## 4 Results
### Dependency of Particle Trajectory on the Time of Release  
In the first experiment, 12 particles of each size released once a month during 2016 were considered. To illustrate that, in most cases, the trajectories of particles of various sizes differ significantly, we chose 4 months in different seasons. Figures 3 and 4 show the trajectories and vertical positions of 0.5 mm and 0.01 mm particles, respectively. The inserts in Figures 3 and 4 demonstrate the differences in the sinking rates of particles of different sizes and the oscillatory behavior of their vertical motion. Figure 3: Model trajectories for selected 0.5 mm particles that were released in the Kara Sea shelf in 2016: March (Mr05, magenta), May (M05, green), October (Oc05, brown), and December (D05, blue). The insets in the corners of the figure illustrate the time series of the immersion depth in the sea for each particle. Positive depth values indicate that the particles are frozen in the ice. The 0.5 mm particle released in March (Mr05, Figure 3, magenta line) crossed the Kara Sea and ended up in the Barents Sea. Immediately after its release, Mr05 was incorporated into the sea ice (the inset for Mr05 in Figure 3 shows positive values). It moved slowly with the ice around the release site. The output of the SibCIOM model indicated that in the winter of 2016, atmospheric dynamics did not force intensive ice transport away from the particle release area. In summer, as the ice melted, the particle gradually settled to the bottom of the Kara Sea, caused by biofouling, as reflected in the constant value of the immersion depth in the inset figure. In winter, the particle rose to the surface due to biofilm degradation and remained in the sea ice for a considerable amount of time, except for short periods when it was released to the sea surface (the inset for Mr05 in Figure 3). Moved by ice drift, it left the Kara Sea and entered the Barents Sea (see Supplementary Materials, Figure S1 for ice drift images). In the summer of 2019, this particle was released from the ice and submerged in water. For the remainder of the calculation, the particle could not be embedded in ice because its trajectory was determined by the Barents Sea Branch of the Atlantic Water (see Supplementary Materials, Figure S2 for ocean circulation images). The intense oscillation and immersion of the particle, forced by the biofouling, to a depth of more than 300 m, as seen in the figure, was also related to its spatial location in the region of warm Atlantic waters. Unlike Mr05, the Mr001 particle (ejected in March, \(d=0.01\) mm) did not travel beyond the Kara Sea, remaining within the shelf the entire time (Figure 4, magenta line). Initially, the Mr001 particle was frozen like Mr05, but after the ice melted, Mr001 quickly sank to the bottom. In about a year, the particle rose to the surface and was frozen again for a short time. Since it was in the water for most of the time, it moved in close proximity to the coast and reached the northern point of Novaya Zemlya at the end of the analyzed period according to the Kara Sea currents (Supplementary Materials, Figure S2a). The plot of  
Figure 4: Model trajectories for selected 0.01 mm particles that were released in the Kara Sea shelf in 2016: March (Mr001, magenta), May (M001, green), October (Oc001, brown), and December (D001, blue). The insets in the corners of the figure illustrate the time series of the immersion depth in the sea for each particle. Positive depth values indicate that the particles are frozen in the ice. location depth shows the repeated fast submergence and slow ascent of the Mr001 particle with small-amplitude oscillation (inset for Mr001 in Figure 4, magenta line). Particles M05 (\(d=0.5\) mm) and M001 (\(d=0.01\) mm), released in May, began to submerge in June (Figures 3 and 4, green lines). The smaller particle sank quickly to the bottom, while the larger particle sank more slowly, allowing it to be entrained by surface currents. As the biofilm disappeared, both particles began to rise to the surface.