It is essential to reach a better understanding of ecological processes in the Arctic, as this ecoregion is hit severely by the consequences of global change. In this context, we study the ecophysiology of little auks (Alle alle), which are the most abundant seabirds of the Arctic, and acknowledged ecological indicators of changing marine ecosystems in this polar region. Via a long-term study of little auks breeding in East Greenland (Liverpool Land), in place since 2005, but also through specific experimental and modelling approaches, as well as through a panarctic network of collaborations, we test the following hypotheses: (1) Arctic climate change is impacting the trophic status, the foraging ecology, the reproductive output, the body condition and the multi-annual survival of adult little auks during the breeding season. (2) Ongoing climate change impacts the migratory ecophysiology of little auks in the North Atlantic. (3) Global warming, sea ice shrinking and mercury exposure synergetically affect the ecophysiology of little auks and other arctic seabirds (4) The pan-arctic seabird community functions as a natural monitoring network for both legacy and emerging contaminants. (5) Past climatic fluctuations and competition with other seabirds and marine mammals had a stronger incidence on little auk populations than current global warming. All of our work participates in the Circumpolar Biodiversity Monitoring Programme (CBMP) of the working group Conservation of Arctic Flora and Fauna (CAFF) of the Arctic Council, and therefore corresponds to the expectations of arctic peoples in terms of environmental research.