The West Antarctic Ice Sheet: Behavior and Environment

295 Pages·2013·10.84 MB·English

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ANTARCTIC
kblume 77 RESEARCH
SERIES
The West Antarctic Ice Sheet
Behavior and Environment
Richard B. Alley and Robert A. Bindschadler
Editors
AmericaGn eophysicUanl ion
Washington,D .C.
2001
THE WEST ANTARCTIC ICE SHEET: BEHAVIOR AND ENVIRONMENT
Richard B. Alley and RobertA . BindschadlerE, ditors
Publishedu ndert he aegiso f the Boardo f AssociateE ditors,A ntarcticR esearchS eries
Library of CongressC ataloging-in-Publication Data
The westA ntarcticic e sheet:b ehavioar nde nvironmen/ tR ichardB . Alley andR obertA . Bindschadleerd, itors.
p. cm. -- (Antarctic researchs eries; v. 77)
Includesb ibliographicarl eferences.
ISBN 0-87590-957-4
1. Ice sheets-- Antarctica. I. Alley, RichardB . II. BindschadleRr,. A. (RobertA .) III. Series.
GB2597 .W36 2000
551.31'2'09989--dc21
00-061074
ISBN 0-87590-957-4
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CONTENTS
Preface
R. B. Alley and R. A. Bindschadler xi
The WestA ntarctic Ice Sheeta nd Sea-levelC hange
R. B. Alley and R. A. Bindschadler
Setting
Morphology and SurfaceC haracteristicso f the WestA ntarctic Ice Sheet
Mark Fahnestock and Jonathan Bamber 13
The LithosphericS ettingo f the WestA ntarctic Ice Sheet
I. W D. Dalziel and L. A. Lawyer 29
History
Evolution of the West Antarctic Ice Sheet
John B. Andersona nd StephanieS . Shipp 45
The Glacial GeologicT errestriaRl ecordf rom WestA ntarcticaW ith Emphasis
on the Last Glacial Cycle
Harold W Borns, Jr. 59
WestA ntarctic Ice Sheet Elevation Changes
Eric (cid:127) Steig,J amesL . Fastook,C hristopherZ weck,I an D. Goodwin,K athy (cid:127) Licht,
James W C. White, and Robert P Ackert, Jr. 75
Interactions
The E1N ifio-SouthernO scillationM odulationo f WestA ntarcticP recipitation
David H. Bromwicha nd Aric N. Rogers 91
GeologicC ontrolso n the Initiation of Rapid Basal Motion for WestA ntarctic Ice Streams:
A GeophysicaPl erspectiveIn cludingN ew AirborneR adarS oundinga nd LaserA ltimetry Results
D. D. BlankenshipD, . L. Morse, C. A. Finn, R. E. Bell, M. E. Peters,S . D. Kernpf,
S. M. Hodge, M. Studingerd, .C. Behrendt,a nd J. M. Brozena 105
Flow
Onseto f StreamingF low in the Siple CoastR egion,W estA ntarctica
Robert Bindschadler, Jonathan Barnher, and Sridhar Anandakrishnan 123
Ice StreamS hearM argins
C. E Raymond,K . A. EchelmeyerL, M. Whillans,a nd C. S. M. Doake 137
BasalZ one of the WestA ntarcticI ce Streamsa nd its Role in Lubricationo f Their Rapid Motion
Barclay Kamb 157
The Contributiono f Numerical Modelling to our Understandingo f the WestA ntarctic Ice Sheet
C. L. Hulbe and A.d. Payne 201
Case Studies
Rutford Ice Stream, Antarctica
C. S. M. Doake, H. Ed. Corr, A. Jenkins, K. Makinson, K. W. Nicholls, C. Nath,
A.M. Smith, and D. G Vaughan 221
A Review of Pine Island Glacier, West Antarctica:
Hypotheseso f Instabilityv s. Observationso f Change
David G VaughanA, ndrewM . Smith,H ugh F. d. Corr,A drian Jenkins,C harlesR . Bentley,
Mark D. StenoienS, tanleyS . Jacobs,T homasB . Kellogg,E ric Rignot,a nd BaerbelK . Lucchitta 237
Ice Streams B and C
L M. Whillans,C . R. Bentley,a nd C. d. van der Veen 257
The Flow Regimeo f Ice StreamC andH ypotheseCs oncerningit s RecentS tagnation
S. AnandakrishnanR, . B. Alley, R. W.J acobel,a nd H. Conway 283
PREFACE
Sea-levelr ise from greenhousew armingi s of consid- Workers from opposites ides of the Atlantic Ocean
erablee conomici mportance.P rojectionsh, owever,t yp- have been journeying to opposite sides of West
ically includeg reat uncertaintyb ecauset he stabilityo f Antarctica to fashion views of the ice sheet. Annual
the West Antarctic ice sheet cannot be guaranteede ven workshopso f the EuropeanF ilchner-RonneI ce Shelf
over the brief time scale of human economies.T hus, the Project (FRISP) and U.S. West Antarctic Ice Sheet
low-probability/high-impaccot llapseo f WestA ntarctic (WAIS) Initiative teams have chartedt he progressb y
ice has stimulatedv igorousr esearcho ver the last 30 each group. Increasing interaction between the groups
years,w hich we summarizei n this volume. led to a joint FRISP/WAIS meeting in September,1 998
Major resultst o date includet he following:t he West at the University of Maine in Orono. An outgrowtho f
Antarctici ce sheeth asl argelyo r completelyd isappeared this historic meeting was the decision to commission
after it formed, but at an unknown rate; the West world expertst o review and advancet he stateo f knowl-
Antarctici ce sheets haresim portants imilaritiesw ith, but edge of the WAIS within the presentb ook. We editors
some differencesf rom, past ice sheetst hat changed eagerly awaitedt he insightsi n each new paper, and we
greatlya nd rapidly on widely separatedo ccasionsp; or- trust that thesep apersw ill prove illuminating to those
tions of the West Antarctic ice sheeta re changingr apid- interestedin sea level, climate, ice sheets,g lacial geolo-
ly now while averageso vert he wholei ce sheets howl it- gy, oceans edimentsa, nd relateds ubjects.
