An Ice-Core-Based, Late Holocene History for the Transantarctic Mountains, Antarctica

Home , Dome C, Queen Maud Mountains, Transantarctic Mountains

University of New Hampshire University of New Hampshire Scholars' Repository

Earth Sciences Scholarship Earth Sciences

1995

An Ice-Core-Based, Late Holocene History for the Transantarctic Mountains, Antarctica

Paul A. Mayewski University of New Hampshire - Main Campus

W. Berry Lyons University of Alabama - Tuscaloosa

Gregory A. Zielinski University of New Hampshire - Main Campus

Mark S. Twickler University of New Hampshire - Main Campus

Sallie I. Whitlow University of New Hampshire - Main Campus

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Recommended Citation Mayewski, P. A., Lyons, W. B., Zielinski, G., Twickler, M., Whitlow, S., Dibb, J., Grootes, P., Taylor, K., Whung, P.-Y., Fosberry, L., Wake, C. and Welch, K. (1995) An Ice-Core-Based, Late Holocene History for the Transantarctic Mountains, Antarctica, in Contributions to Antarctic Research IV (eds D. H. Elliot and G. L. Blaisdell), American Geophysical Union, Washington, D. C.. doi: 10.1002/9781118668207.ch4

This Book Chapter is brought to you for free and open access by the Earth Sciences at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Earth Sciences Scholarship by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. Authors Paul A. Mayewski, W. Berry Lyons, Gregory A. Zielinski, Mark S. Twickler, Sallie I. Whitlow, Jack E. Dibb, P Grootes, K Taylor, P-Y Whung, L Fosberry, Cameron P. Wake, and K Welch

This book chapter is available at University of New Hampshire Scholars' Repository: https://scholars.unh.edu/ earthsci_facpub/561 CONTRIBUTIONS TO ANTARCTIC RESEARCH IV

ANTARCTIC RESEARCH SERIES, VOLUME 67, PAGES 33-45

AN ICE-CORE-BASED, LATE HOLOCENE HISTORY FOR THE TRANSANTARCTIC MOUNTAINS, ANTARCTICA

P. A. Mayewski,x W. B. Lyons,x'2 G. Zielinski,• M. Twickler,• S. Whitlow,x J. Dibb,x P. Grootes,a K. Taylor,4 P.-Y. Whung,• L. Fosberry,• C. Wake,x and K. Welch•

Ice core records(major anionsand cations,MSA, oxygenisotopes and particles)de- velopedfrom two shallow(~200 m depth) sitesin the TransantarcticMountains provide documentation of much of the Holocene paleoenvironmentalhistory of this region. From the more southerly site, Dominion Range, an ~7000-year-long record reveals change in the influence of tropospheric transport to the region. At this site, milder conditions and increased tropospheric inflow prior to ~1500 yr BP are characterized by increasedseasalt (ss), terrestrialand marinebiogenic inputs. Increasedpersistence and/or extentof polar stratospheric clouds accompanyinggenerally cooler conditions characterize much of the period since ~1500 yr BP. From the more northerly site, Newall Glacier, the dramatic influenceof the retreat of groundedice from McMurdo Sounddated at <6600 yr BP [Denton et al., 1989] dominatesmuch of the ice core record. This regionalenvironmental change is documented by massive influxes to the core site of evaporitic salts from areas exposed during low lake level stands. During the past ~150 yr, both Dominion Range and Newall Glacier appear to be experiencingan overall increasein the exposureof ice-free terrain.

INTRODUCTION riod, YoungerDryas) to millennia(e.g., Climatic Op- timum, glacialmaxima). In the Arctic there is abun- The vast extent of the Antarctic Ice Sheet and dant evidence for regional differencesin the onset, its setting amidst rimming oceanscontrast markedly duration and termination of several climatic events with the geography of the Arctic. The effect that [Grove, 1988]. While one might assumethat the this dramatic differencehas had on the paleoclimatic Antarctic would reveal a ]ess dynamic climate his- histories of these two polar regions remains an in- tory because of the internal momentum inherent in triguing and increasingly important scientific issue. the massive volumes of ice and ocean, details of its Paleoclimate studies in the Arctic reveal a variety of paleocliInatic history remain unresolved. Most pale- climatic changesthat vary in duration from decades ocliInatic investigation in the Antarctic has focused to centuries(e.g., Little Ice Age, MedievalWarm Pe- on deep sea sediment recordsand on ice core records from the interior portions of the ice sheet (e.g., Byrd, Vostok,Dome C). Theserecords have primar- •Glacier ResearchGroup, Institute for the Study of ily characterizedmajor paleocliinateevents (glacial- Earth, Oceans and Space, University of New Hampshire, interglacialcycles) and do not yet appear to reveal Durham. notable differencesfrom site to site. It is, however, 2Hydrology/HydrogeologyProgram, Mackay School of within the ]ate Wisconsin and Holocene portion of Mines, University of Nevada, Reno. the climate record that the temporal and spatial sen- ZQuaternary Isotope Laboratory, University of Wash- sitivity of climate changecan best be tested. Not only ington, Seattle. 4Water ResourcesCenter, Desert ResearchInstitute, was there dramatic changeduring theseperiods, but University and Community College System of Nevada, the recordsof theseyounger events are relatively well Reno. preserved. 5RosenstielSchool of Marine and AtmosphericSci- Glacial geologicinvestigations suggest that mas- ences, University of Miami, Florida. sive changesin the extent of groundedice character-

