Wang Jianzhong could not hide his delight after finishing the 159-day scientific expedition in Antarctica.

"Seeing my family after months away is certainly a happy moment," said Wang, captain of the Chinese icebreaker Xuelong, or Snow Dragon, which arrived in Shanghai on Tuesday.

Xuelong left Shanghai on Nov 7 on China's 30th Antarctic expedition, which involved scientific research, construction of the country's new Antarctic research station and the inspection of a new base.

But unlike previous expeditions, this expedition had unexpected, challenging tasks and experienced a bit of difficulty.

"The whole journey had many rough stretches, and it was really not an easy expedition this time. We had a hard time getting all things done and getting back," said Wang, who has been doing ocean work for 25 years and has been Xuelong captain since 2012.

On Dec 25, Xuelong received a request for help from a Russian ship, Akademik Shokalskiy, which had become trapped in ice about 185 km east of France's Dumont d'Urville base.

"After receiving the request, we immediately reported it to superior departments and formed an emergency team to prepare for the rescue work," Wang said. The icebreaker immediately headed toward the Russian ship.

But Xuelong was forced back by blinding snow, heavy ice and strong winds.

"We worked out four plans to rescue them based on the weather conditions," he said.

"About 80 percent of the sea surface was frozen. It was really difficult for us to get near the ship, so we had to adopt the second plan, to use helicopters, after several days' failed attempts and waiting."

All 52 passengers stranded on the Russian ship for nine days were finally rescued by the helicopter Xueying 12, or Snow Eagle 12, from Xuelong.

However, just one day after its helicopter evacuated the passengers from the Russian ship, Xuelong itself was trapped in thick sea ice due to the severe weather conditions.

"We found the icebreaker was unable to free itself on its own," Wang said, adding that they had met the unexpected irregular semidiurnal tide.

"Almost all surface of the sea began to freeze, and there was very limited time for us to respond," he said.

The icebreaker had to wait for the weather to get better to break out of the frozen ice floes in Antarctica. In order to avoid being frozen in, the trapped Xuelong kept warming up its engine, trying to widen a path through the ice.

The situation was not optimistic as the vessel was locked in heavy floes, up to 4 meters thick in some places, with the vessel only able to break ice up to 1.1 meters thick. Meanwhile, fast-moving ice floes and icebergs also threatened the vessel.

After being stranded for five days, Xuelong finally broke through the ice floes on Jan 7 and headed for open water.

"At that time, many of us stood together looking up and down, trying to find out the possible route to break free," said Liang Gaosheng, a pilot of the helicopter. "It was so exciting to see that we had broken free."

After the vessel broke through the floes, Wang called his wife, Ling Li.

"It was the first time I heard him cry," Ling told Xinhua News Agency earlier.

In March, Xuelong was assigned a new task. After arriving at the Western Australian port of Fremantle for replenishment on March 21, the long-serving Antarctic research vessel received an order from the State Oceanic Administration to join the hunt in the southern Indian Ocean for the missing Malaysia Airlines flight MH370.

The Boeing 777, which carried 239 people, including 154 Chinese, en route from Kuala Lumpur to Beijing, disappeared on March 8.

"We took only 8.5 hours to enter the harbor, refuel, store supplies and leave the harbor, and arrived at the search area as quickly as possible," Wang said.

Lacking sophisticated equipment to aid in the search, crew members had to resort to telescopes to look for any possible traces of the missing plane.

"The sea was rough and the waves were so high that the vessel leaned at up to a 25 degree angle. It doesn’t take long to feel seasick after searching with telescopes," said Jia Shuliang, a helicopter pilot.

"Sometimes we found something suspicious, but they later were found to be only buoys or water birds," he said.

On Monday, Wang and the crew members had a drink together to celebrate returning home when Xuelong stopped at the anchorage of the Yangtze River estuary for process requirements for the docking on Tuesday.

"We are so happy to return home soon. We have met many difficulties and finally solved them, which rounded off this Antarctic expedition," Wang said.