MARINE RECORDS OF RIVERINE WATER AND SEDIMENT DISCHARGE IN FJORDS OF NUNATSIAVUT
by
©Elisabeth Kahlmeyer
A thesissubmittedtotheSchool ofGraduate Studies in partialfulfilment oftherequir ementsfor the degree of Master of Science
Department of Earth Sciences Memorial UniversityofNewfoundland
September 20ll
ABSTRACT
Thisthesisfocuseson the understanding of patterns and variabil ityof sedimentandfresh waterdelivery from landto sea,andsediment dispersal in the marinebasinsof twofjords in NorthernLabrador.Multibcam andsub-bottomacoustic dataandsedimentcores were collected in Nach vak andSaglek fjords.Sedimentcores were sub-sampled for X- radiography ,grainsize,and radiochemical analysis (based on the particle-bound radioisotopes2JOPband137es,),tostudysedimentarystructuresanddeterminesediment accumulationrates.Results show that thesedimentsaregenerally mottled and fine grained.Sedimentacc umulationra tesareo na verage O.21 cm/yi n Nachvakfjorda nd O.26 cm/yin SaglekFjord with temporal resolutionsranging from15-68 yearsinNachvak Fjordand 12-49 years in SaglekFj ord .Massaccumul ationrate values suggest thatthe majorityofthesediment isaccumul ating in thecenter ofthe basins. Furtheranalyses suggest that:postglacial sedimentation was onaverageconstant in NachvakFj ord;in Saglek Fjo rdsediment accumul ationwasmore rapid duringthelast-100 y ascompared to post-glacialtimes;the mainsedimentsource inSaglek fjord isfrom riverswith extensive catchments that lack glaciers, and in Nachv akfjord from smaller riverswith steep, small and presently glaciatedcatchmentsaswellas from additionalso urcessuchas fromtheerosionofg laci-marine terraces.
ACKNOWLEDGMENTS
I wouldliketothankmy supervisor Dr.Sam Bentleyforhis guidance,patienceand support.Moreover,I wouldliketothankhim forgiving me thechancetotravelsome of themost spectacular places onEarth,and to meet,befriendand learnfromsomevery special persons, suchasJoey,Leoand DorothyAngnatok,and Elias Obed. 1 wouldalso liketothankDr. TrevorBellforhis scientificadv ice.Specia l thank stoDr.Elliott Burden for servingon my superviso rycommittee.
Further,I wouldliketo thank thecaptainandcrewof the What'sHappeningfortheirhelp in thefieldin2008and 2009,and Parks Canada,the NunatsiavutGovern mentand the Environmenta lScienceGroup for establishing thekANGIDLUASUkbase campand for givingstudents likemetheinvaluable opportunity toexperiencethe beautifulnature of Labrador and thefriendlinessof itspeople.Manythanksto Tanya Brown,Mallo ry Carpenter, TomSheldon, Dave CoteandAngus Simpsonfor theirhelp in the fieldand for their help with fieldwork logisticsandaccommodation in Nain. I wouldalso liketothank Jodie Chadbournforhelpwithinformation onth e glaciere xtend inthe study area.
InsideMemorialUniversity I wouldespecially like to thank Kerry Hiscockforhis patience and readinessto help with anylaboratory and fieldworkrelatedproblem and Michelle Miskellfor herorganizational and mental support throughoutmytime as a student at MUN.I wouldalso like to thank the ISA fortheirhelpwith information on studyand work permits.
Finally, I would like tothankmyfamily,myfatherNorbert Kahlmeyer,mymotherlise Kahlme yer, and my sister Veron ikaKahlm eyerfortheirfinanc ial supportand fortheir perpetualmentalsupport and guidancein life. Morethan anyoneelse, I would liketo thankPeter Huelseforhis scientific advice,hishelp and adviceon fieldwork and in the laboratory,and hisunceasingmental supportand patience.Withouthim and myfamily I could never haveundertakenthisproject.
TABL EOFCONTENT S
Acknowledgment s TableofContents
List ofFigures List of Appendices Co-authorshipStatement
Chapter I-Introduction
Project Overview 1-
Researchin NorthernLabrador -Overview and Incentive I- Researc h todateinNachvakandSaglekFjord 1- GeneralResearchBackgrou nd
Sedimentary Deliveryto theCoastalOcean-
Processes and Application s 1- 6
Fjord Processes 1-10
Chapter2-Dispersal of fluvial sediment in two sub-arcticfjords on the LabradorCoast:NachvakFjordandSaglek Fjord,Canada
Fj ordProcesses 2. Regional Setting
StudyArea Geology
Samplecollection
2-11 2-11 2-12 2-13 2-13
Radiogeoche rnistryr'l'Pb,IJ7Cs) 2-13
Sedimentol ogical ana lyses 2-15
Fluvial measurement s 2-16
Estimationso f lluvia lsediment load 2-17
Estimationo f210Pbsupply tolandsurface 2-18
4. Results 2-20
Profil esof210PbandIJ7Csgeochronology (SAR) 2-20
Granul omet ry 2-35
X-radiograph s 2-35
Inventortesofi 'Pb 2- 36
Extentand thickness of postglaci alsed iment 2-41 Strea m flowcharacteristics
andseasona lwater level changes
Sedi mentdispersalandbudget Compariso nof modem sedimentaccumulation and postglacial sediment thickn ess 210PbFlux
Chapter3-Summary
LIST OF TABLES
Chapter 2 TableI
Inventories andfluxes of210Pb for box cores from NachvakFjord Table2
Inventories and fluxes of210pb for box cores from SaglekFjord Table3
AccousticDoppler Velocimetermeasurementsin McCornick River Tablc 4
AccousticDopplerVelocimetermeasurementsinNakvak Brook Table5
Results fromlaboratory analysesand radioisotopegeochronology for NachvakandSaglekFjord
Table6
Estimates for suppliedand deposited sediment load inNachvakandSaglekFjord Table7
Estimatesfor postglacialsediment thicknessbased on SAR from boxcores
LISTOF FIGURES
Chapter I Figure I
Sediment delivery to fjords,afterSyv itskieta l. 1995
Chapter2 Figure I
Map of studyareashow ing locations of NachvakandSaglekFjord.
Figure2
Mapof NachvakFjordshowingbathymetry, drainagebasins and corelocations.
Figure 3
MapofSaglekFjord showingbathymetry, drainagebasins and corelocations.
Figure4
Radio isotopeand grain sizeplots of cores fromNachvak fjord, collected in2008.
Figure 5
Radioisotope andgrain size plots of cores from Saglckfjord, collectedin2008.
Figure6
Radio isotope and grain size plotsof coresfromNachvak fjord, collectedin 2009.
Figure 7
Radioisotopeand grainsize plotsof cores fromSaglekfjord, collectedin 2009.
Figure8
X-radiograph images ofall box cores.
Figure9 2-41
Compilationof sub-bottom profiles andbathymetrydatain NachvakFjord.
Figure10 2-42 Compilationof sub-bottom profilesand bathymetrydata inSaglekFjord.
FigureII
Temperatureand waterleveldata from waterlevellogger in Nakvak Brook fromAugust2008 to August 2009.
Figure12
Temperatureand waterleveldatafrom water levellogger in McComi ckRiver fromAugust 2008 toAugust 2009.
Figure13
Waterdischargeandvelocity measurement s and depth profile of McComi ckRiver.
Figure 14
Waterdischarge andvelocity measurement s and depthprofileofNakvakBrook.
Figure15
Sedim entbudget map in NachvakfjordusingMARvaluesto show thedispersal ofsediment in the marinebasin.
Figure16
Sediment budgetmap in Saglek fjord usingMAR valuestoshow thedispersa lof sediment in themarinebasin.
LISTOFAPPENDICES
Append ix A
Radiochemistrydatafor box cores2008
Appendix B
Radiochemistrydatafor boxcores2009 Append ixC
Grain sizedata for box cores 2008 Appendix0 Grain size datafor box cores2009
AppendixE
Sub-bottom profilesinNachvakFjord AppendixF
Sub-bottom profilesinSaglekFjord AppendixG
Inventoriesof210Pbin Soilcores
Appendi x- l
Appendix-IO
Appendix-2l
Appendix-29
Appendix-40
Append ix-45
Appendix-49
CO-AUTHORSHIPSTATEMENT
Thefollowingthesischaptersare presented in manuscript format.Chapter2hasbeen developedincollaboration betweenmyself (theauthorof thisthesis) andothers. Forthe manuscriptcontained herewithin I outlinethework personally doneand the contributions madebymy co-authors in thefollowingparagraph.As theauthorofthisthesis,the work ispredom inantlymy own,withguidance frommy supervisorandco-author Dr.Sam Bentley.
Chapter2 evaluatesrecent marine recordsoffluvial sedimentsupply to twosub-arctic fjordsinnorthernLabradoraspart of abaseline ecosystemstudyofTorngat Mounta ins National Park. Fieldwork to collectsedimentcores consisted of two fieldseasons(two weeks inAugust2008,and twoweeksinAugust2009).It wasundertakenbymyself and my supervisor Dr.Samuel Bentley,withhelp from Peter Huelseduringthe fieldseaso n in 2009. All of the authors wereinvolved inthe logistics andplanningof the fieldseason.I prefonnedalldatacollection and analyticalworkforthisproject.l amtheprimary auth or on thismanuscriptwith my superviso r Dr. Samuel Bentleyproviding guida nceand editorialcomments.Funding for thisworkwasprovided in thefonn of agrantfrom ArcticNet,a Networkof Centresof ExcellenceofCanada, toDr. Samuel Bentley.
