Ridged sea ice characteristics in the Arctic from a coupled multicategory sea ice model

In this study, a multicategory sea ice model with explicit ice classes for ridged and rafted ice was used to examine the evolution of deformed ice during the period 1980–2002. The results show that (1) ridged ice comprises roughly 45–60% of Arctic sea ice volume and 25–45% of the sea ice area, (2) most of the perennial ice consists of ridged ice, and (3) ridged ice exhibits a small seasonal variability. Our results also show an increase in mean ridged ice thickness of 4–6 cm yr −1 during the summer in an area north of the Canadian Archipelago and a corresponding decrease in the East Siberian Sea and Nansen Basin. At the same time, Arctic sea ice age has been observed to decline and ice drift speed to increase during the simulation period. We connect these findings with a modeled regional increase in the production rate of ridged ice. Comparison of the multicategory model and a two category reference model shows a substantially increased ice production rate due to a more frequent occurrence of leads, resulting in an ice thickness increase of up to 0.8 m. Differences in ice physics between the multicategory and reference models also affect the freshwater content. The sum of liquid and solid freshwater content in the entire Arctic Ocean is about 10% lower and net precipitation (P‐E) is about 7% lower as compared to the reference model.