NSF Web Site
U.S . An tar ctic P ro gr am , 2 0 04 –
20 0 5
GLACIOLOGY
I. Ae ron o m y an d Astro p hy sics
Icebergs ne ar the Anta rctic P eninsula.
(NSF/ USA P pho to by Je ffre y Kietzma nn,
Ray the on Po lar Ser vice Co rp.)
II . Bio log y an d Me di cin e
II I. Lo n g -Te rm Eco lo g ical
Rese arch
IV. O cea n an d C lim a te Sy stem s
V. G eo lo gy a nd Ge op h ysics
VI. Gl acio lo g y
VII . Arti sts an d W rite rs
Pr og ra m
PD F Ver sion
OP P h om e p ag e
Ant arcti c S cien ce s S ectio n
Po la r Re se ar ch S up p or t S ecti on
U.S . An n ua l An tar ctic T re aty
Ex cha n ge o f In fo rm a tio n
On this page:
z Ov erv iew
z Mechanics of dry -land calv ing of ice cliffs.
z Airbo rne geo physica l surv ey o f the Amundse n Se a em ba yme nt, Antarctica
(AGASEA).
z Late Quate rnary histor y of R eedy Glacie r.
z West Antarctic Ice Sheet stability: The glacia l ge olo gic reco rd fro m the Ohio
Range of the H orl ick Mo unta ins in the Bo ttleneck .
Ea rth's la rge st ice be rgs.
Dry V alle ys Late H olo cene clima te v aria bili ty .
Tidal mo dula tion of ice stre am flow.
Monito ring an active r ift system a t the front of Amer y Ice Shelf, East Anta rctica.
z Is Ka mb Ice S tr ea m Restar ting? Gl aciol ogical inve stiga tions of the Bulge- Trunk
tr ansition on Kamb Ice Strea m, W est A nta rctica.
z Inv estigating a tmospheric chemistry thro ugh o xy ge n a nd sulfur iso topes in
volca nic sulfa te from So uth P ole ice co res.
z
z
z
z
Overview
Ice is indisputably the de fining char acter isti c o f
Anta rctica. The entire continent (with a fe w
exce ptio ns such as the McMurdo Dry Va lley s a nd
so me la ke s a nd mountains) is co ve red by ice
she ets tha t hav e be en laid do wn o ve r e ons, if the
te rm "shee ts" can be used to describe a dynam ic
mass tha t is sev era l tho usa nd mete rs (m) thick,
tha t is large r tha n mo st co untrie s, that rises ov er
2,000 m abov e sea leve l (and pe aks in a n ice
do me nea rly twice that high i n the e ast), and that
is hea vy e no ugh to de pr ess the bedro ck be ne ath it
so me 600 m. Actua lly, the co ntine nt has two
distinctly differe nt shee ts: the much la rger East
Anta rctic Ice S he et, w hich co ve rs the bedro ck co re
of the continent, a nd the sm alle r, m arine - ba sed
West Antar ctic Ice Shee t, which is be yo nd the
Tra nsa ntarctic Mountains a nd ov erla ys a gr oup o f
isla nds and wa ter s.
A scie nce te am lo ads e quipment
on to a sk i- equipped C -130 a ir
tr anspo rt (LC -130). U SAP 's LC - 130
airplane s, flo wn by the Air N atio na l
Guar d of Sche nectady, Ne w Yo rk,
suppo rt rem ote field rese arch
thro ugho ut Antarctica a nd pro vide
essential suppo rt to A mundsen­
Sco tt South P ole Sta tion.
(NSF/ USA P photo .)
The Antarctic Glacio logy Pro gram is concerne d with the history a nd dy na mics of the
antarctic ice she ets; this include s r esea rch o n nea r -surface sno w a nd fir n, flo ating gla cie r
ice (ice shelve s), glacie rs, ice stre ams, and continental a nd mar ine ice shee ts. The se
specie s o f ice facilita te studies o n ice dynamics, pa leo envir onme nts ( de duced fro m ice
co re s) , numer ica l mode ling, glacia l ge olo gy , a nd re mo te se nsing. Curr ent pro gr am
obje ctives include the follo wing:
z co rre lating a nta rctic clim atic fluctuatio ns (fro m ice - co re a na lysis) with da ta fr om
arctic and lo wer -latitude ice co res;
z inte gra ting the ice reco rd with terre strial a nd mar ine re cords;
z inv estigating the phy sics o f fa st gla cie r flo w with e mpha sis o n proce sse s a t gla cier
be ds;
z inv estigating ice -she lf stability; a nd
z ide ntifying a nd qua nti fy ing the r elatio nship be twee n ice dynam ics a nd cl imate
cha nge.
