F/V Tronio conducted CTD deployments in Subarea 48.6 during February-March in 2020, 2021, 2024 and 2025, using two types of CTD equipment: Valeport FastCTD Profilers in 2020-2021 and SeaStar 9.32 CTD in 2024-2025.
According to the T-profiles, the surface (0–10 m) and subsurface (10–50 m) temperatures in 2024 and 2025 were higher than in 2020 and 2021 in both RB4 and RB5. These findings are consistent with SST dynamics and with the sea ice concentration (SIC) distribution in the area.
Vertical mixing occurs in the upper 0–50 m, whereas the 50–200 m layer is strongly stratified and vertically stable. Below 200 m, mixing is minimal, which is consistent with the density structure illustrated by the T–S diagram. Reliable salinity measurements were only available in 2020–2021; therefore, density- and T–S-based analyses are restricted to these years. For 2024–2025, analyses are restricted to temperature-only diagnostics.