**Abstract**

It is broadly recognized that the Arctic area has become highly popular for hosting new activities and new infrastructure. This is due to the combination of the need of exploring new areas to satisfy the ever increased energy demand and also the impact of climate change that has created paths for increased trading and maritime activities. Presently, the Arctic environment poses new challenges and unknown hazards, which are considered unpredictable due to the uncertainties of the emerging phenomena. In this chapter, the effects caused by the higher temperatures in the Arctic region on the increased height of waves and storm surges and the extended erosion of the Arctic coastline are examined and presented. This unpredictability is partly due to the dynamic behavior of the Arctic environment and the annual fluctuations of the permanent ice of the Arctic Ocean. Reduced ice coverage, especially during the fall period, creates longer available sea distances for waves to be developed. As extreme case scenario, the associated consequences for the design wave height on a totally ice-free sea are studied. A comparison between the heights of the waves which are generated by the longest possible fetches and those estimated from today's ice limit situation is made based on coastal engineering methods. Further to this, more open sea areas also allow for increased storm surge heights. In the chapter, it is also shown how the decreased ice coverage has an influence on the coastal erosion phenomenon, which is not only enhanced due to the evolving wave dynamics but also thermodynamics and sediment dynamics. The presented results show significant changes of the characteristic wave heights and strong increase of the pace of the coastal erosion. Based on these observations, the authors of this chapter want to stress the challenges that such future conditions in the Arctic area will pose to any Arctic operations, nearby infrastructures and human activities in the area.

**Keywords:** Arctic Ocean, free ice sea, extreme wave heights, permafrost melting, shore erosion
