In Alaska, the Us coast guards are at the forefront of climate change during the "Arctic Shield" mission every summer, from June to September. These guardians of the Arctic intervene in really harsh conditions in a fast changing environment. The melting of the ice cap opens maritime passages and the region becomes more accessible than ever. Laurent Weyl and Sebastien Daycard-Heid had the opportunity to follow them on duty, facing an increase of maritime traffic, risks of oil spills and melting of permafrost, from the Bering Strait to the north of the Arctic circle.