Depositional environments in the fjord head delta of deglaciated Dicksonfjorden, Svalbard: The impact of global warming after the post-little ice age

Global warming after the Little Ice Age (LIA) has triggered rapid glacier retreat in an arctic coastal region, instigating substantial environmental changes in the fluvial-marine transition zone (FMTZ). A comprehensive understanding of the sedimentary environments affected by glaciofluvial, tidal, and wave processes is imperative for predicting the ongoing impacts of global warming. Despite logistical challenges and limited accessibility, we investigate the influence of glacier melting on the evolution of depositional environments in the Arctic FMTZ, focusing on the deglaciated Dicksonfjorden in Svalbard. Our study involves the collection of undisturbed cores from glaciofluvial rivers, tidal channels, and spits to elucidate the spatial distribution of sedimentary facies. Hydrodynamic observations in tidal channels enable to comprehend sediment transport dynamics. The glaciofluvial river which is nourished by high-turbid snowmelt waters forms braided channels that intricately dissect extensive tidal flats in the downfjord. Sedimentary facies reflect an increasing tidal influence, transitioning from downstream-directed climbing-rippled sands to interlaminated sands and muds towards the sea. Tidal point bars exhibit inclined heterolithic stratification, comprising bidirectional rippled silts and interlaminated silts. Gravelly beds on the spits incline towards the shore, primarily attributed to wave-induced cliff erosion. The microtidal regime, characterized by ebb tidal asymmetry, experiences peaks in suspended sediment concentration during ebb tides. Estimated sedimentation rates calculated from 210-Pb activities averaged 0.14 cm/year from the 1920s to 2020. Notably, the rate has increased from 0.07 cm/year (1980s-2000) to 0.23 cm/year (2000-2020). This study underscores the profound impact of accelerated climate warming on increased meltwater and sediment discharges post-LIA, driving active delta progradation and instigating morphological changes in deglaciated arctic coastal environments.