Observations since the 1950s suggest that the Arctic climate system is changing in response to rising global air temperatures. These changes include an intensified hydrological cycle, Arctic sea ice decline, and increasing Greenland glacial melt. Here we use new δ18O data from the East Greenland Current system at Cape Farewell and Denmark Strait to determine the relative proportions of the freshwater components within the East Greenland Current and East Greenland Coastal Current. Through the comparison of these new data with historical studies, we gain insight into the changing Arctic freshwater balance. We detect three key shifts in the net freshwater component δ18O values, these are (1) a shift to lighter values in the late 1990s that possibly indicates an increased Greenland glacial melt or a reduced sea ice melt admixture and (2) a short-term shift to a ∼10‰ heavier value in 2005 followed by (3) a shift back to the historic average value in 2008. The latter fluctuation reflects a short-term dramatic rise and fall of sea ice meltwater addition into the East Greenland Current system. We infer that this anomalously large inclusion of sea ice meltwater resulted from a short-term peak in Arctic sea ice export via Fram Strait. Our findings, therefore, suggest that the freshwater carried in the East Greenland Current system is susceptible to short-term, high-amplitude changes in the upstream freshwater balance, which may have important ramifications for the global thermohaline circulation through the suppression of deep water formation in the North Atlantic.