Dynamics of the Iokanga River plume according to SAR and optical satellite data

The Iokanga River is one of the largest rivers of the Kola Peninsula, discharging into the southwestern part of the Barents Sea and the northern part of the White Sea. The outflows from the Iokanga River and other regional rivers form a freshened coastal water mass, which extends eastward as the Coastal Murmansk Current. However, the dynamics and variability of small river plumes, which represent a transitional form between river discharge and the coastal water mass, remain practically unexplored in this region. In this study, based on high-resolution synthetic aperture radar (SAR) and optical images, the spatial characteristics of the Iokanga plume were examined and its dynamics were analyzed during the ice-free period. The study provides an assessment of external hydrometeorological factors and their contribution to the variability of the plume positions on various time scales. Notably, a key contribution of tidal currents to the formation of the intra-daily variability of the plume was established, which is nontypical for the majority of river plumes in the Arctic Ocean. The current work also describes the main characteristics of submesoscale eddies in the Iokanga plume and analyzes the mechanisms of their formation. The obtained results are crucial for understanding the process of coastal water mass formation in the southwestern Barents Sea and for identifying potential pathways for river-borne contaminant spread. From a methodological perspective, this work may be valuable for studying the characteristics of small river plumes using SAR and optical satellite data in coastal regions, which are poorly covered by in situ measurements.