The origin of Antarctic icebergs

Icebergs are large chunks of fresh water ice that break off from the coast of glaciers or polar ice sheets and fall into the sea to float, usually around Greenland, Antarctica. Icebergs are mostly formed in spring and summer, and warm weather will accelerate the division of glaciers or ice sheets. Every year, glaciers in western Greenland alone produce about 654.38+00000 icebergs. Where the glacier or ice sheet (shelf) meets the sea, the mutual movement between the ice and the sea causes the end of the glacier or ice sheet to break into the sea and become an iceberg. There is also a kind of glacier that extends into the sea, and the upper part melts or evaporates rapidly, becoming an underwater ice shelf, and then surfaced after breaking. Most Antarctic icebergs are formed when the Antarctic continental ice sheet thins towards the sea surface, protrudes into the ocean and becomes a huge ice shelf with a front several kilometers long, and gradually splits apart. The rate of iceberg formation in the Arctic Ocean is 280 cubic kilometers per year, and that in the Antarctic is 1800 cubic kilometers per year. Most icebergs have a specific gravity of 0.9, so 6/7 of their mass is below the sea surface. Icebergs in the Arctic Ocean can reach tens of meters high, 100 meters long and have different shapes. Antarctic icebergs are generally flat. Compared with Arctic icebergs, Antarctic icebergs are not only numerous, but also huge. Icebergs over 8 kilometers in length are not uncommon. Some are even hundreds of meters high. At present, the largest iceberg in the world is B 15. In March 2000, it broke away from the Ross ice shelf in Antarctica. Its area reaches 1. 1 000 square kilometers, which is larger than Beijing (16800 square kilometers). Now, this iceberg has been divided and named B 15A and B 15J respectively, and it is still drifting slowly in the Ross Sea. The average age of iceberg ice is over 5000 years, which can be said to be clean ice without industrial pollution. Icebergs can last 65,438+00 years at high latitudes, but if they drift to Guang Hai, they will disappear within a year or two. The main driving force of iceberg movement is wind, followed by ocean current. Under the influence of wind speed, some icebergs can move at a speed of 44 kilometers per day, which mainly depends on the shape of icebergs on the water. Icebergs can transport some objects on land, even living animals and plants, from their source to thousands of kilometers away. Scientists can infer the distribution of glaciers thousands of years ago from the sediments in the ocean. Icebergs pose a threat to navigation, and some parts exposed to water are too small to be found. Generally, it can only be found when the sea surface is calm and does not exceed 1.6 km. At present, radar and sonar are used to track icebergs and provide reports to passing ships twice a day. Icebergs are extremely valuable fresh water resources, but unfortunately, there is no way for human beings to use them at present.