DOCSLIB.ORG

Nudlerical Dlodelling of a Fast-Flowing Outlet Glacier: Experidlents with Different Basal Conditions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nudlerical Dlodelling of a Fast-Flowing Outlet Glacier: Experidlents with Different Basal Conditions .1n/lal.r oJ GlaciologJ' 23 1996 (' Internatio na l G laciological Society NUDlerical Dlodelling of a fast-flowing outlet glacier: experiDlents with different basal conditions FR:-\;'-JK P ,\TTYi\ De/Jar/lllen / of G eograjJ/~) I . "rije ['"il'eni/eil Brum/, B-1050 Bumel, BelgiulII A BSTRACT, R ecent o iJse J'\'ati o ns in Shirase Dra in age Basin, Enderb\' L a nd, Anta rcti ca, sholl' tha t the ice sheet is thinning a t the consid(: ra ble ra te of 0,5 (,0 m ai, S urface \'clocities in the stream a rea read; m ore tha n 2000 m ai, making S hirasc G lacier one of the fas test-fl o\l'ing glaciers in East Anta rcti ca, .\ numeri cal im'esti ga ti on of the pITSe nt stress fi eld in S hirase G lacier sholl's the existence of a large tra nsition zone 200 km in leng th w here bOlh shea ring a nd stretching a rc of equal im porta nce, fo ll owed b y a slI Tam zone 0(' a pproxima tely 50 km , \I'here stretchill g is the m ajor deform a ti o n process, In o rder to imprO\ 'e insig ht into the preselll tra nsient beha\'iour of the ice-sheet sys tem , a t\\'o-dimensiona ltime-dependent fl o\l'line model has been d e\'e loped, taking into account the ice-stream m echa ni cs, Bo th bedrock adj ustment a n cl ice tempera ture a re ta ken into ac('oulll a nd the templ'I'a lU re field is full y coupled to the ice-shcet \'C locit)' fiel d, Experiments were carried o ut \\'ith dilTerent basal m o ti o n conditio ns in order to understa nd their influen ce o n the cl\'na mic beha\'io ur of th e ice sheet a nd the stream a rea in pa rticul a r. R es ults revcaled' that \I,hen basa l mo ti o n becom es the d omina nt d eforma ti o n p rocess, (partia l) disintegra ti o n of the ice sheet is counteracted by cold er basal-ice tem pera tures due to hig her ad\'Cc ti on ra tes , This giyes rise to a cycli c behayi o ur in ice-sheet res ponse a nd la rge cha nges in local imba la nce \'a lues, LIST OF SYMBOLS T' T rela ti\'C to p ress ure m elting (K v, H ori zonta l \'elocity (m a I) a Arrhenius consta nt (Pa lIa I) Basal-sliding \'C locit)' ( 111 a I ) A l ee fl ow-l a H ' pa rame ter (Pa 11 m 2" a I ) Vertical m ean \'eloeity (m a I) A, Sliding-l a w para m eter W \ ' crtical \'cloci t y (m a I ) b FI O\\'-ba nd \\' id th (m ) ,1' H o ri zonta l coordina te (m ) cl' S pecifi c heat capacity U kg 1 K I ) Z \'ertieal coordina tc (m ) 2 D DilTusio n coeffi cien t (m a I) G eom etric consta nt (;:::02 ,0 ) g G ra \'ita ti o n consta nt (9,8 Im s 2) W a ter-film d epth (111 ) G Geotherma l heat flu x (-54 ,6 m\\' 2) C ritical pa rticle size ( 111 ) h Bedrock ele\'a ti on a bo\'e present sea Ic\'(' 1 (m ) Kro neckcr d elta H Ice thickn ess (m ) H ori zonta l g radient a t d epth ( k i Therma l cond uctiyi t)' of ice (j m 1 K 1 a I ) Eflccti\'C shear-stra in ra te (a I) L Spec ifi c la tent heat of fu sion (3,35 x 10'; ] 111 1 K 1 a I) Shea r-stra in rate (a I) m Flo\\'-enha ncem ent factor G/ ki (geothe rl11 a l hea t) (Km I ) /lJ S urface m ass ba la nce (m a 1 ice equi\'a lent ) Bo unda ry n due (Q (surface) or I (bo llo m ) N ElTec ti \'e norm a l pressure (Pa ) Lithos ta ti c stress compo nent (Pa ) 11 Glen fl O\\'-l aw exponent (3) Viscosit\, of\l'a ler ( 1. 