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Mechanics of dry-land calving of ice cliffs.
Bernard Hallet and Erin P ettit, University of Was hin gton , and Andrew G.
Fou nt ain, Portland St ate University.
We will pe rform a co mprehe nsiv e study o f land -ba sed pola r ice cliffs. Thro ugh fiel d
mea sure me nts and m odeling, we will identify the phy sics unde rlying the form atio n of ice
cliffs a t the ma rgin o f Tay lor Glacie r in the McMurdo Dry Vall eys.
Pre liminary m odeling sugge sts that horizo nta l ve locity pea ks o ne -third the distance up
the cliff face a nd tha t the highe st shea r stra in ra tes are a t the base . We hy po the size tha t
the displ acem ent field of the glacie r i s mo re impo rtant tha n the loca l a bl atio n patte rn in
maintaining ice cliffs a nd tha t the timing o f calv ing is co ntro lled by r apid tem pe ra ture
fluctua tions tha t ca use tr ansient stre ss fields to de velo p in the ther mal skin of the cliffs.
We will use a combinatio n o f strain ga uge s, tilt se nso rs, therm istors, and a global
po sitioning system surface stra in netwo rk to me asure ice defo rmatio n a nd tempe rature
ne ar the cliff fa ce at three site s. An a blatio n stak e netwo rk will augment existing e nergy
ba lance data, and a sm all seismic netwo rk will monito r local ice quake s a ssocia ted with
cr acking a nd calv ing. Ultima tely , the fie ld data wil l be used to v alidate a model that will
enable us to e xplor e the sensitivity o f ice cliff ev olutio n to basa l sliding ra te, ice
te mpera ture, and a ngle o f inci de nt sola r radia ti on. Fina lly, w e will dete rmine the slope,
aspect, a nd he ight of ice cl iffs using a mo del deriv ed fro m a lase r altime try surve y
co nducted by the N atio na l Ae rona utics and Space A dministra tion.
Our wo rk will pro vide insight into calv ing and glacie r te rminus e vo lutio n a nd will she d
light no t o nly on other la nd - a nd wa ter- ba sed glacie r termi ni on Earth, but a lso po ssibly
on the Ma rtia n ice caps. Mo re ov er, a be tter grasp o f ice cliff proce sses will impro ve
pre dictio ns o f glacier s' re spo nse to climate cha nge. A bette r unde rstanding of mor aine
fo rma tion a t po lar ice cliffs will co ntribute to mo re precise inter pre tatio n o f paleo glacie r
margins in the McMurdo Dry Va lley s a nd the ir co rre latio n with pa leo clima ti c e vents
de rive d from the Taylo r Dome ice co re .
This r esea rch will hav e student invol vem ent a nd will be incor po rate d into the curr iculum
of a w ilde rness scie nce e duca tion progra m fo r high schoo l gir ls, as well a s sev er al
cla ssroo m science wo rksho ps fo r middle a nd high scho ol girls in the S eattle a re a. ( I–
139 –M; NSF /OP P 02 –30338 and N SF/ OPP 02–33823)
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Airborne geophysical survey of the Amundsen
Sea embayment, Antarctica (AGASEA).
John W. Holt, David L. Mors e, and Don ald D. Blankens hip, Ins titu te f or
Geophysics , University of Texas -Au stin.
The We st Antar ctic Ice Shee t, the only ma rine ice sheet re maining from the la st glacia l
pe riod, ha s bee n the subject o f intensive study since it was reco gnize d to be a po tentia l
so urce fo r a rise in sea leve l of up to 5 me te rs, po ssibly o n a short time sca le. The W est
Anta rctic Ice S he et ha s thre e pr imar y dr ainages; the Ro ss Se a a nd Weddell Sea
embay ments ha ve bee n the prima ry fo cus o f atte ntio n, while the Amundse n Se a
embay ment ha s be en studied co mpara tive ly little , prima rily because it is so re mo te.
Ho wev er, sa tellite re mo te - se nsing studies, co mbined with limited da ta on ice thick ness,
indicate tha t the Amundse n Sea embay me nt discha rge s the la rge st ice flux in We st
Anta rctica; furthe rmo re, of all the major a nta rctic draina ge ba si ns, i t is the o nly one to
exhibit significa nt change in e leva tion ov er the pe rio d of rece nt sate llite obser vatio ns.
