Analysis of the relationship between level ice draft, ridge frequency and ridge keel draft for use in the probabilistic assessment of ice ridge loads on offshore structures

Abstract

Level ice draft, ice ridge keel draft and ridge frequency are important variables in the probabilistic assessment of ice ridge loads on offshore structures. We use ice profiling sonar (IPS) measurements of ice draft from the Beaufort Sea to analyse the relationship between these three variables. We propose a probabilistic simulation technique of ridge keel drafts. Two examples of simulations are given. The first example simulates the weekly deepest ridges. The simulated distribution of the weekly deepest ridge keel draft agrees with the measured data. The second example simulates all ridges deeper than 5 m. This simulation results in overestimation of the ridge keel draft in the tail section of the distribution. For both simulations, with the relationships established in this paper, the only needed input is level ice draft. Future studies should investigate whether the relationships found in the Beaufort Sea are valid in other areas or if there is a possibility of scaling the correlations. If the correlations prove predictably scalable for other locations, it could be possible to estimate the ridge keel draft distribution and ridge frequency by knowing only the level ice draft (thickness) statistics. This study is our first endeavour in this direction.