Chapter I
Thisthesisis organizedintothree separatechaptersas stand-a lone papers.Chapter one gives an overviewonthe research uptodate inNorthernLabrador andsummarizes thebasics of sedimentarydeliveryto the coastal ocean andfj ord processes. Chapter two presentsthe researchdone for this MSc thesis, including an introduction to the regional setting,a descriptionofthemethods used,adescri ptionof the resultswitha subsequent discussion, andconclusions.Chapter three summarizestheresearchresults and conclusions, points out the significanceoftheresearch andmentionsfuturestudiesto which this thesismay contributeto.
ProjectOverv iew
ThisMaster'sThesis ispart ofabasel ine ecosystemstudyof theTorngat Mountains National Park sponsored by ArcticNet,a Network ofCentresof Excellence of Canada (NCE). Thegovernmentof Canada togetherwithTheCanadian Institutes for Health Research(Clfl R),theNaturalSciences andEngineeri ng Research Council (NSERC) and theSocialSciencesand Humanities ResearchCouncil (SSHRC)administerthe Networks of Centresof Excellence in partnership with Industry Canada(www.nce-rce.gc.ca, retrieved2010). TheNCEaimstosupporttalentedresearc hersandimprovetheabili J Yto transform theirresearchintoproducts and servicesbeneficialto Canadians.Itlinks
I-I
academ ia,industry,govemment and non-pr ofit organizationsto ensureCanada'sglobal economiccompetit iveness .ArcticNet,as one of Canada'sNCE's, supportsscientists studyingthe impacts of climatechangein thecoastalCanadianA rcticbyl inking natura l, humanhealth and social sciences with their partners fromInuit organizations, northern communities,federal and provincial agenciesandthe private sector.ArcticNet's motivationisdriven bythe factthatclimate warming is causingchanges inthe environmentandsociallife inCanada,and especia lly intheArcticcommunitiesand territories(ArcticNetRationale,2008).Impacts of a warmingclimatein theCanadian Arctic include changes to Inuithuntingtraditions, modificationstohabitats of Arctic fauna,increasedv igilanceonCanadiansovereigntyandsecurityas internationa lshipping waysthroughtheCanadianArcticopen,andre-engineeredtransportationand infrastruc tureonthawingpermafrost. For ArcticNet the collaborationbetwee n Inuit organizations, northerncommunities, universities,research institutes, industry, governmentandinternationalagenciesis very importantto ensureadaptationstrategies areformulatedinmutualagreeme nt.
Phase2 of ArcticNet'scompendiumcontai ns numerousproje cts,suchas projec ts oncoastalmarineecosystems,coastal terrestrial ecosystems, Inuithealth andada ptat ion, and industrialdevelopment in the North(ArcticNetProjects,2008). These projects are grouped into four Integrated Regiona l Impact Studies(IRIS)accordingto a geographica l areainCanada.ThisMSc Project ispart ofIRIS 4.IRIS 4is focusedonCanada's Eastern sub-Arctic including the Inuitterritoriesof Nunavik(northernQuebec)andNunats iavut (northernLabrador). Geographica llyIRIS 4 isboundbyHudson Bay tothe west,Hudson
StraitandUngavaBay tothe north,and the LabradorSea tothe east. The climateofthis areais continentalwith highprecipitation (mainlysnow).Itis expectedto warm by 3-4
°C andhaveprecipitation increaseby 10 to 25%by the middleof the century(ArcticNet Projects, 2008).One study evaluating adaptation in thisareais the project"Nunatsiavut Nuluak", of which this MSe Thesis is a part.Nunatsiavut Nuluak is concernedwith understandingand responding to the effects of climatechangeandmodernizatio nin Nunatsiav ut.Itis led by theNunatsiav utGovernment(NG) throughMarina Biasutti- Brown, and the EnvironmentalScienceGroup(ESG) of the Royal MilitaryCollege throughKenReimer.Parks Canada, theDepartment of NationalDefence,Vale Inco (Voisey'sBayNickel Company),SikumiutEnvironmental Management Ltd.,the Canadian WildlifeService, and theDepartment of Fisheries and Oceanswork togethe r as partnerstoprovide the area with insightsintothehealth of themarine ecosystemin Northern Larbrador and howresidents eanadapt.Forall members of thisresearchproject it is important toknow that Inuit andInuitknowledge arecloselyinvolved in all processes. This helpsto ensure that regionalcommunities understand theimportance of baseline data and trends and thatformulated strategiesarerelevant and meaningful tothe future ofthepeople of NorthernLabrador.
To implementresearchinNorthernLabrador, Parks Canadaand the Nunatsiavut Government have establisheda base camp locatedinkANGIDLUASUk(Inuktit ukfor St.
John's Harbour)in SaglekFiord,200 km north of Nain inNunatsiavutand100 km from Kangiqsualujju aq in Nunavik(http://kangidluasuk.com, retrieved 2010).The base camp was establishedfor the firsttimeinthe summerof 2006,andisrunandmanaged byInuit.
Thebasecamp ' sphilosophyistore-connectInuit to their land;to give Inuit fromNunavik and Nunatsiavutthechance tomeetold friends, toshare memoriesoftheirchildhood in the TorngatMountains, and toteachthe Inuit youthabout theirland;to givescientistsand Inuit thechanceto connect,share,teach and learntogether,andvery importantly for us, it isascience basecamp.
Research10dale in Nachvak and Saglek Fjord
Topromotethemaintenanceof ecological integrityof the TorngatMountains, Parks Canada has startedabaselineecosystem study of the TorngatMountainsNational Park, assisted by ArcticNet and the Internat ional Polar Year program (http://kangidluasuk.com,retrieved 20 10). Projectsinclude the assessmentofmarine ecosystemrecoveryfromPCB contaminationsin SaglekBayand interactionswith ringed seal,paleoceanographicand paleolimnolog icstudies in fiords and lakes,monitorin gfor ecologicalintegrity , glacierobservations,marinefood web modelsand habitatmappin g, the effectsof climate change on Arcticchar,theassessment ofstreamecosystemstructure and function,aswell asthe impactsof climate change on thevegetationin the Torngat Mountains(http://kangidlu asuk .com,retrieved2010,and Brownet aI.,2010;Brownet aI.,2009; Carpenter et aI.,2009; Kinget al., 2009;Richeroletal., 2009).
Projectsto which thisthesismightcontribute,include:
Benthichabitat mappingand communityinventory ofSaglek andNachvak Fjord ,aimingto provide detailedmapsofseabed morphology andsubstrate
type,as wellasan inventory of theof benthicbiotapresent in the fjordsand the distrib utionoftheirhabitats (Ann ualReportof Researchand Monitoringin Tomgat MountainsNational ParkReserve,2007).
Establishingmonito ringmeasure sformarineecologica li ntegrityin both fjords, evaluatingtheimpac tof climatechange,industrializati on,andcontam inantsto the marineenvironment (AnnualReportof Researchand Monitoringin Torngat MountainsNational Park Reserve ,2007).
- Assessmentof potentiallycontaminatedsitesin Tomgat MountainsNationa l Park,studyingifhaza rdous material(suchas fromfuel drumsor pianewrecks) is migrating intotheenvironme nt(Annua l Report of Research and Monitoring in TorngatMountai nsNational Park, 2009).
- Reductio nofPCB contam inationinanArcticCoastalEnvironment, assessing ecosystemrecovery (Brownet al.,2009).
General Research Background
This proj ectprovides abaseline assessmentforenvironmenta l processes, hydrolo gicprocesses as wellas seabedcharacter istics in thefjordsofnorthernLabrador.
waters. Our researchfocuses on understandin g pallernsand variabilityof sedimentand freshwater deliveryfrom thelandto thesea,andspecifically,sedimentdispersal in the marinebasins of Nachvak andSaglekFjord. Studying sediment delivery and dispersal is important because freshwaterand fluvial sedimentcarry nutrientstothecoastalocean wherethey influence boththeterrestrialand marine ecosystems.
Sedimentary Deliverytothe CoastalOcean-Processesand Applications
For this thesis the focusisonthe riverinedelivery ofsedimentfrom the land to the ocean. Thekey factorin the accumulationofriverine sedimenton the continental shelfis theavailability ofaccommodationspace, theamount of spaceavailablefor sediment to accumulateand fill up betweentheseafloor and the seasurface(PosamentierandVail, 1988).Marineaccommod ation space is created when thecoastalplainisfl ooded andi ti s reduced or removedthrough fillingwithsediment.Controlling factorsinclude relative sea-Ievel rises,subside nce,andsedimentaggradation. lngeneral, deltas forrn where the available accomm odation spaceisfilled,whileestuaries form in regionswhere accommodationspace iscreatedfasterthantherateof fluvial sedimentsupplyand accumulation (Boydet al.,1992).Once sedimentisdeliveredto the oceanthere are static
aswellasdynami cprocessesthat controlthe trappin g efficiencyofthe sediment (Sommerfie ld et al., 200 7).Topog raphyand morph ology(i.e. canyo ns,banks,coastline orientation)ofthemarine basin defin ethe static trapping factorand influence sedimen t trapp ing ona widerangeoftime-scales.Dynam ictrappin g,on theother hand,is contr oll edbypropertie sof thewater columnand processestherein,suchasdensity stratification, hydrodyn ami cs, and part iclefloccul ation . Thisisusuallyhappenin g on shorte r time- scales,rangin g fromminutes todays.Currentsinthewater column transport sediment,whileenerge tic waveprocesses can resuspend sediment(Ogsto netaI.,2004).
