Guest editorial: Relationships between coastal sea level and large-scale ocean circulation

Several hundred million people currently live in low-lying coastal regions, and this number will continue to increase in the coming decades. While some coastal areas are already being inundated by rising sea level, many others will also increasingly suffer from sea level rise and more intense extreme water levels during high tides, winter storms and hurricanes in the near future. Many oceanographic factors associated with both local and large-scale variability can influence coastal sea level, from hours to more than decades. Despite this coastal–open ocean link, differences exist between sea levels observed at the coast and over adjacent shallow and deep ocean regions. Distinct coastal sea level variability can arise, for example, due to coastally trapped waves and shelf currents, localized tidal resonances, bathymetric controls and small-scale features in atmospheric forcing. Identifying important influencing factors is essential for understanding, simulating and ultimately predicting sea level variability at the coast—a key societal concern in the context of our changing climate. In practice, this poses a huge and complex scientific challenge because it is region specific and timescale dependent and involves bringing multi-disciplinary expertise together.