Impact of lateral melting on Arctic sea ice simulation in a coupled climate model

Lateral melting is an important process driving the sea ice decay, yet it is not well represented in many Coupled Model Intercomparison Project Phase 6 (CMIP6) models. This study explores the impact of lateral melting on Arctic sea ice simulation by implementing lateral melting and floe size parameterization schemes in the medium resolution version of the Beijing Climate Center Climate System Model. Results from a series of CMIP6 historical-type experiments indicate that inclusion of lateral melting results in a reduction in both the Arctic sea ice concentration and thickness, thus improving the sea ice extent and volume simulation. Lateral melting increases open waters, leading to an enhanced net sea surface heat flux into the ocean and further increased lateral and bottom melting. This positive feedback is intensified from 1982 to 2014, particularly when the floe size parameterization scheme is introduced. This accelerates the Arctic sea ice decline from 1982 to 2014 in the model, which is more consistent with observations. Further analysis indicates that the enhancement of this feedback is associated with accelerated lateral melting due to the increased (decreased) trend of the sea surface temperature (floe size) from 1982 to 2014. This study highlights that sea ice lateral melting is an important factor affecting the simulation of Arctic sea ice decline and needs to be better represented in current climate models.