We present {the} Arctic atmospheric river (AR) climatology based on; twelve {sets of} labels derived from ERA5 and MERRA-2 reanalyses for; 1980–2019. The ARs were identified and tracked in the 3-hourly; reanalysis data with a multifactorial approach based on either; atmospheric column-integrated water vapor ($IWV$) or integrated water; vapor transport ($IVT$) exceeding one of the three climate thresholds; (75th, 85th, and 95th percentiles). Time series analysis of the AR event; counts from the AR labels showed overall upward trends from the; mid-1990s to 2019. The 75th $IVT$- and $IWV$-based labels, as well; as the 85th $IWV$-based labels, are likely more sensitive to Arctic; surface warming, therefore, detected some broadening of AR-affected; areas over time, while the rest of the labels did not.; ; Spatial exploratory analysis of these labels revealed that the AR; frequency of occurrence maxima shifted poleward from over-land in; 1980–1999 to over the Arctic Ocean and its outlying Seas in 2000–2019.; Regions across the Atlantic, the Arctic, to the Pacific Oceans trended; higher AR occurrence, surface temperature, and column-integrated; moisture. Meanwhile, ARs were increasingly responsible for the rising; moisture transport into the Arctic. Even though the increase of Arctic; AR occurrence was primarily associated with long-term Arctic surface; warming and moistening, the effects of changing atmospheric circulation; could stand out locally, such as on the Pacific side over the Chukchi; Sea. The changing teleconnection patterns strongly modulated AR; activities in time and space, with prominent anomalies in the; Arctic-Pacific sector during the latest decade. Besides, the extreme; events identified by the 95th-percentile labels displayed the most; significant changes and were most influenced by the teleconnection; patterns. The twelve Arctic AR labels and the detailed graphics in the; atlas can help navigate the uncertainty of detecting and quantifying; Arctic ARs and their associated effects in current and future studies.;
