The Impact of Glacial Suspension Color on the Relationship Between Its Properties and Marine Water Spectral Reflectance

Abstract

This study enabled us to determine the sources of sediment for glacial catchments and investigate the differences in properties, i.e., suspended sediment concentration (SSC), turbidity measured in the laboratory (TLAB) and in the field (TF), mean particle diameter (MPD), and chemical composition, between two different-colored sediments that flowed from the glacier terminus. Additionally, the relationship between these properties for two types of suspensions and remote sensing reflectance (RRS) was tested, and the factor with the greatest impact on the value of RRS was determined. The results showed that within one catchment area, there were four sediment sources that provide white (S.1) and red (S.2) sediment. Chemical analysis showed that the differences in sediment color may be influenced by the increased content of carbonates in the white sediment (S.1). The S.2 sediment is characterized by mean TLAB, TF, and SSC values higher than 26.6 formazine nephelometric units (FNU), 13.5 FNU, and 50 mg/L, respectively, and the mean MPD was 4.25 lower than that of the S.1 sediment. However, the red sediment had on average 0.1 lower RRS than the white sediment. In addition, the properties of S.1 correlated better with reflectance, reaching a maximum correlation of 0.69 (SSC/RRS 770–810 nm), while S.2 exhibited a negative correlation in 7 out of 12 cases, reaching a maximum correlation of 0.16 (TLAB/SSC/RRS 730–740 nm) and a negative correlation of −0.37 (SSC/RRS 530–570 nm). This result indicated that sediment color may be a key factor in the dependence of glacial suspension properties and spectral reflectance.