231Pa and 230Th in the Arctic Ocean : Implications for boundary scavenging and 231Pa-230Th fractionation in the Eurasian Basin

• Published in: Chemical Geology
• Main Authors: Gdaniec, Sandra, Roy-Barman, Matthieu, Levier, Martin, Valk, Ole, van der Loeff, Michiel Rutgers, Foliot, Lorna, Dapoigny, Arnaud, Missiaen, Lise, Mörth, Carl-Magnus, Andersson, Per S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Stockholms universitet, Institutionen för geologiska vetenskaper 2020
• Subjects: GEOTRACES; Protactinium; Thorium; Arctic Ocean; Boundary scavenging; Geochemistry; Geokemi; Arctic; Makarov Basin; makarov basin; Nansen Basin
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-185828; https://doi.org/10.1016/j.chemgeo.2019.119380

231Pa, 230Th and 232Th were analyzed in filtered seawater (n=70) and suspended particles (n=39) collectedalong a shelf-basin transect from the Barents shelf to the Makarov Basin in the Arctic Ocean during GEOTRACESsection GN04 in 2015. The distribution of dissolved 231Pa and 230Th in the Arctic Ocean deviates from the linearincrease expected from reversible scavenging. Higher 232Th concentrations were observed at the shelf, slope andin surface waters in the deep basin, pointing at lithogenic sources. Fractionation factors (FTh/Pa) observed at theNansen margin were higher compared to FTh/Pa in the central Nansen Basin, possibly due to the residual occurrenceof hydrothermal particles in the deep central Nansen Basin. Application of a boundary scavengingmodel quantitatively accounts for the dissolved and particulate 230Th distributions in the Nansen Basin.Modelled dissolved 231Pa distributions were largely overestimated, which was attributed to the absence of incorporation of water exchange with the Atlantic Ocean in the model. 231Pa/230Th ratios of the suspended particlesof the Nansen Basin were below the 231Pa/230Th production ratio, but top-core sediments of the Nansenmargin and slope have high 231Pa/230Th-ratios, suggesting that scavenging along the Nansen margin partly actsas a sink for the missing Arctic 231Pa. GEOTRACES