ice-filled, and ice-free exposuresare more limited in Scott Glacier extent. These sites effectively serve as "islands" that % G/..... • • Dominion captureenvironmental signatures monitoring local- to QUEENMAUD MTSo% Range ReedyGIo.... / • regional-scalechange in circulation dynamicsand at- Glacier mosphericsource inputs. Our recordscomplement the geologicfindings of Glacier }dGlacier Denton et al. [1989]by providinginformation that documentsprimarily the period since~6000 yr B P, Glacier ROSS ICE SHELF while the latter coversevents >6000 yr BP. By con- trasting our two ice corerecords, we test the response of a vastregion (the coastalsector of the Transantarc- tic Mountains)to a dramatic climate perturbation SOUTHERN VICTORIA (removalof a groundedice sheet) and canassess the LAND Ross Taylor regionalsignificance of such an event. Wright Victoria Valle SAMPLING AND ANALYTICAL TECHNIQUES

The Dominion Range core was collectedin 1984- 1985,and two cores(separated by ~50 m) werecol- lected from the Newall Glacier in 1988-1989. The 90 ø E higherelevation and latitudeof the DominionRange :500 600 km I I versusNewall Glacier is expressedin the lower mean Ice-freeareas annual temperature(-37 and -29øC, respectively, Figure2) and deeperfirn/ice transition(~0.81 g Fig. 1. Location map. cm-3) depth(47 and39 m, respectively,Figure 2). A monopulsesystem modified after Walls and Isher- wood[1978] was used to conductground-based radio- ized the RossSea Embaymentduring the late Wis- echo soundingsurveys in the drainage basinssur- consinand early Holocene[Denton et al., 1989]. In rounding each core site. This method yielded esti- this paper we present paleoclimate recordsfrom two mated ice depths at the core sites of ~220 and ~225 sitesin the RossSea Embayment (Figure 1). The ice m, respectively. A 160 m core with excellent core core records recovered from these two sites differ from quality to ~75 m was recovered at the Dominion other Antarctic ice corerecords because they were re- Range site, and two cores to depths of 170 and 150 trieved from localized accumulation basins within the m-with excellent core quality to depths of 50 and 70 Transantarctic Mountains rather than from interior m, respectively-were recoveredfrom the Newall site portionsof the ice sheet. The Dominion Rangesite (Figure2). is largelydominated by: (1) the interactionof kata- All firn/ice sectioningwas performed in coldrooms batic winds,which flow off the polar plateau and fun- at temperatures that did not exceed -12øC and by nel down outlet glacierson either side of this range, personnelusing particle masks, plastic glovesand and (2) air massesthat movefrom West Antarctica non-particulating clothing. All sample containers inland toward the plateau from the Ross Ice Shell were rinsed four times using ultrapure water. Con- The Newall Glaciersite is dominatedby: (1) kata- tainer blanks sampled on a frequent basis showed batic winds that flow off the polar plateau and funnel that the prepared containers were free of contami- down through the ice-free valleys of Southern Vic- nation. Core processingblanks were also developed toria Land, and (2) circulationdirected southward by sectioningfrozen ultrapure water in the sameway around Northern Victoria Land. Both sites experi- that the core sampleswere prepared. Analysesof ence upslope winds that allow valley bottom air to these processingblanks showednegligible contami- reach the coring sites. At the Newall Glacier site, this nation (<0.01 /•eq/1). All chemicalanalyses were providessufficient loft to allow local dusts and evap- performed with a Dionex Model 4040 ion chromato- oritically produced salts to be deposited at the core graph, using techniquesdescribed by Mayewski el al. site; at the Dominion Range site, nearby valleys are [1990]and Bucket al. [1992],among others. MAYEWSKI ET AL.: LATE HOLOCENE ICE CORE HISTORY, ANTARCTICA 35

Dominion Range Newall Glacier the last few decadespeaks in total beta activity and 0 ß•e• 20 "•"• 21øpbdecay profiles were employed.For the period eee•e covering hundreds to thousands of years major vol- 80 ßßß eeee canicevents were identified and their dating validated I•0 ßßß oo by comparison with a simple layer thinning model. ßeee e %% Finally, identificationof the interglacial/glacialtran- 2•0/ , , , , 80 I , i i I m , m ,% -•8 - •'• -• -•'2 -30 -28 -26 sition was accomplishedby major features in the oxy- Temp (øC) gen isotope record. 0 o -,:....•.. Suitesof sampleswere collected for beta and •1øpb ... 40 .....•:-: activity determinations(Figure 3) to aid in the re- 40 ..' construction of recent chronologies. The Dominion 80 80 : Rangebeta profiledisplayed clear peaks at 253 (mul- ß 120 ..'•' ß 120 tiple) and 173 cm, which reflect the first arrival of 160 . ! , , ! i bombfallout in Antarctica(summer 1954-1955) and 02 04 06 08 I O 0 02 0'4 06 08 I0 Density ( gm. cm-3 ) the maximum fallout (summer 1964-1965),respectively. These marker horizonsindicate averageaccu- Core A mulationrates of 3.5 and 3.4 gcm-2 a-1 for the pre- o vious 30 and 20 yr, respectively. A least squaresexpo- nentialfit to the •1øpbprofile indicates an averageac-

