China's seventh Arctic expedition using the Chinese icebreaker Xuelong returned to its research base in Shanghai on Monday after a 78-day mission.

本周一，中国第七支北极科考队在结束为数78天的科研考查任务后，乘坐中国雪龙号破冰船回到位于上海的研究基地。

Xuelong set out from Shanghai on July 11 and has since traveled 13,000 nautical¹ miles to explore marine² areas such as the Bering Sea, the Chukchi Sea and the Canada Basin.

The team traveled as far as 82.53 degrees north latitude³, and for the first time explored the Mendeleev Ridge⁴ in the Arctic Ocean.

Scientists studied marine meteorology, geology and chemistry, and surveyed seven ice stations, while the expedition smoothly⁵ completed all its scheduled tasks, said Li Yuansheng, chief scientist on the expedition.

The expedition team laid several observation buoys⁶ in various seas and explored deep stratums by creating an artificial seismic⁷ wave.

Xuelong, or Snow Dragon, was equipped with two helicopters, research support and emergency equipment during the expedition. The Ukraine-built ship was first put into use in 1994 and can break ice that is 1.2 meters thick.

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1 nautical
adj.海上的，航海的，船员的
参考例句：
A nautical mile is 1,852 meters.一海里等于1852米。
It is 206 nautical miles from our present location.距离我们现在的位置有206海里。

2 marine
adj.海的；海生的；航海的；海事的；n.水兵
参考例句：
Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

3 latitude
n.纬度，行动或言论的自由(范围)，(pl.)地区
参考例句：
The latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
The two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。

4 ridge
n.山脊；鼻梁；分水岭
参考例句：
We clambered up the hillside to the ridge above.我们沿着山坡费力地爬上了山脊。
The infantry were advancing to attack the ridge.步兵部队正在向前挺进攻打山脊。

5 smoothly
adv.平滑地，顺利地，流利地，流畅地
参考例句：
The workmen are very cooperative,so the work goes on smoothly.工人们十分合作，所以工作进展顺利。
Just change one or two words and the sentence will read smoothly.这句话只要动一两个字就顺了。

6 buoys
n.浮标( buoy的名词复数 )；航标；救生圈；救生衣v.使浮起( buoy的第三人称单数 )；支持；为…设浮标；振奋…的精神
参考例句：
The channel is marked by buoys. 航道有浮标表示。来自《现代汉英综合大词典》
Often they mark the path with buoys. 他们常常用浮标作为航道的标志。来自辞典例句

7 seismic
a.地震的，地震强度的
参考例句：
Earthquakes produce two types of seismic waves.地震产生两种地震波。
The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。