8 x 10 :l Pas) " 'l p Sliding-l a \\' coeffi cient (0 3) Ice d enSity (9 10kg m ') Pg Press ure g rad ient (P a 111 I) Sea-wa ter d ensit y ( 1028 kg 111 3) q Sliding-l a w coeffi cient (0 2) K orma l stress a t the base (P a ) Q Acti n llio n energy fo r creep U m oll ) Ice-shell' back-pressurc (Pa ) Q\\' W a ter flu x (m:ls I ) T cmpera ture-corrcctio n facto r (0 ,0 0, I Cl ) R U ni\'ersal gas consta nt (8,3 14J m ol I K I ) Basal shear stress (Pa ) R i) R es isti w' stress (Pa ) Effec ti \'(:' slress ( Pa ) S Basal-melting ra te (m a 1 ice equi\'a lent ) Dri\'ing stress Pa l t Time (a rycar j) Stress IPa ) T Ice tempera ture (K ) Stress d C'\, ia tor (Pa) 7() Absolute temperature (2 73 ,1 5 K ) V ertical dimensio n\css coordina te 237 Pattyn: Numerical modelling of a fast-flowing outlet gLacier INTRODUCTION The d ynamic behaviour of a large polar ice sheet is well understood; grounded ice flow is basically governed by shearing close to th e bed. In its most simplisti c form, the basal shear stress equals ice density times gravity times overburden depth times surface slope, whi ch Hutter (1993) defined as the glaciologist's first commandment. H owever, likc a ny physical sys tem, a n ice sheet is not onl y controlled by its internal d ynamics but a lso by its bounda ry conditions, which are less well understood. The environmental processes such as surfacc tempera ture a nd mass balance act as the upper bounda ry a nd a re in ma ny ice-shee t models regarded as the ex ternal sys tem forcing. The present environmenta l conditions th ereby se rve as a reference. The two remaining boundaries, on which we will further concentra te in this pa per, are th e basal motion as a lower and the margin d yna mics as th e outer boundary condition. The basal vclocity depends on the interna l ice dynamics, the bedrock conditions and the prese nce of water a t the ice-shee t base. Basa l velocity will thus play a role when the tempera ture of the basal ice is a t the melting point and will gain more importance cl ose to the ma rgin where it interacts with the ma rgin ice d ynamics . \Vhen the ice-sheet ma rgin termin a tes at th e sea in th e form of a flo a ting ice shelf, a tra nsition zone can be d efin ed where the ice-shee t dynami cs gradua ll y e\'olve towards ice-shelf d ynamics. E labora te studi es on this Fig. 1. Location mal) of Shirase Drainage Basin . The grounding zone have revealed th a t for small basal mo ti on dashed line represen ts the celltral.J7owline, as Inimm)' in/)lIt the width of the transition zone is of the same order of Jar the model/ing experiments. The.J7owLille starts at Dome magnitude as the ice thickness, so tha t the grounding zone F, folLo ws more or less t/ie 40° E meridian towards is reduced to a grounding line a nd the shallow-ice Llil:;,ow-Holmbukta , and ends at Sizirase GLacier in a approximation still holds, provided that there is no floating ice tongue. passive grounding of th e ice shelf. A full deri vati on of the Stokes ba la nce equa ti ons is not necessary; it suffices to calculate the longitudina l stress deviator along the grounding line and prescribe a longitudinal stress near Dome F (77 °22' S, 39°37' E ) to LLitzow-Holmbukta. gradient (Van der Veen, 1987). Grounding-lin e mO\'e­ Shirase Glacier is one of the fastes t-flowing Antarctic ment is thus only governed by ice-sheet mecha ni cs glaciers, with " elocities up to 2700 m a- I in the ice-stream (Hindma rsh, 1993). This situa ti on is the commones t region (Fujii, 1981 ). The ice flow in the central drainage outer boundary a t the edge of the East Anta rcti c ice shee t basin is furthermore characteri zed by large submergence where a steep surface slope, cha racterizing grounded ice, \'eloci ti es (Naruse, 1979). Consecutiye measurements in a bruptly changes to a sma ll surface gradient where the ice this area (N aruse, 1979; Nishio a nd others, 1989; T oh and begins floating. Shibuya, 1992) have pointed to a large thinning rate However, la rge amoun ts of An ta rctic ice are not ra nging from 0.5 to 2.0 m a I in the region where the drained along th ese ma rgins but through fas t outlet surface elevation is lower than 2800 m. K ameda and glaciers or ice streams, which a re beli eved to be more others (1990) concluded from a study of the tota l gas sensiti\'e to environmenta l changes.