160 cumulationrate of 3.5 gcm -• a-1 for approximately IPoor'FairGood Excellent the preceding century, in very good agreement with 4 0 the rates determined from total beta marker horizons. Quality tCore B • Newall Glacier total beta marker horizons were found 80t__ .• between 250 and 365 cm, which, based upon fits be- 1601PoorFo•rGood Excellent DOMINION RANGE I 5 Quality Beto Activity (cts/hr/kg) 210pbActivity (dpm/kg) 0 moo 200 500 400 0.5 1.0 I 5 20 Fig. 2. Downhole temperature, core density and core 0 I ...... , .... • .... , .... , .... i 0 quality for both sites. Excellent-core contains <3 core breaks/m and no fractures. Good-corecontains >3 to 5 corebreaks/m and <25% fractures.Fair-core contains <7 core breaks/m and <50% fractures. Poor-corecontains >5 to 7 corebreaks/m and/or >50% fractures. 6 15

8 20- beta and 21øpbactivities were determined by meth- ods previouslydescribed [Dibb, 1990, 1992]. Beta 25 activity samples were melted and concentrated onto NEWALL GLACIER cation exchangefilters at McMurdo Station. Oxy- 0 I00 200 500 400 0 0.5 1.0 1.5 2.0 gen isotope analyseswere performed at the Univer- ...... I .... I .... i .... J.... i .... i .... i 0 .... I .... I .... I .... sity of Washingtonby gas sourcemass spectrometry on CO2 equilibrated at 25øC with the water samples. Insolublemicroparticle concentrations (divided into 64 logarithmicallyspaced channels from 0.65/•m to • ,o 13/•m) weredetermined with an Elzone280 PC particle counter housed in a Class 100 clean room.

20 ICE CORE CHRONOLOGIES

io 25 Depth/age relationshipsfor the two coresites were developedby a step-wiseprocess. For the period of Fig. 3. Betaactivity and 21øPb profiles for both 36 CONTRIBUTIONS TO ANTARCTIC RESEARCH IV

Dominion estimates of the probable interhemispheric volcanic 6- Range markersfor this period (definedby J. Palaisand P. 7 19I0 Kyle, personalcommunication, 1991). Due to the relatively similar surface accumulation rates at Dominion Range and Newall Glacier, the volcanic signaturesidentified in the Dominion Range core were tentatively assignedto nss sulfate peaks

' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I [ I ' I ' I found at nearly equivalent depths at Newall Glacier (Figure4). For NewallGlacier, peaks in nsssulfate -J Glacier minusestimated sulfate salt concentration(discussed later in this paper)were used in orderto removethe potential influenceof large local evaporitesources. $ 6 Both core sites containrelatively thin ice (~200 m), irregularsubglacial topography [Mayewski et al., 1990] and potentially high variability in accumulation rate. The proximity of the Newall Glacier site 03 0 to the Ross Sea, coupled with known Holocene fluc- •- ' ' [ ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I tuations in the extent of ice cover over this portion 0 20 40 60 80 I00 120 140 of the Ross Sea, would suggestthat variations in ac- Depth ( m ) cumulation rate are probable, at least at this site. Fig. 4. Nsssulfate (Dominion Range) and usssulfate mi- Based on these uncertaintieswe sought initial guid- nusevaporitic source sulfate (Newall Glacier) depth series ance in the choiceof a layer thinning model for the usedto identify volcanicevents. Concentrations in/•eq/1. two sites by utilizing only a simplified, first approx- (1) Agung(eruption date 1963A.D.); (2) Tambora,Sub- imation model. The Haefeli [1961]model employed awa (eruptiondate 1815A.D.); (3) I-Iuaynaputina,Peru for this task is not expected to necessarilybe suitable (~1600 A.D.), equalto Kirchner's[1988] 1635 A.D. event; (4) Mt. St. Helen's(1480 A.D.), equalto Kirchner's[1988] 1450 A.D. event; (5) 1259event [œangwayet al., 1988], Dominion Range Newall Glacier equalto Kirchner's[1988] 1250 A.D. event;(6) Rabaul, New Britain (~540 B.C.); (7) WaJmihia,New Zealand '1 ' ! ' ' ' I ' ' ' (~1290 B.C.), or Taupo, New Zealand(~1450 B.C.); (8) Whakataine, New Zealand (~2840 B.C.); (9) Mr.

Mazama,Oregon (~4650 B.C.); and (10) Towada,Japan 5O 56 6 B.c.). tween peaks and fallout dates, yields accumulation ratesof 3.7 and 3.8 gcm -2 a-•, respectively.The 2•øPbprofile yields an averageaccumulation rate of 3.6 gcm-2 a-•. 150 Kirchner's[1988] 1000-year-long, non-seasalt (nss), sulfate-derived(based on sodiumas seasaltindicator

[Legrandand Delmas, 1988]) volcanic stratigraphy for 200 ' ' ' ' ' ' South Pole provided guidancefor the choiceof vol- 0 4000 8000 •2000 0 4000 8000 canic events in the Dominion Range since the two Age (yBP) sitesare relativelyclose (~800 km apart). At South Pole, seasonalsignatures in sodium[Kirchner, 1988] Fig. 5. Depth/age plots developedusing Hae. feli's [1961] relationshipfor both siteswhere the age (t in yrs) down allowedrelatively accuratedating to depthsin excess the corecan be computedsuch that t = (H/a)ln(H/H- of 200 m. Identification of volcanic events in the Do- z), where H is total ice thickness,a is accumulationrate, minionRange (Figure 4) is basedon the agesimilar- and z is depth and all are expressedin ice equivalentsin ity of theseevents with thoseat South Pole. Someof m. Values for H and a appear in the text. Numbers 1-10 Kirchner's[1988] events have been renamedas well refer to the location of volcanic events. These events are as some small adjustment in dates made based on named in the caption for Figure MAYEWSKI ET AL.' LATE HOLOCENE ICE CORE HISTORY, ANTARCTICA 37

o 0 0 0 0 0 O0 0 000 o 0 0 0 0 0 O0 0 000 Age(yBP) o 0 • 0 0 0 0 0 0 000 i i I I i i I i i i i i -55 Dominion, Range

