were it to do so,的意思明白了, it 指代 “the polar ice”。但是 the polar ice 在前面的半句中只在that后面出现,不是句子的主语,为什么it(作为后半句的主语)可以指代它呢?
Antarctica ..., yet the temperatures are so cold and the ice cap is so reflective that little of the polar ice melts during the summer; were it to do so ...