MOSCOW — The recent diplomatic thaw between Russia and the United States over the crisis in Ukraine has had little impact there, but it is being felt somewhere else — in the Arctic Ocean, near the North Pole.

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 quickly becoming realistic.

The United States, Russia and three other nations with Arctic Ocean coastlines agreed last year to regulate trawling in Arctic waters newly free of ice. But the deep freeze in East-West relations after Russia’s annexation of Crimea delayed the expected signing.

The day after Secretary of State John Kerry met with President Vladimir V. Putin in the Black Sea resort of Sochi last week, Russia announced it would sign the fishing agreement.

“I think the Arctic genuinely is shaping up to be the exception to the rule,” said Scott Highleyman, director of the Arctic Program at the Pew Charitable Trusts. “The U.S. and Russia seem to be trying really hard to keep talking to each other.”

The fishing deal was negotiated in February 2014 among Russia, Norway, Canada, the United States and Denmark, which controls Greenland, where the talks were held.

It was expected to be signed within weeks of the meeting, but the timing turned out to be dismal when, that month, street protesters in Kiev, Ukraine, overthrew President Viktor F. Yanukovych, a Russian ally, and most East-West cooperation froze.

As recently as April, ill-will over Ukraine carried into a meeting of the Arctic Council, an international organization created to foster cooperation in the region, despite diplomats’ appeals to focus on the melting ice instead.

“There is no room here for confrontation or for fearmongering,” said Russia’s envoy to the meeting, Sergei Y. Donskoi, the minister of environment and natural resources.

The United States opened negotiations on the fishing accord six years ago, after concluding that enough of the polar ice cap melted regularly in the summertime that an agreement to regulate commercial fishing near the North Pole was warranted.

The accord would regulate commercial harvests in an area far offshore — in the so-called doughnut hole of the Arctic Ocean, a Texas-size area of international water that includes the North Pole and is encircled by the exclusive economic zones of the coastal countries.

The part of the doughnut hole that is thawing most quickly, above Alaska and the Russian region of Chukotka, is well within the range of Asian industrial fishing fleets. Whatever their disagreements over Ukraine, Russia, the United States and the other shoreline states have a shared interest in protecting the high Arctic from unregulated fishing that could affect these countries’ coastal stocks, conservationists say.

“Some people call this Arctic exceptionalism,” Clive Tesar, the spokesman for the Arctic Program at the World Wildlife Fund, said in a telephone interview. “We can have our disagreements elsewhere, but in the Arctic, we have to cooperate.”

The agreement among the five countries is seen as a first step to a broader international accord to protect the open water until the fish stocks there, like Arctic cod, can be more fully studied. Fish may migrate into the ice-free area as the ocean warms, tempting fishing fleets to follow.

The accord is unusual for protecting a huge area from human exploitation before people have had much chance to exploit it. Before the last decade, scientists estimate, the doughnut hole had been icebound for about 100,000 years.