We　present　a　new　approach　to　estimate　time　variations　in　J(2).　Those　variations　are　represented　as　the　sum　of　contributions　from　individual　sources.　This　approach　uses　solely　Gravity　Recovery　And　Climate　Experiment　(GRACE)　data　and　the　geoid　fingerprints　of　mass　redistributions　that　take　place　both　at　the　surface　and　in　the　interior　of　the　solid　Earth.　The　results　agree　remarkably　well　with　those　based　on　satellite　laser　ranging,　while　estimates　of　the　sources　explain　the　observed　variations　in　J(2).　Seasonal　variations　are　dominated　by　terrestrial　water　storage　and　by　mass　redistribution　in　the　atmosphere　and　ocean.　Trends,　however,　are　primarily　controlled　by　the　Greenland　and　Antarctic　ice　sheets　and　by　glacial　isostatic　adjustment.　The　positive　trend　from　surface　mass　variations　is　larger　than　the　negative　trend　due　to　glacial　isostatic　adjustment　and　leads　to　an　overall　rising　trend　during　the　GRACE　period　(2002-2017).　Plain　Language　SummaryJ(2)　variations　indicate　changes　in　the　flattening　of　the　Earth,　which　are　mainly　due　to　the　Earth＇s　response　to　large-scale　mass　redistribution　at　its　surface　and　related　to　ongoing　climate　change.　Though　monitored　over　four　decades　by　Earth　observations　satellites,　the　contributing　sources　to　J(2)　variations　have　not　yet　been　accurately　constrained,　mostly　due　to　deficiencies　in　geophysical　models.　In　this　study,　we　propose　an　approach　to　simultaneously　estimate　and　interpret　J(2)　temporal　variations　based　on　gravity　observations　from　the　Gravity　Recovery　And　Climate　Experiment　satellite　mission.　We　reconstruct　the　observed　gravity　changes　by　a　superimposition　of　spatial　patterns　characteristic　of　individual　sources.　We　find　that　the　seasonal　and　interannual　variations　are　well　explained　by　mass　changes　in　atmosphere,　oceans,　and　land　water　storage.　The　secular　trend,　on　the　other　hand,　is　mainly　caused　by　ice　sheet　melt,　which　has　a　positive　effect　(causing　the　Earth　to　be　flatter),　and　by　the　ongoing　solid　Earth　response　to　past　glaciations,　which　has　a　negative　trend　(causing　the　Earth　to　be　rounder).　The　trend　due　to　ice　sheet　melting　during　2002-2017　has　a　larger　absolute　value,　so　that　the　overall　trend　is　rising,　and　the　Earth　is　currently　becoming　flatter.