Parameterization of drag coefficients over polar sea ice for climate models

• Main Authors: Lüpkes, Christof, Gryanik, Vladimir
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2015
• Subjects: Arctic; Sea ice
• Online Access: https://epic.awi.de/id/eprint/37699/; https://epic.awi.de/id/eprint/37699/1/LupkesGryanik-Mercator-newsletter-proof.pdf; http://www.mercator-ocean.fr/eng/actualites-agenda/newsletter/newsletter-Newsletter-51-Special-Issue-with-ICE-ARC; https://hdl.handle.net/10013/epic.45315; https://hdl.handle.net/10013/epic.45315.d001

A parameterization of drag coefficients has been developed in recent years that accounts for the impact of edges at ice floes, leads, and melt ponds on momentum transport. Melt ponds are a common feature in the inner Arctic during summer while drifting ice floes and their edges influence the surface roughness especially in the marginal sea ice zones during all seasons. Governing parameters in the parameterization that can be easily applied to climate models are the sea ice concentration and aspect ratio h/D where h is the ice freeboard and D is the characteristic length of floes and ponds/leads. When these parameters are not available from a sea ice model, the aspect ratios can also be parameterized as a function of the sea ice concentration so that the new schemes can also be used in stand-alone atmospheric models using observed sea ice concentration. The parameterization is evaluated for idealized meteorological forcing and prescribed sea ice and melt pond concentration in the Siberian Arctic and in parts of the Central Arctic. The required sea ice data are available from remote sensing. The distributions of drag coefficients obtained from traditional parameterizations and from the new one show large differences in this test scenario especially in the region south of 80°N.