets, ports, bakeries etc., but only during Imperial Antiquity (1- 230s CE). No such structures were built during Late Antiquity (4th-6th/7th c.) or the Early Middle Ages (8th-930s CE). [See already https://q-mag.org/gunnar-heinsohn-the-stratigraphy- of-rome-benchmark-for-the-chronology-of-the-first-millennium-ce.html] Since the ruins of the 3rd c. CE lie directly beneath the primitive new structures that were built after the 930s CE (i.e., BEGINNING OF THE HIGH MIDDLE AGES), Imperial Antiquity belongs stratigraphically to the period from 700 to 930s CE. The steep decline in the population of Rome from 1.5 million to 650,000, dated in the diagram to "450" CE, must be accommodated archaeologically within Imperial Antiquity. This decline is due to the crisis caused by the Antonine Plague and Fires, the burning of Rome's State Archives (Tabularium), the Comet of Commodus before the rise of the Severan Emperors (190s-230s CE), and the invasion of Italy by proto-Hunnic Iazyges and proto-Gothic Quadi from the 160s to the 190s. The 160s ff. are stratigraphically parallel with the 450s ff. CE and its invasion of Italy by Huns and Goths. Stratigraphically, we are in the 860s ff. CE, with Hungarians and Vikings. The demographic collapse in the CRISIS OF THE 6th CENTURY (“553” CE in the diagram) is identical with the CRISIS OF THE 3rd C., as well as with the COLLAPSE OF THE 10th C., when Comet HEINRICH-Swift-Tuttle (after King Heinrich I of Saxony; 876/919-936 CE) with ensuing volcanos and floods of the 930s CE ) damaged the globe and Henry’s Roman style city of Magdeburg).
    [Show full text]
  • On the Origin and Timing of Rapid Changes in Atmospheric
    GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 14, NO. 2, PAGES 559-572, JUNE 2000 On the origin and timing of rapid changesin atmospheric methane during the last glacial period EdwardJ. Brook,• SusanHarder, • Jeff Sevennghaus, ' • Eric J. Ste•g,. 3and Cara M. Sucher•'5 Abstract. We presenthigh resolution records of atmosphericmethane from the GISP2 (GreenlandIce SheetProject 2) ice corefor fourrapid climate transitions that occurred during the past50 ka: theend of theYounger Dryas at 11.8ka, thebeginning of theBolling-Aller0d period at 14.8ka, thebeginning of interstadial8 at 38.2 ka, andthe beginning of intersradial12 at 45.5 ka. Duringthese events, atmospheric methane concentrations increased by 200-300ppb over time periodsof 100-300years, significantly more slowly than associated temperature and snow accumulationchanges recorded in the ice corerecord. We suggestthat the slowerrise in methane concentrationmay reflect the timescale of terrestrialecosystem response to rapidclimate change. We find noevidence for rapid,massive methane emissions that might be associatedwith large- scaledecomposition of methanehydrates in sediments.With additionalresults from the Taylor DomeIce Core(Antarctica) we alsoreconstruct changes in the interpolarmethane gradient (an indicatorof thegeographical distribution of methanesources) associated with someof therapid changesin atmosphericmethane. The resultsindicate that the rise in methaneat thebeginning of theB011ing-Aller0d period and the laterrise at theend of theYounger Dryas were driven by increasesin bothtropical
    [Show full text]
  • “Year Zero” in Interdisciplinary Studies of Climate and History
    PERSPECTIVE Theimportanceof“year zero” in interdisciplinary studies of climate and history PERSPECTIVE Ulf Büntgena,b,c,d,1,2 and Clive Oppenheimera,e,1,2 Edited by Jean Jouzel, Laboratoire des Sciences du Climat et de L’Environ, Orme des Merisiers, France, and approved October 21, 2020 (received for review August 28, 2020) The mathematical aberration of the Gregorian chronology’s missing “year zero” retains enduring potential to sow confusion in studies of paleoclimatology and environmental ancient history. The possibility of dating error is especially high when pre-Common Era proxy evidence from tree rings, ice cores, radiocar- bon dates, and documentary sources is integrated. This calls for renewed vigilance, with systematic ref- erence to astronomical time (including year zero) or, at the very least, clarification of the dating scheme(s) employed in individual studies. paleoclimate | year zero | climate reconstructions | dating precision | geoscience The harmonization of astronomical and civil calendars have still not collectively agreed on a calendrical in the depths of human history likely emerged from convention, nor, more generally, is there standardi- the significance of the seasonal cycle for hunting and zation of epochs within and between communities and gathering, agriculture, and navigation. But difficulties disciplines. Ice core specialists and astronomers use arose from the noninteger number of days it takes 2000 CE, while, in dendrochronology, some labora- Earth to complete an orbit of the Sun. In revising their tories develop multimillennial-long tree-ring chronol- 360-d calendar by adding 5 d, the ancient Egyptians ogies with year zero but others do not. Further were able to slow, but not halt, the divergence of confusion emerges from phasing of the extratropical civil and seasonal calendars (1).
