An offshore structure, adapted for operation in an ice infested arctic environment, includes a floating caisson that can be actively heaved in the water to break ice. The caisson comprises a radially tapered upper portion, preferably conically shaped. Means for vertically moving the caisson are provided so that the upper portion of the caisson can obliquely contact ice sheets and other ice masses with sufficient dynamic force to pierce and break the ice. A plurality of mooring lines anchored to the sea floor are attached to the caisson to secure its position in the water.
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