Ocean acidification is occurring at a rapid and accelerating pace, and the Arctic Ocean is on the frontline of this global change. AMAP’s 2013 assessment of Arctic Ocean acidification provides the first Arctic-wide perspective on today’s progressively increasing seawater acidity. The assessment report presents current scientific knowledge on the changing state of ocean acidification in the Arctic and how these changes are affecting the Arctic marine environment. In addition to reporting on what is happening now, the assessment considers how these changes could continue to develop in the future and what this could mean for Arctic marine plants and animals and Arctic peoples.