Abstract
Wind-induced sea level blowouts, measured as negative storm surge or extreme low water (ELW), produce public safety hazards and impose economic costs (e.g., to shipping). In this paper, we use a regional hydrodynamic numerical model to test the effect of historical environmental change and the time scale, direction, and magnitude of wind forcing on negative and positive surge events in the New York Harbor (NYH). Environmental sensitivity experiments show that dredging of shipping channels is an important factor affecting blowouts while changing ice cover and removal of other roughness elements are unimportant in NYH. Continuously measured water level records since 1860 show a trend towards smaller negative surge magnitudes (measured minus predicted water level) but do not show a significant change to ELW magnitudes after removing the sea-level trend. Model results suggest that the smaller negative surges occur in the deeper, dredged modern system due to a reduced tide-surge interaction, primarily through a reduced phase shift in the predicted tide. The sensitivity of surge to wind direction changes spatially with remote wind effects dominating local wind effects near NYH. Convergent coastlines that amplify positive surges also amplify negative surges, a process we term inverse coastal funneling.
Highlights
A negative surge, which occurs when the difference between observed water level and predicted astronomical tide is negative, is produced when winds “blow out” the water from a harbor or estuary
The strong currents associated with negative surge cause erosion and pose a recreational hazard, similar to the much more-often studied positive surge events
Due to their potentially large influence on water levels in the Hudson River, we evaluate their possible role in negative surges in New Jersey Harbor (NYH)
Summary
A negative surge, which occurs when the difference between observed water level and predicted astronomical tide is negative, is produced when winds “blow out” the water from a harbor or estuary ( the name “sea level blowout”). Changes to atmospheric forcing or coastal geometry can shift this balance; for example, Raicich [7] studied the trends in positive and negative surges in the Adriatic Sea and showed that the frequency of strong surges decreased over the period of study (1939–2001), while weak and moderate surges did not exhibit any clear trend. This trend was attributed to a weakening of atmospheric forcing over the period.
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