Marin e sedi me ntcan be charac te rizedasthree gradationallayersbene ath the sediment-wa ter interface:aresuspensionlaye r,a zone of bioturbat ion, anda zoneof prese rvati on (Sommerfie ldet aI.,2007).Factors con trollin gparticletransport , sett ling, deposition,resuspen sionandpreserva tio nare curre ntvelocity,suspended-sedimen t conce ntratio n,particl e-settlin g velocity, biolog icalmixing,depositionrate,and accum ulatio n rate.Sedi mentacc um ulatio n links sedi mentsupplyand dispe rsal ina tempora landspecia l reference frame.Most scientists who studysediment flux transform sed imentaccumulationratesinto mass accumulatio n rates express ing themass of sediment buried per unit areaper unittime (e.g. g crni yr").
anthro poge nicradio isotopes,suchas 137Cs,239.24opu,2,oPb,7Be,and234Th(Turekia nand Cochra n,1978).Theserad ioisotopesarescavenged byfine-grain edpart iclesin the water colum nandthus del iveredtotheseabedand buried . Once they areremoved from their source their conce ntratio ndecreasesthrou ghradioactivedecayasafunctio nof the
isotope' shalflife.Therefore,activitiesoftheradioisotopedecreasewith depthin the seabeddue to thelaw ofradioactive decay,andcan beusedtodetermine sediment accumulationrates.This methodhasbeen appliedin fjord setlingsbyo thersc ientistss uch asJaeger et al.(1999).
Theradioi sotope 210Pboccurs naturally asamemberof the 238Udecayseries, where insedimentsit is generallycharacterizedas oneof twocategor ies: supportedand unsupport ed (Noller,2000).Unsupported(orexcess jt''Pbisproducedin the atmosphere as an unsupporte ddaughterproduct ofthe gas222Rn,an elementproducedfrom226Ra decay,andwhich quicklyescapesto the atmosphere todecay. Unsupportedi 'Pbsert les outofthe atmosphereor is scavenged byrain,deposited on land or in the ocea n,and scavenged by fine-grainedparticles.By leaving theatmosphere,itis in disequilibrium withitsparent 222Rn.This meansthat once unsupported210Pb isdepositeditwill decay anddecreasein concentration.Supported 210Pb isproducedbyinsitu decay of226Ra withinmineral grains,and222Rn risingfrom sedimentsandrocks at depth.In sediment cores total concentrationsandactivitiesOf210Pbcan bemeasured andseparated into supportedand unsupported concentrations andactivities.The decrease in unsupported activity with core depthduetoradioactivedecaycan thenbeused as amethodto calculatesedimentaccumulation rates.The followingassumptions haveto bemadein order tosuccessfullyapplythis method incontin ental-mar gin sedimento logy:a)2IOPb is quicklyremoved from the atmosphereandstreams andsequesteredinsoilsand sediments,b)2IOPbisimmobileo nceit is deposited,c)Unsupported210Pbisindependent
of depth and doesnot migratedown insedimentary column, and d) Supported210Pbisin secular equilibriumwithits grandparent226Ra.
The radioisotope 137Cshasbeenintroducedinto the atmosphere from nucleartesting or from releasefromnuclearreactors.It wasfirstreleasedbyearly nucleartestsin 194 5 (Carter and Moghissi,1977),becoming widespreadgloballyin November1952(Perkins and Thomas,1980).It isdetectableinsediments formedaround 1952±2yr (Robbinset al.,1978),and peaksin weaponstestsin 1963(Ritchieand McHenry,1990).Maximum penetration depth and peaksin theactivity-depth profilearecommonly usedtodate sediment and estimate sedimentaccumulation rates.Itis a second approachto validate resultsfrom otherra diotracers (i.e. 21OPb) (Ritchie and McHenry,1990).
Tostudy thedispersalof fluvial sediment on the continentalshelf it isusefulto compilea sediment budgetto quantifythe relation sbetweensediment production, transport, storage and burial (Sommerfield et al.,2007).To dothisoneneedsto quantify source andsink termsforsediment. River dischargeis a crucial factor in deliveringfine- grainedsediment to the coastalocean. Today,manyriversworldwideare gauged, which makesit easytodefine an accurate source termin theseregions.However,many smaller rivers,especially at high latitudesand in remote placesare under-gaugedor ungauged.
Fortunately,there hasbeen greatprogressin developin gmodelstoestimatefluvial sediment dischargebyusingothersimple environmental factors. Todetermin e avaluefor asedimentsink for a regionof interest,thereare mainlytwoways: a)measure sub- bottomprofiles(graphic method) or b) measuresedimentaccumulation rates(burialflux method). Thegraphic method uses sub-bottom profilesto measurethethickness and
extentofsedimentof a knownage and density (GrOtznerandMeinert,1999).Theburial flux methodisbased onsedimentaccumulat ionrate measurementsfrom severalstations distributed withinthedispersal system(Nittro uerandSternberg,198 1).
Fjord Processes
Modernfjords,theproducts of the advanceandretreat ofglacial ice andrelativesea levelfluctuations (Syvitskiet aI.,1995),occurinthe midtohighlatitudes of both hemispheres andform so-calledfjord belts (Howe et al., 2010). They canbe classifiedas polar, subpolar,and temperatefjords accordingtotheirclimateregime.They are immatur e,non-steady state systems,formed bypost-glacial erosionof coastalvalleys, evolvingandchangi ngover relativelyshort time scalesofcenturiestomillenn ia(Syvitski etal., 1995).Inappearance,theyarelong,narrow,deep andsteep-sidedvalleysthat may remainconnectedtothe sea (Syvitsk i, 1987).Theycan bebranched,but also maybe remarkably straig htwhere icefollowed fault lines (SyvitskietaI.,1995). Theyoften containoneor more submarinesillscreatedfrom bed rock,moraines or other glacioma rine deposits (Fig. I).Thisoftcn leads to poorlycoupledoceanc irculationabovc and below the sill height andpronouncedverticalhydrographicgradientsinwater propert ies. Therestricted deep watercirculationandresulting low currents,reduce d oxygen,and reducedbioturbationmake silled basins in fjordsexcellent naturalse diment traps. Fjordsare oftenviewedasproxyminiature ocean basinswith uniquehydrography, fauna, biogeochemistry, andsedimentation,andare interesting to study(Syvitskietal.
1987).Fjord research is notonly scientificallyimportant,but alsoimportant from a
historical andsocial pointofview (HoweetaI.,20 10).For at least 9.5 ka, fjords have beenaplace forcommunities.Easilyaccessed,shelteredandfertile,theyareoften used forfarm ing andfishing.Thisalso applies to fjordsontheLabrado rCoast asHistoric Inuit, Thuleand Dorset have usedand occupied the area forcenturies (http://kangidluasuk.com,retrieved20 10).Thus,itis importantto scientistsas wellas local communitiestounderstandthe fate of afjord ' s ecosystem ina changing
1 ·· ~ _, ~~? :r I~~~ ·~'7: ~ ; JI"I ~'
Fig./: Sediment deliveryto fjords, aft er Syvitsk iet al. 1995
Fj orddynamics includesedimentary(suspended-sediment deposition,gravity currents),oceanographic(wave,tidal,estuarine), andglacial processes (meltwater discharge,ice rafting),which work inconcerttoproducesedimentary strata atanumber of timescales(minutesto centuries)(Fig. I) (JaegeretaI.,1999).Thefluvialinputof river-influencedfjordsmainly consistsof erosional productsfromweathering,reworked glacioge nicand raisedmarinedeposits,as wellas freshly produced glacialfl our (Syvitski etal.,1995). Areas withvegetationcancontribute terrestrial organic matter (pollen, leaves,twigs,humic substances) transportedfrom landtothe fjordbasin.Oceanogra phic and meteorologicalprocesses alsoexertstrong control on thedischa rge,transport, and
deposition of sediment in fjords (Jaegeretal.,1999).Freshwaterinput atthe fjord head createsa buoyancy gradient,whichleadsto a surfaceflow down fjord andthe establishmentof estuarinecirculation.Thistwo-layerflow, with an outward flowing surfacelayer andan inward-movi ngcompensat ingcurrent,is influenced by theCoriolis effect (which forces flow totheright in the northem hemisphere), the centrifugalforce, bathymetry, pressure gradientsdevelopedfrom meteorolog icalconditio ns(windstructure, freshwate rdisc harge),and by surfacemixing from strong winds(Syvitskietal.,1995).
Estuari necirculat ionin high-latitude fjords is alsostronglyinfluencedby sea ice, icebergs andtidewa terglaciers(Fig. I) (Syvitski,1987).Seaicemay stimulatecirculationby rejectingbrineon freezingor it may limitcirculationas it preventswindwaves and currents,dampenstides andtidalcurrents,andenhancesstratificationby productionof meltwater (Gilbertet aI.,1983).
