Sensitivity of ferry services to the western isles of Scotland to changes in wave climate

The Western Isles of Scotland and the rest of the Highlands and Islands of Scotland is a remote, sparsely populated region with a high dependency on marine activities. In particular, ferry services are vital to the region. At the same time, the seas to the west and north of Scotland are among the roughest in the world during autumn and winter, making maintenance of a reliable ferry service both difficult and expensive. Ferry routes avoid the open ocean, but some waters are exposed to ocean waves. The inter-annual variability of the ocean wave climate to the west is very high, primarily in response to the North Atlantic Oscillation (NAO). This sensitivity to NAO extends to partially sheltered waters and ferry routes. A deterioration in wave climate in response to either natural variability of the NAO, or as a regional response to anthropogenic climate change is distinctly possible. By analyzing the contemporary response to shifts in the NAO, there is predicted to be a disproportionately large increase in ferry service disruption in response to any deterioration in wave climate.