Quantifying Changes in Suspended Sediment Concentration in Glacier-fed Streams Using Large Scale Remote Sensing

Glaciers are prolific sediment producers, and climate-forced glacier retreat, often accompanied by proglacial lake formation, will impact downstream sediment dynamics. Fluvial suspended sediment concentration (SSC) modulates ecologically-important quantities such as nutrient availability, the ability of sunlight to penetrate water, and channel dynamics. In this work, we characterize changes in fluvial SSC following glacier retreat using satellite data, which enables SSC estimation at large scale in remote environments where in situ measurements are too costly or otherwise infeasible. We extend a previously-developed technique for satellite-derived SSC estimates and find it performs well in proglacial systems (r2 = 0.80). This technique uses all Landsat bands as well as several band ratios, which provides more accurate SSC estimates than approaches utilizing a single band. Combined with a previously-published inventory of Alaskan proglacial lakes and their change over the Landsat-era, wee analyze SSC trends as these glacier-lake-stream systems evolved in response to modern climate warming. We use Google Earth Engine to generate SSC time series spanning 1984 - 2021 at three points (1, 2, and 5 km) downstream from glaciers with and without proglacial lakes to investigate the role of proglacial lake formation on modulating downstream sediment dynamics. Further, we compare SSC in these systems to rivers without headwater glaciers. Preliminary results show that all 7 rivers downstream from proglacial lakes demonstrate a statistically significant change (p<0.05) in SSC over the study period. These findings present a first-order estimate of how sediment fluxes in Arctic rivers are changing in a warming world, with impacts for aquatic habitat and water resources.