Thefluvial sedimententering the fjord separates into two componentsseawardof the river mouth:thebedloadand thesuspended load (Syvitsk iet aI.,1995). Stream discharge,hydraulic slope,bottom roughness,bed compactio n,andgrain properties contro l bed-load transport.Thebedload is of coarsergrainsizethan thesuspended load and,therefore,settles quickly ontodeltaforeset beds oncethe velocityofastreamfa Jls belowa thresholdvaluefor depositionofaparticular grain diameter. The fine-grained suspendedsedimentload is carried seawardwithin theriver plume andits concentration increasesex ponentia Jlywit hincreasingstream discharge.Thus,a change in riverrunoff willbereflected in the sedimentsdeposited.Theriverplume is created bylow-density freshwaterwhichenters the fjord and spreadsandthinsovermoredense saline waterof the fjord.
Astheriverplume mixeswithsaline water,Ilocculati on canoccur. Dyer (1995) describesflocculat ion as aresultof the total surface ioniccharge0n theparticl es and the envelopingelcctricaldoublelayer.He states thatthere is anoverallattraction whenthe particles are in closeproximity whichl eadst othe format ion of aggregates ofp articles, or noes.As a result the grainsizeof the noesis greater than that oftheirindividual componentsand theirsettlingveloeity is increasedover thato f parentg rains(Syvitski et al., 1995).Humana ctivities,suchas land useand deforestation,can increaseriverrun-off and thusthe supply offluvial sediment tothe fjord(Howe eta l.,2 0 10).
Apartfromthemajornuvial inputother sedimentsourcesincludeaeolianterrestrial sources,anthropogenic sources, continenta lshelf sources(viaestuarinecirculation),input from wave and tidal erosion,inputfrom landslides,biogenic input aswellasinput from icebergsor land-fastice (SyvitskietaI., 1995).The study oftheglacial sediments
importanteontributor stodeep-seasedimentbudgets,andinterpretationsof marine cores are used asindicatorsofabrupt climatechange(Andrews etal.,2002).Icc coverofa fjord also hasan influenceon thesedimentation withinthefjord.Sedimentcan accumulateon orwithin theice by windaction,stream discharge, rock fall, seafloor erosion,wave andcurrent wash-over or bottom freezing (Syvitski eta l., 1995).Drift ice
sediments fromtheground,transportitwithin the fjord and deposititsomewhere inthe fjordbasin .The presenceof coarser- grained sediment in an otherwisefine-grainedmatrix is often evident instudies of fjord sedimentandisoften interpretedas an indicatorforice- raftedandaeolian materialorsediment depositedby glaciers,suehas inAmera likFj ord,
SWGreenland(Melleret al.,2006),JosephFjo rd,East Greenland(Evans et.aI.,2002), Icy Bay, Alaska(Jaegeret aI., 1999),andothers.A studybyYoon etal. (1998) in Maxwe llBay,Antarcticashowstheinfluenceof glaciersonsedimentatio n.The distribution of suspended particulatematter inthe watersof MaxwellBay indicatesthat the glaciofluvial discharges fromglacierswhichend on land introduce more suspended sediment than the fjord- head trunkglacier.
Most sedimentdelivered tothe fjordsis closely tied to processes0nland.Therefore, fjord sediment depositsretain highqualityrecordsofterrestrial processes,whilealso recordingtheinfluence ofmarineprocesses (Howeet aI.,2010).Fjo rdsoftenhavethe advantage of reflectinga continuoussedimentaryrecord throughoutthe Holocenet hatca n be correlatedwithterrestrialclimate records suchastree-rin gs andl ake varves (Cageand Austin2010).Because fjords provide such high-resolution insightsinpreviousclimatic changes,they area valuable predictive tool.
Even thoughfjords aresucha valuable predictivetool,there have beenonlyfew trulyintegratedquantitativestudiesof sedimentbudgetsincold environme nts(Beylichet aI.,2009).A few studiesonsedimentbudgetsin fjordsincludefjords onGreenlandand Iceland,and inCanada,Alaska,Norway,Scotland andAntarctica(i.e. JaegeretaI.,1999;
Yoon et al.,1998;Mlillieretal.,2006;Paetzeletal.,1994and2010;Beylich etal.,2009;
Seidenkrantzetal.,2007;Evansetal.,2002;Barrie,1983;Rosen,1980;HassetaI.,2010;
ForwicketaI.,2010;Dallimoreand Jmieff, 2010; Mcintyre and Howe, 2010).Comparing thefindings in thesestudiessuggests thatthe sediment budget depend s on each fjord's individualgeometryandenvironmenta lconditionsrather than followinga geographical
trend.Some fjords govern permanent or periodically anoxic conditions, such as the Barsnesfjord and the Nordasvannet fjord in western Norway (Paetzelet al.,1994 and 2010) and several fjords on Vancouver Island,Canada (Dallimore and Jmieff,2010).The distribution of oxygen depends on factors such assill depth,photosyntheticproduction, and the level of oxygen consumption (Dallimore and Jrnieff, 2010).For example,in the inlets ofVancouver Island the water column is usually highly stratified due to high rainfall, shallow sills, weak freshwater recharge,and the interrupted inflow of marine water, leading to dysoxic or anoxic bottom waters and restricted bioturbation.In these basins annually laminated sediments canbe preserved.Although both Barsnesfjordand Nordasvannet fjord are in geographical proximity and have much in common (i. e.
shallow sills,anoxic conditions) the rates of sedimentation are verydifferent(0.85cm/y in Barsnesfjord and 0.4 mm/yin Nordasvannet fjord) due to differences in fjord geometry and drainage basins. Fjords with less restricted watercirculation govern oxic conditions and usually homogenous sediments with indications for bioturbation, such as Ameralik Fjord in SW Greenland (Seidenkrantzetal.,2007).
Dallimore and Jmieff(201O) summarize Canadian west coast fjord environments and characterize two types of fjords: a) areas where rivers drain high mountainsand ice fields and most of the sediment input to the fjords is from snowmelt and glacier runoff in springand summer with high sediment accumulation rates (i. e. 30 cm/yin Bute Inlet), such as fjords on the mainland in British Columbia, and b) fjords located in a milder marine climate which receive most of the sediment during heavy rains in autumn and
winte randlower sedimentaccumu lationrates(i. e.0.25cmlyinEffingham Inlet),suchas
The fjordsstudied inth ispaper arelocated in northernLabradorand are both uninha bitedand pristine (Bentleyand Kah lmeye r,2008).Both NachvakandSaglek fjord apparent lyreceive mostof their sed imentfrom river catchme nts(I-77km2,2-809 km2 insize,respectively),drainingthroughrelativelyhighmount ains (upto1400 mhigh ).
RiversenteringNachvakfjord drainfromsnowandice fieldsand small glaciers,while the drainagebasins of rivers enteringSaglek fjord do notcontainglaciers.Maximum water depth sinthemar inebasins are 180metersin Nachvak fjordand300meters in Saglek fjord.Sedimentsare fine-grained withadmix turesof ice rafted debris.Sed ime nt accumu lationrates are ontheorderof several millimetersper year.Thesed ime ntary texture is comparableto sedimentsin otherfjords,suchas MakkovikBay,Labr ador (Barrie, 198 3); andAmeralikFjord,SW Greenland(SeidenkrantzetaI.,2007);and sedimentaccumulationrates(0.12-0.52cmlyinNachva kfjordand0.08-0.36cmlyin SaglekFjord)are comparab letofjordssuchas IcyBay, Alaska(Jaeger et aI.,1999);
Amera likFjo rd,SW Greenland(MolleretaI., 2006); Sogndalsfjor d,westernNorway (Paetze letal.,2010);andinlets onVancouver Island(Dallim ore and Jm ieff,2010).
Andrews,J.T.,and Principato, S.M., 2002.Grain-sizecharacteristics and provenanceof ice-proximal glacialmarinesediments. Geological Society,London,Special Publicationsv,203, p.305-324.
ArcticNet home page.Retrieved December 17,2010,from ArcticNetWeb site:
http://www .arcticnet.ulaval .ca/index .php
ArcticNet Rational (2008).Retrieved October 8,2008,from ArcticNetWeb site:
http://www.arcticnet.ulaval .ca/index .php?fa=ArcticNet.aboutUs Barrie,C.Q.,1983.LateGlacialandcontemporary depositionof ciay-size mineralsin
Makkovik Bay,Labrador. MarineGeology,v .53,p.199-209.
Bentley,S.J.,and Kahlmeyer, E., 2008.Marinerecords of sediment flux fromglaciated and unglaciated catchments, Torngat Mountains,Canada. Arctic Change2008, ConferenceProgramme andAbstract s,p.184-185.
Beylich,A.A.,and Kneisel ,C.,2009.Sediment Budget and Relief Developmentin Hrafndalur, Subarctic Oceanic Eastern Iceland.Arctic, Antarctic,and Alpine Research,v .4I ,no.1 ,p .3-17 .
Boyd,R.,Dalrymple,R.and Zaitlin,B.A.,1992. Classificationof clast ic coastal depositionalenvironments.Sediment.Geology,v .80,p.139-150.
Brown,T.M.,Sheldon, T.A.,Burgess,N.M. and Reimer,K.J., 2009. Reductionof PCIl Contamination in an ArcticCoastalEnvironment: A FirstStep in Assessing EcosystemRecovery after the Removal of a Point Source.Environmental Science
&Technology,v.43,no.20,p.7635-7642.
