{"paper_id":"34b3ce55-955b-49d2-8f2c-66cdcf27de28","body_text":"Exploring the existence of quasi-500-day Wobble in polar motion inspired by gravity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Exploring the existence of quasi-500-day Wobble in polar motion inspired by gravity Chenchen Wang, Gong Xu, Guocheng Wang, Yaxin Zhao, Zheng Mu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8560409/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Recent geodetic observations reveal a prominent oscillatory component in Earth’s polar motion (PM) with a period of approximately 500 days, hereafter referred to as the quasi-500-day wobble (quasi-500 dW). This signal is considerably more pronounced than other minor periodic components, such as the quasi-biennial and near-decadal terms, yet its excitation mechanism remains unresolved. By applying the standardized normal time–frequency transform (NTFT), we quantitatively characterize the period, amplitude, and phase of the quasi-500-day component in both PM and gravity observations, thereby providing observational constraints on internal Earth processes at this timescale. To investigate its excitation mechanism, we first assess contributions from external geophysical processes, including atmospheric, oceanic, and hydrological mass redistribution and angular-momentum exchange. The results indicate that these processes lack sufficient energy near the 500-day band and cannot account for the observed signal, implying an internal origin. Previous studies show that core–mantle coupling predominantly excites variability on interannual to decadal scales and is unlikely to provide a persistent contribution at ~500 days. Meanwhile, quasi-500-day periodicity has also been reported in several inner-core–related geophysical phenomena, such as geomagnetic activity, solar-wind interaction, and auroral variability, offering indirect observational support for an internal source. Motivated by this evidence, we test the hypothesis that internal excitation should produce signals of comparable periodicity in gravity. Analysis of superconducting gravimeter records from multiple globally distributed stations reveals significant quasi-500-day signals, with spatially variable amplitudes and phases that are broadly consistent with those extracted from polar motion. Taken together, the PM and gravity observations support the presence of a quasi-500-day dynamical process within Earth’s interior, which serves as the primary excitation source of the quasi-500 dW. Earth and environmental sciences/Climate sciences Earth and environmental sciences/Planetary science Earth and environmental sciences/Solid earth sciences Polar motion Quasi-500-day wobble Earth’s interior processes Gravity variations Core-related excitation mechanisms Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-8560409\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":598832255,\"identity\":\"ac8dd70c-de2a-405a-9efd-d266e3c8f526\",\"order_by\":0,\"name\":\"Chenchen Wang\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Chenchen\",\"middleName\":\"\",\"lastName\":\"Wang\",\"suffix\":\"\"},{\"id\":598832256,\"identity\":\"2d5b1d43-a85a-4d84-9db7-fbe019f97e51\",\"order_by\":1,\"name\":\"Gong Xu\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYPACCTl+/uYDBz78IF6LhbHkjGOJB2f2EK+lInHDgRzjwxxsRKg1uJF+8XHBL4nEmQ1nPhxm4GGQ5xc7gF+L5IycYuOZfRLG/cy9Gw4XWDAYzpydgF8Lv0ROmjRvj4TszIazGw7P4GFIMLhNQAsbVAsj0C8PDvOwEaGFXyL9mDTPDwlFoBYG4rRI9rxhNuZtkAAFsgEwkCUI+8XgePrDxzx/6kBR+fjDhx828vzSBLQwMPAYMDC2wXkShJSDAPsDBoY/xCgcBaNgFIyCEQsAdXlIvb3PL8sAAAAASUVORK5CYII=\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Gong\",\"middleName\":\"\",\"lastName\":\"Xu\",\"suffix\":\"\"},{\"id\":598832257,\"identity\":\"6893b3bc-064e-4fc8-9f08-96bad8efc92e\",\"order_by\":2,\"name\":\"Guocheng Wang\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Guocheng\",\"middleName\":\"\",\"lastName\":\"Wang\",\"suffix\":\"\"},{\"id\":598832258,\"identity\":\"a4c9bb68-d308-490a-8984-c1724360ecda\",\"order_by\":3,\"name\":\"Yaxin Zhao\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Yaxin\",\"middleName\":\"\",\"lastName\":\"Zhao\",\"suffix\":\"\"},{\"id\":598832259,\"identity\":\"40a8baeb-ebb7-416b-8e4c-f97cd3285a4b\",\"order_by\":4,\"name\":\"Zheng Mu\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Zheng\",\"middleName\":\"\",\"lastName\":\"Mu\",\"suffix\":\"\"}],\"badges\":[],\"createdAt\":\"2026-01-09 11:23:32\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-8560409/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-8560409/v1\",\"draftVersion\":[],\"editorialEvents\":[],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":104782880,\"identity\":\"e29a733e-af43-4ea1-8a4d-c7a8b301be10\",\"added_by\":\"auto\",\"created_at\":\"2026-03-17 07:57:54\",\"extension\":\"pdf\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":1249374,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"Exploringtheexistenceofquasi500dayWobbleinpolarmotioninspiredbygravit.