Biogeochemical properties of seawater and suspended particulate matter in an Arctic fjord under contrasting glacier influence (Hornsund, Svalbard, 2022–2023)

Abstract Retreating glaciers are altering sediment and micronutrient fluxes to coastal waters, yet the magnitude and environmental impacts of change remain unclear. Here we examine how contrasting glacier systems in an Arctic fjord control the export and speciation of dissolved and particulate iron (Fe) and manganese (Mn) by comparing locations influenced by marine-terminating and land-terminating glaciers. Data was collected from two glacierized bays in Hornsund, a southern Svalbard fjord, during research cruises conducted in 2022 and 2023. Highly labile ascorbate‑extractable particulate Fe was a major component of the Fe pool in both systems, exceeding dissolved Fe even beyond the inner coastal zone, indicating that labile particulate Fe is transported farther offshore than previously assumed. The tidewater glacier influenced bay exhibited substantially higher concentrations of labile particulate Fe and Mn, elevated dissolved Mn, and sedimentation rates one to two orders of magnitude greater than in the bay with a land‑terminating glacier. These differences might be a result of higher subglacial discharge, a larger glacier cover with enhanced chemical weathering, and a higher abundance of freshly weathered mineral surfaces in the marine-terminating glacier influenced bay. The presence of a shallow bathymetric sill at this field site was also found to constrain circulation of water and limit transport of labile micronutrients out of the bay, resulting in stronger but more localized influence of the tidewater glacier. In the tidewater glacier influenced bay, there was also a more pronounced decrease in dissolved Mn and Al over the salinity gradients. In contrast, the input of suspended particulate matter and labile micronutrient phases from the land‑terminating system was lower, as advanced glacial retreat has led to stabilisation of proglacial sediments and the glacier is smaller. Based on this dataset, coastal micronutrient inputs are likely to decline as glaciers continue to retreat, due to falling glacier discharge and supply of labile sediment enriched in labile micronutrients. Our results indicate that two contrasting glacial systems investigated here showed various controls on iron and manganese concentration and lability. Thus, this study contributes to understanding the consequences and processes related to glaciers retreat onto land in the Arctic fjords. Database consists of following data obtained from two ablation seasons in 2023 and 2022 in Hornsund fiord (Svalbard Archipelago, High Arctic): sediment-bound and dissolved, physiochemical properties of freshwater and seawater (2023_2022_Hornsund_fiord_physiochemical_properties_of_water_sediment_bound_and_dissolved_Fe_Mn_Al_v1.csv), concentration of suspended particulate matter, dissolved and particulate carbon and nitrogen, inorganic nitrogen species, phosphate, and stable C and N isotopes in water (2023_2022_Hornsund_fiord_macronutrients_organic_carbon_total_nitrogen_concentration_suspended_particulate_matter_v1.csv); suspended particulate matter, dissolved and particulate carbon, inorganic nitrogen species and phosphate from 2022 were extracted from the open-access dataset by Koziorowska et al. (2026). Glacier fjords as a natural analogue of mineral-based ocean alkalinity enhancement? (dataset from Southwest Spitsbergen) [Dataset]. Zenodo. https://doi.org/10.5281/zenodo.20378563, total dissolvable elements (2023_2022_Hornsund_fiord_total_dissolvable_Fe_Mn_Al_v1.csv), Berger leach experiment (2023_2022_Hornsund_fiord_berger_leach_Fe_Mn_Al_v1.csv) Keywords Iron, Manganese, macronutrients, micronutrients, seawater, High Arctic, land-terminating glacier, marine-terminating glacier Acknowledgement The research leading to these results has received funding from the Polish National Science Centre SONATA (FLOURISH, award no. UMO-2021/43/D/ST10/00687), Norwegian Financial Mechanism 2014–2021 projects GRIEG-1 (RAW award no. 2019/34/H/ST10/00504, ArcticSGD award no. 2019/34/H/ST10/00645) and within the statutory activities of the Institute of Oceanology Polish Academy of Science. ŁS was supported by the Bekker Programme (award no. BPN/BEK/2021/1/00431) at the Polish National Agency for Scientific Exchange, and project from the National Science Centre in Poland (FLOURISH, award no. UMO-2021/43/D/ST10/00687). JH acknowledges funding from the US National Science Foundation (project MEGA award no. 2232980) and Research Council of Norway through its Centres of Excellence funding scheme, project number 332635 (iC3: Centre for ice, Cryosphere, Carbon and Climate).