{"refrec":{"BRefID":15902,"RR":"<b>Geibert, W.</b> (2001). Actinium-227 als Tracer für Advektion und Mischung in der Tiefsee = Actinium-227 as a tracer for advection and mixing in the Deep-Sea. <i>Ber. Polarforsch. Meeresforsch. 385</i>: 1-112","BEntID":15902,"PublicFlag":1,"CheckedFlag":0,"wosflag":0,"vabbflag":null,"RefStringPartII":". <i>Ber. Polarforsch. Meeresforsch. 385</i>: 1-112","DocTypID":13,"DocType":"Reports","MarineFlag":1,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Geibert, W.","OrigTitleTranslFlag":0,"Authorstringtrunc":"Geibert, W.","Englishabstract":"The natural radionuclide Actinium-227 (<sup>227</sup> Ac, half-life 21.77 years) is presented in this work as a tracer for mixing and advection of deep-sea water masses. Vertical profiles of <sup>227</sup> Ac were determined at 9 locations via a counting of its daughter <sup>227</sup>Th. Previous to this work, three vertical profiles of <sup>227</sup> Ac existed, all of them in the Northern Pacific. Here I report <sup>227</sup> Ac data from the Central Arctic, the Southeast Pacific, the Antarctic Circumpolar Current (ACC) and the Weddell Gyre. For the first time, ratios of particulate and dissolved <sup>227</sup> Ac in the water column were obtained. Not more than 1.7% of <sup>227</sup> Ac were found on particles. <sup>227</sup> Ac was found to be depleted on particles with respect to its mother <sup>231</sup>Pa. Only 11% of the <sup>231</sup>pa activity were observed on particles. In the Southeast Pacific, high <sup>227</sup> Ac <sub>ex</sub> activities were found close to the seafloor. Due to its decay, no <sup>227</sup> Ac <sub>ex</sub> was found far above the seafloor. This finding is in agreement with earlier results. In contrast, for the Antarctic Circumpolar Current and the Weddell Gyre <sup>227</sup> Ac <sub>ex</sub> could be shown to reach the surface via mixing and advection. A location in the Central Arctic with a strong influence of shelfwater near the sea surface (ca. 100 dpm/m³ <sup>228</sup>Ra) had only 0,17± 0.07 dpm/m³ <sup>227</sup> Ac<sub>ex</sub>. This indicates that shelf sediments are a minor source for <sup>227</sup> Ac<sub>ex</sub>. This observation is confirmed by model results. A model for the release of <sup>227</sup> Ac and <sup>228</sup>Ra from sediments at different water depths is applied. The results indicate that deep-sea sediments release at least nine times more <sup>227</sup> Ac than shelf sediments. The fluxes of <sup>227</sup> Ac and <sup>228</sup>Ra strongly depend on bioturbation rates. A comparison of model results and data revealed that inputs from deep-sea sediments and shelf sediments are similarly overestimated by the model. Based on water column measurements the total amount of <sup>227</sup> Ac<sub>ex</sub> in the ocean is estimated ta be 12.6 kg. Considering its source at the deep-sea floor, its half-life of 21.77 years, and its low particle reactivity, <sup>227</sup> Ac<sub>ex</sub> is an ideal tracer for water masses that were in contact with deep-sea sediments. Four possible applications of <sup>227</sup> Ac<sub>ex</sub> are presented. 