At prese nt, we la ck the k no wledge of the ice thickne ss and subgla ci al bo undar y
co nditio ns nee de d to unde rstand the ev olutio n o f this e mbay ment or its se nsitiv ity to
clim atic cha nge . We the refor e intend to per fo rm com pre hensive a ero ge ophysica l surve ys
of the two ma jo r dr ainage basins w ithin the Am undsen S ea e mbaym ent: the Thw aites
Gla cier Ba sin and the P ine I sl and Ba sin. We will ana lyze the data we gather a nd ge nera te
maps o f la ser sur fa ce ele va tion, ra da r sur fa ce ele vatio n a nd ice thi ck ness, ice
accum ul atio n ra te from shal low rada r la ye r inte rpola tion, inter na l laye r pr eser vatio n
de pth, cre va sse cla ssifica tion, gra vity a nd magnetic anom alie s, deta iled ba sa l
morpholo gy and ro ughness sta tistics, and co he re nt ra da r echo strength a nd sca ttering
cha racte rizatio n.
Our surve ys and ana lyses will be achiev ed thro ugh co llabo ratio n with the Br itish Antarctic
Sur vey a nd will include graduate stude nts in all pha se s o f the project. Unde rgraduate s
and high scho ol a ppre ntice s will al so be fully inte grate d into da ta ana lysis. Giv en the
substantial public and scientific inter est tha t re cent r eports o f change in We st Antar ctica
ha ve gener ate d, we ex pe ct fundam ental re sea rch in the Amundse n Se a em ba yme nt to
ha ve a wide spre ad i mpa ct. ( I–141–M; NSF /OP P 02 –30197)
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Late Quaternary history of Reedy Glacier.
John O. Ston e an d H oward B. C onw ay, University of Was hin gton , and Bren da L.
Hall, University of Maine.
The stability o f the marine W est Anta rctic I ce S he et rem ains a n impo rtant, unreso lve d
issue for predicting future changes in sea le vel . Studie s indicate that the mass ba lance o f
the ice shee t to da y co uld be nega tive o r po sitive. The a ppar ent diffe rence could ste m in
pa rt fro m sho rt -te rm fluctuatio ns in flo w. By co mpariso n, geo logic o bse rva tions pro vide
evide nce o f behav ior o ver m uch longe r time scale s. Re cent wo rk sugge sts that
de gla ciatio n o f both the Ro ss e mba ym ent a nd coa stal Ma rie Byr d Land co ntinue d into the
late H olo cene (a bout the past 2,000 ye ar s) a nd lea ve s o pe n the possibility of ongoing
de gla ciatio n a nd gro unding- line r etre at. H owe ve r, prev ious wor k in the Ross em ba yme nt
was ba sed o n data fro m just three lo catio ns that are a ll fa r no rth o f the pr esent
gro unding line. Additio na l da ta fr om farther so uth are ne eded to de termine whethe r the
recessio n has ended o r whether the rate a nd patter n of deglacia tion infe rred fro m our
pre vio us study still apply.
We will the re fo re re construct the ev olution of Ree dy Gla ci er, in the southern
Tra nsa ntarctic Mountains, since the last gla cial ma xim um . Beca use the glacie r eme rges
fro m the m ountains a bov e the grounding line , its sur fa ce slope and e lev atio n should
reco rd changes in the thick ne ss o f grounded ice in the R oss Sea up to the prese nt. The
de gla ciatio n chrono logy of Ree dy Gla cier can thus indica te whether the H olo cene retr eat
of the We st Anta rctic Ice Shee t e nde d thousands o f ye ars ago o r is still continuing.
We will ma p, da te, a nd cor rela te mor aines at sites alo ng the le ngth o f the gla cier o ve r
tw o fie ld sea sons and ma ke r adar and global positio ning sy stem me asurem ents to
supple me nt ex isting ice thickness and v elo city da ta. W e will also co nstr uct a mo de l o f
gla cier dynamics and use it to rela te geo logic m ea sure ments to the grounding- line
po sition do wnstr eam . U ltimate ly, w e will inte gr ate the ma pping, da ting, and ice - modeling
co mpone nts of the study i nto a re constructi on tha t defines cha nges in ice thickne ss in
the so uther n Ro ss Se a since the la st glacia l max imum and re late s these changes to the
histo ry of gro unding- line r etre at.
