Sea ice loss enhances wave action at the Arctic coast

Erosion rates of permafrost coasts along the Beaufort Sea accelerated over the past 50 years synchronously with Arctic‐wide declines in sea ice extent, suggesting a causal relationship between the two. A fetch‐limited wave model driven by sea ice position and local wind data from northern Alaska indicates that the exposure of permafrost bluffs to seawater increased by a factor of 2.5 during 1979–2009. The duration of the open water season expanded from ∼45 days to ∼95 days. Open water expanded more rapidly toward the fall (∼0.92 day yr⁻¹), when sea surface temperatures are cooler, than into the mid‐summer (∼0.71 days yr⁻¹).Time‐lapse imagery demonstrates the relatively efficient erosive action of a single storm in August. Sea surface temperatures have already decreased significantly by fall, reducing the potential impact of thermal erosion due to fall season storm waves.