-50 I I I I I 0 2_0 40 60 80 I00 12_0 140 Depth(m) Newall' Glacier' I 0 -30

-35 I ' , , , , , 0 20 40 60 80 I00 120 140 Depth(m) I I oI • oI oI I I o o Age(yBP) o•3 0o o•3 o0

Fig. 6. Oxygenisotope (in ø/oo)profiles for the DominionRange and NewallGlacier. Shadedarea belowsmoothed line providesa visual referencefor the variability in the two series. for much more than the upper few hundred years of sulfate volcanic events in this record. Since there is no the record since it assumes uniform vertical strain apparentglacial]interglacial transition in the Newall rate and constant snow accumulation. More sophisti- Glacieroxygen isotope record, the accumulationrate catedflow modelingrelationships were precluded be- at this site must have been higher at sometime prior causeof the limited glaciologicaldata availableat the to the period 1259 A.D. to ~540 B.C. (the two old- sites. Estimated depth/age relationshipsdeveloped est volcanic events correlated in both the Dominion from these simplifiedlayer thinning modelsallowed Rangeand NewallGlacier cores). We can only esti- us to test the choice of volcanic events at each site mate that the depth at ~150 rn is less than ~10,000 (Figure 5). Our volcanicevent designations appear yr BP. to be plausiblebased on their closecorrespondence to the layer thinning models. OXYGEN ISOTOPES, CHEMISTI•Y, AND A rise in oxygenisotopes of ~5.0%0 from ~130 PARTICLES to ~110 m in the DominionRange core (Figure 6), believedsimilar to the 5.4ø/ooand ~5.0%0 changes The DominionRange core was initially sampledat marking the glacial/interglacialtransition observed selectedintervals that were believed, basedon in-field at DomeC [Loriuset el., 1979Jand Vostok [Lorius et electrical conductivity measurements,to contain ev- el., 1985],respectively, is discussedby Meyewskiet el. idenceof strongacid events(potential volcanic sig- [1990].Verification of the presenceof glacialage ice natures)because the identificationof these events in the lower section of this core was also based on the was essentialto the developmentof the depth/age analysisof crystalsize, fabric, isotopic composition of scale for this record. This primary investigation en- trappedO2 and N2, and chemistry[Meyewski et el., tailed 3 cm resolution sampling over sectionsrang- 1990].By constrainingthe deeperend of the Domin- ing in length from 1-9 meters. Once a preliminary ion Rangerecord with this oxygenisotope event, we depth/age scalewas developed,the remainingcore have attempted to estimatethe age of the other nss was analyzed in integrated 20 cm segmentsand 38 CONTRIBUTIONS TO ANTARCTIC RESEARCH IV

