A CONCEPTUAL STUDY OF INFRA-GRAVITY DRIVEN CROSS-SHORE TRANSPORT

Infra-Gravity (IG) waves, characterized by periods exceeding typical wind-generated gravity waves have received increasing attention in the study of coastal dynamics. IG waves in the surf zone explain the well known surf beats and are connected to various other nearshore and coastal processes such as rip currents, run-up/overtopping, as well as beach and dune erosion (Munk, 1949; Russel 1993; Roeber and Bricker, 2015; Bertin et al., 2018). The creation of IG waves is due to a secondary generation mechanism, distinct from the wind forcing which drives gravity-wave creation. IG waves can be categorized into two principal types: bound waves, phase-locked to deep-ocean wave groups, and free IG waves, generated in the surf zone. The present work aims to provide a firm explanation of how IG waves drive oscillatory cross-shore movement. Employing analytical, linear, and numerical modeling, we try to discern the fundamental mechanism through which IG waves propel cross-shore currents. We will provide the theoretical underpinning of why IG waves dominate nearshore particle transport, explaining empirical observations with a clear kinematic framework to illuminate the subtle yet consequential role of IG waves in nearshore dynamics and in shaping coastal landscapes.