Brown,T.M.,Sheldon,T.A.,Luque,S.P.,A.T.Fisk,Iverson,S.J.and Reimer, K.J.,2010.Use of chemical tracers andsatellite telemetry to assessdiet, forag ing patterns and contaminant exposure in northern Labrador ringed seals (Phoca
I
hispida). Contaminants inFreezingGround 7th International Conference, Proceedings(talk).
Cage,A. G.and Austin,W. E. N.20 10. Marine climate variabil ityduringthelast millennium:the LochSunart record, Scotland,UK.QuaternaryScience Reviews.
Carpenter, M.,Brown,T.,Bell,T. andEdinger,E.,2009. BenthicHabitatMapp ing in shallowenvironmentsofNachvakandSaglekFjords,Labrador.2009ArcticNet Annual Conference Proceedin gs.
Carter,M.W.,and Moghissi, A.A.,1977. Three decadesof nucleartesting.HealthPhys.
v,33,p.55-71.
Dallim ore,A., and Jmieff,D.G., 20 10.Canadian west coast fjords and inlets oftheNE PacificOceanasdepositional archives.GeologicalSoc iety, London, Special Publications,v.344, p.143-162.
Dyer,K.R.,1995.Sedimenttransportprocessesinestuaries.Geomorphologyand Sedimentology ofEstuaries (Ed. G.M.E.Perillo),p.423-4 49.
Evans, J.,Dowdeswell,J.A., Grobe, H.,Niessen, F.,Stein,R.,Hubberten,H.-W., and Whittington ,R.J.,2002.LateQuaternary sedimentation in Keij ser Franz Joseph Fjordand the continenta l marginofEast Greenland. Geolog icalSociety,London, Specia l Publications,v .203, p.149-179.
Forwick, M.,Yorren,T.O.,Hald,M.,Korsun,S.,Roh,Y.,Yogt, C.,and Yoo, K.-C., 20 10. Spatialand temporalinfluence ofglaciersand rivers on thesedimentary environment inSassenfjorden and Tempelfjo rden, Spitsbergen.Geological Society,London,SpecialPublicat ions,v. 344, p.163-193.
Gilbert,R.,1983.SedimentaryProcesses ofCanadian Arctic Fjo rds.Sedimentary Geologyv.36, p. 147-175.
Grtltzner, J. and Meinert, J.,1999.Lateralchangesofmass accumulationratesderived from seismicreflection profiles:an examplefromthe Western Atlantic.GeoRes.
Forum,v.5,p. 87-108.
Hass,H.C.,Kuhn,G.,Monien,P., Brumsack, II.-J.,andForwick, M., 2010.Climate fluctuationsduringthepasttwo millenniaasrecorded insediments from Maxwell Bay,SouthShetland Island s, WestAntarct ica.Geologica lSociety,London, Special Publications, v.344,p. 243-260.
Howe, J.A.,Austin,E.N.,Forwick,M.,Paetzel, M.,Harland,R.,andCage, A.G., 2010.
Fjord systemsandarchives:a review.GeologicalSociety,London,Special Publicat ions 2010,v. 344,p.5-15.
Jaeger, J.M.,andNittrouer,C.A., 1999.Sediment Deposition inanAlaskan-Fjo rd:
Controlsonthe FormationandPreservationofsedimentarystructuresinIcyBay.
JoumalofSedimentaryResearch,v.69,no.5,p.1011-1026.
kANGIDLUASUkhomepage.Retrieved December17,20I0 fromweb site:
http://kangidluasuk.com
King, J.R.,Bell,T.,Barrand, N.E.,andSharp,M., 2009.Measuringandmodelingglacier change intheTorngat Mountains,northernLabrador.2009 ArcticNe tAnnual Conference Proceedings.
Mcintyre,K.L.,and Howe,J.A., 2010.Scottishwest coast fjordssince the last glaciations:a review.Geologica lSociety,London,SpecialPublications,v. 344,p.
Moller,H.S.,Jensen,K.G.,Kuijpers,A.,Aagaard-Se rensen,S., Seidenkrantz,M.-S., Prins, M., Endler, R., andMikkelsen,N., 2006.Late-Holoceneenvironmentand climaticchangesinAmeralikFjord, southwest Greenland:evidencefromthe sedimentary record.The Holocene,v.16,no .5, p.685-695 .
Networksof Centresof Excellence of Canada,Governmentof Canada homepage.
Retrieved December 17,2010 fromwebsite:www.nce-rce.gc.ca Nittrouer,e.A.,and Sternberg,R.W., 198 1. The formation of sedimentarystrata inan
allochtho nous shelfenvi ronment: theWashingto n continenta lshelf.Marine Geology,v.42,p.201-232.
Noller,J.S.,2000.Lead-2 10Geochronology.QuaternaryGeochrono logy:Methods and Applications,p.115-120.
Ogston,A.S.,Guerra,J.V.andSternberg,R.W.,2004.Interannual variabilityofnearbed sedimentnuxonthe EelRivershelf,northern California.ContinentalShelf Research, v.24, p. 117-136.
ParksCanada,2007.2007 AnnualReport ofResearch and Monitoring inTorngat Mounta ins National Park Reserve.
ParksCanada, 2009.2009 Annua lReport ofResearch andMonitoringin Torngat Mountains NationalPark.
Paetzel, M., Schrader, H.,andCroudace,I.,1994.Sewagehistory in the anoxicsediments of the fjord Nordasvannet,westernNorway:(I)datingand trace-metal accumulation.The Holocene,v.4,no .3,p .290-298.
Paetzel, M.,andDale,T.,2010.Climateproxiesforrecent fjordsedimentsin the inner Sognefjordregion,western Norway.GeologicalSociety,London,Spec ia l Publications,v.344,p.271-288.
Perkins,R.W.,andThomas,C.W.,1980.Worldwidefallout. InW.e.Hanson(ed.) Transuranicelementsin theenvironmet.USDOEff IC-22800.US DOE, Washingto n, DC,p.53-82.
Posamentier, H.W.andVail,P.R.,1988.Eustatic contro lsonclasticdeposition11- sequenceandsystems tractmodels.ln:Sea-leveIC hanges;an lntegrated Approach(EdsC.K.Wilgus, B.S. Hastings, C.A. Ross, et al.),p.125-154.Special
l'ublication 42, Society of Econom icl'aleontologists andM ineralogists,Tulsa,
Richerol, T.,Pienitz, R.and Rochon, A.,2009. Paleoceanographic conditionsin three Labradorfjord ecosystems(Canada):Prel iminary results.Arct icFrontier2009 Congress,Tromso(Norway).
Ritchie,J.e.,and McHenry,J.R.,1990.Applicationof Radioactive FalloutCesium- 137 forMeasuring SoilErosionandSedimentAccumulation Rates and Pattern s:A Review.JournalofEnvironmenta lQuality,v,19,1' . 215-233.
Robbin s,J .A., 1978.Geochemicalandgeophys icalapplications ofradioactivelead.In J.O.Nriagu(ed.)Thebiochemistryoflead in the environment.ElsevierlNorth HollandBiomedicalPress,p.285-393.
Rosen,P.S.,1980 . CoastalEnvironments of theMakkovikRegion, Labrador. inThe Coastlineof Canada,S.B.McCann ,editor;Geolog icalSurveyof Canada,Paper 80-10,1' . 267-280.
Seidenkrantz,M.-S.,Aagaard-S eren sen,S.,Sulsbruck,H.,Kuijp ers,A.,Jensen,K.G., and Kunzendorf,H.,2007 .Hydrography and climate ofthelast4400Years ina SWGre enland fjord:implications forLabradorSeapalaeoceanography.The Holocene, v.17 ,no. 3,p . 387-401.
Sommerfield,C.K.,Ogston,A. S.,Mullenbach,B.L.,Drake,D.E.,Alexander,C.R., Nittrouer,e.A.,Borgeld,J. e.,Wheatcroft,R.A.,and Leithold,E.L.,2007.
Oceanicdispersal andaccumulationofriversediment.Continental-Ma rgin Sedimentation:Transport toSequence.BlackwellPublishing.
Syvitski, J.P.M., Burrell,D.C.andSkei, J.M.1987.Fjord s-Processes and Products.
Springer, NewYork.
Syvitski,J.P.M.,and Shaw,J.,1995.Sedimentologyand Geomorphology of Fjords.
Geomorphology and SedimentologyofEsutaries.Developmentsin Sedimentologyv.53,p.11 3-178 .
Turckian, K.K.and Cochran, J.K.,1978.Determinationof marine chronologiesusing natural radionuclides.Chemical Oceanograph y,v.7,p. 313-360.
Yoon,H.I.,Park,B.-K.,Domack,E.W.,and Kim,Y.,1998.Distributionand dispersal pattern ofsuspended particulatematterin Maxwell Bayand itstributary,Marian Cove,in the South Shetland Islands,WestAntarctica.Marine Geology,v.152,p.
Chapter2
Dispersal of fluvialsediment in two sub-arcticfjords on theLabrador Coast:
Nachvak Fjord and Saglek Fjord,Canada
Recentmarinerecords of fluvial sedimentsupply to two sub-arctic fjordsinnorthern Labrador(EasternCanada) havebeen studied in ordertodeterm inefluvialtransfer of terrestrialmaterialto the fjords,and to developbaselineknowledgefor futurestudies.
andSaglekfjords inNorthern Labrador,withinCanada'sTorngat Mount ainsNational Park, aspartofthemost extensive study ofthepark'smarineresourcestodate.In orde r to assess sediment dischargeand thefjord's sediment dispersal system, data collection was concentratedon marinebasinsfedbythe largestfluvial catchments associatedwith eachfjord.Eachcore was sub-sampledforX-radiography,grainsize,andradiochemica l analysis,and was analyzed forsedimentarystructuresandsedimentaccumulationrates.
