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.
To address the problem, five nations with Arctic shorelines completed negotiations on Thursday with countries farther south that operate major trawling fleets. The agreement imposes a moratorium on fishing in newly ice-free areas in the high Arctic, at least until scientists can study the ecology of the quickly thawing ocean.
The agreement was a step forward for conservation in the Arctic, and was reached despite tensions between the United States and Russia that had delayed an earlier, more limited moratorium, and despite President Donald Trump's skepticism about global warming. Trump has said he intends to work with Russia to solve common problems.
The deal prohibits trawling in the international zone of the Arctic Ocean that is newly free of ice for 16 years, or until a plan for sustainable fishing is in place.
The deal is an example of what some diplomats call "Arctic exceptionalism," referring to a willingness of Russia and the United States to set aside other geopolitical differences for their common interests in the far north.
"It's an example where the United States and Russia have very similar interests as coastal states fronting the Arctic Ocean," said Scott Highleyman, vice president of conservation policy and programs at Ocean Conservancy, said in a telephone interview. "Can the Arctic remain an area of cooperation? Yes, it can, and that is a good thing."
To take effect, the agreement on a high-latitude fishing ban must be signed by all the countries involved: the United States, Norway, Denmark, Canada and Russia, which all have Arctic shorelines; and South Korea, China, Japan, the European Union and Iceland, which operate ocean trawling fleets.
The coastline states had already agreed in 2015 to a voluntary moratorium on trawling in Arctic waters. But the agreement had little meaning if nations to the south did not also join in.
That the center of the Arctic Ocean was unregulated was hardly a concern when it was an icebound backwater. That is changing. Today, about 40 percent of the central Arctic Ocean melts in the summertime. Though nobody fishes there now, the ice-free water could have lured in industrial fleets.
"This is a landmark agreement," said David A. Balton, the deputy assistant secretary for oceans and fisheries at the State Department, who negotiated the agreement for the United States. "It's a rare case of governments doing something in advance, to prevent a problem from arising."
The accord regulates commercial harvests in an area far offshore — in the 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 lies above Alaska and the Russian region of Chukotka, meaning Russia and the United States have the most at stake. This area is also well within the range of Asian industrial fishing fleets.
The intention of the accord is to eventually manage for commercial exploitation any stocks of fish that already inhabit the ocean but used to live under the ice, like Arctic cod, as well as fish that may migrate into the new ice-free zone from farther south.