Our wo rk dir ectly a ddresse s the ke y go a ls o f the West Antarctic Ice Shee t Initia tive ,
which are to understa nd the dyna mics, re ce nt history , a nd po ssible futur e be havi or of
the W est Anta rctic Ice Shee t. ( I–175–M; NSF /OP P 02–29314 and N SF/ OPP 02–29034)
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West Antarctic Ice Sheet stability: The glacial
geologic record from the Ohio Range of the
Horlick Mountains in the Bottleneck.
Haro ld W. Borns , University of Maine, an d S ujoy Mukhop adhyay, Harvard
University.
We will study the We st Antar ctic Ice Shee t a t the Ohio Ra nge nea r the hea d of Merce r Ice
Strea m; this is loca ted in the B ottlene ck, a unique, rela tive ly narro w pa ssage in the
Tra nsa ntarctic Mountains co nnecting the We st a nd East A nta rctic Ice S he ets.
We will ma p glacial deposits and e rosio n fea tur es and co mbi ne these with cosmo ge nic
surface -expo sure da ti ng on Ohio Ra nge nunatak s to dete rmine the chr onolo gy of pa st ice
she et leve ls a nd glacie r fluctua tions. Exposure a ge s o f fresh gla cial er ratics, up to 60
mete rs a bo ve the prese nt le vel , will be used to constra in the timing o f the last high sta nd
and draw - do wn o f the ice she et in this secto r, while e xposure a ge s o f debris ba nds on
the surface will co nstra in the dura tion of co ntinuo us ice cov er nea r the pre se nt e leva tion.
A co mpleme nta ry lo cal pr ox y cl imate r ecor d will also be o bta ined fro m a chro nolo gy o f
local glacie r mora ines.
These glacie rs are se nsitiv e to cha nge s in sno w accumul atio n and predo minant w ind
dire ction. W he n co mpare d with the re cord of the fluctua tions o f the adjacent ice she et,
the timi ng of a lpi ne gla cie r a dv ance will yie ld info rma tion tha t ca n be use d to te st clima te
reco nstructions ba sed o n a nta rctic ice co re re cords. Our da ta will co ntribute to the
de vel opment of tim e -de pe nde nt, no ne quilibrium mo dels si nce the last glacia l ma xim um
20,000 yea rs ago. Mor eo ver , such data a re critical to te sting a nd calibra ting the m odels
ne cessary to pre dict the be havi or of the ice shee t i n re spo nse to clima te cha nge s.
The behav ior o f thi s ice shee t is significant beca use of its link to se a lev els. M elting wo uld
raise se a lev els, nega tively affe cting the lar ge por tion of the populatio n liv ing ne ar the
co asts. B ecause the We st Antar ctic Ice Shee t is lar ge ly gr ounde d belo w se a lev el, it is
subje ct to gra vita ti onal colla pse tha t co uld be o ngo ing or triggere d by glo bal warm ing.
In addition,
of the We st
hy po the ses
yea rs ago) .
the glacia l r ecor d in the Bo ttleneck will re fle ct the histo ry o f the inte ra ctio n
Anta rctic a nd Ea st Antar ctic Ice Shee ts, which could be used to test
on the co llapse of the for mer dur ing the P lei sto cene (10,000 to 1.8 m illion
(I –187–M; NSF /OP P 03 –38189)
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Earth's largest icebergs.
Douglas R. MacAyeal, Univers it y of Ch ic ago; E mile A. Okal, Nort hwes tern
University; and Ch arles R. St earns , Un iversity o f Wisc ons in -Madis on.
Icebergs r ele ased by the a nta rctic ice shee t r eprese nt the la rge st m ov eme nts of fr esh
water within the natura l e nviro nment. Se ve ral of the se icebergs, B –15, C –19, a nd other s
ca lve d since 2000, re pr esent ov er 6,000 cubi c kil ome ters of fre sh wa ter —an a mo unt
roughly e quiv ale nt to 100 ye ars o f the flo w o f the N ile Rive r.