Load more

Recommended publications
  • Air and Shipborne Magnetic Surveys of the Antarctic Into the 21St Century
    TECTO-125389; No of Pages 10 Tectonophysics xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Air and shipborne magnetic surveys of the Antarctic into the 21st century A. Golynsky a,⁎,R.Bellb,1, D. Blankenship c,2,D.Damasked,3,F.Ferracciolie,4,C.Finnf,5,D.Golynskya,6, S. Ivanov g,7,W.Jokath,8,V.Masolovg,6,S.Riedelh,7,R.vonFresei,9,D.Youngc,2 and ADMAP Working Group a VNIIOkeangeologia, 1, Angliysky Avenue, St.-Petersburg, 190121, Russia b LDEO of Columbia University, 61, Route 9W, PO Box 1000, Palisades, NY 10964-8000, USA c University of Texas, Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, Texas 78759-4445, USA d BGR, Stilleweg 2 D-30655, Hannover, Germany e BAS, High Cross, Madingley Road, Cambridge, CB3 OET, UK f USGS, Denver Federal Center, Box 25046 Denver, CO 80255, USA g PMGE, 24, Pobeda St., Lomonosov, 189510, Russia h AWI, Columbusstrasse, 27568, Bremerhaven, Germany i School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH, 43210, USA article info abstract Article history: The Antarctic geomagnetics' community remains very active in crustal anomaly mapping. More than 1.5 million Received 1 August 2011 line-km of new air- and shipborne data have been acquired over the past decade by the international community Received in revised form 27 January 2012 in Antarctica. These new data together with surveys that previously were not in the public domain significantly Accepted 13 February 2012 upgrade the ADMAP compilation.
    [Show full text]
  • The Ministry for the Future / Kim Stanley Robinson
    This book is a work of fiction. Names, characters, places, and incidents are the product of the author’s imagination or are used fictitiously. Any resemblance to actual events, locales, or persons, living or dead, is coincidental. Copyright © 2020 Kim Stanley Robinson Cover design by Lauren Panepinto Cover images by Trevillion and Shutterstock Cover copyright © 2020 by Hachette Book Group, Inc. Hachette Book Group supports the right to free expression and the value of copyright. The purpose of copyright is to encourage writers and artists to produce the creative works that enrich our culture. The scanning, uploading, and distribution of this book without permission is a theft of the author’s intellectual property. If you would like permission to use material from the book (other than for review purposes), please contact [email protected]. Thank you for your support of the author’s rights. Orbit Hachette Book Group 1290 Avenue of the Americas New York, NY 10104 www.orbitbooks.net First Edition: October 2020 Simultaneously published in Great Britain by Orbit Orbit is an imprint of Hachette Book Group. The Orbit name and logo are trademarks of Little, Brown Book Group Limited. The publisher is not responsible for websites (or their content) that are not owned by the publisher. The Hachette Speakers Bureau provides a wide range of authors for speaking events. To find out more, go to www.hachettespeakersbureau.com or call (866) 376-6591. Library of Congress Cataloging-in-Publication Data Names: Robinson, Kim Stanley, author. Title: The ministry for the future / Kim Stanley Robinson. Description: First edition.
