Microplastic pollution in the Arctic Ocean poses potential risks to local ecosystems, particularly as global warming accelerates sea ice loss. Although high microplastic abundances in sea ice have been documented, the relationships among microplastic distributions in different sea ice-linked environmental compartments remain unclear. Here, we investigated the occurrence and distribution of microplastics in sea ice, snow, melt-pond water, and under-ice seawater in the northwestern Arctic Ocean. Sea ice showed the highest average microplastic abundance (95.1 ± 15.2 items/L), exceeding that in snow (63.8 ± 106.4 items/L), melt-pond water (8.7 ± 11.2 items/L), and under-ice seawater (13.6 ± 10.4 items/L). Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) showed weathered morphologies on the surfaces of identified PET fibers in sea ice. An exploratory co-occurrence network based on Bray-Curtis similarity suggested that sea ice acted as a temporary reservoir for microplastics, whereas snow, melt-pond water, and under-ice seawater reflected more recent or ongoing microplastic inputs. These findings provide a scientific basis for understanding the fate and transport of microplastics in the Arctic sea ice environment.
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