We will study the dr ift and bre ak up of the Earth's largest ice be rgs, which wer e rece ntly
rele ased into the R oss S ea a s a re sul t o f calv ing fr om the Ross Ice Shelf. W e will attem pt
to ascerta in the physics o f icebe rg mo tion withi n the dy na mic contex t o f o ce an curre nts,
winds, a nd sea ice , which dete rmine the fo rces tha t driv e ice be rg mo tion, a nd the
rela tionship be twee n the iceber g and the geo gr aphi ca lly and to pographically de te rmine d
pinning po ints o n which it can gro und. I n addition, we w ill study the pro cesses by which
ice bergs influence the lo cal env ironme nt (se a ice nea r Antar ctica , a cce ss to penguin
roo ke ries, air -se a hea t e xchange and upwelling a t ice be rg ma rgins, nutrie nt fluxes) , as
well as the proce sses by which ice be rgs gener ate globa lly fa r- rea ching o cea n a coustic
signals that are dete cted by seism ic- se nsing ne twork s.
In addition, w e will a ttem pt to deploy a uto ma tic we ather statio ns, seismo me ter ar ray s,
and global positio ning sy stem tra ck ing statio ns o n sev era l of the la rgest ice be rgs
pre sently adrift, o r a bo ut to be adrift, in the R oss S ea. Data gener ated and re lay ed v ia
sa tellite to our ho me institutio ns will le ad to the ore tical anal ysis a nd computer simulatio n
and will be archive d o n a We b site ( http:/ /am rc.sse c.wisc.edu/ice be rg.html ) that
scie ntists and the gener al public ca n a cce ss.
A bette r understa nding of the im pa ct o f ice be rg drift o n the e nv ironme nt, and pa rticula rly
the im pa ct o n o ce an stratificatio n a nd mix ing, is e sse ntial to under sta nding the a brupt
glo ba l cli mate changes witne ssed by prox y during the Ice Age a nd future gree nho use
warm ing. M ore specifically , the study will gener ate a k no wledge ba se useful for the
be tte r mana ge ment of antarctic logistical re sources that can occasio nally be influe nce d
by the adve rse e ffects icebergs hav e on sea ice ( the shipping la nes to McMurdo Statio n,
fo r e xam ple ). (I–190–M; NSF /OP P 02 –29546, NSF /OPP 02 –29492, and N SF/OP P 02 –
30028)
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Dry Valleys Late Holocene climate variability.
Karl J. Kreut z and Paul A. Mayew ski, Univers it y of Maine.
We will colle ct a nd de ve lop high -reso lutio n ice -co re re cords fro m the Dry Vall eys in
so uthe rn Victo ria La nd and pro vide interpre tatio ns of inte ra nnual to decada l clima te
var iability duri ng the past 2,000 ye ars (la te Ho loce ne). We will test hypothese s re late d to
ocea n/atm osphe re te leconnectio ns (e .g., El Ni ño Southern Oscillatio n, Antarctic
Oscilla tion) that ma y be re spo nsible fo r ma jo r late H ol ocene clima te ev ents such a s the
Little Ice Age in the So uthe rn H emisphere .
Conceptual and quantitativ e mo de ls o f these proce sses i n the Dr y Va lley s during the late
Ho loce ne a re critica l for unde rstanding re cent clim ate changes. W e pla n to co llect
inte rme dia te -length ice co res (100 to 200 me ters) a t four sites alo ng transects in Tay lor
and Wr ight Valle ys and a na lyze e ach co re a t high re so lution fo r stable iso topes, m ajor
ions, a nd tr ace e leme nts. A suite o f statistica l te chniques w ill be a pplied to the
mul ti var iate glacio che mica l data se t to ide ntify chemica l a ssocia ti ons a nd to ca libra te the
tim e -se rie s re cords w ith av aila ble instrume nt data .
Broa de r impacts of the project include:
z co ntributio ns to sev era l ongoing interdisciplina ry a nta rctic re sea rch progra ms;
z gra dua te and unde rgraduate stude nt invo lve ment in field, la bo ra to ry , and da ta
inte rpr eta ti on a ctivitie s;
z use o f project da ta and i de as in sev era l Unive rsity of Maine co urse s a nd outre ach
activitie s; and
z da ta disse minatio n through pee r- rev iewe d publicatio ns, U niv ersity o f Ma ine and
other pale oclima te data a rchiv e We b sites, a nd pre sentatio ns a t natio nal and
inte rnatio na l m ee tings. ( I–191–M; NSF /OP P 02 –28052)
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Tidal modulation of ice stream flow.
