The aerodynamic roughness of different types of sea ice

Abstract

The aerodynamic roughness for all major types of sea ice is specified on the basis of surface layer measurements from ship and ice floe platforms. Median neutral surface drag coefficients, Cdn×1000, for grease and nilas ice are 0.7 and 1.6. Small, medium, large, and fused pancake ice have Cdn equal to 0.9, 1.6, 2.4, and 1.9. Young ice Cdn ranges from 2.3 to 3.1. Very smooth first‐year or multiyear ice with no pressure ridges has Cdn equal to 1.5. Pack ice has median values of 2.0 and 2.2 for first‐year and multiyear ice. Marginal ice zone ice averages 3.1 and 3.4 (first‐year, multiyear) if unaffected by wave action. Wave‐affected ice has Cdn values of 4.2 and 4.6 (first‐year, multiyear). Extremely rough multiyear ice in intense shear or compaction regions has Cdn equal to 8.0. Open ocean areas within 100 km of an ice edge averaged 1.8, while ice‐free water downwind of ice, with small or no waves is 1.4. These values can be adjusted if heat fluxes are present. The accuracy of the Cdn averages is estimated to be 20% or better.