tle changea; nd,s omem odelso f the ice sheetp rojects ta- We thank the European and U.S. National Science
bility while others suggestt hat rapid changesr emain Foundationsf or funding, H. Borns and co-workersa t the
possibleI.t shouldc ome as no surpriseth at we lack a University of Maine for hostingu s, and numerousd edi-
consensupsr edictiono f ice-sheest tability. catedr eviewersf or raisingt he qualityo f the papersw ith-
The road toward a consensusp rediction is long, in this volume.
owingt o the vastd ifficultieso f characterizinag subcon-
tinental block of ice more than 3 km thick in places,o f R. B. Alley
reconstructinigts history,l earningh ow it behavesa, nd The PennsylvaniaS tate University
understandinigts linkagesw ith the surroundingo ceans
and atmospherea nd the geologyb eneath.D espitet he R. A. Bindschadler
difficultiesr, ecentp rogressh asb eeng ratifyinglyr apid, NASA/GoddardS paceF light Center
and our view of the ice sheet and its environment is
becomingi ncreasinglyc lear. Editors
xi
THE WEST ANTARCTIC ICE SHEET: BEHAVIOR AND ENVIRONMENT
ANTARCTIC RESEARCH SERIES, VOLUME 77, PAGES 1-11
THE WEST ANTARCTIC ICE SHEET AND SEA-LEVEL CHANGE
R.B. Alley
EnvironmenInt stitutea ndD epartmenot f GeoscienceTsh, eP ennsylvanSiat ateU niversityU, niversitPy ark,P ennsylvania
R.A. Bindschadler
Oceansa ndI ce Branch,N ASA/GoddardS paceF light Center,G reenbeltM, aryland
A collapseo f the West Antarctic ice sheeti s consideredp ossiblei f not highly
likely over the next few centuries,w ith potential to raise global sea level ap-
proximately 5 m, and larger sea-levelr ise possiblei f changesp ropagatei nto the
East Antarctic ice sheet. Continuation of recent West Antarctic ice-sheet retreat
may contributet o sea-levelr ise for somet ime even if completei ce-sheetc ollapse
doesn ot occur. While there is no proof that collapseo f the West Antarctic ice
sheet is or is not imminent, a growing body of evidence shows that some ice
sheetsh ave the potential for rapid collapse,a nd that regional dynamic changes
are occurring within the West Antarctic ice sheet. Fundamentala dvancesi n our
understandinga re being made by improved observationso f the ice sheet and its
environment,r econstructiono f the ice sheet'sh istory, and modeling of the ice
sheet's future evolution. However, further advancesa re requiredt o learn the fu-
ture of the West Antarctic ice sheetw ith the confidencen eededt o assistp olicy-
makers.
INTRODUCTION advanceo r to an acceleratingre treat. Thomasa nd Bentley
[1978] usedc omputerm odelingt o solvea more-complete
In 1968, JohnM ercer arguedf rom geologice vidence set of equations than addressedb y Weertman[ 1974].
that the West Antarctici ce sheet( Figure1 ) may have dis- Discussing changeso ver ice-age cycles, they suggested
appearedi n the geologicallyr ecent past. Glaciological that "...for a suitably precariousm arine ice sheet a small
insightss uggestedth at the ice sheetc ould shrink and dis- changei n climate couldt rigger growth or decayw hich,
appeara gain. If too much futurew armingw ere to occur onces tartedm, ay be irreversible"[p . 164].
for any reasoni ncluding" industrialp ollution of the at- Hughes[ 1972, 1973] producedth e first sciencep lan
mosphere",t hen "the unstable West Antarctic Ice Sheet for studyingt his radical idea of marine-ice-sheeitn stabil-
will become a threat to coastal areas of the world within 6 ity. Many individuala nd coordinaterde searchp rojects
m of sea level" [Mercer, 1968, p. 223], perhapsc ausing have taken place over the three decadess ince Mercer's
"...major dislocationsin coastalc ities,a nd submergence first paper on this subject. The list of projectsi ncludes
of low-lying areass ucha s much of Florida and the Neth- the RossI ce ShelfP roject( RISP, whichp enetratedth e ice
erlands"[ Mercer, 1978, p. 325]. shelf during the 1977-78 and 1978-79 seasonsa) nd the
Weertman[ 1974] followed Mercer's warnings by Ross Ice Shelf Glaciologicala nd GeophysicalS urvey
identifying a glaciologicalm echanismt hat might allow (RIGGS, with field seasons1 973-1977), the Siple Coast
ice-sheetc ollapse. Basedo n a simplem odel, he argued Project (SCP, 1983-1991), and the ongoing Filchner-
that a marine ice sheet (one groundedw ell below sea Ronne Ice Shelf Project (FRISP, for which a subcommit-
level) such as the West Antarctic ice sheeth as only two tee of the Scientific Committee on Antarctic Research
stable configurationsg: roundedt o the edge of the conti- Working Group on Glaciologyw as establishedin 1983)
nental shelf, or completely collapsed. In theory, the and the West AntarcticI ce Sheeti nitiative (WAIS, started
slightestp erturbationc ould drive the ice sheett o a slow in 1991). The hard sciencep roducedb y the earlier of
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