Sridh ar Anandakrishn an, Richard B. Alley, and Don ald Voigt , P en ns ylvania St ate
University; Robert Binds chad ler, God dard S pace Fligh t C ent er, N ational
Aeronau tics and Sp ace Ad minist rat ion ; an d Ian Jou ghlin , Jet Propu ls ion
Labo rat ory, National Aeronau tics and Sp ace Administ rat ion .
We will investigate the new fo und, star tling sensitivity o f ma jo r we st a nta rctic ice stre am s
to tida l o scillatio ns to le arn the e xte nt a nd cha racte r o f the effect and its ram ifica tions.
Ice str ea ms D, C , a nd Whillans (B) a ll show stro ng but distinct tida l signals. The ice plain
of W hill ans is usua lly stoppe d o utr ight, for ward motio n being limi te d to two brie f perio ds
a da y, at high tide a nd on the falling tide. Motio n pro pa ga tes acro ss the ice plain at
se ismic wav e v elo ci tie s. N ea r the mo uth o f D, tides ca use a diurnal v aria tion of a bo ut 50
pe rcent in ice -str eam spee d that pr opagate s upgla cier mo re slo wly tha n o n W hilla ns, and
se ismic da ta sho w tha t C e xperie nce s e ven slowe r upglacie r signal pr opagatio n. Tida l
influences are o bse rve d mo re than 100 k ilom ete rs ( km) upgla cier o n C and m ore than 40
km upglacie r on D and m ay be respo nsible for fluctuatio ns in basa l wa ter pressure
repor te d 400 km upstrea m on W hillans.
During the first y ea r, five co ordinate d seism ic a nd glo ba l positio ni ng sy stem (GP S)
instrume nt packa ges pla ced 100 k m apart on e ach stre am me asure d Whilla ns and ice
str eam D. These pack ages were deploy ed at sites se lecte d by sa tellite i mager y and
opera ted a uto nomo usl y fo r tw o luna r cy cles to study the sensitivity o f the stre ams to
spring a nd ne ap tide s. Also , we e xam ine d e xisting data sets for clues to the m echanisms
inv olv ed a nd deve lope d pr elimina ry mo dels.
During the seco nd and third se aso ns, we will exa mine in gre ate r deta il the tidal behav ior
of W hill ans a nd D. We will focus e spe cia lly o n at le ast o ne source a rea for W hill ans,
assum ing tha t a rea s inferre d fro m pre liminary da ta rem ain a ctive . Ve rtical mo tions hav e
no t y et be en de tected, but diffe rentia l GP S will increa se sensitiv ity. Se ismic
instrume nta tion will gre atly incre ase te mpo ra l re solution and the a bility to m ea sure the
pro pagatio n speed and a ny spatia l hete ro ge ne ity.
Improv ed k nowle dge o f ice -str eam beha vio r w ill co ntr ibute to a sse ssing the po tential fo r
rapid ice - she et cha nge a ffecting globa l sea leve ls. Re sul ts will be dissem inated thr ough
scie ntific publica tions a nd talk s a t pro fe ssional me etings, as well a s conta cts with the
pre ss, univ ersity cla sses, v isits to schoo ls a nd com munity groups, a nd other a ctiv ities.
(I –205–M; NSF /OP P 02–29629 and N SF/ OPP 02–29659)
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Monitoring an active rift system at the front of
Amery Ice Shelf, East Antarctica.
Helen A. Fric ker and Jean -Bernard Min ster, S crip ps Ins tit ut ion of
Oceano graphy, Un iversity o f C alifornia– San Dieg o.
Anta rctic ice shee ts lo se ma ss prima rily by iceberg ca lving fro m the fr ont o f the fringing
ice she lves. This mass contribute s to the freshwa ter flux o f the Southern Ocean, but do es
no t ca use a cha nge in se a lev el, since the ice wa s a lrea dy flo ating. H owe ver , ice shelv es
ca n influe nce the discha rge of inla nd ice via the stre ams that fe ed the m; in pa rticula r, a
reductio n in ice she lf could increa se the discharge ra te. Furthe rmo re , any changes in the
mass lo st by calv ing could be an indica tor of regio na l e ffe cts of climate change and co uld
modify fre shwate r m ass pro ductio n ra tes, which might ha ve global co nse quences.
There fore , it is im po rtant no t o nly to mo nitor the fr eque ncy of ca lving, but also to
understa nd the me cha nisms behind it.
