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Atlantic water (AW) carries large amounts of salt, oceanic heat, and biological richness into the Arctic Ocean. The inflow of AW has a twobranch structure via the West Spitsbergen Current (WSC) in the Fram Strait and the Barents Sea Opening (BSO), and the impact of AW on the Arctic Ocean ecosystem depends on the entrance route. Using data collected during the summers of 2001-2014, the zooplankton standing stock and community structure were studied in these two branches. Generally, there was a higher abundance and biomass of Calanus finmarchicus in the BSO than in the WSC, where Oithona spp. numerically dominated. The observed AW temperature and volume flux modifications measurably affected zooplankton variability, with additional effects likely related to diverse contributions of advected and local zooplankton production. During the study period, the AW temperature in both branches increased noticeably but in an oscillating manner. This gradual change manifested as C. finmarchicus forming an increasing proportion of the biomass. The high abundances of Oithona spp. (predominantly O. similis) and C. finmarchicus were attributed to warm AW temperature anomalies. During the warm event in 2011, predomination of young copepodids of C. finmarchicus in the WSC was observed, which represented probably the second generation of the species, reported from this region for the first time. The obtained results show the effects of warming on the zooplankton community transported with the Atlantic water, before they enter the Arctic Ocean. In practical terms, the findings can be used to construct and tune the plankton components of ecosystem models. [ABSTRACT FROM AUTHOR]