Strong high-frequency sea level oscillations observed along the U.S. East Coast between 2006 and 2011

A systematic survey of high-frequency sea level oscillations (< 6 h) has been performed using raw 1-min resolution sea level data taken along the U.S. East Coast. Twenty tide gauge stations have been used in the survey, with data coverage spanning from 2006 to 2011. Several quality check analyses indicated a number of problems with a 1-min raw data, from a presence of isolated spikes, gaps in the time series and sometimes several hours of continuous aberrant values. After removing bad quality data, the nine most intense high-frequency sea level events were identified, with recorded maximum wave heights ranging from 40 to 100 cm. The study of the strongest waves among these nine events enabled us to highlight different generation and propagation mechanisms. Waves with highest periods (5-6h) were found to propagate along the coast and to be a significant contributor to the strongest observed oscillations. Our study suggests that these waves are coastal waves trapped topographically as edge waves, presumably generated by a landfall of a cyclone. Shorter period waves (1h-5h) with a standing nature were also observed over some enclosed shelf areas, having around a meter crest-to-trough maximum value. Their high amplitudes are presumably a result of efficient energy transfer from the atmosphere towards the sea through different resonance mechanisms, the Proudman resonance over a wide shelf and the harbor resonance in coastal embayments. Phase lag of 2-3 hours between the atmospheric forcing and the observed sharp sea level oscillations have been observed at some stations, being characterized by an energetic atmospheric disturbance propagating offshore. These disturbances created long ocean waves that were topographically channeled towards the shelf break, then reflected and amplified towards the coastline. The importance of a proper data quality control should be emphasized and a need for 1-min sea level quality-checked data for research purposes emerged from the study. Also, an assessment of the importance and efficiency of wide shelves in trapping and amplifying high-frequency energy from the atmosphere may follow, through an inter-comparison of sea level data along both U.S. East and West coasts. A reproduction of the observed oscillations is a part of a future work, which will include an assessment of a generating force in the atmosphere, allowing for a better prevention of potential flooding along the U.S. East Coast.