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-8560409/v1_covered_e36e90d9-7ed9-4d89-9a2e-cb42e0b6c060.pdf\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"Exploring the existence of quasi-500-day Wobble in polar motion inspired by gravity\",\"fulltext\":[],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":false,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":false,\"hideJournal\":true,\"highlight\":\"\",\"institution\":\"\",\"isAcceptedByJournal\":false,\"isAuthorSuppliedPdf\":true,\"isDeskRejected\":\"\",\"isHiddenFromSearch\":false,\"isInQc\":false,\"isInWorkflow\":false,\"isPdf\":true,\"isPdfUpToDate\":true,\"isWithdrawnOrRetracted\":false,\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true},\"keywords\":\"Polar motion, Quasi-500-day wobble, Earth’s interior processes, Gravity variations, Core-related excitation mechanisms\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-8560409/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-8560409/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eRecent geodetic observations reveal a prominent oscillatory component in Earth’s polar motion (PM) with a period of approximately 500 days, hereafter referred to as the quasi-500-day wobble (quasi-500 dW). This signal is considerably more pronounced than other minor periodic components, such as the quasi-biennial and near-decadal terms, yet its excitation mechanism remains unresolved. By applying the standardized normal time–frequency transform (NTFT), we quantitatively characterize the period, amplitude, and phase of the quasi-500-day component in both PM and gravity observations, thereby providing observational constraints on internal Earth processes at this timescale. To investigate its excitation mechanism, we first assess contributions from external geophysical processes, including atmospheric, oceanic, and hydrological mass redistribution and angular-momentum exchange. The results indicate that these processes lack sufficient energy near the 500-day band and cannot account for the observed signal, implying an internal origin. Previous studies show that core–mantle coupling predominantly excites variability on interannual to decadal scales and is unlikely to provide a persistent contribution at ~500 days. Meanwhile, quasi-500-day periodicity has also been reported in several inner-core–related geophysical phenomena, such as geomagnetic activity, solar-wind interaction, and auroral variability, offering indirect observational support for an internal source. Motivated by this evidence, we test the hypothesis that internal excitation should produce signals of comparable periodicity in gravity. Analysis of superconducting gravimeter records from multiple globally distributed stations reveals significant quasi-500-day signals, with spatially variable amplitudes and phases that are broadly consistent with those extracted from polar motion. Taken together, the PM and gravity observations support the presence of a quasi-500-day dynamical process within Earth’s interior, which serves as the primary excitation source of the quasi-500 dW.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Exploring the existence of quasi-500-day Wobble in polar motion inspired by gravity\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2026-03-02 12:31:08\",\"doi\":\"10.21203/rs.3.rs-8560409/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"3e8fbb0f-1793-4be0-8417-1af601d9aea6\",\"owner\":[],\"postedDate\":\"March 2nd, 2026\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"posted\",\"subjectAreas\":[{\"id\":63723114,\"name\":\"Earth and environmental sciences/Climate sciences\"},{\"id\":63723115,\"name\":\"Earth and environmental sciences/Planetary science\"},{\"id\":63723116,\"name\":\"Earth and environmental sciences/Solid earth sciences\"}],\"tags\":[],\"updatedAt\":\"2026-03-16T13:58:11+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2026-03-02 12:31:08\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-8560409\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-8560409\",\"identity\":\"rs-8560409\",\"version\":[\"v1\"]},\"buildId\":\"XKTyCvWXoU3ODBz1xrDgd\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}