Large-scale climate oscillations induce accelerated high tide flooding along the U.S. East Coast

High tide flooding time, the annual cumulative duration when local sea level exceeds flooding threshold, has increased rapidly along the U.S. East Coast in recent decades. However, quantitative contributions from different processes and the underlying drivers are not well understood. Here, we combine observational analyses with model experiments to quantify and understand the increase and acceleration of high tide flooding across both a long-term period (1950-2020) and recent decades (2001-2020), showing that the decadal sea level anomalies are as important as the sea level rising trend for the long-term flooding acceleration and are the dominant factor for the flooding increase and acceleration in recent decades. Decadal Indian Ocean Dipole remotely impacts the North Atlantic, accelerating flooding in the Mid-Atlantic Bight by weakening the Atlantic Meridional Overturning Circulation and exciting Rossby waves. The North Atlantic Oscillation accelerated flooding in the South Atlantic Bight largely through wind-driven Rossby waves. Therefore, remote forcing from the Indian Ocean, together with the North Atlantic Oscillation and global mean sea level, must be jointly considered to achieve more reliable decadal predictions of U.S. East Coast high tide flooding. Both the Indian Ocean Dipole and North Atlantic Oscillation have acted to accelerate high tide flooding along the U.S. East Coast in recent decades, according to combined observational analyses and model experiments.