This dataset has been produced using a CPOM (Centre for Polar Observation and Modelling) version of the Los Alamos Sea Ice model v 5.1.2, with additional physics including form drag, a prognostic ocean mixed layer, and floe size distribution model. This dataset is used within the associated paper ‘Toward a marginal Arctic sea ice cover: changes to freezing, melting and dynamics’ (Frew et al., 2025) to investigate how processes that drive either the loss or gain of sea ice volume will change as the summer Arctic transitions from majority pack ice in the 1980s to majority marginal ice zone (MIZ) in the 2040s. Results are presented to show a different balance of processes control the volume budget of the MIZ compared to the pack ice. It is also demonstrated that the balance of processes is different for the future MIZ compared to the historical MIZ.