For voyager and green promoter Zhai Mo, the 504-day non-stop voyage to the Arctic Ocean has stimulated his concern about the climate and awareness of his responsibilities.

Navigating more than 28,000 nautical miles (51,856 kilometers) in harsh conditions, Zhai, a renowned Chinese explorer, returned to Shanghai on his aluminum sailboat on Nov 17, along with two crew members, becoming the first man to successfully circle, both ways, the Arctic Ocean without stop.

"This non-stop Arctic Ocean circle route can be said to be unprecedented. We voyaged both the northeast and northwest routes while previous explorers only chose one route. This is a self-challenge and transcendence in the history of human navigation," the 54-year-old says.

Zhai undertook this task as an ambassador of the Chinese navigation science and marine public welfare, and also the ForNature Campaign of the United Nations Development Program. He set sail on June 30 last year to raise public awareness of global warming, climate change and land degradation.

During the trip, he crossed the East China Sea, the Western Pacific, the Bering Strait, the Chukchi Sea, the East Siberian Sea and the Beaufort Sea. He saw dolphins, whales, walruses, sea lions and seals, as well as shoals of cod and wolf fishes.

"When we passed through the Northwest Pacific Ocean on our way back, we encountered three typhoons within a week, which barely happened in the past," Zhai recalls.

Zhai didn't see any floating ice during his one-week voyage in the Kara Sea while the previous meteorological data showed ice there.

"My own experience tells me that climate abnormality is obvious now," Zhai says.

The voyage, to enter the Arctic Ocean from the Bering Strait before making a round trip returning to Shanghai, was planned to take four months, but the return schedule was delayed for more than a year.

"As soon as we entered the Bering Strait, we encountered a polar cyclone. A large number of ice floes and icebergs were blown to the coast. However, the Arctic Ocean can only be navigable near land, so we had been carefully crossing between ice floes and icebergs for a long time and the speed was only 1 to 3 knots," Zhai says.

But for Zhai, the most difficult part of the whole voyage was around 75 degrees north.

The Arctic Ocean is known as the "dead channel", Zhai says, adding that the location where the Titanic went down was on his route and dotted with countless icebergs.

After entering the iceberg region, Zhai navigated the sailboat while the two crew members went on watch to report on the menacing ice. Despite the precaution, the boat hit an iceberg near Greenland, causing water seepage below the waterline that had to be dealt with.

Meanwhile, compasses and electronic goods on the boat failed because of the magnetic field.

"I had never encountered this situation in sailing before," says Zhai. Fortunately, he took a fiber optic compass specially used for high latitude navigation, and managed to leave this area with visual aids.

In addition to ice floes and icebergs, Zhai and his team also faced severe tests such as heavy fog, strong winds and huge waves.

When sailing through the Chukchi Sea, the boat navigated around a large area of ice floes and heavy fog resulting in visibility of no more than 10 meters. They spent nearly 11 hours to get just 50 nautical miles.

"We tried to leave as soon as possible during our voyage in the Arctic Ocean," he says, adding that there was a constant danger of being trapped by the ice.

To be fully prepared, Zhai and crew members hoarded supplies for one year, including nang, a kind of crusty pancake, and yak meat. A native of Shandong province, he also prepared two boxes of Shandong-style pancakes.

"I grew up eating pancakes, so I had to take a lot of pancakes with me," says Zhai, adding that eating food from his hometown helped boost morale.

To protect against the coldness, they prepared sleeping bags that could withstand -50 C to -70 C in Arctic winter. They also carried firecrackers to frighten polar bears away if the boat became entrapped.

"My plan to circumnavigate the Arctic Ocean had been developing for nearly 20 years, and I had this idea before I sailed around the world," Zhai says.

Zhai was attracted by sailing when holding an art exhibition abroad in 2000. In 2007, he got a second-hand sailboat with simple supplies, such as instant noodles, pancakes and potatoes, and started his voyage trip around the world.

After that 35,000-nautical-mile voyage, Zhai eyed an Arctic Ocean journey.

"Navigation is a comprehensive discipline. You should know not only astronomy but also geography. You also need to be a carpenter, fitter, hammerer and painter, and should be able to survive in a harsh, outdoor environment," Zhai says.

He adds that he hopes more young people would participate in navigation, to promote and publicize the ocean awareness and navigation spirit.

"Sailing has developed relatively late in China. The first choice for the world's top event is the America's Cup, which has not yet been held in Asia. There are schools in the United States, Canada and France. I hope to cultivate more marine reserve talents in this way and make more Chinese voices in the field of world navigation," Zhai says.

He is preparing for the third voyage trip around the world next year or the year after that.

"Antarctica is also a very big challenge. I hope to explore more unknowns, and I also want to launch a transoceanic sailing competition."