Transport and transformation of riverine neodymium isotope and rare earth element signatures in high latitude estuaries: A case study from the Laptev Sea

• Published in: Earth and Planetary Science Letters
• Main Authors: Laukert, Georgi, Frank, Martin, Bauch, Dorothea, Hathorne, Ed C., Gutjahr, Marcus, Janout, Markus, Hölemann, Jens
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2017
• Subjects: Arctic; Arctic Ocean; Laptev Sea; laptev; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/39289/; https://oceanrep.geomar.de/id/eprint/39289/2/Laukert_Suppl1.xlsx; https://oceanrep.geomar.de/id/eprint/39289/3/Laukert_Suppl2.pdf; https://oceanrep.geomar.de/id/eprint/39289/14/Laukert.pdf; https://doi.org/10.1016/j.epsl.2017.08.010

Highlights • First comprehensive seawater Nd isotope and REE data for the Laptev Sea. • Dissolved Nd isotopes, salinity and stable oxygen isotopes trace water masses. • No evidence for REE release from particles of the organic-rich Siberian Rivers. • Preferential estuarine LREE removal follows increasing salinity from 10 to 34. • Formation and melting of sea ice redistribute REEs within water column. Abstract Marine neodymium (Nd) isotope and rare earth element (REE) compositions are valuable tracers for present and past ocean circulation and continental inputs. Yet their supply via high latitude estuaries is largely unknown. Here we present a comprehensive dissolved Nd isotope (expressed as εNd values) and REE data set together with seawater stable oxygen isotope ( O) compositions of samples from the Laptev Sea recovered in two Arctic summers and one winter. The Laptev Sea is a shallow Siberian Shelf sea characterized by extensive river-runoff, sea-ice production and ice transport into the Arctic Ocean. The large variability in εNd (−6 to −17), REE concentrations (16 to 600 pmol/kg for Nd) and REE patterns is controlled by freshwater supply from distinct riverine sources and open ocean Arctic Atlantic Water. Strikingly and contrary to expectations, except for cerium no evidence for significant release of REEs from particulate phases is found, which is attributed to low amounts of suspended particulate matter and high dissolved organic carbon concentrations present in the contributing rivers. Essentially all shelf waters are depleted in light (L)REEs, while the distribution of the heavy REEs shows a deficiency at the surface and a pronounced excess in the bottom layer. This distribution is consistent with REE removal through coagulation of riverine nanoparticles and colloids starting at salinities near 10 and resulting in a drop of all REE concentrations by ∼30%. With increasing salinity preferential LREE removal is observable reaching ∼75% for Nd at a salinity of 34. Although the delayed onset of dissolved REE ...