ProcessesControllingArc/cAerosolNumberandSize:SeabirdNH3–ClimateConnec/onsB.Cro'1,G.R.Wentworth2,R.V.Mar6n1,3,W.R.Leaitch4,P.Tunved5,J.G.Murphy2,B.N.Murphy5,J.Kodros6,T.J.Breider7,S.D’Andrea6,J.P.D.AbbaO2,J.R.Pierce6,1 1DepartmentofPhysicsandAtmosphericScience,DalhousieUniversity,Halifax,NS,Canada 2DepartmentofChemistry,UniversityofToronto,Toronto,ON,Canada 3Harvard-SmithsonianCenterforAstrophysics,Cambridge,MA,USA 4ClimateResearchDirectorate,EnvironmentandClimateChangeCanada,Toronto,ON,Canada5DepartmentofEnvironmentalScienceandAnaly6calChemistry,StockholmUniversity,Stockholm,Sweden 6DepartmentofAtmosphericScience,ColoradoStateUniversity,FortCollins,CO,USA7SchoolofEngineeringandAppliedSciences,HarvardUniversity,Cambridge,MA,USA

Introduc/on:•  Thesummer6meArc6cispris6neduetoefficientcleaningbyrain/drizzle,andstronglyinfluencedbynatural,localemissions,which

havepoorlyunderstoodclimateeffectsrelatedtoaerosolsandclouds(IPCC,2013;Leaitchetal.,2013;Riddicketal.,2012;Cro'etal.2015).•  RecentevidenceindicatesthatNH3emissionsfrommigratoryseabirdguanoareaprimarycontributortosummer6mefreeNH3levels

measuredintheCanadianArc6c(Wentworthetal.,2015).NH3togetherwithsulfuricacidandwatercontributestopar6cleforma6on.•  Inthisstudy,weusetheGEOS-Chem-TOMAS(GCT)coupledchemistry-aerosolmicrophysicsmodel(www.geos-chem.org)toinves6gate

theimpactofseabirdcolonyNH3onpar6cleforma6on,growthbysulfuric-acidandorganicvaporcondensa6ontosizesthatnucleateclouddroplets,andthesubsequentpan-Arc6caerosolindirecteffectduetochangesincloudradia6veproper6es.

Summary:•  PeriodicN10burstsareobservedfromMay-September

inthehigh-Arc6catAlert,Nunavut,Canada.•  Thepris6neArc6csummer6mefavorspar6cleforma6on

andgrowthofthesepar6clestosizeslargerthan10nm.•  GEOS-Chem-TOMASsimula6onsshowthatseabird

coloniesprovidesufficientNH3toyieldtheseN10bursts.•  Growthofseabird-influencedpar6clesto~80nm

increasespan-Arc6cclouddropletnumberby10-50%.•  Thepan-Arc6cOceanmeanaerosolindirecteffectis-0.5Wm-2,asignificantregionalcoolingtendency.

•  EmissionsfromRiddicketal.(2012):circlesAddi6onalcoloniesfromwww.seabirds.net:stars.

[MgNHyr-1]

0.0010.010.11101001000

[pptv]

1310301003001000

•  GEOS-Chem-TOMAS(GCT)simula6onofthesummer6me-meansurfacelayerNH3fromseabirdcolonyemissions.

Alert,Nunavut,CanadaObservatorysite

•  Offlinecalcula6onof%changeinsummer6me-meansurfacelayerCDNCusingAbdul-Razzak-Ghanscheme.

[%]

-5040-30-20-1001020304050

Guano+H2O+O2àNH3(g)

•  GCTwithternary(NH3+H2SO4+H2O)nuclea6onscheme(Baranizadehetal.,submiOed),excludingaminesandiodine.

4.FreeNH3AAributedtoSeabirdColoniesReachesUpto1000pptvinBaffinBayRegion

References:Leaitchetal.,Elem.Sci.Anth.,2013;Riddicketal.,Atmos.Environ.,2012;IPCC,2013;Wentworthetal.,Atmos.Chem.Phys.Discuss.,2015,Cro'etal.,Atmos.Chem.Phys.Discuss.,2015,Baranizadehetal.,GMDDsubmiOed.Acknowledgements:FundedbyNSERCCanadaClimateChangeandAtmosphericResearchProgram.ThankstoS.Sharma,D.ToomandA.PlaOforsupportofAlertmeasurementsandtoI.Riipinen,T.OleniusandJ.JulinforACDCpar6cleforma6oncode.

3.Arc/cSeabirdColoniesEmit~40GgNH3betweenMay-Sept

Year:2011

Year:2011

[Wm-2]

-3-2-10123

Summer6meMeanAIEAOributedtoSeabirdColonyNH3Emissions

%ChangeSurface-LayerCDNCwithSeabirdColonyNH3Emissions

7.Seabird-InfluencedPar/clesCanGrowto50nm+andModifyPan-Arc/cCloudDropletNumberConcentra/onby>50%

8.Pan-Arc/cOceanMeanAerosolIndirectEffectDuetoSeabirdNH3is-0.5Wm-2

6.SeabirdColonyNH3ControlsAerosolNeutraliza/onStateatAlert

NH 4

+ /(2

SO42-+NO3- )

AMJJASO

AMJJASO

5.SeabirdColonyNH3isSufficienttoSimulateSummer/meN10BurstsObservedatAlert

AerosolN

10Num

berC

oncentra6o

n[cm

-3]

2.KeyProcessesforSummer/meArc/c:WetRemoval,Par/cleForma/on,Growth

Allratesarethemeanoveren6retropospherenorthof66°N.

Dp<10nm 10nm<Dp<100nm

Dp>1000nm100nm<Dp<1000nm

Efficientremovalbyprecipita6onfromwarmcloudscleanstheArc6cinsummer.

1.ObservedArc/cAerosolSeasonalCycleWinter6metoearlyspring-buildingofaccumula6onmode(Dp>100nm)

AlertZeppelin

__

Measurementsfrom:AlertSMPSZeppelinDMPS

Summer6me-Aitkenmodedominates(Dp<100nm)

Fall-aerosolnumberminimum

Alert,Nunavut,CanadaObservatorysite

•  Summer6meaerosollessacidic.GCT-simulatedneutraliza6onra6oisstronglyimpactedbyseabirdcolonyNH3emissions.