    [Show full text]
  • TBM NEWSLETTER N°12 Your New TBM Newsletter !
    If this message is not correctly displayed please click here TBM NEWSLETTER N°12 www.tbm.aero Your new TBM Newsletter ! EDITO "With the very fast turboprop aircraft, “connection” means that TBM owners and operators become more closely linked with their travel requirements – flying rapidly and efficiently to airports that are nearer to their final destinations. At Daher, our goal is to build on this cornerstone benefit of the TBM family, with continual enhancements to the aircraft itself and the service we provide. " Read more Nicolas CHABBERT NEWS A new Service Center for Croatia "Brings on the heat" on Model Year 2018 . Daher has selected Aero Standard, an EASA New features for 2018 production TBM 910s and Part 145 maintenance organization based at TBM 930s include the first electrically-heated Zadar International Airport, as the Croatia seats for an aircraft in its single-engine turboprop Service Center for the TBM aircraft (...) category (...) . PILOT PROFILE NETWORK PROFILE Ron Guynn Jim and Laura Penn AVEX TBM 910 SN1213 . The TBM Network is one of Daher’s strongest Jim and Laura Penn are husband and wife assets in ensuring world-class support for owners certified public accountants from Fort Worth, and operators of its very fast turboprop (...) Texas, USA. Jim is a founding partner of (...) 885 1,5M 54 TBM FLIGHT HOURS SERVICE CENTERS SUPPORT TECHNICAL DOCUMENTATION SUPPORT NEWS The value of our Network What's new ? Our Network of authorized TBM Service Centers Get the latest documentation update and TBM Distributors brings added value to Daher’s family of very fast aircraft: a fact that is SUPPORT CORNER recognized and highly appreciated every day by the worldwide TBM owner/operator The first G1000 NXi upgrade community.
    [Show full text]
  • 1 Making a Difference in Tenth-Century Politics: King
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by St Andrews Research Repository 1 Making a Difference in Tenth-Century Politics: King Athelstan’s Sisters and Frankish Queenship Simon MacLean (University of St Andrews) ‘The holy laws of kinship have purposed to take root among monarchs for this reason: that their tranquil spirit may bring the peace which peoples long for.’ Thus in the year 507 wrote Theoderic, king of the Ostrogoths, to Clovis, king of the Franks.1 His appeal to the ideals of peace between kin was designed to avert hostilities between the Franks and the Visigoths, and drew meaning from the web of marital ties which bound together the royal dynasties of the early-sixth-century west. Theoderic himself sat at the centre of this web: he was married to Clovis’s sister, and his daughter was married to Alaric, king of the Visigoths.2 The present article is concerned with a much later period of European history, but the Ostrogothic ruler’s words nevertheless serve to introduce us to one of its central themes, namely the significance of marital alliances between dynasties. Unfortunately the tenth-century west, our present concern, had no Cassiodorus (the recorder of the king’s letter) to methodically enlighten the intricacies of its politics, but Theoderic’s sentiments were doubtless not unlike those that crossed the minds of the Anglo-Saxon and Frankish elite families who engineered an equally striking series of marital relationships among themselves just over 400 years later. In the early years of the tenth century several Anglo-Saxon royal women, all daughters of King Edward the Elder of Wessex (899-924) and sisters (or half-sisters) of his son King Athelstan (924-39), were despatched across the Channel as brides for Frankish and Saxon rulers and aristocrats.
