A dynamic model of ice ridge buildup Aleksey Marchenko a,b, * , Aleksander Makshtas b,c a Theoretical Department, General Physics Institute of the Russian Academy of Sciences, 38 Vavilova Street, Moscow, 117952, Russia b Arctic and Antarctic Research Institute, 38 Bering Str., St.-Petersburg, Alaska c International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Dr., P.O. Box 757335, Fairbanks, AK 99775, Alaska Received 11 February 2002; accepted 6 October 2004 Abstract Dynamic models of ice rafting and ice ridge buildup are elaborated. The milestone of the models is the conception of a ridgeline accumulating broken ice due to vertical displacements of ice blocks separated from the edges of compressed floes. The ridgeline is considered as a discontinuity line over which ice drift velocity is changed by a leap. The estimated characteristics of ice continuum along the ridgeline are the linear densities of volume, impulse, and energy. The equations describing the motion of the ridgeline and the growth of ridge volume are constructed. The expression for internal ice stress on the ridgeline is found in explicit form for arbitrary scenario of ridge buildup. Elaborated theory is used for the estimations of ice stresses for most typically observed scenarios of ice rafting and ice ridging. Simulated stresses are compared with the results of laboratory experiments and discrete particle modeling. D 2004 Elsevier B.V. All rights reserved. Keywords: Ice ridges; Rafted ice; Discontinuity lines; Energy dissipation; Potential energy; Elastic energy; Internal stresses 1. Introduction Ice ridges are important features of sea ice cover in the Arctic Basin and adjacent shelf seas. They are formed due to the pressing-out of broken ice blocks below and on the surface of level ice. Aerial photo- graphs show that the ridging can be represented as a linear accumulation of ice caused by the compression and shearing interactions of ice floes (Hibler and Ackley, 1973). Numerous reports estimate that ridged ice occupies from 10% to 40% of ice-covered areas in different regions of the Arctic Basin. Thus, ridges increase the inertia of drifting ice and effective roughness of upper and bottom surfaces of sea ice (Garbrecht et al., 1999). Recent numerical experi- ments with a dynamic–thermodynamic sea ice model with the simplest accounting of ridges (Makshtas et al., 2001) show that Arctic ice thinning in the 1990s (Rothrock et al., 1999) can be explained by the decrease of sea ice ridging during years with prevail- ing cyclonic activity in the polar atmosphere. 0165-232X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.coldregions.2004.10.004 * Corresponding author. General Physics Institute of RAS, 115409 Moscow, Vavilova str. 38, Russia. E-mail address: amarch@kapella.gpi.ru (A. Marchenko). Cold Regions Science and Technology 41 (2005) 175– 188 www.elsevier.com/locate/coldregions