This study aims to investigate natural convection phenomena in the estuarine waters of the Arctic region and to analyze the unique plume patterns and their formation mechanisms. Saline solutions of varying concentrations were prepared to simulate seawater and river water, and experiments were conducted in an acrylic tank to model the convective interactions between saltwater and freshwater at a river-sea boundary. In addition, a syringe and a custom-built tank were used to simulate localized convection and plume formation, and the plume velocities were measured under different salinity conditions. The experimental results show that when the density difference between saltwater and freshwater is small (salinity below 20 psu), the convection velocity is slower, and stable, mushroom-shaped plumes are more likely to form. Conversely, when the density difference is larger, the convection velocity increases, leading to the development of unstable, irregular plumes.