Thawing and refreezing each year, an active layer of soil lies over permafrost.

覆盖在永冻层上方的一层活冻层土壤,每年都会融化和重新冻结.

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Arctic sea ice follows an annual cycle of melting and refreezingmeltingand refreezing in the winter.

北冰洋的海冰,有融化和重新凝结的一年周期,夏融冬凝.

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