Why did Snow Dragon hit an iceberg with radar?

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 Why did Snow Dragon hit an iceberg with radar?


Our reporter Chen Yu

During Chinas 35th Antarctic Expedition, Xuelong collided with an iceberg in the dense ice area of the Amundsen Sea at 10.47 a.m. on January 19, Beijing time. No one was injured. Ship power equipment and communication and navigation equipment were operating normally.

Why do ships collide with icebergs when they are equipped with radar to identify obstacles? A captain with experience in navigation in the Antarctic Sea told Sci-tech Daily that Ship-borne Radar is an effective means of detecting obstacles in polar navigation, but it also has drawbacks, such as the difficulty of distinguishing ice floes from icebergs based on reflected signals. The Ministry of Natural Resources also mentioned in its briefing that the Snow Dragon was sailing in the dense ice area of the Amundsen Sea.

The Amundsen Sea is the most intense melting area at the bottom of the Antarctic ice shelf collapse and the most active area at the front of the ice shelf collapse. Professor Cheng Xiao, Dean of the Academy of Global Change and Earth System Sciences, Beijing Normal University, told reporters that satellite imagery from January 13 to 20 showed that there were a large number of crushed ice floes in the sea area, mixed with small icebergs. Affected by the coastal downwind, the floating ice drifted northward as a whole, which had a certain impact on the navigation of the Xuelong.

Comparing the satellite images of the same period in 2018, Cheng Xiao found that the floating ice in the sea area was relatively stable in 2018, mostly in large areas, and the broken floating ice increased greatly in 2019. In terms of weather conditions, the cloudiness in the sea area varies greatly in 2018 and 2019, but the cyclone conditions in 2018 are relatively stable, so the sea ice situation is relatively stable and the sea ice edge line is relatively clear; the cyclone activity in 2019 is relatively strong, resulting in a high degree of sea ice fragmentation.

The report also mentioned that the impact of the iceberg was due to heavy fog.

Another issue of concern is why there is a dense fog in the polar region. The captain said that the perennial low-pressure trough around the Antarctic continent surrounds the continental high-pressure area like a closed life-forbidden zone. There are often cyclones around the polar region in the trough. At the same time, there may be more than 4-5 cyclones around the polar region with moderate intensity. The cyclone will bring the warm and wet air flow of the westerly zone to the high latitude cold sea area and form a large area of sea fog. When the cyclone passes through or the low pressure trough controls the area, it is easy to appear thick fog (sea fog) weather, which seriously affects navigation safety.

According to the captains analysis, the area between 55 and 65 in the south latitude is the active area of westerly cyclone and circumpolar cyclone, with high wind and waves, more ice floes and icebergs near the shore, and complicated navigation conditions. Icebergs, floating ice and dense fog all add up to increase the risk of navigation in the ice area of dense fog. In the accident, the speed of the Xuelong was 3 knots (about 5.56 km/h) when it collided with the iceberg. How much momentum this speed will generate is also a matter of concern. The captain also said that the cruising speed of different ships is different, the general economic speed is 10-15 knots. The speed of 3 knots is slower than that of normal people, which is close to the speed of ice breaking, and is also a safe speed recognized by the industry. But he also said that although the speed is not fast, as a 20,000-ton icebreaker, Xuelong will have a lot of momentum due to inertia, the collision will cause some damage to the hull. (Science and Technology Daily, Beijing, January 22) This article is from: Science and Technology Daily - Responsible Editor of China Science and Technology Network: Wang Fengzhi_NT2541

According to the captains analysis, the area between 55 and 65 in the south latitude is the active area of westerly cyclone and circumpolar cyclone, with high wind and waves, more ice floes and icebergs near the shore, and complicated navigation conditions. Icebergs, floating ice and dense fog all add up to increase the risk of navigation in the ice area of dense fog.

In the accident, the speed of the Xuelong was 3 knots (about 5.56 km/h) when it collided with the iceberg. How much momentum this speed will generate is also a matter of concern.

The captain also said that the cruising speed of different ships is different, the general economic speed is 10-15 knots. The speed of 3 knots is slower than that of normal people, which is close to the speed of ice breaking, and is also a safe speed recognized by the industry. But he also said that although the speed is not fast, as a 20,000-ton icebreaker, Xuelong will have a lot of momentum due to inertia, the collision will cause some damage to the hull.

(Science and Technology Daily, Beijing, January 22)