Identification and classification of storm surge events at Red Dog Dock, Alaska, 2004–2014

Powerful storms in the Bering and Chukchi Seas west of Alaska frequently bring high winds that drive positive and negative surge events (storm surges). Positive surge events can cause inundation of coastal regions, extending far inland in low-relief locations. A 10-year record (2004–2014) of water level data from Red Dog Dock located to the north of the Bering Strait on the Alaskan coast was analysed for observed severe surge events. A climatology of events was developed, in which event occurrences were grouped by temporal evolution of the event. The length of time (speed) it took for a given storm system to move over the region largely dictated the temporal evolution of the surge events. The mapped time series evolution of the measured storm surge was grouped into four distinct surge event types. The primary synoptic control on these events is the orientation of the pressure gradient caused by the passage of low-pressure systems. The orientation of the pressure gradient, and therefore dominant wind direction, determine the magnitude, duration, and positive or negative storm surge inundation. The climatology resulted in 44 observed events—21 positive, 23 negative—that tended to occur during the months of November, December, and January. It was also noted that surges also regularly occurred when sea-ice cover was present. The primary synoptic forcing mechanism for positive surges was an extra-tropical cyclone positioned over the North Bering Sea/Chukotka Peninsula area, and for negative surges, an extra-tropical cyclone positioned over the Alaska Peninsula/western Gulf of Alaska.