On the relationship between atmospheric rivers and high sea water levels along the U.S. West Coast

Atmospheric rivers (ARs) are narrow filaments of high moisture transported within extratropical systems. The role of ARs as drivers of heavy precipitation and flooding has been well documented; however, little is known about the contribution of landfalling ARs to high sea water levels, which are the leading cause of coastal flooding. Here we assess the relationship between ARs and extreme hourly sea level time series at 15 tide gauges along the continental U.S. Pacific Coast. Results indicate that ARs are associated with 15% to 50% of the annual sea level maxima before (and 22% to 65% after) removing tidal oscillations. Strong associations are also found when using other high sea level metrics. From a climatic perspective, the frequency of extreme hourly sea levels tends to increase during the negative phase of the Arctic Oscillation and during the positive phases of the Pacific-North American pattern and the El Niño–Southern Oscillation.