Evidence for a Global Warming at the Termination I

1EvidenceforaGlobalWarmingattheTerminationIBoundaryandItsPossibleCosmicDustCausePaulA.LaVioletteTheStarburstFoundation6706N.ChestnutAve.,#102Fresno,CA93710USAAbstractAcomparisonofnorthernandsouthernhemisphericpaleotemperatureprofilessuggeststhattheBölling-AllerödInterstadial,YoungerDryasstadial,andsubsequentPreborealwarmingwhichoccurredattheendofthelasticeagewerecharacterizedbytemperaturesthatchangedsynchronouslyinvariouspartsoftheworld,implyingthattheseclimaticoscillationswereproducedbysignificantchangesintheEarth'senergybalance.Thesegloballycoordinatedoscillationsarenoteasilyexplainedbyoceancurrentmechanismssuchasbistableflippingofoceandeep-waterproductionorregionaltemperaturechangesinvolvingtheNW/SEmigrationoftheNorthAtlanticpolarfront.TheyalsoarenotaccountedforbyEarthorbitalchangesinseasonalityorbyincreasesinatmosphericCO2orCH4.Ontheotherhand,evidenceofanelevatedcosmicrayfluxandofamajorinterstellardustincursionaround15,800yearsB.P.suggestthatacosmicraywinddrivenincursionofinterstellardustandgasmayhaveplayedakeyrolethroughitsactivationoftheSunandalterationoflighttransmissionthroughtheinterplanetarymedium.1.IntroductionClimaticprofilesfromvariouspartsoftheworldhavebeenfoundtoregistersynchronousclimaticchanges.Mörner(1973)hasdescribedevidenceofcorrelatedclimaticfluctuationsoccurringduringthepast35,000yearsinNorthernhemisphereclimaticprofilesandhasconcludedthattheymusthavebeenglobalinextent.LaViolette(1983,1987,1990)laterconductedaninter-hemisphericstudywhichcomparedprofilesfromtheBritishIsles(Atkinsonetal.,1987),NorthAtlantic(Ruddimanetal.,1977),GulfofMexico(Leventeretal.,1983),andSouthernChile(HeusserandStreeter,1980)andconcludedthattheBölling-Alleröd/YoungerDryas(B/AL/YD)climaticoscillationoccurredsynchronouslyinbothnorthernandsouthernhemisphereswiththeBölling-Allerödmarkingaperiodofglobalwarming.Dansgaard,White,andJohnsen(1989)have2comparedoxygenisotope(δ18O)datedprofilesfromtheGreenlandDye3icecoreandasedimentcorefromLakeGerzen,SwitzerlandandhaveshownthatclimaticoscillationsduringtheB/AL/YDcloselytrackoneanotherinbothcores.Also,Kudrassetal.(1992)haveshownevidenceoftheB/AL/YDclimaticoscillationinradiocarbondatedsedimentcoresfromtheSuluSeaofSoutheastAsiaandnotethatitoccurredcontemporaneouslywiththeB/AL/YDoscillationdetectedinaNorthAtlanticcore.TheynotethattheYoungerDryascoldperiodisrecordedinradiocarbondatedcoresfrommanypartsoftheworld(e.g.,GulfofMexico,NorthPacificOcean,Argentina,equatorialAtlantic,BengalFan)andconcludethatitmustberegardedasaglobalphenomenon.Tofurtherevaluatethepossibilitythatclimatehasvariedinagloballysynchronousmanneroverrelativelyshortintervalsoftime,thispapercomparesdatedclimaticprofilesfromvariouspartsoftheworldthatspantheTerminationIboundaryatthecloseofthelasticeage.Thisboundarywaschosenasthefocusforthisstudybecauseofthegreateravailabilityofwell-dated,high-sample-densityclimaticprofilesspanningthisperiod.Whenconsideredtogether,thesedataindicatethatclimateatdistantpartsoftheglobevariedinasynchronousmannerandimplythattheEarth'sthermalenergybalanceunderwentmajorchangesattheendoftheiceage,andpossiblyonearlieroccasionsaswell.Variousmechanismsareexaminedtoseewhetheranycanaccountforsuchabruptgeographicallycoherentclimaticchanges.2.HemisphericSynchronyoftheTerminalPleistoceneClimaticOscillationLandandSeaClimaticProfilesClimateattheendofthelastglaciationdidnotproceedirreversiblytowardinterglacialwarmth,butratherwascharacterizedbyasequenceofinterstadial-stadialoscillations(seeTableI).TheB/AL/YDclimaticoscillationisapparentinradiocarbondatedclimaticprofilesfrombothNorthernTableIScandinavianClimaticZoneDatesClimaticZoneAcronymCalendarDate(YearsB.P.)C-14Date(YearsB.P.)PreborealwarmingPB11,550-11,30010,000-9,700YoungerDryasStadialYD12,700-11,55011,000-10,000AllerödInterstadialAL13,800-12,70012,100-11,000OlderDryasStadialOD13,870-13,80012,150-12,100BöllingInterstadialBO14,500-13,87013,000-12,150ListaStadialLI14,850-14,50013,300-13,000Pre-BöllingInterstadialP-BÖ15,750-14,8504,200-13,300CalendardatesforthesezonesarebasedondatesassignedtocorrespondingclimaticboundariesevidentintheGRIPGreenlandSummiticecore.3Figure1.AcomparisonofradiocarbondatedpaleotemperatureprofilesfromtheNorthernandSouthernHemispheres.TheBritishIslesColeopteranprofileshownin(a)(afterAtkinsonetal.,1987)iscomparedtopollenprofilesfrom:(b)theElAbraCorridor,Colombia(afterSchreve-Brinkman,1978),c)centralBrazil(afterLedru,1993),andd)Alerce,Chile(afterHeusser&Streeter,1980).4andSouthernHemispheres(seeFigure1).TheBritishIslesColeopteranbeetleprofile(52°N,2°W),showninFigure1-a,istime-calibratedwith49radiocarbondates(afterAttkinsonetal.,1987)andcorrelateswellwiththeannual-layer-datedGISP2GreenlandSummiticecoreprofile.ThepollendiagramsfromColombia(5°S,74°W),CentralBrazil(19°S,46.8°W),andAlerce,Chile(41.4°S,72.9°W),Figures1-b,-c,and-d(afterSchreve-Brinkman,1978;Ledru,1993;HeusserandStreeter,1980),arecontrolledby20,10,and13radiocarbondatesrespectively.Acomparisonoftheseprofilesindicatesthatthisclimaticoscillationwascontemporaneousinthesedivers