Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Abstract

Marine-terminating outlet glaciers discharge mass through iceberg calving, submarine melting, and meltwater run-off. While calving can be quantified by in situ and remote-sensing observations, meltwater run-off, the subglacial transport of meltwater, and submarine melting are not well constrained due to inherent difficulties observing the subglacial and proglacial environments at tidewater glaciers. Remote-sensing and in situ measurements of surface sediment plumes, and their suspended sediment concentration (SSC), have been used as a proxy for glacier meltwater run-off. However, this relationship between satellite reflectance and SSC has predominantly been established using land-terminating glaciers. Here, we use two Svalbard tidewater glaciers to establish a well-constrained relationship between Landsat-8 surface reflecance and SSC and argue that it can be used to measure relative meltwater runoff at tidewater glaciers throughout a summer melt season. We find the highest correlation between SSCs and Landsat-8 surface reflectance by using the red + NIR band combination (r 2 = 0.76). The highest correlation between SSCs and in situ field spectrometer measurements is in the 740-800 nm wavelength range (r 2 = 0.85), a spectral range not currently measured by Landsat. Additionally, we find that in situ and Landsat-8 measurements for surface reflectance of SSCs are not interchangeable and therefore establish a relationship for each detection method. We then use the Landsat-8 relationship to calculate total surface sediment load, finding a strong correlation between total surface sediment load and a proxy for meltwater run-off (r 2 ≥ 0.89). Our results establish a new metric to calculate SSCs from Landsat-8 surface reflectance and demonstrate how the SSC of subglacial sediment plumes can be used to monitor relative seasonal meltwater discharge at tidewater glaciers. ARTICLE HISTORY

Automatic detection of calving events from time-lapse imagery at Tunabreen, Svalbard

“…1b). The main subglacial plume, plume 1, is described in detail in Schild et al (2017). A second subglacial plume, plume 2, less visible, is intermittently present on the pictures (see Fig.…”

Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations

“…Specifically, temperature and conductivity readings (from which salinity measurements were derived) were collected at the fjord surface and at depths of 2.5, 5, 7.5, 10, and 12.5 m below sea level (b.s.l.) (Schild, 2017). All of these measurements (including the location of each spot measurement) are included as supplementary material.…”

Investigation of Sediment-Rich Glacial Meltwater Plumes Using a High-Resolution Multispectral Sensor Mounted on an Unmanned Aerial Vehicle

“…These results are similar to data from previous research in the Arctic, where red light reflectance provided by satellite imagery was affected by the water turbidity values. From these studies, the determination coefficients were r 2 = 0.70 for Landsat 8 [61] and r 2 = 0.90 [62] and r 2 = 0.89 [13] for the Moderate Resolution Imaging Spectroradiometer (MODIS).…”