initial sampling was adjusted to reflect this 20 cm Although the exact sourceof nitrate in south po- samplingscheme resulting in a continuouslysampled lar precipitation is not fully understood,Legrand and record with a 20 cm resolution. Unfortunately, sec- Kirchner[1990] suggest that it is a combinationof: tionsfrom 12-18m (DominionRange core) and 102- (1) lightningsource nitrate, (2) NOx producedfrom 114m (NewallGlacier core) were destroyed in trans- N20 oxidationin the lowerstratosphere, (3) galactic port from McMurdo Station when a freezer unit on cosmicrays and/or (4) surfacesources such as soils board the transport ship malfunctioned. (ice-freevalley soilscan haveextremely high nitrate The Newall Glacier core was sampled continuously concentrations[Campbell and Claridge,1987]. in 25 cm integratedsegments to a depth of 128 m. In Antarctica, oxides of nitrogen in the strato- Samplingfrom 128-169m is discontinuousdue to de- sphereare thoa•ght[o be convertedfirst to N205 and creasingcore quality. then to nitric acid [McKenzie and Johnson,1984; Evans el al., 1985]. Since the freezing tempera- Ozygen Isotopes ture of a nitric acid-water vapor mixture is higher than that of pure water vapor, polar stratospheric Several trends are discernible in the oxygen iso- clouds(PSCs) are thoughtto be composedprimar- tope series(Figure 6). However,the relativelylow ily of frozennitric acidsolutions [Toon et al., 1986]. accumulation rates at both sites have resulted in Nitrate in Antarctic snowis thought to originate pri- significantdamping of original signals. As noted marily from dissolutionof gaseousnitric acid in cloud previously,the Dominion Range recordencompasses droplets [Legrand and Delmas, 1986]. Rainout of a near-complete Holocene sequence,extending well theseparticles could be a significantsource of nitrate past the glacial/interglacialtransition, perhaps back to the troposphereand is believed to be linked to to ~30,000 yr BP, basedupon a visual comparison the extentand/or persistenceof PSCs[Mayewski and with the Vostokrecord [Lorius el al., 1985;Jouzel el Legrand,1990]. al., 1987]. Oxygen isotopevalues during the period Sulfur is depositedin Antarctic snow primarily as fromthe onsetof the Holocene(~120 m) to ~1500 yr sulfate. This sulfate has five primary sources:(1) BP (~45 m) suggestrelatively mild conditions(less naturalstratospheric sulfate aerosols; (2) seasalt(ss) negative)interrupted by a very slight decreasefrom aerosol[Delmas and Boutton, 1980; Delmas, 1982; ~6000-3000 yr BP. Another low occurs at ~38 m Delrnasel al., 1985; Legrandand Delmas,1988]; (3) (~1000 yr BP), followedby a smallincrease peaking oxidationof dimethylsulfide(DMS) producedby phy- closeto ~32 m (~750 yr BP). The variationsare all toplanktonand emittedfrom the oceans;(4) volcanic relativelysmall (lessthan ~1ø/00) and haveproba- stratosphericsulfate aerosols;and (5) sulfateasso- bly been modified by diffusionas a consequenceof the ciated with evaporitic mineral dusts. The strato- low accumulation rate at this site. The last ~175 yr sphericaerosol is principally composedof sulfuricacid of record are characterized by relatively low values, droplets formed from decompositionof sulfur gases although the relationshipbetween this portion of the suchas carbonylsulfate and sulfur dioxide[Turco el record and deeper sectionscannot be definitively in- al., 1982].Seasalt aerosol contains particulate sulfate ferred due to the missingsection of core between 12 as well as other major ss components.The deposition and 18 m. The Newall Glacier oxygen isotopeseries of this coarse-sizedaerosol in Antarctic snow rapidly records only mild fluctuations. In general, the oxy- decreaseswith distanceinland or elevation[Delmas gen isotoperecords from thesesites appear to only be and Boutton,1980] and comprisesonly about 10%of valuable in the identification of major climate events total sulfate deposition at inland sites in Antarctica, (e.g., Holoceneversus glacial). such as Dome C. Accordingto Churlsonel al. [1987], DMS is the Chemistry major reduced sulfur gas in the marine atmosphere. DMS is excretedby phytoplankton;however, the level Major cations (sodium, calcium, potassiumand of excretion is highly species-dependent.In the tro- magnesium),major unions(sulfate, chloride and ni- posphere,DMS reacts with hydroxyl radical to form trate) and methane-sulfonicacid (MSA) time-series sulfurdioxide and methane-sulfonicacid (MSA). Sul- were produced for both cores. To aid in the inter- fur dioxide is oxidized further, forming sulfuric acid pretation of those series, the following summarizes aerosol. This aerosol is ubiquitous in the marine at- the sources,pertinent reactionsand geographicvari- mosphere and serves as the major source of cloud ations of the chemical speciesfound in Antarctic snow condensationnuclei in these areas [Charlsonel al., and sampled as part of this study. 1987]. Accordingto Shaw [1982], this fine MAYEWSKI ET AL.' LATE HOLOCENE ICE CORE HISTORY, ANTARCTICA 39

CATIONS is a dramatic change in the accumulation rate and No Co K Mg chemicalcomposition of the Newall record, general

I comparisonof the bulk chemistry of these two cores is restricted to this period. Figure 7 is a box plot representingthe major differencesin chemistry be- • , , ,001DRINO I D• ,I tween the two sites for this period. The closerprox- • ANIONS imity of the Newall site to the ocean and to ex- c% nss S04 C I NOs tensive ice-free areas containingdusts and evaporitic minerals is reflected by higher concentrationsof 2O marinesource species--sodium, chloride, magnesium, potassiumand MSA--and crustalsource species (including evaporites)--sodium,chloride, magnesium, DR NG DR NG DR NG potassium, calcium, sulfate and nitrate. The SO4'C1 MSA ratio of Newall snow is twice that of seawater,while 50 the Ca:Na ratio is ~9x greater than seawater. This increaseof Ca2+ andSO4 •+ 'inNewall precipitation • 20 relative to seasaltis apparent throughout the entire • •o timeframe representedby this core. Severalbroad patterns of changecan be identified in the Dominion Range chemicalseries (Figure 8), •'ig. 7. Box plots displayingthe integrated ]000 yr chem- including:an increasein all species(except nitrate) istry a• bo[h si•es. Box encompasses•he mean value peaking at ~90 m; a fluctuating decline in calcium -t-25%. Cappea line con•,.ins 5-95% oœthe data. DR, from ~90-45 m; an increase in nitrate between ~50-0 Dominion Range; NG, Newall Glacier. m; an increase in MSA from ~40-0 m; and a rise in calcium, sodium and potassiumwithin the upper ~10 m of the record. is distributed throughout the Antarctic troposphere Since the sourcesof the specieswhich display in- and accountsfor the majorityof the non-seasalt(nss) creasedlevels peaking at ~90 m (~7000 yr BP) are sulfatedeposited in snow[Delmas, 1982]. High con- both marine (sodium, chloride,magnesium, potas- centrations of MSA in the atmosphere are associated sium,nss sulfate and MSA) and continental(calcium, with areas of high D MS flux from the ocean to the nsssulfate, sodium,magnesium and potassium),it atmosphere. appears that either circulation strength was rela- Three sources are known for chloride found in tively moreintense and/or marineand terrestrialdust Antarctic snow: (1) marine seasalt(assuming that sourceswere greater (more ice-free area). Concentra- sodiumis the primary seasaltindicator/Legrand and tionsduring this period (~7000 yr BP) are closerto Delmas,1988]); (2) HC1emitted during volcanic erup- those currently characterizingNewall Glacier. Levels tions;and (3) HC1which is releasedupon reaction of of all speciesexcept those characterizingthe marine sulfuricacid with ssparticles/Herron, 1982]. environment(sodium, chloride, nss sulfate and MSA) Magnesium, calcium and potassium have two po- stayrelatively high until ~75 m (~4000 yr BP), sug- tential sources:seasalt (based on the use of sodium gestingthat marine air incursionsto this site had de- as the seasaltindicator /Legrand and Delmas,1988]) clined prior to this time. Decreasinglevels of calcium and crustally derived aerosol. Near the coast from 90-45m (~7000-~1250 yr BP) suggestthat dur- the ss-derived calcium and potassium predominate ing this period either transport strength weakened /Boutton,1980; Boutton and Martin, 1980;Aristarain and/or the extentof localice-free areas decreased (in- et al., 1982; Herron, 1982;Mumford and Peel, 1982]. creasedsnow cover). Increases in crustal sourcesof these species, as well The marked increase in nitrate from ~50-0 m co- as of silicate and iron, have been interpreted as in- incides with the period ~1500-0 yr BP. Recent in- dicatorsof increasedatmospheric turbidity and/or of creasesin nitrate at South Pole and Dominion Range increasesin the exposureof ice-freeareas [Mayewski havebeen proposed by Mayewskiand Legrand [1990] and Lyons,1982a; Mumford and Peel, 1982]. asindicative of increasedpersistence and/or extent of Since both the Newall and the Dominion Range polar stratosphericclouds (PSCs). SincePSCs serve cores have similar accumulation rates over the last as a major reservoir for the multi-source nitrate found ~1000 yr, and because prior to this period there in the atmosphere over Antarctica, the periods of 40 CONTRIBUTIONS TO ANTARCTIC RESEARCH IV

