Direct and indirect wind impacts on coastal sea level along the US Atlantic and Gulf shorelines

Abstract:

Coastal communities along the US Atlantic and Gulf coasts have experienced an increased number of flooding events due to rising sea level, especially since the early 2000’s. Most severe events were caused by storm surge induced by strong winds of extreme weather systems. Other less dramatic flooding events, aka nuisance flooding, typically occur during the King tide season, between September and November, and were attributed to various causes, including weakening of the Gulf Stream and winds.

In this study, I evaluate direct and indirect wind impacts of coastal sea level, by conducting annual correlation analyses between observed daily mean sea level and three daily mean parameters: coastal normal wind component, Gulf Stream parallel wind component, and the Florida Current transport record. Daily mean coastal sea levels were calculated from 18 tide gauge records located along the Gulf and Atlantic coasts, from Pensacola (northwestern FL), through Key West (southern tip of FL), all the way north to Montauk (northeastern Long Island, NY) for the period of 1997-2019 (Figure 1a). Daily mean wind components were calculated from NCEP/NCAR Reanalysis results for (1) each tide gauge within a 1°x1° area loacted offshore the gauge, and (2) within three regions that follow the location of the Gulf Stream offshore Florida and along the south and middle US Atlantic coast. The Florida Current transport observations were provided by NOAA.

The annual correlation analyses revealed medium-high correlations (R² > 0.4) or anti-correlations (R² < -0.4) between observed daily mean sea level and three daily mean parameters in selective tide gauges suggesting that in some sections of the coasts a regional-scale wind impact of coastal sea level but not everywhere (Figure 1). The main outcomes of the analyses are: (1) Direct impact of coastal winds are dominant in the middle Atlantic and northern Gulf coasts. (2) Wind shear over the southern Gulf Stream dominates coastal sea level in the southern Atlantic. (3) The strength of the Florida Current dominates coastal sea level in the southern Atlantic and the Florida Atlantic coasts, but only since 2006. (4) Wind shear over the southern Gulf Stream began impacting the strength of the Florida current since 2006, possibly due to a long-term weakening of the current.