Nearshore ice-complex morphodynamics within an urban embayment, Southwestern Lake Michigan: Insights from a winter 2021–2022 monitoring study

Process-based insights into ice-shoreline morphodynamics are generally lacking, yet are critical for modeling and managing cold climate coastlines. In this study, conducted during the winter of 2021–2022 at an engineered Lake Michigan pocket beach, we address this knowledge gap by integrating repeat footage from beach cameras, aerial photographs acquired during sub-weekly drone flights, weather station information, and precision pre- and post-ice topo-bathymetric survey data to document and categorize the geomorphic evolution of a nearshore-ice complex under varying meteorologic and hydrodynamic conditions. While ice-complex formation and collapse were largely temperature-driven, episodes of sudden expansion followed multi-day wave events, with nearshore wave heights >1.5 m. These conditions promoted the accumulation and integration of brash ice and slush ice, brought in from elsewhere, along the ice front. Rapid nearshore ice-complex (re)expansion, following active erosion of the ice front during the high-energy wave events, was promoted by the calmer marine states to follow, during subzero temperature conditions. The cumulative impacts of shore ice on the lake bottom were captured in pre- and post-ice survey datasets. Up to ∼0.5 m of elevation loss occurred across the nearshore zone of ice advance and retreat, given wave scour along the ice front. Sand losses were roughly balanced by accretion of the lakeward part of the urban embayment. This study offers valuable insights into cross-shore dynamics obscured along more open sections of coast by complex littoral dynamics. Better understanding of ice-shoreline morphodynamics has implications for coastal resiliency planning for anticipated climate change.