1, The determination of coefficients for diapycnal mixing 2. The identification of inputs of nutrients and trace elements to the euphotic zone of the ACC by deep upwelling 3. The simultaneous determination of diapycnal mixing, isopycnal mixing and advection in global circulation models.4. The determination of upwelling velocities in the Weddel Gyre.For the eastern Weddell Gyre, the upwelling velocity is calculated to be about 55 m/year. This value is somewhat higher than earlier calculations for the entire Weddell Gyre. The possible influence of upwelling on particle preservation is investigated by a simplified model for particle sedimentation. The results indicate that upwelling can enhance particle dissolution in the water column of the Weddell Gyre in conjunction with other factors, e.g. small particle sizes. Altogether, <sup>227</sup> Ac<sub>ex</sub> turns out to be a promising tracer for several questions in marine geosciences.","AbstractOtherLang":null,"BibLvlCode":"AS","StandardTitle":"Actinium-227 als Tracer für Advektion und Mischung in der Tiefsee = Actinium-227 as a tracer for advection and mixing in the Deep-Sea","OrigTitleLangCode":"de","OrigTitleLangCodeExtended":"ger","OrigTitleLangID":13,"DateLastModified":{"date":"2024-12-10 01:32:52.928458","timezone_type":1,"timezone":"+01:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":2001,"MonPub":null,"DateUpdate":"2001-11-14","DateCreate":"2001-08-17","SecASFANote":null,"ConfID":null,"PeerRev":1,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":0},"refs":null,"anarec":{"AnaID":15902,"PubliDate":2001,"Pagination":"1-112","XtraPublOfAnaID":null,"ISBN":null,"Volume":"385","Issue":null,"BRefMon":null,"BRefMonRR":null,"BRefXtra":null,"BRefXtraRR":null,"SerBRefID":42241,"SerRR":"Berichte zur Polar- und Meeresforschung = Reports on Polar and Marine Research. Alfred-Wegener-Institut für Polar- und Meeresforschung: Bremerhaven.  ISSN 1618-3193; e-ISSN 1866-3192","StandardTitleSer":"Berichte zur Polar- und Meeresforschung = Reports on Polar and Marine Research","ISSN":"1618-3193","AbbrevSer":"Ber. Polarforsch. Meeresforsch.","StandardTitleMon":null,"StartPage":1,"Pages":112,"ToPubliDate":null,"BRefBibLvlCode":"S","SerNotes":null},"monrec":null,"serrec":null,"relations":null,"relationsRev":null,"addrec":null,"othpubs":null,"ownerships":null,"authors":[{"AutName":"Geibert","Firstname":"Walter","Initials":"W.","Affiliation":null,"Discriminator":null,"CorporateFlag":0,"BEntID":15902,"AutID":19647,"OrderNr":1,"DegrID":null,"EditorFlag":0,"CorrespFlag":0,"IllustratorFlag":0,"ReviserFlag":0,"TranslatorFlag":0,"InsAcronym":null,"InsFSN":null,"ORCID":null,"PersID":null,"InsID":null}],"mapdetails":null,"datasets":null,"monographs":null,"monparts":null,"serparts":null,"BEntOpen":null,"BEntPrivate":null,"availability":null,"litstyles":[{"LitStyID":20,"Style":"Project report"}],"thespers":null,"arch2discl":null,"SERpubls":[{"PublName":"Alfred-Wegener-Institut für Polar- und Meeresforschung","City":"Bremerhaven"}],"MONpubls":null,"pictures":[],"thestermsPath":null,"thestermsASFA":null,"taxtermsASFA":null,"geotermsASFA":null,"collections":null,"conf":null,"proj":null,"Physdatasets":null,"spcols":null,"doi":null,"publs":null,"serparttypes":null,"monauthors":null,"MParts":null,"SParts":null,"hLibs":null,"langs":[{"BEntID":15902,"AbstractFlag":0,"LangID":13,"LangCode":"de","Lang":"German","DutchTerm":"Duits","LangCodeExtended":"ger"},{"BEntID":15902,"AbstractFlag":0,"LangID":15,"LangCode":"en","Lang":"English","DutchTerm":"Engels","LangCodeExtended":"eng"}],"urls":null,"thesterms":null,"taxterms":null,"geoterms":null,"othterms":null,"asfacodes":null,"asfa2codes":null,"thestermsFRIS":null,"taxtermsFRIS":null,"geotermsFRIS":null,"othtermsFRIS":null,"resmessage":"","complete":1,"sessions":{"newSesName":"Haspeslagh, Jan, J.","newSesDate":{"date":"2001-08-17 08:31:12.023000","timezone_type":3,"timezone":"Europe/Brussels"},"updSesName":"Haspeslagh, Jan, J.","updSesDate":{"date":"2001-11-14 11:50:31.853000","timezone_type":3,"timezone":"Europe/Brussels"}}}