Salinity and stable oxygen isotope (δ18O) data collected from eight estuaries distributed throughout the Canadian Arctic Archipelago were used to apportion contributions from local meteoric water (MW) and sea ice meltwater (SIM) sources during July and August of 2015 and 2016. The size of the rivers flowing into the estuaries varied by an order of magnitude (in terms of mean annual discharge); however, the inventories of MW were always greater or equal to SIM inventories, indicating that MW was the dominant freshwater source. Residence times of MW generally ranged between 1 and 8 days, with longer times (> 20 days) computed for estuaries in the Somerset Island and Baffin Island regions. Shorter residence times indicate, but do not confirm, that river waters move through the estuaries and proceed offshore relatively quickly. Despite this swift transport, nonconservative behaviors were observed for barium and dissolved organic carbon (DOC). These behaviors were identified via examination of total alkalinity, barium, and DOC concentrations that remained after accounting for contributions from MW and seawater . Remaining concentrations/anomalies that deviated significantly from a linear correlation with SIM were attributed to nonconservative behaviors (e.g., desorption of barium from river-borne particles, remineralization of DOC) or inaccurate assignments of endmember values in the water type analyses. Thus, these anomalies offer a means to better inform water type analyses in the correct assignment of endmember properties that best represent the environment studied.