"A clearer understanding of how Arctic marine ecosystems will react to global changes is essential and urgent. Indeed, while ecological responses to climate change are evident across many ecosystems, the largest changes are predicted in the Polar Regions, and especially in the Arctic where there is growing evidence for warming trends. I therefore propose to lead a comprehensive study of the potential consequences of ongoing and future climate change upon seabirds, an essential component of these fragile ecosystems. More specifically, I will focus this project on the little auk (Alle alle) during its mysterious wintering season. These Arctic diving seabirds that feed on zooplankton are among the smallest (150g), yet they are the most abundant (>80 million) seabird species in the North Atlantic and potentially feature powerful ecological indicators of regional food webs. I will use new and trans-disciplinary approaches combining biotelemetry, bioenergetic modelling, ice-associated biomarkers or stable isotope analysis to study impacts of climate change on the distribution, survival and population dynamics of this seabird species at a large geographical scale (the North Atlantic) by studying and comparing populations distributed across its whole range of distribution. I will firstly provide detailed knowledge of little auk wintering grounds and of their phenotypic plasticity when facing ongoing global changes. Then, I will model and predict how their winter distribution will be affected by a change of their surrounding energetic environment (including both climate and resource) and by sea-ice retreat. Finally, I will estimate indirect consequences of these environmental changes on little auk survival and on their population dynamics. This project will thereby serve seabird conservation strategies and will provide crucial information to understand future consequences of climate change upon the entire North Atlantic and Arctic food webs and ecosystems."