Decadal changes in fluvial suspended sediment concentrations in glacierized systems from large scale remote sensing

Suspended sediment affects water quality, aquatic ecosystems, and fluvial geomorphology by inhibiting sunlight penetration into water, carrying nutrients, and modulating deposition rates and channel mobility. Glaciers are prolific sediment generators, and we expect suspended sediment in proglacial systems to change as glaciers recede in a warming world. Satellite observations allow estimation of suspended sediments in remote proglacial systems by exploiting a relationship between near infrared (NIR) reflectance and suspended sediment concentration. Recent work utilizing this remote sensing technique has estimated the importance of ice bodies as sediment generators, but has not investigated changes in sediment concentration over time. We employ the cloud-based Google Earth Engine to compute time series of total suspended sediment (TSS) concentration in lakes and streams in glacierized systems across Alaska and the continental United States over the Landsat record. We utilize the recently published AquaSat dataset to relate field-measured TSS concentrations and concurrent satellite-observed NIR reflectance values for 4 lakes and 28 streams with hydrologic links to glaciers. We calibrate an equation that relates NIR reflectance and TSS to estimate suspended sediment concentrations in water bodies from times in which we do not have in situ observations. Preliminary results indicate that a similar relationship between NIR and TSS exits in our focus area to that found in previous studies, though it is uncertain how the relationship between TSS and NIR differs between rivers and streams, across large spatial scales, and between different Landsat missions. We analyze the TSS time series to investigate how glaciofluvial sediment transport has evolved in Arctic and alpine freshwater systems as the world warms. This investigation of changes in glaciofluvial sediment transport will promote better understanding of impacts of glacier retreat on aquatic life and channel form.