Effect of sea ice morphology during Arctic summer on atmospheric drag coefficients used in climate models

Realistic modeling of polar sea ice dynamics and atmospheric processes over sea ice needs a detailed representation of the near‐surface atmospheric fluxes of momentum. In this study, parametrizations of neutral drag coefficients mostly used in different general circulation models are compared with a recently developed parametrization including the impact of sea ice morphology. The new parametrization, using the sea ice and melt pond fraction as governing parameters, accounts for the effect of form drag caused by edges at leads, melt ponds, and floes. Based on remote sensing data of ice and melt pond fraction, it is shown that during Arctic summer the traditionally used drag coefficients differ from the new ones by a factor 0.5–1.2. The geographic distribution of drag coefficients obtained from both parametrizations is very different. Differences are due to a nonlinear and non‐monotonic dependence of drag coefficients on sea ice concentration in the new parametrization. Key points Surface drag distribution in polar regions is not correctly reproduced by GCMs Parametrizations of drag coefficients over sea ice should account for melt ponds Remote sensing data of sea ice can be used to determine drag coefficients