Trends toward increased temperatures, reduced sea ice extent, and longer open water seasons have resulted in changing Arctic ecosystem dynamics. Expected changes include shifts in distribution and abundance of prey species for seabirds and marine mammals. Using stable isotope analysis, we studied spatial and interannual variation in ringed seal (Pusa hispida) feeding ecology in Hudson Bay in relation to environmental variables, between 2003 and 2010. Ringed seal muscle and hair samples collected from Arviat and Sanikiluaq, Nunavut, were analyzed for stable isotope ratios of nitrogen (δ15N) and carbon (δ13C). Seals from western Hudson Bay (Arviat) had higher δ15N and lower δ13C than seals from eastern Hudson Bay (Sanikiluaq), and stable isotope ratios varied interannually within each region. Peak δ15N occurred in years with spring air temperatures between approximately −5°C and −2°C. This temperature range was characteristic of warm years in western Hudson Bay and cool years in eastern Hudson Bay. We hypothesize that the high δ15N observed in ringed seals is indicative of greater importance of capelin (Mallotus villosus) in ringed seal diet. A comparison of ringed seal isotopic niche widths indicated greater dietary differences between western and eastern Hudson Bay with warming, suggesting a possible ecological divergence related to climate change.