Influence of suspended particulate matter on the optical properties of seawater in the western Eurasian Arctic shelf

Abstract

This comparative study discusses the concentration and major phase composition of suspended particulate matter (SPM) derived from observations collected in the White, Barents and Kara seas in 2001-2021. A selective synthesis is based on our field data on SPM concentrations obtained from water samples and optical data determined from beam attenuation coefficient and light scattering revealed a pronounced difference of seawater optical properties of the western Arctic shelf of Eurasia. The heterogeneous origin of SPM in the studied Arctic seas largely determines different particle size distribution (PSD) and major phase composition of particulate matter in this region. This impacts the optical properties of the water column and hence primary production and sedimentation processes on the western Eurasian Arctic shelf. In recent decades, the dramatic changes in the Arctic climate system, including sea ice, affecting the concentration and composition of SPM as well as optical properties of sea water on the Barents Sea shelf becomes close to ice-free and seasonally ice-free shelves of the White and Kara seas. A pronounced benthic nepheloid layer (BNL) was reveled widespread in the studied seas but it has different thickness and SPM concentration. SPM distribution in the euphotic zone of the seas is much differs due to mostly various catchment-derived material, including river discharge (particulate and dissolved), and other natural geographical conditions. It is necessary to develop regional and seasonal algorithms linking in situ data with remote sensing of bio-optical characteristics of sea water of the Eurasian Arctic shelf.

Characterization of suspended particulate matter in the South Kara Sea (Arctic Ocean) in September 2022 as part of the climate experiment

“…Beam C(530) is linearly correlated with SPM concentration where the composition and size distribution are uniform 18,23 . In the Kara Sea, the R 2 coefficient of linear dependence of C(530) vs. SPM mass concentration reached 0.97 and in some cases -0.99 due to the high contribution of fine terrigenous particles less than 20 μm 24 . The reliable correlation between the volume concentration of SPM derived from LISST-Deep and chlorophyll fluorescence indicates that the volume concentrations primarily reflects the biogenic particles 19 .…”

“…Therefore volume concentration can be a proxy for biogenic particles, especially in the top of water column. The presence of two particle populations (or bimodality) is a characteristic feature of the particle size distribution in the euphotic zone of the water column 24 . Therefore, we consider separately the characteristics of SPM in the surface layer and in the water column.…”