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1、JOURNALOFGEOPHYSICALRESEARCH,VOL.105,NO.B12,PAGES28,199-28,209,DECEMBER10,2000Modelsofisostaticanddynamictopography,geoidanomalies,andtheiruncertaintiesSvetlanaV.Panasyuk•EarthandPlanetarySciences,HarvardUniversity,Cambridge,MassachusettsBradfordH.HagerEarth,Atmosp
2、hericandPlanetarySciences,MassachusettsinstituteofTechnology,Cambridge,MassachusettsAbstract.KnowledgeofthedynamictopographyatEarth'ssurfacecausedbysublithosphericdensitycontrastswouldprovidecrucialconstraintsonmodelsofmantledynamics.Wecalculateglobalmodelsofthisdy
3、namictopographybysubtractingfromtheobservedtopographyestimatesofthetopographycausedbyassumedisostaticallycompensateddensityvariationsinthecrust,theoceaniclithosphere,andthecontinentaltectosphere.Wealsocalculatetheisostaticgeoidanomalythatwouldresultfromthesecompens
4、atednear-surfacedensityanomalies.Becausethereiscontroversyaboutthethermalstructureofoldoceaniclithosphere,weinvestigatetwomodelsofthecoolingoftheoceaniclithosphere(half-spaceandplate)andcalculatetheeffectofeachontheinferreddynamictopography.Peakamplitudesofdynamict
5、opographyfi,omsublithosphericsourcesexpandedtosphericalharmonicdegree6areapproximatelyñ1km.Weestimatetheuncertaintiesinthecalculateddynamictopographyandgeoidbycombiningtheerrorsinthedataandsystematicerrors.Toobtainthespectralcoefficientsofthefields,weuseweightedlea
6、stsquaresinversions.Thecalculateddynamictopographyarisingfromsublithosphericsources,residualgeoid,anderrorsassociatedwiththesefieldscanbeusedinstudiesofmantledynamics.1.Introductionexistenceofextensiveregionsanomalouslyshallowfortheirage(e.g.,PacificSuperswell[McNu
7、ttandFischer,1987;DaviesandEarth'ssurfacetopographyshowssubstantialvariation,mostPribac,1993])hasbeeninterpretedasrequiringsublithosphericofwhichisrelativelywellexplainedbyisostaticcompensationofdensitycontrasts.densitycontrastswithinthecrustandlithosphere.Forexamp
8、le,ComparisonofEarth'stopographyandbathymetryETOPO5the-•5kmexcesselevationoftheTibetanPlateauaswellasthe[U.S.DepartmentofCommerce,1992]andthenonh