Radiochemical analysis isbased on theparticle-bound radioisotopes2IOPb and137Cs, whichhavebeenusedtodetermine sedimentaccumulationrates(SAR),and210Pb
in thefjord basinswere studied from sub-bottom profiles and bathymet rydata.Results show that in both fjords sediment is accumulating indepocentre sin thecentreofeach basin.In NachvakFjord,whichis fedprimarilyby small riverswith very steep,small,
presently glaciatedcatchments,the thicknessofpostglacial sedimentobservedinsub- bottom profiles compareswell with thicknesses projected fromrecentsediment accumulat ion rates and impliesthatpostglacial sedimentationwas on avcragc constant.l n SaglekFjord, which isfedbylarger riverswith more extensive catchmentsthat lack glaciers,postglacia lsedimentth ickncssisonaverage 40% lessthanthat proje cted from recent sedimentaccumulation rates, suggesti ng more rapidsedimentaccumulation forthe past-IOOyth anforthat averaged overp ost-glacialtime.Presentmass accumulation rates for theNachvak fjord basinareo naverage39,000t/y for theentire basin,and forSag lek 43,000t{' forthe entire basin. Comparison betweenMAR valuesand resultsfroma previouslypublished statistical modelestimatingfluvial sedimentsupplyfromcatchment properties support thehypothesisthatthemarinebasins of both fjords areexcellent natur al sediment trapswith thecapac itytotrapthemodeled sediment load entire ly.
ResultsforNachvak Fjo rd suggesta high sedimentyield of therivercatchment sdraining into the fjord and/orasignificant supplyofsediment from sources additional tor ivers.
Thegoalofthis studyis to evaluaterecentmarinerecordsof fluvialsedime nt supplyto two sub-arc ticfjordsinnorthernLabradoraspart ofabaseline ecosystem stud y of Tornga t Mount ains National Park.Sediments deliveredby rive rsto thefjords play an impo rtantrolein thetransport ofnutrientsfromland to the ocean.Terrestria lanima ls suchas bea rs feedon marine life,and m igratory fish,s uchasc har,inhabit both ocean and rivers.Sofluvial-m arine interac tions influe nce both terr estr ial andmarineecosystems.
Riverrunofflinksproce ssesin the atmos phere, the land surface,and the oceans and is cont rolledby climate-sensitiv e factorssuchas air tem peratur es,precipitation, snowcover, or perrnafrost( Dery etal.,2 005) . Thus,changesi n rive r runoffaresensitiveindica tors for changes in climate andare reflected inthe fluvial sed iment acc umulated in marin ebasins (Sy vitskie tal.,1995).Resulti ngobserv ation s ofthis study willprovide inforrnationabout environmentalprocesses,hydrol og icprocesses aswell as seabe dcharac teris ticsinthe fjord s ofnorthern Labradorand willbe usefulas someof the first such measurementsin
This study ispart ofa largerproject called"Nunatsiavut Nuluak",directed at under standin g and respondin gto the effectsofclimate changeand moderni zat ionin Nunatsiavut , and lead andspo nso red by ArcticNet(ReimeretaI.,2008).ArcticN etis a researchnetworkconcern edwithcreat inglinks amongnatural, humanhealth and social sciences, regard ingclimate change in thecoasta lCanadian Arct ic (ArcticNe t Rat ion al, 2008).Th is project in part icularis conce rned with the impact s of climatechange, mod ern ization andconta minantson thehealth of commun itiesand themar ine~"Y''= I
" ~
in northemLabrador(ArcticNetProjec ts,2008). Inuit are cioselyinvolvedin theresearch to ensurethat adaptation strategies arerelevantforthe communitie s (ArcticNetProjects, 2008).
/.ig.I Map ofstudy area showing locations of Nachvak andSaglek Fjord
Thestudyareasare twosubarcticfjords on theNunats iavutlLabradorcoast (Canada),NachvakFjord andSaglekFjo rd(Fig. I). Sedimentcoreswere collectedin the mainbasin ofeach fjord and havebeen analyzed forsedimentary structuresand sediment accumulationrates(Fig.2and 3).These results havebeen comparedfor each basin and usedto describehowsediment isdispersedwithin the basin.Sediment accumulat ionrates (SAR)havebeen usedtoestimate anaveragesediment discharge, assumingrivers tobe
the onlysedimentsource. These results havebeen compared tomodeled sediment dischargeand usedtodraw conclusionsonsedimentsourcesand dispersal of fluvial sediment. Basic observa tionsof seasonalstreamflowhave beenconductedto getanidea of prevailingflowcond itions in thetworiversunder study.Sub-bottomprofilesand bathymetrydatacollectedin thefjordshavebeenusedto describe sediment thickness and extent in the fjordbasins.
Fig.2 Mapof NachvakFjordshowingbathymetry,drainage basins (blueshaded.
bright blue shaded are drainagebasinof interestfor thisstudy) andcore locations.
Fig.3 Map of Sag lek Fjord showing bathymetry,drainagebasins (blueshaded,bright blueshaded aredrainagebasinof interestfor thisstudy)andcorelocation s.
2 Fjord processes
Fjords are a product of glacial erosionand can be found along glaciatedbeltsatmid to high latitudesin both hemispheres(Howe,2010).Depending onclimate,glaciogene regimes and environmental factors, fjords canbe classified as polar fjords (narrow bays permanently covered with sea ice,with a resident headwater glacier,and major sediment supply from glacial processes), subpolar fjords (seasonally open narrow bayswith summer mean air temperatures above 0DC,common iceberg s,some hinterland rivers, and major sediment supply from subglacial meltwater) and temperate fjords (narrow, formerly glacial bays with sediment from hinterland rivers,and sea ice generally absent).
Fjords are geomorphological features that representthe transitionfrom the terrestrialto the marine environment. They typicallyhave entrance sills restrictingwater circulation, making fjordsideal depositional environments forpreserving high-resolution environmental changes.Sillscan be createdfrom bedrock,morainesor other glaciomarinedeposits(Syvitski et aI.,1995).Fjord processesare controlledby sedimentological (suspended-sediment deposition ,gravitycurrents),oceanographic (wave,tidal,estuarine),and glacial processes(meltwater discharge,ice rafting),which work in concert to producesedimentary strata at a number of timescales (minutes to centuries)(Jaegeretal., 1999). During the EarlyfMid-Holocene ,the disappearanceof ice, crustalunloading and associated isostatic sea level changes led to the reactivationof faults, increasedsub-aerialandsubmarine landslides,rockfalls,andincreased sedimentation(ForwickandVorren 2002 and Bee et al. 2003).Sedimen tinpolarfjordsi s typically glacier-derived;in temperatefjordsit is river-derived(Howe,2010).
Bathymetry,depth, andthe hydrog raphicregime steer the distribution of thesediment.
Depositionin form ofsediment creep,slides,debris flowsand turbidityflows are commonin fjordsdueto high sedimentsupply onsteepslopes(Syvitskietal. 1987).
Sediment accumulationratesare typically on the orderofmillimeterstocentimetersper year( Howe,20 10).
Innon-glaciatedfjordsthe main sedimentsupply is fromterrestrial rivers, especially ifthe fjordbasinisprotectedfromcoastal processesbya sill. Processes associated with the depositionof fine-grained fluvial sediment includedensitycurrents, flocculation and turbulence (Reilingand Nordseth,1979).Density currents carry sediment insuspension, which isthen depositedby settling outof the watercolumn.
Flocculationcausestheformation of aggregates and an increasein grain sizeleadin gto morerapiddepositionof the sediment.Turbulence causes erosionof deposited sediment and resuspension.In the fjords of this studythe main sediment inputisthoughtto befrom riversand mainly consistingof erosionalproductsfromweatherin g,reworkedg laciogenic andraised marinedeposits , andsome freshlyproduced glacia l flour.Theriver plume carries the fine-grainedsuspended sediment load (sand to clay)seawardand its concentrationincreasesexponentiallywithincreasingstream discharge(Syvitski et aI., 1995).
Apart from the major fluvial input other sedimentso urces include wind-transported terrestrial sources,anthropogenicsources, continentalshelfsources (viaestuarine circulation), input from wave and tidalerosion, input from landslides, biogenicinputas wellasinput fromicebergs or land-fastice(Syvitskietal.,1995).Ice cover of afjord also
has aninfluence on the sedimentationwithinthe fjord.Sedimenteanaccum ulateonor within the ice by windaction,stream discharge,rock fall,seafloorerosion,wave and current wash-over or bottom freezing.Drift-icecanbecome sedimentladen land-fast ice as it freezes nearshore.Land-fastice returningto drift ice can transport sediment from theshoreanddistribute itinthe basin.Mostsediments de liveredto fjords are closelyt ied to processes onland. Therefore,sedimentdepositsinfjords retain high qualityrecordsof terrestrial processes,whilealso record ing localmarineprocesses andconditions.