Icebergs ca lve whe n rifts— cr eva sses tha t pene trate fro m the ice shelf surface to its
ba se —pro pagate far e no ugh tha t a par t o f the shelf be co me s deta che d. Beca use this
pro cess is not we ll unde rstoo d, we wil l co mbine in situ a nd rem ote -se nsing da ta with
nume rical mo de ling to study ri ft gr owth o n the Ame ry Ice Shel f, a n a ctiv e rift sy stem
co mbining two longitudinal - to - flo w r ifts tha t o rigina ted a t the ice shelf fro nt in the suture
zo nes be twee n me rging flo wbands a nd tw o transve rse -to -flo w r ifts tha t fo rme d at the tip
of the we ste rn lo ngitudina l rift a bo ut 7 y ea rs a go. The propa ga tion of the two tra nsver se
rifts is no t independent, and the lo nge st o f the m is gro wing at ar ound 8 me ters a day .
When this rift me ets the e aste rn lo ngitudi na l r ift, which we e xpect to occur i n mid- 2006,
a huge iceberg will ca lve . Once it doe s, we will ex am ine the e ffects on the dyna mics o f
the ice shelf a nd on pre vio usly i na ctive rifts.
Iceberg ca lving ha s a histor y of spar king a grea t de al of media a nd public inter est,
espe cially since the rece nt la rge ca lving fro m the Ro ss and R onne Ice Shelv es and the
bre ak -up of the La rsen Ice Shelf. W e intend to re po rt our results wide ly at confere nce s
and in the scientifi c lite rature, and we w ill display o ur re sul ts to lo cal faculty and
resea rchers, undergra dua te and graduate stude nts, and schoo l children and their
te acher s. (I –277–E; N SF/ OP P 03–37838)
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Is Kamb Ice Stream Restarting? Glaciological
investigations of the Bulge-Trunk transition on
Kamb Ice Stream, West Antarctica.
Slaw ek M. T ulac zyk, Un iversity of C alifornia –Sant a Cruz ; I an Jou ghlin , Jet
Propulsion Laboratory, Nat ion al Aeron autics an d S pace Adminis tration; and
Rob ert W . Jaco bel, St. Olaf C ollege.
The We st Antar ctic Ice Shee t co nta ins e no ugh ice to raise the global se a lev el by se ve ral
mete rs, and co ncerns ha ve bee n ra ised a bo ut its po ssible r etre at or colla pse. H ow eve r,
mea sure me nts have shown tha t the Ro ss Se a secto r o f this i ce she et is in a po sitive
mass ba lance. This is surprising, be ca use ge olo gic a nd gla ciolo gi c data indicate that the
ice she et ha s bee n re trea ting fo r abo ut 10,000 y ea rs. It is possible that the o bserv ed
po sitive ma ss bala nce is a result of a sho rt- te rm (deca da l- or century -sca le) o scillatio n in
ice discharge, rathe r tha n an indica tion o f a lo ng- te rm shift in ice -she et be ha vio r. I n
pa rticula r, the Ro ss Se a secto r of the We st Antar ctic Ice Shee t co ul d return to ne utral or
ne ga tive m ass ba lance if the Ka mb Ice S tr ea m (forme rly ca lled " Ice Stre am C" ), which
ha s stopped, re starts and begins flo wing at ice -str eam -like v elo citie s. Be cause the
tr ibutar ies of this strea m are still activ e, a massiv e ice bulge is building up where the y
run into the lo cke d- up tr unk o f the Ka mb Ice Stre am , nea r the site o f the fo rme r
Upstr ea m C C amp. On mo unta in glacie rs, buildup o f ice bul ge s is associa ted with a sharp
incre ase in ice ve locity in a rela tive ly sho rt ti me.
We will test to see whethe r the Ka mb Ice S tr ea m m ay a lrea dy be in the proce ss o f
restar ting. If so, w e will establish wha t the ra te of re activ atio n is a nd what me cha nism s
are co ntr olling it. If not, w e will deter mine what physica l co ntrols are pre ve nting surging
and what the alte rnative sce na rio s for the ev olutio n o f the str eam a re. One scenario is a n
incre ase in ice div ersio n to ward ne ighbo ring W hilla ns Ice Stre am ; this could pre vent a
co mplete sto ppage o f the stre am, which has be en slo wing down fo r almo st the past 25
yea rs.
