Graduation date: 2007Nares Strait is one of three main passages of the Canadian Archipelago that channels freshwater from the Arctic Ocean to the North Atlantic. There are very few observations regarding the role of this region on the present day Arctic freshwater budget, and even less regarding the changes in freshwater fluxes through time. Larger scale Arctic Ocean circulation features have recently been observed to shift. Such changes will likely be manifest in Nares Strait before propagating into Baffin Bay and Labrador Sea. The δ18O of the water in Nares Strait strongly co varies with salinity. We analyzed the isotopic composition of bivalve shells collected live from the Greenland and Ellesmere Island sides of the Strait in an effort to reconstruct salinity changes with time along this passage over the 5-30 m depth range where these organisms live. Specimens of Hiatella arctica and Astarte borealis collected at the northernmost station show a strong shift towards lighter δ18O values in the most recently accreted sections of their shells, which corresponds to significant freshening with salinity as low as 23. These specimens at the northern end of Nares Strait began experiencing an increase in freshwater input as far back as 20 years ago. Similar freshwater pulses occur with diminishing frequency and magnitude through the 30 and 40 year timeslices. Lesser signals occur further south, probably reflecting significant along channel mixing.