2( coast, at Newall Glacier, have been suggestedto be directlyrelated to increasesin seaice cover[Welch et al., 1993]. The increasesin MSA observedin the I 5 Ca** Dominion Range appear to representan increasein

. K* the transport of marine biogenicsource air massesto I0 Mg++ the Dominion Range either by intensifiedtransport CI- from oceansources and/or increasedsource strength. '; 5' The rise in sodium, potassium and calcium from .•_ No+ ~10-0 m (the last ~150 yr) is not paralleledby an

t• - increase in chloride or other marine species. Hence •: NO• o •lOJ this increasewould appear to reflect an increasein •_ 8 transportof crustalmaterial to the site and/or an increasein localsources (an increasein the extentof local ice-freeterrain). 8•o '•õ i nssMSAS04: Among the notablefeatures in the Newall Glacier chemistryseries (Figure 9) are markedlyhigher lev- • 2 els below 120 m for all speciesexcept nitrate (which

1.5

1.0

0.5 4( Ca++•l.,J..,, J, • Partic les 3• K+ 0.0 Mg++ 0 :•0 40 •0 •i0 •60 •0 140 20 Cl- Depth(m)

'-' N%- o o o o oo _ IO Na+, ======• o-- •-- •o? oo•oo•::) Age(yBP)

Fig. 8. Dominion Range chemicaland particle series. • , All concentrationsin t•eq/l exceptMSA (in ppb) and particles(number). Conversionfor true concentration

is (calcium/5)-12,(potassium/20)-10.5, (magnesium/5)- • 6 MSA 8, (chloride/2)-4,(sodium/2)-2, (nitrate/5)-l, MSA/100, usssulfate/1, and total particles(105). Smoothedline 4 nssS04= throughoriginal data is a triangularfilter movedover 10 0 m sections. Shaded area below smoothed line provides a 1o5.= visual referencefor the variability in the smoothedseries. Missingsections in the total particlesplot representareas 0.5- Totol in which insufficientsample volume and/or core quality Portlcles prevented analysis. O.O ß Depth(m)• 2'0 4'0 dO E•O I•0 •0 I•0

j o6 66oo Age(yBP) o creasednitrate depositionat the DominionRange site mayprovide a paleorecordof PSC extentand/or per- Fig. 9. Newall Glacier chemicaland particle series. All concentrationsin /teq/l, except MSA (in ppb) and sistence.(Increases in eitherlead to increasedlikeli- particles(number). Conversionfor true concentration hoodof nitrate depositionon the ice sheet.) i• (½a½i.m/5)-35,(pot•i.m/aO)-30, (m•n•i.m/5)- Levelsof MSA increasebetween ~40-0 m (~100- a0, (½a]o.i&/a)-]o,(•odi.m/a)-s, nit.•t•/S, •SA/]0, 0 yr BP). Peaksin MSA at SouthPole havebeen nsssailate/I, and totM particles(105). Smoothedline correlatedwith the incursionof upper troposphericor throughorigin• data js ß triangular•]ter movedover l0 lower stratosphericair masses/Legrand and Feniet- m sections. Shaded area above smoothed •ne provides $aigne,1991], while increasesin MSA closerto the visu• referencefor the wfiability in the s•oothed MAYEWSKI ET AL.: LATE HOLOCENE ICE CORE HISTORY, ANTARCTICA 41

