The Arctic hydrological cycle undergoes rapid and pronounced changes, including marine and terrestrial ice loss, increased atmospheric humidity, shifting ocean circulation regimes, and changes in the magnitude and frequency of extreme weather events. Stable water isotopes (δ18O, δ2H) and the secondary parameter d-excess can be used to trace the processes within this new evaporative system including the potential feedback of them into the global climate system. However, characteristics of δ18O, δ2H and d-excess and the processes governing them are yet to be quantified across the Arctic due to a lack of long-term empirical data. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provided a unique opportunity to collect, analyze, and synthesize discrete samples of the different hydrological compartments in the central Arctic, covering a complete seasonal cycle over the course one year. These observations can lead to a new insight into coupled climate processes operating in the Arctic. Here, we present the isotopic traits of more than 1,900 discrete samples (i.e., seawater, sea ice, snow, brine, frost flower, lead ice, ridge ice). We found that: (i) average seawater δ18O of -1.7‰ conforms to observed and modelled isotopic traits of the Arctic Ocean with more depleted seawater closer to the north pole in winter and relatively enriched seawater in lower latitudes in spring; (ii) second year ice is relatively depleted compared to first year ice with average δ18O values of -3.1‰ and -0.7‰, respectively. This might be due to post-depositional exchange processes with snow; (iii) snow has the most depleted isotopic signature among all compartments (mean δ18O=-15.1‰) and a gradual enrichment trend in snow profiles from top to bottom might be partially due to sublimation of deposited snow. Our dataset provides an unprecedented description of the present-day isotopic composition of the Arctic water covering a complete seasonal cycle. We try to assess the relative contribution of snow, sea ice, leads, and melt ponds spatially and temporally on regional and local moisture in the Arctic. This will ultimately contribute to resolve the linkages between sea ice, ocean, and atmosphere during critical transitions from frozen ocean to open water conditions.