Suspended Sediment Transport and Storage in Arctic Deltas

Abstract

River fluxes to the Arctic Ocean impact sea ice extent, nutrient availability, and coastal ecosystems. Arctic river deltas modulate fluxes of water, sediment, and nutrients reaching the Arctic Ocean. Many large rivers have estimates or measurements of discharge and sediment concentration upstream of the delta apex, but the magnitude, timing, and spatial distribution of sediment fluxes to the Arctic coast are unknown. We developed a novel reduced-complexity model of suspended sediment transport in Arctic deltas to address this knowledge gap. The model estimates suspended sediment delivery to the coast based on a computed channel network and sediment transport rules. We applied this model to six high-latitude deltas during their open water seasons with different boundary conditions to account for their differences in morphology, seasonality, and hydrology. Flux distributions at the coast are found to be more uneven in larger deltas due to uneven channel spacing and larger variability in channel widths compared with smaller deltas. Given typical active season conditions, the deltas exhibit periods of deposition and erosion but are net depositional overall. Net sediment trapping during the active season ranges from 10% to 70%. Our results suggest that larger, more complex deltas with higher sediment supply and less flashy hydrographs store the most sediment and may therefore be more resilient to land loss. The sediment flux distribution can be used in future studies of coastal biogeochemistry and geomorphology and in regional models to capture the impacts of fluxes on turbidity, marine primary productivity, and Arctic warming.