to ease tension, awkwardness, or formality (between people)
X растопил лед = X melted (thawed) the ice.
(authors usage) Он почти представил, как он, Лева, найдет все-таки, очень постепенно, очень тонко, подход к деду, ключ, растопит лед обид и горя и, хотя на закате дней, деду улыбнется любовь и очаг... (Битов 2). Не (Lyova) could almost picture it: despite all, very gradually, very subtly, he would find an approach to Grandfather, a key, he would thaw the ice of resentment and woe, and, though in the sunset of his days, love and home would smile on Grandfather... (2a).