Rapid decline in Arctic summertime sea ice extent has produced extensive seasonal ice zones, where broad marginal ice zones separate pack ice from open water. This session focuses on the processes that control evolution of the marginal ice zone and the potential changes that may accompany increased seasonality of sea ice. The complex interplay between ice, ocean and atmospheric processes, and the potentially strong feedbacks among them, modulate sea ice melt and the transfer of momentum and buoyancy into the upper ocean. For example the influence of wind, waves and passing storms drives highly variable floe size distributions, which impact melt or formation rates of sea ice, momentum and heat transfer, light fields and phytoplankton productivity. In particular, the relative importance of wave attenuation and scattering in an increasing wave climate remains unknown. Similarly, increased areas of open water may lead to stronger coupling between atmosphere and ocean, internal wave generation and elevated upper-ocean mixing. This session invites presentations that describe observational, experimental, theoretical and numerical investigations of MIZ processes in both the Arctic and Antarctic.