The article discusses seasonal variability of the strength properties of ice formations typical for the Arctic offshore. Thermal states of stamukhas and ice ridges were experimentally studied in the Khatanga Bay of the Laptev Sea in 2019-2020. Maps of temperature distribution in the consolidated layer of hummocks/stamukhas were built based on data from 12 thermistor chains installed on ice formations; ice freezing rate at the contact of the freezing front with various phases located in the unconsolidated part of the keel was also measured. Ratios of the thermal conductivity for the sail and the keel of the hummock were calculated based on the readings from the thermistor chains; it is shown that the sail provides thermal insulation of the keel zones located under it. The local strength of deformed ice composing a consolidated layer was determined as a function of the ice temperature. Maps of the strength distribution of the consolidated layer were constructed for the entire life cycle of the ice formation; these maps were constructed based on the thermal history of the hummock and obtained dependence of the local strength on the ice temperature. The thermal state of the hummock is fundamentally important for assessing its mechanical properties. A weakened (warm) zone under the hummock sail, as well as the uneven growth of the consolidated layer, significantly affect the distribution of internal stresses in the hummock during its further evolution and destruction, as well as in the case of interaction with an offshore structure. The article also discusses strength properties of stamukhas in the spring-summer period, when they can drift in the sea and interact with infrastructure facilities. The results presented in the article can be used for modeling of ice loads on offshore structures in the Arctic zone; they also allow to determine the properties of ice formations in different seasons.

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