Controlled weakening of model ice: Replicating the mechanical response of summer-warmed sea ice in laboratories and test basins

This study examines how the mechanical properties of model ice can be tuned to approximate the weakening of natural sea ice as it warms during summer. The work is motivated by satellite-derived observations and projections indicating that warm-ice conditions in the Arctic are increasing. The observed warming trend, coupled with the seasonal timing of Arctic shipping activities, challenges the traditional focus on winter conditions in model tests and suggests that incorporating weaker ice is increasingly relevant to ship–ice interaction and ship design. Laboratory tests for ship-performance optimization are often a crucial intermediate step toward implementation in the final maritime application. To provide a broader range of test conditions, we explore methods to adjust two key parameters – the elastic modulus and flexural strength – in model ice under laboratory conditions. The overarching goal is to establish a testing regime capable of representing selected summertime sea-ice properties. Experiments conducted at the Hamburg Ship Model Basin demonstrate that surface treatment of columnar model ice with saturated sodium chloride solution effectively reduces its flexural strength by 71 %. Furthermore, we investigate how variations in the amount of applied solution influence mechanical properties, highlighting differing sensitivities of elastic modulus and flexural strength to modifications of the ice surface layer.