Wind Impact on Sea Level Variability along the US Atlantic and Gulf Coasts: Implications to Coastal Flooding

Coastal cities worldwide have experienced increased flooding due to rising sea levels. The US Atlantic and Gulf coasts have been particularly affected, as the rate of high-tide flooding during normal sunny days has increased, leading to significant disruption and damage to infrastructure. Global, regional, and local factors contribute to this phenomenon, including steric changes, polar ice melt, ocean currents, winds, and vertical land movements (VLM). Global processes (steric changes and polar ice melt), some regional processes (ocean currents), and local VLM contribute to long-term (> decade) sea level change variability. Shorter-term sea level change variability (days-months) is associated with atmospheric processes, including pressure changes and winds.

In this study, we seek to evaluate the contribution of wind direction and magnitude on short-term sea level variability. As much of the short-term variability is caused by ocean tides, which are well-studied and observed, we exclude tidal variability from our study and focus on understanding wind impact on non-tidal residual (NTR). Our study analyzes sea level records obtained by 18 NOAA tide gauges located along the US Atlantic and Gulf coasts and wind fields calculated from North American Regional Reanalysis/National Centers for Environmental Prediction (NCAR/NCEP) reanalysis covering a 1⁰ by 1⁰ area on the offshore side of the tide gauges. Our analysis was conducted using daily averages, where the wind data were decomposed into 12 directions (0⁰ to 165⁰). A correlation analysis was performed at one-year intervals for each wind direction at each station. An average R² score for all the years was obtained to determine the dominant wind direction (Fig1). The study reveals a regional pattern amongst 10 stations along the North Atlantic, mid-Atlantic, and Gulf coast, with an R² score between 0.32-0.46, with the dominant wind direction ranging between 30⁰-75⁰ relative to the coastline orientation. The remaining 8 stations showed no coherent wind pattern, while their R² score ranged between 0.02-0.29, with the dominant wind direction fluctuating anywhere between 0⁰-105⁰. For the 10 stations with high correlation, more than 40% of NTR sea level variability is explained by the winds in specified directions, while further analysis is needed for the remaining 8 stations.