An undated image shows two trucks used by the Russia-Canada Arctic exploration expedition members cross the North Pole. The explorers crossed the North Pole from the Russian archipelago Severnaya Zemlya to Resolute Bay, Canada. (AFFANASSI MAKOVNEV/AFP/GETTY IMAGES)

Russia is evacuating a drifting Arctic research station that was supposed to last until September, because the ice it is built on is starting to break up.

The cracks are another indication of the rapid decline of the Arctic ice sheet — especially so because the encampment is on the Canadian side of the Arctic Sea, where the ice is oldest and most durable.

“It’s a huge loss for us, and for science,” Vladimir Sokolov, director of the expedition, said in a telephone interview from his office in St. Petersburg. “For us, it is very important to get information about the climate system in the high-latitude Arctic.”

The station — the 40th in a string of North Pole drift stations that began in 1937 — went into operation Oct. 1, later than usual because the leaders of the project had a difficult time finding a sufficiently robust floe to base the camp on. In fact, according to the U.S. National Oceanic and Atmospheric Administration, the extent of sea ice in September was the lowest on record, 18 percent lower than the previous minimum, in 2007.

Last year’s ice conditions, Sokolov said, forced the Russian researchers to look for a base floe closer to Canada than to their own country.

In years past, drift stations have remained in operation for 12 months or longer, with the exception of 2010, when an early breakup also caused a premature evacuation.

One station in the Soviet era, called North Pole-22, was launched Sept. 13, 1973, and stayed in service until April 8, 1982.

Because there is no land at the North Pole, the drift stations provide one of the most important means of studying sea-level conditions. The 16 researchers on North Pole-40 have been collecting data on low-altitude atmospheric conditions, ozone concentrations, ice thickness, sea temperature and the ocean bottom.

For its first several months, the station drifted in a seemingly aimless fashion, about 85 degrees North latitude, according to the Arctic and Antarctic Research Institute, the sponsor of the research.

Then from Jan. 1 to May 1 it drifted almost directly due south, to about the 81st parallel, before starting to loop about again. All told, it drifted about 1,000 miles, although it has ended up just over 250 miles from where it began. The research station, like its predecessors, is at the mercy of the movement of the ice sheet.

NOAA’s “Arctic Report Card” notes in particular the decrease in older ice — that is, ice more than four years old. A long-lasting tongue of older ice that extended toward Russia virtually disappeared last year. Throughout the Arctic, older ice accounted for 26 percent of the ice cover in March 1988 and just 7 percent in March 2012.

On Tuesday, Russian President Vladimir Putin declared May 21 to be Polar Researchers Day, in honor of the St. Petersburg institute. He also called on Russia’s United Shipbuilding Corp. to provide the icebreakers, drilling rigs and extraction platforms that Russia will require for more efficient exploitation of Arctic resources.

Climate change has been linked by many scientists to the release of carbon into the atmosphere through the burning of fossil fuels, but Putin has suggested that the melting of the ice sheet provides an economic opportunity for Russia — opening up shipping lanes and making the continental shelf more accessible for drilling. At a meeting of the Arctic Council in Sweden this month, Russia, the United States and other member nations recognized the potential threat posed by climate change to the Arctic environment but did not pursue the question further.

Sokolov said the North Pole-40 researchers will be evacuated within weeks.