    [Show full text]
  • Page 1 0° 10° 10° 110° 110° 20° 20° 120° 120° 30° 30° 130° 130° 40
    Bouvet I 50° 40° 30° 20° 10° 0° (Norway) 10° 20° 30° 40° 50° Marion I Prince Edward I e PRINCE EDWARD ISLANDS ea Ic (South Africa) t of S exten ) aximum 973-82 M rage 1 60° ar ave (10 ye SOUTH 60° SOUTH GEORGIA (UK) SANDWICH Crozet Is ISLANDS (France) (UK) R N 60° E H O T C U Antarctic Circle E H A A K O N A G V I O EO I S A N D T H E S O U T H E R N O C E A N R a Laurie I G ( t E V S T k A Powell I J . r u 70° ORCADAS (ARGENTINA) O E A S o b N A l L F lt d Stanley N B u a Coronation I R N r A N Rawson SIGNY (UK) E A I n Y ( U C A g g A G M R n K E E A E a i S S K R A T n V a Edition 6 SOUTH ORKNEY ST M Y I ) e E y FALKLAND ISLANDS (UK) R E S 70° N L R ø ISLANDS O A R E E A v M N N S Z a l Y I A k a IS ) L L i h EN BU VO ) v n ) IA id e A IM A O S e rs I L MAITRI N S r F L a a S QUARISEN E U B n J k L S F R i - e S ( r ) U (INDIA) v Kapp Norvegia P t e m s a N R U s i t ( u R i k A Puerto Deseado Selbukta a D e R u P A r V Y t R b A BORGMASSIVET s E A l N m (J A V FIMBULHEIME E l N y Comodoro Rivadavia u S N o r t IS A H o RIISER LARSENISEN u H t Clarence I J N K Z n E w W E o R Elephant I W E G E T IN o O D m d N E S T SØR-RONDANE z n R I V nH t Y O ro a y 70° t S E R E e O u S L P sl a P N A R e RS L I B y A r H O e e G See Inset d VESTFJELLA LL C G b AV g it en o E H n NH M n s o J N e n EIA a h d E C s e NE T W E M F S e S n I R n r u T h King George I t a b i N m N O d i E H r r N a Joinville I A O B .
    [Show full text]
  • Preliminary Science Flight Report Operation Icebridge Antarctica 2011
    Preliminary Science Flight Report Operation IceBridge Antarctica 2011 Flight: F07 Mission: Slessor 1 Flight Report Summary Aircraft DC-8 (N817NA) Flight Number 120111 Flight Request 128008 Date Friday, October 21, 2011 (Z), Day of Year 294 Purpose of Flight Operation IceBridge Mission Slessor 1 Take off time 12:00:12 Zulu from Punta Arenas (SCCI) Landing time 23:23:40 Zulu at Punta Arenas (SCCI) Flight Hours 11.5 hours Aircraft Status Airworthy. Sensor Status All installed sensors operational. Significant Issues None Accomplishments Low-altitude survey (1,500 ft AGL) Bailey IceStream, Slessor Glacier and Recovery Glacier. Completed entire mission as planned. Collected data over an ice core site on Berkner Island. ATM, MCoRDS, snow and Ku-band radars, gravimeter, and DMS were operated on the survey lines. Conducted two ramp passes (2000 ft AGL) at Punta Arenas airport for ATM and DMS instrument calibration. Geographic Keywords Bailey Ice Stream, Slessor Glacier, Recovery Glacier, Berkner Island, Thyssen Höhe, Shackleton Range, Theron Mountains, Antarctica ICESat Tracks 0404 Repeat Mission None. Page | 1 Science Data Report Summary Instrument Instrument Operational Data Volume Instrument Issues Survey Entire High-alt. Area Flight Transit ATM 42 GB None MCoRDS 1.5 TB None Snow Radar 200 GB None Ku-band Radar 200 GB None DMS 98 GB None Gravimeter 2 GB None DC-8 Onboard Data 40 MB None Mission Report (Michael Studinger, Mission Scientist) Today’s mission is a new design. The intention is to sample the grounding line and lower part of Slessor Glacier and Bailey Ice Stream using all IceBridge low-altitude sensors.
    [Show full text]
  • 1 Compiled by Mike Wing New Zealand Antarctic Society (Inc
    ANTARCTIC 1 Compiled by Mike Wing US bulldozer, 1: 202, 340, 12: 54, New Zealand Antarctic Society (Inc) ACECRC, see Antarctic Climate & Ecosystems Cooperation Research Centre Volume 1-26: June 2009 Acevedo, Capitan. A.O. 4: 36, Ackerman, Piers, 21: 16, Vessel names are shown viz: “Aconcagua” Ackroyd, Lieut. F: 1: 307, All book reviews are shown under ‘Book Reviews’ Ackroyd-Kelly, J. W., 10: 279, All Universities are shown under ‘Universities’ “Aconcagua”, 1: 261 Aircraft types appear under Aircraft. Acta Palaeontolegica Polonica, 25: 64, Obituaries & Tributes are shown under 'Obituaries', ACZP, see Antarctic Convergence Zone Project see also individual names. Adam, Dieter, 13: 6, 287, Adam, Dr James, 1: 227, 241, 280, Vol 20 page numbers 27-36 are shared by both Adams, Chris, 11: 198, 274, 12: 331, 396, double issues 1&2 and 3&4. Those in double issue Adams, Dieter, 12: 294, 3&4 are marked accordingly. Adams, Ian, 1: 71, 99, 167, 229, 263, 330, 2: 23, Adams, J.B., 26: 22, Adams, Lt. R.D., 2: 127, 159, 208, Adams, Sir Jameson Obituary, 3: 76, A Adams Cape, 1: 248, Adams Glacier, 2: 425, Adams Island, 4: 201, 302, “101 In Sung”, f/v, 21: 36, Adamson, R.G. 3: 474-45, 4: 6, 62, 116, 166, 224, ‘A’ Hut restorations, 12: 175, 220, 25: 16, 277, Aaron, Edwin, 11: 55, Adare, Cape - see Hallett Station Abbiss, Jane, 20: 8, Addison, Vicki, 24: 33, Aboa Station, (Finland) 12: 227, 13: 114, Adelaide Island (Base T), see Bases F.I.D.S. Abbott, Dr N.D.
