UsingMODISOceanColorDataandNumericalModelstoUnderstandtheDistribu:onofColoredDissolvedOrganicMa=er

intheSouthernOcean

C.E.DelCas:llo1,3,S.Dwivedi2,andT.W.N.Haine31OceanEcologyLaboratory,Na:onalAeronau:csandSpaceAdministra:on,GoddardSpaceFlightCenter,Greenbelt,MD20771,USA2DepartmentofAtmosphericandOceanSciences,UniversityofAllahabad,Allahabad,UP211002,INDIA3DepartmentofEarthandPlanetarySciences,JohnsHopkinsUniversity,Bal:more,MD21218,USA

MODIS/VIIRSScienceTeamMee:ng,SheratonSilverSpringHotelJune9,2016

Hypotheses:1-ThatCDOMdistribu:onintheSouthernOceanin:mescalesof~weeksiscontrolledbyphysicalprocesses.Biologicalprocessesarenegligible.2-Thatdataassimila:onofremotesensingandfielddatacanproduceIOPfields.Modeledproductscancompensateforlackofimageryincloudyenvironments.

Goals:1-Toes:matethethree-dimensional:meevolvingdistribu:onofCDOMduringtheSouthernOceanGasExchangeExperiment(SO_GasEx).2-TodiagnosethephysicalprocessescontrollingCDOMdistribu:on.Ul:matelywewanttomodelevolu:onofagʎ(andotherIOPs)tofillgapsinsatellitecoverageoverperiodsofweeks.

Background:

SeasonalchangesinCDOMcanbeexplainedbybacterialproduc:onandphotodegrada:on(Nelsonetal.,2004).

Background:

OurGESEestatees:ma:onshowedconsiderableskillinmodelingupperoceanphysicalvariablesalongthespa:alandtemporaldomainsoftheSOGASEX

Issues:1-Wehadpoormatch-ups.However,CDOMretrievalsusingQAAwhereinfamilywiththefieldsamples.2-Don’thavephotodegrada:onparametersfortheSO,assumethatmarineCDOMissimilareverywhere.

Methods:

WedevelopedapackageforMITgcmtosimulateadvec:onanddiffusionofCDOMatmul:plewavelengths.WetreatedtheCDOMabsorp:oncoefficientsaspassivetracerswith:meandspace-varyingsourcesandsinks.Theabsorp:onoflightbyCDOMandtheassociatedphotobleaching(photolysis)actedasthemainsink.FollowingDelVecchioandBlough[2002],theCDOMabsorp:oncoefficientaCDOMakerillumina:onforashort:meΔtis

aCDOM(λ,z)=aCDOM(λ)e–f(λ,z)Δt,

wheref(λ,z)isthephotobleachingrateatwavelengthλanddepthz.Itisgivenby

f(λ,z)=σP(λ)E(λ)e–k(λ,z)z

whereσP(λ)isthephotobleachingcross-sec:on,E(λ)isthesolarirradianceatwavelengthλtransmi=edthroughtheseasurface,andk(λ,z)isthever:cala=enua:oncoefficientwhichisapproximatedas(4/3)aCDOM(λ,z).

TheCDOMmodelwasrunforthreedifferentwavelengths350nm,380nm,and400nmusingthehourlysurfacesolarirradianceobtainedfromtheOASIMradia:vetransfermodel(GreggandCasey[2009]).

Whythemismatches?~1.Wearemeasuringremotelyat440nmandextrapola:ngtoshorterwavelengthsusingtheSparameter.~2.Canthemodelresolvebe=erthefirstop:caldepth?~3.Thisisapoormatchup.

Comparisonofthe:meaveragedMODIS-AQUAderivedSCDOMfieldat350nm(upperpanel),380nm(middlepanel)and,400nm(lowerpanel)withthecorrespondingGESE-CDOMSCDOMfieldsfortheSOGasExdomain.The:meaverageisover21,22,24,and27March2008(thedatesofthesatellitedata).ThestaranddiamondsshowtheSOGasExcruisesta:onon20thMarchand22ndMarch,respec:vely.

Comparisonofthe:meseriesofSOGasExin-situsurfaceCDOM(circles)at350nm, 380nm, and 400nm with the corresponding GESE-CDOM surfaceCDOMvalues(dots).ThesamplesarefromsurfaceCTDsta:ons.

Comparisonbetweenfielddata(allCTDsamplesandmodeledCDOM)

Iknowthatthisisahorribleslide….

…...sorry......

Conclusions:1-CDOMdistribu:onintheSouthernOceanin:mescalesof<weeksiscontrolledbyphysicalprocesses.Biologicalprocessesarenegligible.2-Dataassimila:onofremotesensingandfielddatacanproduceIOPfields–atleastCDOM.Modeledproductscancompensateforlackofimageryincloudyenvironments.

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