Abstract/Summary

Sea ice formation processes occur on sub‐grid scales and the detailed physics describing the processes are therefore not generally represented in climate models. One likely consequence of this is the premature closing of areas of open water in model simulations, which may result in a misrepresentation of heat and gas exchange between the ocean and atmosphere. This work demonstrates the implementation of a more realistic model of sea ice formation, introducing grease ice as a wind‐ and oceanic‐ stress‐dependant intermediary state between water and new sea ice. We use the fully coupled land‐atmosphere‐ocean‐ sea ice model, HadGEM3‐GC3.1 and perform a three member ensemble with the new grease ice scheme from 1964 to 2013. Comparing our sea ice results with the existing ensemble without grease ice formation shows an increase in sea ice thickness and volume in the Arctic. In the Antarctic, including grease ice processes results in large local changes to both simulated sea ice concentration and thickness, but no change to the total area or volume.