    [Show full text]
  • New Last Glacial Maximum Ice Thickness Constraints for The
    Edinburgh Research Explorer New Last Glacial Maximum Ice Thickness constraints for the Weddell Sea Embayment, Antarctica Citation for published version: Nichols, KA, Goehring, BM, Balco, G, Johnson, JS, Hein, A & Todd, C 2019, 'New Last Glacial Maximum Ice Thickness constraints for the Weddell Sea Embayment, Antarctica', Cryosphere. https://doi.org/10.5194/tc-13-2935-2019 Digital Object Identifier (DOI): 10.5194/tc-13-2935-2019 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: Cryosphere Publisher Rights Statement: © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 09. Oct. 2021 The Cryosphere, 13, 2935–2951, 2019 https://doi.org/10.5194/tc-13-2935-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica Keir A. Nichols1, Brent M.
    [Show full text]
  • November 1960 I Believe That the Major Exports of Antarctica Are Scientific Data
    JIET L S. Antarctic Projects OfficerI November 1960 I believe that the major exports of Antarctica are scientific data. Certainly that is true now and I think it will be true for a long time and I think these data may turn out to be of vastly, more value to all mankind than all of the mineral riches of the continent and the life of the seas that surround it. The Polar Regions in Their Relation to Human Affairs, by Laurence M. Gould (Bow- man Memorial Lectures, Series Four), The American Geographiql Society, New York, 1958 page 29.. I ITOJ TJM II IU1viBEt 3 IToveber 1960 CONTENTS 1 The First Month 1 Air Operations 2 Ship Oper&tions 3 Project MAGNET NAF McMurdo Sounds October Weather 4 4 DEEP FREEZE 62 Volunteers Solicited A DAY AT TEE SOUTH POLE STATION, by Paul A Siple 5 in Antarctica 8 International Cooperation 8 Foreign Observer Exchange Program 9 Scientific Exchange Program NavyPrograrn 9 Argentine Navy-U.S. Station Cooperation 9 10 Other Programs 10 Worlds Largest Aircraft in Antarctic Operation 11 ANTARCTICA, by Emil Schulthess The Antarctic Treaty 11 11 USNS PRIVATE FRANIC 3. FETRARCA (TAK-250) 1961 Scientific Leaders 12 NAAF Little Rockford Reopened 13 13 First Flight to Hallett Station 14 Simmer Operations Begin at South Pole First DEEP FREEZE 61 Airdrop 14 15 DEEP FREEZE 61 Cargo Antarctic Real Estate 15 Antarctic Chronology,. 1960-61 16 The 'AuuOiA vises to t):iank Di * ?a]. A, Siple for his artj.ole Wh.4b begins n page 5 Matera1 for other sections of bhis issue was drawn from radio messages and fran information provided bY the DepBr1nozrt of State the Nat0na1 Academy , of Soienoes the NatgnA1 Science Fouxidation the Office 6f NAval Re- search, and the U, 3, Navy Hydziograpbio Offioe, Tiis, issue of tie 3n oovers: i16, aótivitiès o events 11 Novóiber The of the Uxitéd States.