peaksbefore and after ~130 m), followedby a fluctu- From 132-118 m, the CI:Na ratio is greater than 1, ating decline. Concentrations drop at progressively as is the Ca:(Na+K+Mg) ratio. Although the cal- shallower depths in the order: nitrate, MSA, chlo- culated carbonate values are lower here than at the ride, nss sulfate, magnesium,sodium, potassiumand previouslymentioned depth, they are still high, with calcium. Levels of MSA increaseslightly from ~50- valuesranging between ~2 and 8/•eq/1. Thesesam- 20 m, and all speciesexcept MSA, potassium and ples reflect higher amounts of CaCOa, and perhaps magnesiumincrease very moderately in the ~10-0 m CaCl•, relative to other salts than do the deepersec- range. tions. The Na:SO4 ratios vary around 2, suggesting Major ion concentrations(excluding nitrate) 3 to the possibleimportance of mirabilite. By 118 m, the 10 times the averagecharacterize the Newall core be- concentrationsof the major ions have fallen to lev- low 120 m (Figure 9). Althoughsampling is discon- els typical of the remaining core, with characteristic tinuous over this interval, dramatic variations in con- CI:Na and Ca:(Na+K+Mg) ratiosgreater than I and centration between some pairs of adjacent samples less than 1, respectively. are still evident, implying episodicinputs. A variety The input of locally derived evaporitic dusts de- of salts characterize this interval. However, the data scribed above reflects environmental conditions that available do not allow a unique identification of these have not recurred at the Newall site. They also im- salts. ply a salt sourcemuch larger than is availabletoday. A major distinction between the three composi- The evaporitic dust influx was more than 250 times tional groupsdefined in this study is the Cl:Na ratio greater(based only on carbonateinput) duringthis and the Ca:(Naq-Kq-Mg)ratio. Carbonatewas not highest evaporitic input period. The probable source analyzed but is assumed to be an important com- of these evaporitic materials is adjacent Taylor and ponent. We have calculated the carbonate concen- Wright Valleys. Today thesevalleys contain a number tration by balancing the cations and anions in each of ice-coveredlakes, including both stratified saline sample. (e.g.,Lake Vanda and LakeBonney) and fresh water Spot samples were collected below 145 m in por- (e.g.,Lake Fryxell and LakeHoare) lakes [Matsubaya tions of the core that were of sufficient quality to et al., 1979; Greenet al., 1988]. The volumesof these sample. Although not included in Figure 9, three lakes fluctuated greatly over the time period 4750- of the four samplesanalyzed (from 152-169m) are 6000 yr BP, with both lower levelsand higher levels characterized by a Cl:Na ratio of 1. One of these having been demonstrated[Wilson, 1964; Lawrence three (from 152 m) is additionallycharacterized by and Hendy, 1985]. High levelsoccur during more a Ca:(Na-!-K-I-Mg) ratio of 3. The excessCa in "humid" periods, and low levelsduring more "arid" this sample is interpreted as representinginputs of periods[Lawrence and Hendy,1985]. Moisture avail- CaSO4-2H20 and CaCO3. From 150-132 m, the sam- ability could have been controlledby alternationsbe- ples are characterized by Cl:Na ratios of 2.0-2.5 and tween open and closed ocean conditions in the Ross a Ca:(Naq-Kq-Mg)ratio lessthan 1. Calciumagain Sea. The transition from humid to arid conditions exceeds sulfate. Our calculated carbonate values ex- allowedfor massiveamounts of salts to be produced ceed~4, with a maxima ~50 peq/1. This sequenceis on the valley floors as well as in residual lake basins interpreted to reflect high inputs of chloride-richsalts [Lawrenceand Hendy, 1985; Lyons et al., 1985]. and CaCO3. The very high Cl:Na ratio precludesa Increased levels of MSA noted above and between major influx of mirabilite and also indicates that al- ~50-20 m (~1250-300 yr BP) suggestthat marine kaline metal and probably chloridesalts such as KC1, productivity source areas were either closer to the MgC12 and even CaC12 are important contributors. core site or that increasedtransport to the site was Saline groundwaters,as well as the deep waters of achieved. Welchet al. [1993]have demonstrateda Lake Vanda in Wright Valley, have well documented correlation between increased Ross Sea sea ice extent chemistries[Matsubaya et al., 1979; Cartwrightand and increased Newall Glacier core MSA levels over Harris, 1981]. These watersare unusualin having the last few decades.Gibson et al. [1990]provide the very high Ca:Na and Ca:Mg ratios. The K:Na ra- processlinking MSA and sea ice extent, citing direct tio of the deep lake waters is also greater than that measurementsrelating sea ice extent with increased of seawater. If these waters were to evaporate com- DMS productionby phytoplankton.Using this ana- pletely, they would produce Cl-rich salts in the order log, the periods documentedby increasedMSA levels Ca•Mg•Na•K. This is similar to the relative dis- are assumedto be periodsof sea ice growth and at- tribution of these cations in this depth interval. tendant increasedmarine 42 CONTRIBUTIONS TO ANTARCTIC RESEARCH IV

