Rare Earth Elements input from proglacial sediments into Kongsfjorden, Svalbard

Torben Stichel1 and Susann Henkel1,2, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (2)MARUM - University of Bremen, Bremen, Germany
Rare earth elements (REE), such as the lanthanides, yttrium and scandium together with neodymium isotopes (εNd) are useful tracers in geochemistry to characterise sediment provenances. Furthermore, they can help to comprehend other elemental fluxes from land to sea. However, input mechanisms of REE into seawater are still being investigated to better understand REE cycling. Particularly, shelves in glacial areas are subject to environmental transformations due to modern climate change. Retreating glaciers expose relatively reactive sediments which are ideal to study aquatic geochemical processes governing REE distribution.

We have collected filtered (0.45 µm) seawater from the Kongsfjord (Svalbard) and meltwater samples from the glaciers draining into the fjord for REE and εNd. Samples were analysed for REE on a ThermoFisher® Element2 after an offline pre-concentration using a seaFAST®. The REE were quantified with a known amount of thulium (Tm) as an internal standard prior to pre-concentration. With a neglectable fractionation amongst REE on the seaFAST column, this method allows an efficient and accurate quantification of such elements. Neodymium isotopes will be analysed at a later stage to better understand the provenance of the meltwater distributaries. The distributions of REE in the meltwater show clear enrichment of MREE and low HREE/LREE, in particular close to one land terminating glacier front on the Brogger-peninsula, typical for freshwater. Patterns from the fjord show a seawater distribution with high HREE/LREE and low Ce/Ce* in the deep outer fjord. Lower salinity surface waters are enriched in REE and show lower HREE/LREE than deep waters. Surface samples in the outer fjord show highest REE concentrations, suggesting that at this location REE inputs from the large tidewater glacier Kronebreen at the head of Kongsfjorden are subordinated to the inputs by smaller glaciers draining meltwater over proglacial sediments from the Brogger-peninsula.