The breakup of sea ice in the Arctic and Antarctic has been studied during three field trips in the spring of 1993 at Resolute, N.W.T. and the fall of 2001 and 2004 on McMurdo Sound via <i>in situ</i> cyclic loading and fracture experiments. In this paper, the back-calculated fracture information necessary to the specification of an accurate viscoelastic fictitious (cohesive) crack model is presented. In particular, the changing shape of the stress separation curve with varying conditions and loading scenarios is revealed.This article is part of the theme issue ‘Modelling of sea-ice phenomena’
