WAVE PROPAGATION IN ICE - A LABORATORY STUDY

摘要

The opening up of the Arctic increases the possibility of shipping and offshore engineering. The challenge, however, is the insufficient understanding of the air-ice-ocean system. In particular, more open water in the Arctic has increased the wave intensity. As a consequence, wave propagation through the dynamically changing ice covers in the Marginal Ice Zone (MIZ) has become an important topic for all maritime operations in the Arctic. Waves and ice covers mutually affect each other. At the formation stage, waves create grease/pancake ice from open water. As the ice edge extends, waves damp out to allow the pancake ice field consolidate into a solid ice cover. At a later stage, waves may fracture an existing solid ice cover. While field data, in-situ or remotely sensed, are required to parameterize and validate models for the "new Arctic ocean", laboratory experiments provide a much more controlled and less expensive alternative. At present, there are only a few international field campaigns planned. For engineering needs, well-controlled test conditions and the investigation of a broad range of parameters are required. At present there are several engineering projects/activities in ice-covered waters: wind farms, oil/gas rigs, ice navigation route planning, and oil spill mitigation. These will be located in the MIZ, where dynamically changing ice conditions prevail. Because different challenges exist for different projects/activities, all of them need to have an accurate prediction of the wave climate. Results from a systematic investigation of wave attenuation and velocity change carried out in HSVA's ice tanks for various types of ice (frazil, pancake ice, ice floes of different sizes and thickness) are presented.