In a world where the climate is changing at a rate not exceeded in the geological record, the Arctic is on the front lines, experiencing the most rapid warming of any region on the planet. Once considered remote and disconnected, now we know that changes within the Arctic can have a direct impact on the rest of the world, affecting physical and biological systems near and far at regional and global scales. Such changes range from how much solar radiation the region reflects back into space to the structure of the ecological communities in Arctic waters; meanwhile, melting permafrost is driving the transformation of frozen tundra into wetlands, and grassy plains are shifting into lusher landscapes of bushes and trees. To understand the scope and details of these changes, scientists have intensified their efforts across all areas of Arctic research. This collection highlights some of their most important and interesting findings, as published in the pages of Science as well as in other journals, offering an overview of the direction of the field.