Our wo rk will ha ve two co mpone nts:
z fie ld obser va ti ons o f bed pro pe rtie s, ge om etry o f interna l ra da r reflecto rs, surface
str ain r ates, and v elo city /to po graphy changes using ice -pe ne trating r adar and
diffe re ntia l glo ba l positio ni ng sy stems and
z nume rical mo de ling of the e vo lution o f the Ka mb Ice Str eam o ve r the nex t 100 to
1,000 ye ars.
This pro je ct is a colla bora tion of scie ntists fr om three diffe rent ty pe s o f U .S. institutio ns—
a libe ral a rts co llege (St. Ola f Co llege) , a public rese arch unive rsity (U niver sity of
Califor nia –Santa Cruz), and a N atio nal Aero nautics a nd Space Administratio n r esea rch
labora tor y (the Je t P ropulsion Labor ato ry) . W e will m ak e pr oject results a va ilable to the
public a nd educa tors thro ugh dow nlo adable gra phics a nd anima tions po sted o n the
resea rch W eb site . Fie ld data re sulting fro m the pro je ct will be sha re d with o the r
inv estigato rs thro ugh the Antar ctic Glacio logical Data C enter. ( I–345–M; NSF /OP P 03–
38295 and N SF/ OPP 03 –37567)
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Investigating atmospheric chemistry through
oxygen and sulfur isotopes in volcanic sulfate
from South Pole ice cores.
Jih ong Cole -Dai, S out h D akota Stat e Un iversity, an d Mark H. Thiemens ,
University of California –San Dieg o.
It is well kno wn that lar ge , sulfur -rich vo lcanic eruptions ca n influe nce the ra di ative
budge t o f the atmo sphe re and the global clima te. Less understo od i s the dir ect impact o n
atmo spher ic chemica l pro cesses, especia lly the im pa ct o f ma ssive e ruptio ns that a lter
the co mpositio n of the e ntire atm osphe re.
We will use mass -independent isoto pe chem istr y, which ha s bee n shown to be an
effe cti ve too l in unde rstanding a va riety o f gas -phase a tmo spheric proce sse s. P relim ina ry
results o f o xygen and sulfur isoto pe mea sur eme nts in sa mples fro m sev era l e ruptio ns
indicate tha t the isoto pic com po sition of v olca nic sulfa te in a nta rctic snow a nd ice
co ntains v alua ble inform atio n o n atm osphe ric chemica l and dynam ic proce sses tha t hav e
no t bee n prev iously inve stiga ted. Fo r ex ample , ma ss- independently fractio na ted sulfur
iso tope s demo nstrate that atm osphe ric photo lysis (chem ical deco mpositio n induced by
light) of sulfur co mpounds o ccurs at longer ultra vio let (UV ) wav elengths than tho se in
the Ar che an a tmo spher e ( Pre cambria n er a) , possibly reflecting a tmospheric ozo ne or
oxy gen co nce ntra tion (o r bo th) . This suggests tha t the iso topic co mpositio n o f
atmo spher ic sulfa te ma y be use d to tra ck the e vo lutio n ( oxy genatio n) o f the atm osphe re
and the origin of life o n Earth.
Using teste d me tho do lo gy , we will:
z locate a nd isola te kno wn v olcanic ev ents in six sha llow So uth P ole ice co res,
z extra ct v olca nic sulfa te fr om a t le ast fiv e majo r e ruptio ns ( Pinatubo, Ta mbo ra ,
Unknown 1809, Kuwa e, U nknown 1259) fr om these sa mple s,
z use e sta blishe d isoto pe analy tical proce dure s to dete rmine o xyge n and sulfur
iso tope s, and
z inte rpr et the da ta we ga ther.
These ste ps will he lp us a ddre ss a number of importa nt questions:
z What impact do m assive v olca nic e ruptio ns have on the o xidativ e capacity o f the
atmo spher e?
z What ox ida nts and m echanisms are inv olv ed in the o xida tion o r co nv ersio n o f
volca nic sulfur diox ide to sulfate in the stra tosphe re?
z What isoto pic criter ia could be use d to diffe rentia te ice co re signa ls o f
str atospheric er uptions fr om those o f tro po spher ic e ruptio ns?
z What is the ro le of UV radia tion i n sul fur dio xide co nv ersio n in the a tmosphere ?
z Do es the photo - oxida tion mechanism of vo lcanic sulfur diox ide depend o n a nd
reflect ozo ne /o xy ge n le vels in pa st atm osphe re s? ( I–355–S; NSF /OPP 03–37933)
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