    [Show full text]
  • Resolving Milankovitch: Consideration of Signal and Noise Stephen R
    [American Journal of Science, Vol. 308, June, 2008,P.770–786, DOI 10.2475/06.2008.02] RESOLVING MILANKOVITCH: CONSIDERATION OF SIGNAL AND NOISE STEPHEN R. MEYERS*,†, BRADLEY B. SAGEMAN**, and MARK PAGANI*** ABSTRACT. Milankovitch-climate theory provides a fundamental framework for the study of ancient climates. Although the identification and quantification of orbital rhythms are commonplace in paleoclimate research, criticisms have been advanced that dispute the importance of an astronomical climate driver. If these criticisms are valid, major revisions in our understanding of the climate system and past climates are required. Resolution of this issue is hindered by numerous factors that challenge accurate quantification of orbital cyclicity in paleoclimate archives. In this study, we delineate sources of noise that distort the primary orbital signal in proxy climate records, and utilize this template in tandem with advanced spectral methods to quantify Milankovitch-forced/paced climate variability in a temperature proxy record from the Vostok ice core (Vimeux and others, 2002). Our analysis indicates that Vostok temperature variance is almost equally apportioned between three components: the precession and obliquity periods (28%), a periodic “100,000” year cycle (41%), and the background continuum (31%). A range of analyses accounting for various frequency bands of interest, and potential bias introduced by the “saw-tooth” shape of the glacial/interglacial cycle, establish that precession and obliquity periods account for between 25 percent to 41 percent of the variance in the 1/10 kyr – 1/100 kyr band, and between 39 percent to 66 percent of the variance in the 1/10 kyr – 1/64 kyr band.
    [Show full text]
  • New Glacier Evidence for Ice-Free Summits During the Life of The
    www.nature.com/scientificreports OPEN New glacier evidence for ice‑free summits during the life of the Tyrolean Iceman Pascal Bohleber1,2*, Margit Schwikowski3,4,5, Martin Stocker‑Waldhuber1, Ling Fang3,5 & Andrea Fischer1 Detailed knowledge of Holocene climate and glaciers dynamics is essential for sustainable development in warming mountain regions. Yet information about Holocene glacier coverage in the Alps before the Little Ice Age stems mostly from studying advances of glacier tongues at lower elevations. Here we present a new approach to reconstructing past glacier low stands and ice‑ free conditions by assessing and dating the oldest ice preserved at high elevations. A previously unexplored ice dome at Weißseespitze summit (3500 m), near where the “Tyrolean Iceman” was found, ofers almost ideal conditions for preserving the original ice formed at the site. The glaciological settings and state‑of‑the‑art micro‑radiocarbon age constraints indicate that the summit has been glaciated for about 5900 years. In combination with known maximum ages of other high Alpine glaciers, we present evidence for an elevation gradient of neoglaciation onset. It reveals that in the Alps only the highest elevation sites remained ice‑covered throughout the Holocene. Just before the life of the Iceman, high Alpine summits were emerging from nearly ice‑free conditions, during the start of a Mid‑Holocene neoglaciation. We demonstrate that, under specifc circumstances, the old ice at the base of high Alpine glaciers is a sensitive archive of glacier change. However, under current melt rates the archive at Weißseespitze and at similar locations will be lost within the next two decades.
    [Show full text]