利用GRACE測高資料和海洋溫度及鹽度資料研究海洋質量變化ConstraintstudiesofoceanmassvariationsusingGRACEandsatellitealtimetrycombinedwithstericsealevel摘要南極洋藉由南極洲冰原和附近海冰融化和積累之複雜交互作用連結世界其他海洋，然而除了近年來近極地衛星所觀測的資料外，此處觀測資料相當貧乏。本研究利用三種獨立資料分別計算季節性之南極洋質量變化：(1)GRACE重力衛星所測之海底壓力（oceanbottompressure,OBP)資料；(2)改正stericsealevel後之測高資料；(3)ECCOmodel之OBP資料。測高衛星觀測海水面高和利用海溫資料計算之stericsealevel間的差值含有因地球彈性負載所造成的地殼垂直位移，因此我們提供一公式來計算，並證明此改正量在區域性研究中不可忽略。本文利用此三種資料分別計算全球海洋質量變化，並相互比較，結果顯示三種結果相當吻合，相關係數可達0.81，而差異量之RMS為3~5公厘，然而計算之南極洋質量變化相對較不吻合，RMS為12~17公厘。不精確之地心變化資料和J2資料會降低利用GRACE求得之海洋質量變化精度，另外精度不足之stericsealevel也會影響比較結果。最後本研究指出GRACE和測高衛星可提供計算南極洋質量變化之約制。ABSTRACTTheSouthernOceanisamajorlinkbetweentheworldoceansviacomplicatedprocessesassociatedwiththemeltingandaccumulationofthevastAntarcticicesheetsandthesurroundingseaice.TheSouthernOceansealevelispoorlyobservedexceptfromrecentnear-polarorbitingspacegeodeticsatellites.Inthisstudy,theSouthernOceanmassvariationsattheseasonalscalearecomparedusingthreeindependentdatasets:(1)theGravityRecoveryAndClimateRecoveryExperiment(GRACE)observedoceanbottompressure(OBP),(2)steric-correctedsatellitealtimetry(ENVISAT)and,(3)theEstimatingtheCirculationandClimateoftheOcean(ECCO)modelOBPdata.HeightdifferencebetweensealevelderivedfromaltimetryandstericsealevelcontainstheverticaldisplacementoftheEarthsurfaceduetoelasticloading.Hereweprovideaformulationofthisloadingtermwhichhasnotbeenconsideredbeforeinotherstudies,anddemonstratethatitisnotnegligibleespeciallyforregionalstudies.Inthisstudy,wefirstconductaglobalcomparisonusingsteric-correctedJASON-1altimetrywithGRACE,tovalidateourtechniqueandtocomparewithrecentstudies.Theglobaloceanmassvariationcomparisonshowsexcellentagreementwithhighcorrelation(~0.81)andwithdiscrepanciesat3–5mmRMS.However,thediscrepanciesintheSouthernOceanaremuchlargerat12–17mmRMS.Itisfoundthatthemis-modelingofgeocentervariationsandthe2nddegreezonalharmonic(J2)degradetheaccuracyofGRACEderivedmassvariations,andthechoiceofoceantemperaturedatasetsandneglectingtheloadingcorrec