Abstract: A method and apparatus is disclosed for forming and maintaining an offshore ice structure in an Arctic environment. The structure is formed by a series of caissons oriented in a ring forming an enclosure capable of retaining a predetermined amount of water and thereby defining an ice island when frozen. The structure includes a passive heat extracting system which removes heat from the water within the enclosure and from the soil immediately below the enclosure and the caissons thereby advancing the freezing of the soil beneath the enclosure and water within the enclosure. In this manner, the lateral stability of the structure is improved by providing a single frozen mass of water and soil bonded in unitary construction increasing the foundational base of the structure. In addition, refrigeration means are provided to prevent surface melting of the ice within the enclosure and preserve the integrity of the ice structure during warmer months.