Relatively minor increasesin marine sourcespecies the north, reveals a <10,000--year-longrecord. Ac- suchas sodium,chloride and nsssulfate, plus terres- cumulationrates at both sitesare quite low (~3.0 g trial sourcespecies such as calcium and sodium plus cm-2 a-l), preventingthe datingaccuracy and at- nitrate (potentiallyan evaporiticsource for thissite) tendantstatistical analyses possible at higheraccu- withinthe upper10 m of thecore (<150 yr BP) in- mulationsites (>20 gcm-2 a-1). Asa3 consequence, dicate an increasein the exposureof ice-free terrain details of shorter period oscillationsin climate on the and open ocean or evaporite sourceinputs. order of decadesto <500 yr cannotbe adequatelyad- dressedin this study. However,the recordsfrom these Particles sites are still extremely valuable, sincelittle is known about even the long-period(,-,1000 yr) elementsof Figures 8 and 9 show downcoreconcentrations for the late Holocenehistory of the Transantarctic Moun- total particles(< 13 pm) for both cores.Plots for the tains. Differences in the palcoclimatic records re- othersize ranges investigated--fine (<1 pm), medium trieved from the DominionRange and Newall Glacier (1-3.2pm) andcoarse (3.2-13 pm)--are notpresented ice core sitessuggest that the TransantarcticMoun- because at both sites they parallel closely those for tain regionhas experienceda regionallydiverse and total particles. Increasesin particle concentrations dynamic climate history during the Holocene that have been routinely related to increasesin circulation warrants further investigationutilizing higher accu- strengthand/or sourcearea. mulationrate records(higher resolution). Most notable in the Dominion Range particle Comparisonof the two multivariate ice corerecords record is the decrease in concentration between ,-,80- from the Transantarctic Mountains, combined with 60 m (,-,5000-2500yr BP) and the increaseat ,-,30 glacial geologic,glaciological and sediment infor- m (,-,750yr BP) that cannotbe definitivelyfollowed mation, revealsseveral palcoenvironmental divisions above,,-20 m due to missingsections of core. The pe- which are summarizedchronologically. riod of decreaseparallels a decreasein calcium which has been interpreted as the product of decreasedter- • •.o, ooo-- • 6000 yr BP restrialsource input (a resultof decreasedsource area and/or transportstrength). The increasein particles From ~10,000 yr BP to ~6000 yr BP, relative since ,-,750 yr B P is not completely paralleled by an temperaturesbased on oxygenisotopic measurements increase in calcium. It is possible that the majority suggestthat the climatein the southernTransantarc- of the particles measuredare not calcium but rather tic Mountains(Dominion Range) was relatively mild. silicate or iron. These speciesare commonly exposed By no later than ~7000 yr B P, terrestrial, seasalt in the Transantarctic Mountains. Increased ice-free and marinebiogenic influences were at their Holocene exposureand/or circulationstrength would lead to peak in this region, suggestingthe presenceof in- their incorporation into the core. creasedice-free areas and intensified transport of ma- The total number of particles in the Newall core rine sourcetropospheric air massesto the region. By closelyparallel trends in the primary evaporitesource ~6000 yr B P, marine sourcetropospheric air masses chemical speciesin sections >90 m in depth. In- no longer penetrated this far south with the same creasedparticle levels appear again at <30 m depth intensity, but local ice-freeterrain was relatively ex- (<500 yr BP). NewallGlacier chemical series display tensive. some increases below 30 m depth but not sufficient to closely parallel the particle record. This particle 6000-- • x5oo yrBP increasemay alsoreflect increasedinput of terrestrial sourcespecies such as silicate and iron, not measured To the south in the Dominion Range, the oxy- in this study. gen isotoperecord provides evidence of slightlycooler conditionsfrom ~6000-3500 yr BP, and the extent of CONCLUSIONS ice-freeexposure declined through this period. Prior to ~4000 yr B P, the influence of marine air masses An estimate of the late Holocene paleoenviron- in this region had declinedmarkedly. Conditionsin ment of the Transantarctic Mountains is developed the DominionRange became gradually milder during on the basis of two multiva•'late ice core records. the period ~3500-1500 yr BP. Terrestrial input to The more southerly Dominio• Range site yields an the core increasedfrom ~3000-2000 yr BP as ice-free ~30,000-year-longrecord, and the Newall Glacier, to exposureincreased in MAYEWSKI ET AL.: LATE HOLOCENE ICE CORE HISTORY, ANTARCTICA 43

To the north alongthe coastof southernVictoria conditionscomes from MeserveGlacier (Wright Vai- Land, a groundedRoss Ice Sheethad retreatedcom- ley), whereincreased exposure of ice-freeterrain since pletelyfrom McMurdoSound [Denton et al., 1989] ~325 yr BP has been documented[Mayewski and by ~6600-6020yr BP. Accumulationrates at Newall Lyons,1982b], and Lake Hoare (Taylor Valley), where Glacier were markedlyhigher than today sometime lake ice thinning has been documentedsince 1972 between~2000 and ~10,000yr BP, we assumein re- A.D. [Whartonet al., 1992]. spouseto the deglaciationof McMurdo Soundand in- creasedavailability of moisture. Prior to this period Acknowledgments.We would like to thank several col- of increased accumulation, Newall Glacier may not leaguesfor their involvementin variousaspects of our field havebeen as large an icemass as it is currently(avail- and laboratory investigations: Chris Buck, Henry Rufli, able moisturewould have been severelyrestricted). Barry Lopez and Michael Morrison. The Polar Ice Cor- Evaporite salts dominate the Newall record below 120 ing Office(University of Nebraska,Lincoln) accompanied rn depth(a probableresult of the loweringof lakelev- the field team and provided the equipment and personnel els formerlydammed by the RossIce Sheet). Once (BruceKoci, ScottWatson and Ted Clarke)to recoverthe initiated, fluctuations in lake levels continued to char- ice cores used in this study. Support in the field was pro- acterizethe regionas a result of fluctuationsin avail- vided by the efforts of VXE-6 and Antarctic Support Ser- able moisture, due perhaps to alternations in sea ice vices. This research was supported by NSF DPP grants extent, which are documented in the ice core by in- 8411018 and 8613786. creasedmarine productivity [Welch et al., 1993].

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J. Dibb, L. Fosberry, B. Lyons, P. A. Mayewski, M. Twickler, C. Wake, K. Welch, S. Whitlow, and G. Zielin- ski, Glacier ResearchGroup, Institute for the Study of Earth, Oceansand Space, University of New Hampshire, (Received March 1, 1993; Durham, NH 03824. acceptedSeptember 17,