Assessing the impact of freshwater discharge on the fluid chemistry in the Svalbard fjords

Changes in the cryosphere extent (e.g., glacier, ice sheet, permafrost, and snow) have been speculated to impact (bio)geochemical interactions and element budgets of seawater and pore fluids in Arctic regions. However, this process has rarely been documented in Arctic fjords, which leads to a poor systematic understanding of land-ocean interactions in such a warming-susceptible region. Here, we present the chemical and isotopic (δ¹⁸O, δD, δ¹¹B, and ⁸⁷Sr/⁸⁶Sr) compositions of seawater and pore fluids from five fjords in the Svalbard archipelago. Compared to bottom seawater, the low Cl⁻ concentrations and depleted water isotopic signatures (δ¹⁸O and δD) of surface seawater and pore fluids delineate freshwater discharge originating from precipitation and/or meltwater of the cryosphere (i.e., glacier, snow, and permafrost). In contrast, the high Cl⁻ concentrations with light water isotopic values in pore fluids from Dicksonfjorden indicate a brine probably resulted from submarine permafrost formation during the late Holocene, a timing supported by the numerical simulation of dissolved Cl⁻ concentration. The freshwater is influenced by the local diagenetic processes such as ion exchanges indicated by δ¹¹B signatures as well as interactions with bedrock during fluid migration inferred from pore fluid ⁸⁷Sr/⁸⁶Sr ratios. The interactions with bedrock significantly alter the hydrogeochemical properties of pore fluids in each fjord, yielding spatiotemporal variations. Consequently, land-ocean interactions in combination with the hydrosphere-cryosphere-lithosphere are critical factors for understanding and predicting the hydrology and elemental cycling during global climate change periods in the past, present, and future of the Svalbard archipelago.