    [Show full text]
  • New Last Glacial Maximum Ice Thickness Constraints for the Weddell Sea Embayment, Antarctica
    The Cryosphere, 13, 2935–2951, 2019 https://doi.org/10.5194/tc-13-2935-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. New Last Glacial Maximum ice thickness constraints for the Weddell Sea Embayment, Antarctica Keir A. Nichols1, Brent M. Goehring1, Greg Balco2, Joanne S. Johnson3, Andrew S. Hein4, and Claire Todd5 1Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA 2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA 3British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, UK 4School of GeoSciences, University of Edinburgh, Drummund Street, Edinburgh, EH8 9XP, UK 5Department of Geosciences, Pacific Lutheran University, Tacoma, WA 98447, USA Correspondence: Keir A. Nichols ([email protected]) Received: 27 March 2019 – Discussion started: 14 May 2019 Revised: 12 September 2019 – Accepted: 2 October 2019 – Published: 8 November 2019 Abstract. We describe new Last Glacial Maximum (LGM) surements indicate that the long-lived nuclide measurements ice thickness constraints for three locations spanning the of previous studies were influenced by cosmogenic nuclide Weddell Sea Embayment (WSE) of Antarctica. Samples col- inheritance. Our inferred LGM configuration, which is pri- lected from the Shackleton Range, Pensacola Mountains, and marily based on minimum ice thickness constraints and thus the Lassiter Coast constrain the LGM thickness of the Slessor does not constrain an upper limit, indicates a relatively mod- Glacier, Foundation Ice Stream, and grounded ice proximal est contribution to sea level rise since the LGM of < 4.6 m, to the modern Ronne Ice Shelf edge on the Antarctic Penin- and possibly as little as < 1.5 m.
    [Show full text]
  • (2006) Switch-Off of a Major Enhanced Ice Flow Unit in East Antarctica
    GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L15501, doi:10.1029/2006GL026648, 2006 Click Here for Full Article Switch-off of a major enhanced ice flow unit in East Antarctica David M. Rippin,1 Martin J. Siegert,2,3 Jonathan L. Bamber,2 David G. Vaughan,4 and Hugh F. J. Corr4 Received 20 April 2006; revised 1 June 2006; accepted 7 June 2006; published 10 August 2006. [1] The East Antarctic Ice Sheet (EAIS) is the largest ies: flow in two of the three tributaries of Slessor Glacier reservoir of ice on the planet by an order of magnitude. can largely be explained by ice deformation (with basal Compared with the West Antarctic Ice Sheet (WAIS), it is motion, within the range of uncertainties, playing a minor traditionally considered to be relatively stable, with only role), while flow in the third (under a similar glaciological minor adjustments to its configuration over glacial- setting), could only be explained by significant basal motion interglacial cycles. Here, we present the results of a radio- [Rippin et al., 2003a]. echo sounding survey from Coats Land, East Antarctica, [4] Radio-echo sounding (RES) data-sets from many which suggests that parts of the EAIS outlet drainage regions of Antarctica have revealed that internal layers are system may have changed significantly since the Last common and traceable continuously over >100 km (e.g., Glacial Maximum. We have identified an enhanced flow Robin and Millar, 1982; Siegert, 1999; Hodgkins et al., unit from buckled internal layering and smooth bed 2000). Internal layers occur as a result of electromagnetic morphology that is no longer active.
    [Show full text]
  • Antarctica and Academe
    LARGE ANIMALS AND WIDE HORIZONS: ADVENTURES OF A BIOLOGIST The Autobiography of RICHARD M. LAWS PART III Antarctica and Academe Edited by Arnoldus Schytte Blix 1 Contents Chapt. 1. Return to Antarctic work, 1969 …………………………………......….4 Chapt. 2. Antarctic Journey, 1970-1971 ………………………………………......14 Chapt. 3. Reorganising BAS Biology, 1969-73 ………………………………...... 44 Chapt. 4. Director of BAS, 1973- 1987 ……………………………………….....…50 Chapt. 5. First Antarctic Journey as Director: 1973-74 …………………….........56 Chapt. 6. Continuing Antarctic Journey ……………………………………....… 80 Chapt. 7. Antarctic Journeys: 1975-1982 ……………………………………….. 104 The 1975-1976 Season ……………………………………………….…104 The R/V “Hero” voyage: 1977………………………………………... 137 The 1978-1979 Season ………………………………………………… 162 The 1979-1980 Season ………………………………………………… 173 The 1981-1982 Season ………………………………………………… 187 Chapt. 8. South Georgia and the Falklands War: 1982 ………………………. 200 Chapt. 9. After the war: BAS Expansion, 1983-1987 ……………………….… 230 Chapt. 10. Antarctic Journey: 1983-84 ………………………………………..…234 Chapt. 11. Great Waters: The Southern Ocean …………………………….…. 256 Chapt. 12. Last Antarctic Journey as Director: 1986-87 ……………………... 274 Chapt. 13. Scientist Among Diplomats …………………………………….….. 302 Chapt. 14. SCAR: Four Decades of Achievement ……………………………. .318 Chapt. 15. Master of St. Edmund’s College ………………………………........ 328 Chapt. 16. Last Antarctic Journey, In Retirement: 2000-2001 ………………... 378 R. M. LAWS. Publications ………………………………………………………. 398 R. M. LAWS. Short Curriculum vitae …………………………………………... 418 2 3