Kah lmeyer (2008)provides first basicdata onsedimentdelivery inNachvak, Saglek,andAnaktalakfjords.Sedimentaccumulat ionratesinthis area rangebetween 0.18cm/yand0.33 cm/y,and estimatedsedimentdischargerangebetween 32,000 ± 30,000tly and 580,000 ±330,000tly(Kahlmeyer,2008).However, for this 2008 study onlyonetotwo box coresper fjordwere analyzed.A greate r number of cores have now been analyzed,covering anareafromtheriver mouthto thecentreof thebasin,to improveinterpretat ionsforthe mode anddispersa lof sedimentand to improve estimationsforsedimentdischarge.
Thespecific objectivesof thispaper are,to deterrnine:
I. dispersa lpatterns offluvial sediment inonemajor basin for eachfjord 2.themodeofsedimentde liveryfro m land toocean
3.thethickness,extent,andage of sedimentdepositsof fluvialor iginin marine
4a temporal resolutionforpalaeoenvironmental marinerecordsin thisarea
Regional Setting
Study Area
The two fjords in this study (Nachvak Fjord and Saglek Fjord)are located in the northern part of Labrador (Fig.I, 2 and3). Nachvak Fjord,the northernmost fjord,isa pristine,uninhabited fjord (Bentley and Kahlmeyer, 2008) and receivesmost of its sediment from river catchments such as the glacierized McCornick River catchment.
Nachvak Fjord consistsof three marine basins with water depthsnear 180 meters.
Nachvak Fjord offers the opportunity to study natural environmental conditions in the fjords in northern Labrador.In contrast, Saglek fjord sediments have been influenced by human activities (Richerol et aI.,2007). A major source of sediment to Saglekfjord is Nakvak Brook (a non-glacierized catchment). SedimentsinSaglek fjord have been affected by produced wastes of a former military site and have been contaminated with PCB's (Richerol et aI., 2007). Maximum water depth in Saglek fjord is near 300 m.
The inner shelf of northern Labrador is covered by land-fastsca icc for several months each year and, farther offshore, drifting pack ice covers theshelf for 6-11 months each year (Hall et aI.,1999). Large numbers of icebergs, from western and north-western Greenland,and from the Canadian High Arctic,cause iceberg scouring as they drift southward along the shelf in the Labrador Current (Hall etal., 1999),and are a possible source for ice-rafted debris deposited in fjords in Labrador. The glacial landscape of Labrador isa result of the action and retreat of the Laurentide Ice Sheet.lnthe sedimentary record ofa small lake (Square Lake) in the catchment of Nakvak Brook Clark et al. (1989) detected a distinct shiftin the depositional environment accompanied
by an increasein organic matler around8 kaBP,indicatingice retreat from theSaglek Moraine.Remainsofthisiceretreat and the accompanying isostaticuplifl have exposed deposits ofthicktillandglaciomarinesedimentsalong thefjord coast(Syvitskieta!., 1997).Climate model simulationsshow thatthe Labradorsectorofthe LaurentideIce Sheetwasparticularly sensitive to the abruptchanges inNorthAtlanticsea-surface temperatures that characterizedthelastdeglaciation(Fawcetlet a!.,1997;H ostetleret a!., 1999).Thissuggeststhat this area may showanequallystrongsensitivity toclimatic changes at thepresent.Therefore,thelakes and fjordsoffer excellentopportunitiesfor studies relatedtoclimate change.
Geology
Northea sternLabrador consists oftheArcheanNain Prov ince craton,an ancient crustalmass>600km long and:S100 kmwide (Wilton,1996).The Nain Provincehas been intrudedby the Nain PlutonicSuiteandseparatedinto twoparts:the Saglek Block to theNorthand the HopedaleBlocktotheSouth. The Saglek Block is complex high- gradegneisses unconform ablyoverlain by sedimentaryand metasedimentary strata ofth e Ramah Group, the rockswhichformthelandscape of Nachvak andSaglekFjord. Ramah strataconsistof 1.7km thickdeposits ofshallow-watersiliciclasticsoverlainbydeep- water shales,carbonatesandsandstones deformed intoanorth-trending foldbelt (Wardle 1983).
Samp/eco//ection
Marinegeologica lsurveysandsamplingwereconductedfrom theM/V What's Happeningin the summersof2008and2009.Sedimentsamplesincludefive box coresin each fjord in2008 andfivebox cores ineach fjordin 2009.Box cores weresubsampled on boardfor X-radiography,grainsize analysis,andradio isotopegeochronology.In summe r2008sub-botto m profiles andsidescansonar datawere collectedbyusing a 100/500Hz sidescansonar(Edgetech4100p)anda 2-16kHz Chirpsystem(Edgetec h 3200XS).Multibeambathymetry datawerecollectedand initiallyprocessedbythe UniversityofNewBrunswick Ocean Mapping Group,withfinalcompilationby Bell et at. (2009).On land, stream flowmeasurementshavebeen conducted in the twomaj or rivers(McCornick RiverandNakvakBrook) using ahandheld accoustic doppler velocimeter.Streamstagewas measured byusingHOBO water levelloggers thatwere deployed ineachstreamfor oneyear.Soilcoreswere collectedclose toriver banksto estimatethesupply of210Pbtotheland surface.
Radiogeochemistry(210pb,Il7e s)
Forradiogeoc hemistry measurementsthe cores wereextrudedin I-2 eminterva ls onboard theshipand packed in airtightplasticbags fortransporttoStJohn's.lnthe laboratory atMUN, sampleswere dried in anovenataround90DC, and thengroundand sealedin petri dishes.Water contentandporosity weremeasuredby weightlossin
drying. Tomeasurethe activity of2IOPband131Cs,dried sampleswerecount edfor 24 hours on Canberra low-ba ckgroundplanar gamma detector s.Thenatural rad ioisoto pe 210Pb isprodu ct ofthe U-se ries decay and has ahalf-li fe of 22 years(Nittrouerand Sternb erg,1979),wh ile131Cs, aproductofnuclear fissionin nuclea rreactors and bomb s, hasbeendispe rsed globallyintheenvironmentsince 1952 (Perkins and Thomas,1980).
Itshalf-lifeis 30.7years.Correctio n for self-adsorption of 210Pbwasdon eusingthe methodof Cutshall etal.(1983).Tota l210Pbwasdetermined bymeasurement of the46.5 keYgamma peak.Supported210Pb(from decay of226Ra withinthe seabed) was determinedbymeasurementof thegrandda ughtersof226Ra:214Pb (295 and352 keY) and 214Bi (609 keY).The unsupported210Pb (excess210Pb) wasdetermined by subtracting the supported210Pb from the total 21OPb.131Csactivities weredeterminedbymeasurin gthe 662 keY peak directly.
Apparentsed iment accumul ationrate s(S, cmil)werecalculated, assum ing no bioturbati onbelowtheobserv edbioturbat iondepth.Bioturba tiondepthsweredetermined by inflection point sin210Pb profiles,andbymeasur ingdepths of burrowsvisiblein x- radi ograph softhe cores. If accumulationisthe dom inantprocessandstea dy-state conditionsare assumed(e.g.,Nittrouer andSternberg,1981),mixingcanbe ignored and acc umulat ionrates (S,erny.l) canbe estimatedby a least squares fitto:
A(Z)=A(o»)~l
Eq. 1whereA.isthedecay constant fortherad ionuclid e ofinte rest(year")andA isexcess activity (dpmg·1)atdepthz (Nittro uereta l., 1984).
Anthropogenic I37Cscanbe used as a seco ndapproach to calculatin g accumulation rates and thusvalidatethe210Pb"results.Thesed iment accumul ati onrate can be
Eq.2 whereZpisthe maximumpenetration depth ofIJ7Cs,Zbisthe bioturb at iondepth ,toisthe yearof sam ple collection andt,istheyearIJ7Cswasintroduced intothe atmos phere (Nittroueret al.,1984).
Thetemp oralresoluti on(T,)of thecore' s sedimenta ry record iscontrolled by bioturbati onrate,SAR, anddepthof bioturb ation .It canbeestimated fromthe residence timeforaparcel ofsed iments withinthe region oftheseabedinfluenc edbybioturb ati on:
Eq.3
whereLbis the depth of bioturb ation, estimated from x-rayimages and210Pb"profil es, and S is thesedi me ntation rate (Whea tc rofte tal.,2006).
Sedimentological analys es
ForX-rad iog raphicsamp lingofboxcore s,a three-sidedPlex igla stray (2. 5 cm thick x16 cm wide) was inserted verticall y into the sed iment and afourthside wasthen inserted into machined groo ves with greatcare not to disturbthesed imentaryfabric.The tray sweresealedairtight with rubberand electrical tape forshipment. Slabsfor X- radiogr aph ywere returned to the labo rato ry at Memorial Un iversity,andimage d using a
Thales Flashscan 35 digital X-ray detector panel,illuminated with a Medison Acoma PX l5HF X-ray generator.X-ray images were used to study sedimentary structures,which is useful for interpretation of and correlation with radioisotope profiles (Bentley and Nittrouer,2003). Granulometric measurements were done with a HORIBA Partica LA- 950,usingalaserscatteringmethodwheretheinstrumentcorrelatesthe intensityandthe angleoflightscatteredrromaparticle(Horiba,2006).
