Insights from Sediment Export Variability in Three Glacier-Fed Fjords in Disko Bay Kalaallit Nunaat (Greenland)

The Greenland Ice Sheet (GrIS) is undergoing accelerated melt and dynamic shifts that influence sediment export, with critical implications for regional biogeochemical cycles and cryospheric processes. However, direct observations of sediment export variability remain limited. To address this gap, we analyzed sediment cores from three glacier-fed fjords in Disko Bay, encompassing diverse catchment areas and glacier dynamics. The spatial extent of sediment packages and ice-rafted debris (IRD) within the cores was assessed, alongside decadal-scale sedimentation rates. These rates were integrated with sedimentary facies analyses and subbottom profiling.

By examining sedimentation rate variations with respect to glacier retreat histories, velocity data, and meltwater flux estimates, we identify contrasting behavior in sediment export amongst the fjords and catchments. The findings highlight the differential roles of glacier dynamics, catchment size, land or marine-terminating glacier fjord type, and meltwater contributions in modulating sedimentation patterns. Furthermore, several hyperpycnal deposits are present that could be the result of glacier outburst floods. We discuss their potential role in supplying sediment to the fjord and the challenges they introduce when trying to establish climate effects. This study underscores the importance of sediment production and mobilization processes from the GrIS and emphasizes the need for regional sediment export assessments to refine predictions of future discharge scenarios.

These results link sedimentary processes to ice sheet dynamics, offering a framework to evaluate processes controlling sediment fluxes in response to ongoing ice sheet retreat and climate change.