MOSCOW — Relations between Russia and the United States are in a deep freeze, but they share a looming common problem north of their Arctic coastlines — the prospect that commercial trawling fleets might overfish the thawing Arctic Ocean.

Out on the sea, the polar ice cap has been melting so quickly as global temperatures rise that once improbable ideas for commercial activities, including fishing near the North Pole, are becoming realistic.

While Russia, the United States and three other countries with Arctic coastline control the exclusive economic zones near their shores, overfishing in the international waters at the central Arctic Ocean could collapse fish stocks.

Whatever their disagreements elsewhere, the countries have a shared interest in protecting the high Arctic from such unregulated fishing, which could affect coastal stocks as well, conservationists say.