For basic stream flow measurements two pressure sensors (HOBO U20 Water Level Logger) were deployed in the streams, one in Nakvak Brook and one in McComick River. They were programmed to measure pressure and temperature in 30-minute intervals and were recovered one year after deployment. Another HOBO U20 Water Level Logger was deployed on land in St. John's Harbour in Saglek Fjord to measure air temperature and atmospheric pressure.The Onset HOBOware Software Barometric CompensationAssistant was used to create a water level/sensor depth series by combining the barometric datasets from the HOBO U20 Water Level loggers in the
Additionally, stream discharge and velocity profiles were conducted in the summer in both streamsby using the SonTekHandheld AcousticDoppler Velocimeter FlowTracker.The FlowTracker measures the change in frequency of sound reflected off particles in the water and uses the Doppler principle to determine stream velocity.
Measuring stream depth and velocity at different locations along a profile across the river
perpendicular to its stream flow allows measurements of stream discharge.Discharge is computedby using the Mid SectionEquation based on ISO/USGSprocedures (SonTeklYSI FlowTracker Handheld ADV Technical Manual,2009).
Estimations offluvial sediment load
A digital elevation model for land surrounding each fjord was extracted from Space Shuttle Topography Mission data (USGS, 2008). The DEM was then processed using RiverTools and GIS Modeling software to outline terrestrial river drainage basins.These data were then loaded into ArcGIS for analysis. These data were then used to estimate fluvial sediment discharge, using the model ofSyvitski and Milliman (2007) for areas wherebasin-averagedtemperatureofthedrainagebasinisbelow2't:
Eq.4
where Q,is the long-term sediment load (kg/s),Qis freshwater discharge (krrr'zy),R is maximum relief from sea level to mountain-top(krn),A is basin area (km') ,OJis 0.02and Bis an environmental factor accounting for important geological and human factors (Syvitski and Milliman, 2007).Freshwater discharge Q is defined as (Syvitski and Milliman,2007):
Q=0.075Ao.8 Eq.5
And the environmental factorB is defined as (Syvitski and Milliman, 2007):
Eq.6
whereIis a glacier erosion factor,L is anaverage basin-wide lithology factor,TEis the trappingefficiencyoflakes and man-madereservoirsso that(I-Tel::::I,andEhis a human- influenced soilerosionfactor (Syvitskiand Milliman, 2007).Forthe lithology factorL weuse a valueof 0.5 as assigned by Syvitsk iand Milliman (2007) forbasins composed principallyofhard,acidplutonic and/or high-grade metamorphicrocks.The sedimenttrappingterm (I-Tel is designed to vary between0.1 for basinswith high quantity of man-madereservo irsandIforbasins with no sediment trapping (Syvitskiand Milliman,2007).Weusethe averagevalue inthe databaseof SyvitskiandMilliman (2007) of 0.8for the term(I-Tel. Thisreflects thelack of man-madereservoirs inthe studyareabutallowsfornaturalsedimen t trappi ng (i. e.bylakes). ForEhweusethe valueIas assigned by Syvitskiand Milliman (2007)for basins with lowhuman footprint.
TheglaciererosionfactorIis definedas:
1=1+0.09 A9 Eq.7
whereAgisthe surfaceareaof glaciersas a percentageofthe drainage basin area (SyvitskiandMi lJiman,2007) .
Estima tionof21oPh supply toland surface
Soilcores werecollected near riverbanksby usingahand augerof 10cmdiameter withan approx imatecoredepth of 60 cm.These coreswere subsampledfor radiochemical analysistodeterminelong-term average21°l' bsupplyto the landsurface.
Thecoreswere slicedinthe LaboratoryatMUN,dried,groundandsealed inpetridishes.
Activitiesof210pbhave been measuredbycountingthe intervals for24hourson Canberra low-back groundplanar gamm adetectors as above.
Profilesof2/oPband137Cs geoc hro nology(SAR)
210Pb and137Cs activities areshown in figure s4-6. 2JOPb activity profilesof both fjordssho wacharacteristic shape withaninflection pointat the baseofa mixed surface layerduetobioturb ation andalogarithmicdecreasein activitiesbelowthispoint.
Sediment accumulation rates(SAR)were calculated using Eqs. Iand2asdescribedin 3.2foractiv ities below theinflectionpoint.137Cs wasusedasa complementarytoolfor 210Pbgeochrono logy,usingEq.2to estimateSAR.Temporalresolutionwas calculated for eachfjordbyusing Eq.3.InNachvak FjordSAR derived from210Pb(Eq. I) range from 0.12cm/y(WH0809 BCNI)to 0.52cm/y(WH0809BCN5).In theprofile of WH0808 BC3(Fig.4)a sing le inflection pointcannot bc determin ed,Inthiscore activities decreasedownwardin astep-like manner.Bioturbat iondepthsin Nachv ak Fj ord rangefrom 4 cm (WH0808 BC4,Fig.4) to9 cm (WH0809 BCNI,Fig. 6).Tempora l resolut ionrang esbetween15 years (WH0808 BC4,Fig.4)and 68 years (WH0809 BCN5,Fig.6).Wherethe maximum penetration depth of137Cs wasdetectable,137Cs SAR isequalto or lessthan the210Pb SAR.
In SaglekFjordSAR derivedfrom2JOPb activitie srangefrom 0.08cm/y(WH0808 BCIO,Fig.5)and 0.36cm/y(WH0808 BCI2 ,Fig.5). Bioturbat iondepth rangesfrom3 cm (WH0809 BCS2,Fig.7) to 9 cm (WH0808 BCII,Fig.5).Temporal resolution ranges from 12 years(WH0809 BCS2,Fig.7) to 49 years(WH0808 BCIO,Fig.5).Maximum
penetration depth oflJ7Cs was detectable in all cores from Saglek Fjord with SAR
e
J7Cs)Fig.4a
210p buAct IVlty( dpm/Q)
WH0808 BC1
137CsActiVityjd pmJ9)
Fig.4b
WH0808 BC2
137CsActivity (dpmlgJ
Fig.4 c
210P bxsAetlvity (dpm/g)
WH0808 BC3
137CsActlVltyldpm/g)
Fig.4d
WH0808 BC4
210PbxsActlvitY ldpm/g)
137Cs ActI Vlty(dpm'9 )
Fig.4e
WH0808BC5
210PbxsActivtty(dp m/g)
137CCOACflvl tyldpm/g)
eo 10 ) Cli3Iy/SiltJS andPercenta g e1%)
I I
\ / I
Fig.4
1~~r£f;~~~~~E;:i:~:£{:~~~r!e;ei:::~:~~;if!:;{~:~:~~r{:~
iro;~;~~~~!g'~::::1:~~~~1~e~~;~:;:sa~~~/;~~;:"I(:;b:~~i~e;~:edfrom
radioisotopeactivi ty graphs. The grainsizegrap hs aredividedintoan areaplot, where thedarkgrey istheclay fractionin the core,lightgreyis silt and whiteis sand, and a lineplot, where the dashed line shows themean grainsize inthe core and the continuous line shows median grainsize.
Fig.5u
WH080 8 BC?
so '00 Cli'l rJSiltlS<'lndP~rQ>nt...g~(%) t37C...Activity(d pmlg )
!~ l ~
E ·~o.2"tm:Y.1l2.o.97
34SAlt(nlC~I:o.22 t:fTl.Y
:O,QTr=O:O.67~O 1.6 ::0:::6 ~O 4flOl--~~~~~---'
Fig.5b
WH0808 BC10
05 1 0 1.5 : : : 0 : : : S ) 0 X I . . o 60
Clay/S~tJSandP.".e..-ntagO!(%)
Fig.5c
:ll UP bxsAeti Vity(d pm/g)
WH0808 BC11
Fig.5d
I37C');Activity(dp m/gj
WH0808 BC12
210PbxSActivity (dp m/g)
137C'SActi vity(dpm /g )
I !
::0 4 0 GO eo 100
Clay/SilUS.lnd Percenloge(%)
Fig.5e
Fig.5
WH0808BC 13
21OpbxsActlVltyld pm/Q)
137C .. ActIVlty(dpm/Q)
~~;~ol~S;:;;~~sa;:/~:~;e;~~:~~ 1. Wi~:;~~~i~~;I;;!;:a~;:;;;~~:1.~7o~~08.
activity are plottedin black. Trendlinesin the1/0Pb activities show theresultof theleast square fit to Eq.I,usedto calculateSARs .SARsderi ved from1/OPb and /37Csdata and temporal resolution sare shownin boxesin theradioisotope activitygraphs. Thegrainsize graphsare divided into an areaplot,wherethe dark grey istheclay fractionin the core, lightgreyis silt and white issand,and a lineplot, where thedashedline shows the mean grainsize in the core and the continuous line shows median grainsize.
Fig.6a
Fig.6b
210Pb xS ActIVlTy(dpm/Q)
SARI210Pbl:O.15cmty R2.. Q.'l6
~~:~~:)C;::0.12c~
137C 'SiAetl vity (dpm /ol
137C '"AC1lVITyldpm lg j
WH0809 BCN1
WH0809 BCN2
Fig. 6c
WH0809 BCN3
210PbxsActi'Aty(dp m/g)
O~) ~~
{: -=-
>
co -40 60 ClayISdtlS and Percentag-=\%)
i l~' .. )~ ~?j !~
ce SARj210 pbl0 19 cIlVy
JO R2. o.S-I 30
t T'~:"",~ "
ro"'0 .f--~~~~~----'
Fig.6d
WH0809 BCN4
137C ,;,;Act ivlty(d pm lg )