    [Show full text]
  • Ice Shelf Basal Melt and Influence on Dense Water Outflow in The
    RESEARCH ARTICLE Ice Shelf Basal Melt and Influence on Dense Water 10.1029/2019JC015710 Outflow in the Southern Weddell Sea Key Points: 1 1 1 2 • Water masses outflowing from Camille Akhoudas , Jean-Baptiste Sallée , Gilles Reverdin , Giovanni Aloisi , beneath Filchner Ice Shelf in the Marion Benetti3 , Lucie Vignes1, and Maria Gelado4 Weddell Sea are identified and linked to two distinct inflow sources 1Sorbonne Université, CNRS/IRD/MNHN (LOCEAN UMR 7159), Paris, France, 2Institut de Physique du Globe de • The two inflow sources interact Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, Paris, France, 3Institute of Earth Sciences, University with different ice shelf 4 characteristics, with meltwater, of Iceland, Reykjavik, Iceland, Chemistry Department, University of Las Palmas de Gran Canaria, Las Palmas de Gran being ∼0.4% of the outflowing Canaria, Spain water masses • The freshest outflow mixes with ambient waters to ultimately sink Abstract We use new observations of stable water isotopes from a research cruise in early 2017 to along the continental slope and entrains overlying warmer waters highlight ocean-ice interactions occurring under Filchner-Ronne Ice Shelf, the largest Antarctic ice shelf. In particular, we investigate the properties of Ice Shelf Water with temperature lower than the surface freezing point, in the Filchner Depression. We identify two main flavors of Ice Shelf Water emerging from Correspondence to: C. Akhoudas, beneath the Filchner Ice Shelf, which originate from High Salinity Shelf Water end members with distinct [email protected] characteristics. Furthermore, these two High Salinity Shelf Water end members interact with areas of the ice shelves with different basal properties to produce different versions of Ice Shelf Water.
    [Show full text]
  • A Simple Inverse Method for the Distribution of Basal Sliding Coefficients Under Ice Sheets, Applied to Antarctica
    The Cryosphere, 6, 953–971, 2012 www.the-cryosphere.net/6/953/2012/ The Cryosphere doi:10.5194/tc-6-953-2012 © Author(s) 2012. CC Attribution 3.0 License. A simple inverse method for the distribution of basal sliding coefficients under ice sheets, applied to Antarctica D. Pollard1 and R. M. DeConto2 1Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA, USA 2Department of Geosciences, University of Massachusetts, Amherst, MA, USA Correspondence to: D. Pollard ([email protected]) Received: 26 March 2012 – Published in The Cryosphere Discuss.: 12 April 2012 Revised: 13 August 2012 – Accepted: 19 August 2012 – Published: 12 September 2012 Abstract. Variations in intrinsic bed conditions that affect where C is a basal sliding coefficient that depends on intrin- basal sliding, such as the distribution of deformable sedi- sic bed properties such as small-scale roughness, and N is ment versus hard bedrock, are important boundary conditions the effective pressure, i.e., ice overburden not supported by for large-scale ice-sheet models, but are hard to observe and basal water pressure (Cuffey and Paterson, 2010). In models remain largely uncertain below the modern Greenland and without an explicit hydrologic component, basal temperature Antarctic ice sheets. Here a very simple model-based method is often used as a surrogate: is described for deducing the modern spatial distribution of n basal sliding coefficients. The model is run forward in time, ub = C(x,y)f (Tb)τb , (2) and the basal sliding coefficient at each grid point is peri- odically increased or decreased depending on whether the where Tb is the homologous basal temperature (relative to local ice surface elevation is too high or too low compared the pressure melt point), and f is zero for Tb below some to observed in areas of unfrozen bed.
    [Show full text]