The cold Malvinas Current (MC) is one of the main circulation patterns in the southwestern South Atlantic Ocean (Peterson & Whitworth III, 1989). This current originates as a branch of the Antarctic Circumpolar Current (ACC) (Provost et al., 1996), rounds east of the Falklands/Malvinas Islands, and flows northward along the continental slope of South America (Figure 1) (Willson & Rees, 2000). The MC follows the Subantarctic Front (SAF), one of three main fronts of the ACC in the Drake Passage (Barre et al., 2011;Sokolov & Rintoul, 2009). It is generally accepted that the MC starts near the Burdwood Bank at around 55°S; upstream from the sharp northward turn of the SAF, the flow is referred to as the northern branch of the ACC (Artana et al., 2016). At approximately 38°S, the MC meets with the Brazil Current, generating a thermohaline front known as the Brazil Malvinas Confluence zone (Brennecke, 1921;Deacon, 1937). Further downstream, both currents retroflect and instabilities generate prominent mesoscale structures (Chelton et al., 1990;Zyrjanov & Severov, 1979). On average, the front intersects the

The inflow of warm and saline Atlantic water from the North Atlantic to the Western Arctic is provided by two branches, namely, the Fram Strait branch water and the Barents Sea branch water. The pathways of these branches merge at the St. Anna Trough, and then both branches propagate eastward along the continental slope, albeit at different depths. As a result, the local interaction between these branches in the trough affects the properties of the large-scale Atlantic water flow to the Eastern Arctic and the deep Arctic basins. In this study, we report extensively in situ measurements with high spatial coverage (56 hydrological stations organized into 7 transects) in the St. Anna Trough, obtained in August and October 2021. Based on these data, we reconstructed the thermohaline structure and circulation in this area and obtained new insights, which are crucial for the assessment of the interaction and heat balance of water masses in the trough. First, we state that the majority of the Fram Strait branch water is recirculated in the trough within the stable cyclonic gyre, while a smaller fraction returns to the continental slope. The formation of this gyre increases the residence time of the Fram Strait branch water in the trough and decreases the intensity of water and heat exchange between the trough and the continental slope. Second, we describe the dynamic interaction between the northward flow of the Barents Sea branch water and the surface layer. It causes intense transport of warm surface water from the Kara and Barents seas adjacent to the Novaya Zemlya toward the continental slope and its mixing with the Barents Sea branch water along the eastern part of the trough. These processes result in increased surface temperature at the eastern part of the trough, which enhances ice melting at the study area and increases the duration of the ice-free period.

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Seawater properties in two intense rings in the South Atlantic are considered. One ring separated from the Brazil Current and the other from the Malvinas Current. The analysis is based on the CTD casts and SADCP measurements from the onboard velocity profiler. The optical properties, chemical parameters, methane concentration, and biological properties such as primary production, plankton, and fish were also analyzed. Analysis of strong differences between the eddies is supplemented by observations of whales and birds in the region.

The detailed environmental survey of the coastal zone of the Kaliningrad Region northern coast was carried out. The pollutants distribution in the silty clay fraction and calculation of ecological indexes allowed the evaluation of distribution of potentially harmful elements (PHEs). The sources of pollution in the most intensively used areas were identified, and transit and accumulation zones were allocated. A large area of anomalous content of PHEs was revealed on the underwater coastal slope of the Curonian Spit National Park, which is situated far from the sources of pollution. The alongshore bed load transport provides the contamination of the underwater slope whereas the beaches are less exposed to pollution.