Figure1:Modelgrid(LLC90)

ECCO-SeaLevel:Thenextphaseinthe“EstimatingtheCirculationandClimateoftheOcean”Project

IchiroFukumori1,PatrickHeimbach2,ChrisHill3,DimitrisMenemenlis1,RuiM.Ponte41JetPropulsionLaboratory,CaliforniaInstituteofTechnology,Pasadena,CAUSA,2UniversityofTexas,Austin,TXUSA,

3MassachusettsInstituteofTechnology,Cambridge,MAUSA,4AtmosphericandEnvironmentalResearch,Lexington,MAUSA

Characteristics ECCOVersion4Release3model MITgcm

gridsystem latitude-longitude-capresolution 0.3˚~1˚,50levels

sea-icemodel prognostic

externalforcing bulkparameterization,geothermalheating

period 1992-2015correlation separatemeanfromanomaly

Variable ObservationsSealevel TOPEX/Poseidon(1993-2005),Jason-1&2(2002-2015),

CryoSat-2(2011-2015),SARAL/AltiKa (2013-2015)Temperatureprofiles Argofloats(1995-2015),XBTs(1992-2008),CTDs(1992-2011)Salinityprofiles Argofloats(1997-2015),CTDs(1992-2011),SEaOS (2004-2010)Seasurfacetemperature AVHRR(1992-2013),AMSR-E(2002-2010)Seasurfacesalinity Aquarius(2011-2013)Sea-iceconcentration SSM/IDMSP-F11, 13,&17(1992-2015)Oceanbottompressure GRACE(2002-2014)Meandynamictopography DTU13 (1992-2012)

Table2:CharacteristicsofECCOVersion4Release3(Fukumorietal.,2017)Table1:DataemployedinthelatestECCOestimate(Version4Release3).(Newitemsinred.)

References:1.Fukumori,I.,etal.(2015),Prog Oceanogr,134,152-172,doi:10.1016/j.pocean.2015.01.013.2.Fukumori,I.,etal.(2017),ftp://ecco.jpl.nasa.gov/Version4/Release3/doc/v4r3_summary.pdf3.Piecuch,C.G.(2017),J.Geophys.Res.,122(9),7181-7197,doi:10.1002/2017JC012845.4.Roemmich,D.,andJ.Gilson(2009),Prog Oceanogr,82,81-100,doi:10.1016/j.pocean.2009.03.004.5.Schodlok,M.P.,etal.(2016),J.Geophys.Res.,121(2),1085-1109,doi:10.1002/2015JC011117

Acknowledgement:ThisstudywasconductedinpartattheJetPropulsionLaboratory,CaliforniaInstituteofTechnology,underacontractwiththeNationalAeronauticsandSpaceAdministration.©2017.Allrightsreserved

Figure2:Globalmeansealevelchange

ECCO

Altimetry

Figure5:SubpolarNorthAtlanticheatcontentchange:(A)ECCO-datacomparison,(B)ECCObudget.(Piecuchetal.,2017)

data variance

Roemmich & Gilson (2009)

ECCO

Figure3:Differenceswithdata(temperature).ECCO(red)hasmoreuniformvaluesacrossdifferentdatasetsthandoesgriddedArgo(black).Significantly,ECCOvaluesareslightlysmallerthangriddedArgoformostexceptArgo

datathemselves.Figure4:Globalmeansalinitychange:(A)Argo,(B)ECCO

Noteabsenceofseasonalcycleandtrendin(A).

(A)

(B)

Figure6:CoherentvariationofArcticoceanbottompressure:(A)ExplainedvariancebyvariationatNorthPole,(B)Explainedvariancebywindatdifferentlocations,(C) Sensitivitytoalong-bathymetrywind.(Fukumorietal.,2015)

Figure7:Meanbasalmeltrate(m/y)forFilchnerRonneIceShelf:(A)observations,(B)MITgcm.(Schodlok etal.,2016)

Theoceanstateestimatesofthe“EstimatingtheCirculationandClimateoftheOcean”(ECCO)Consortium(http://www.ecco-group.org/)combinesnearlyallextantobservationsoftheocean(Table1)withastate-of-the-artoceangeneralcirculationmodelspanningtheglobe(Figure1,Table2)byadjustingitsatmosphericforcingandotherindependentcontrolstominimizemodel-datadiscrepanciesusingtheadjointmethod.Theestimateprovidesadescriptionoftheoceanconsistentwithobservations(Figures2,3,4)anddynamicalandkinematicalfirstprinciples.Forinstance,propertybudgetscanbeclosedintermsofexplicitprocesses,makingamenableinvestigationsofattributionandcausationoftheoceanicstate(Figures5,6).

EffortsareunderwaytofurtheradvancetheECCOestimatetostudyEarth’sclimatewithafocusonimprovingunderstandingandpredictionofglobalandregionalsealevelchange.Thenewinitiativewillincorporatecapabilitiesforcoupledoceanandicesheetestimation(Figure7)withmodelresolutionrefinedtoeddy-permittingscales(1/3°&1/6°).Simultaneously,thescopeandusabilityoftheestimatewillbeexpandedinsupportofthebroaderclimatesciencecommunity,forinstance,byanopensourceadjointoftheoceanmodel.

Heatbudgetcanbeanalyzedbyevaluatingitscontributingelements(Figure5);

Themodeladjointprovidesaneffectivemeanstoexamineattributionandcausation(Figure6);

( ) Ft q qq q¶= -Ñ× +Ñ× +

¶u D 0p

t V

c dVdtr´ ò òòò

( ) ( )( ) ( ),,

dffD

¶» - D

¶ - Dååå ii t i

J tJ t t t

t txx

x

(A)

(B)

(A) (B)