Stable Sediment Plumes Despite Tidewater Glacier Retreat in a South Greenland Fjord

Abstract Tidewater glaciers play a critical role in ice sheet mass loss and fjord hydrography, as meltwater runoff volume and injection depth can influence sediment transport, fjord circulation, and fjord stratification. As tidewater glaciers retreat and transition from marine‐ to land‐terminating, the impacts of shifting meltwater delivery depth on fjord dynamics remain poorly understood. We collected 150 in situ measurements of suspended sediment concentrations (SSCs) in South Greenland fjords and used them to establish an empirical relationship between satellite‐derived surface reflectance and SSC, enabling an 11‐year time series (2013–2023) of fjord‐averaged SSC to assess fjord response to the retreat of Qalerallit Sermia, South Greenland. Despite a ∼1.6 km retreat and transition from 8% to 83% land‐terminating, average fjord SSC remained seasonally consistent. These results suggest that despite significant retreat during the study period, there was no detectable change in fjord‐averaged surface SSC, either because surface meltwater delivery remained stable throughout the transition or because any changes in meltwater routing primarily affected subsurface layers below the detection capabilities of our remote sensing approach. Our findings indicate that fjord surface sediment dynamics may not directly track glacier retreat in systems where the average grounding depths are shallow (