## 4 Results
### Dependency of Particle Trajectory on the Time of Release
The figures show that the larger particle rose much faster than the smaller particle. As a result, particle M05, which was frozen in the ice, moved out of the Kara Sea and into the deep region. The inset in Figure 3 for M05 shows that the particle was mostly incorporated into the sea ice. Moving with the sea ice (Supplementary Materials, Figure S1b) along the continental slope region in the Laptev Sea, M05 appeared in the ice-free region in the summer months. The extreme warming of the Arctic shelves and adjacent northern regions at the end of the second decade of the 21 st century, analyzed both on the basis of observations and SibCIGM model output, was discussed in [70]. A positive sea surface temperature, which was unusual for this region, resulted in the biofouling of M05, but its immersion was short-lived since the subsurface layer in the water column was very cold. The small particle, M001, remained on the shelf (Figure 4, green line) for the entire period. The particle moved in the same area as Mr001 (Figure 4, magenta line), but their trajectories were different. The character of vertical displacement was similar for these particles, namely rapid submergence during biofilm formation and slow rise during biofilm disappearance (Figure 4, insets Mr001 and M001). However, unlike Mr001, M001, due to its movement towards a slightly northern position, was incorporated into the ice each winter. In contrast to the previous cases, the trajectories of particles Oc05 (\(d=0.5\) mm) and Oc001 (\(d=0.01\) mm), released in October (Figures 3 and 4, brown lines), practically coincide during the first half of the calculation. The initial reason for this result was the unfavorable environment for biofouling in October, as indicated by the absence of chlorophyll-a in the release area. Both particles remained in the surface layer and were subject to the same current fields. Subsequently, the particles were frozen into the ice and transported to the north, beyond the shelf. Having been in the ice for an extended period of time, they followed identical pathways. As a consequence of the particles movement with ice drift (Supplementary Materials, Figure S1), they approached the vicinity of Spitsbergen; the region of entry for Atlantic warm water into the Arctic Ocean. At this point, particles Oc05 and Oc001 were released into the ocean, resulting in discernible differences in their subsequent trajectories. The smaller particle Oc001 (Figure 1, brown line) sank to the bottom layer and was unable to rise to the surface due to the formation of a heavy biofilm, which was favored by the conditions for biofilm growth, even during the winter season. In contrast, the larger Oc05 (Figure 3, brown line) demonstrated a greater degree of mobility, exhibiting multiple periods of sinking and rising before reaching the ocean surface, where it became embedded into the sea ice. Subsequently, the ice drift contributed to its transport to the Greenland Sea, where it was carried by an intense surface current, ultimately making its way around Greenland. Another variant of different trajectories is demonstrated by particles D05 (\(d=0.5\) mm) and D001 (\(d=0.01\) mm) released in December (Figures 3 and 4, blue lines). After their release, both particles were simultaneously frozen into the ice, where they remained until next July (Figure 5a). During this period, their trajectories, determined by ice drift, coincided. Once in seawater due to ice melting, the particles began to accumulate biofilms that led to their submersion. To clarify some details, we have plotted the graph of the immersion depth as well as the biofilm thickness for both particles in one image (Figure 5). The plot shows that after melting in summer 2017, particles D001 and D05 returned to the ocean with the same biofilm that had been formed in the sea ice (Figure 5a). This biofilm was gradually lost by both particles over a period of two weeks.