The Antarctic ice sheet covers an area of 13.98 million square kilometers, with a maximum thickness of more than 4000 meters. From the air, it looks like a huge "white plateau". If someone tells you that this seemingly motionless white behemoth is actually moving slowly all the time, do you believe it?
Such is the case! The Antarctic ice sheet is moving slowly at a speed imperceptible to the naked eye, ranging from a few meters to kilometers a year. Why does the Antarctic ice sheet flow? To answer this question, we have to start with the topography of the Antarctic continent. On the whole, the topography of the Antarctic continent shows a trend of high in the middle and low around. The farther inland the south pole, the higher the terrain; The farther to the Antarctic coast, the lower the terrain. Therefore, under the action of gravity, the Antarctic ice sheet has the potential energy to move from the middle to all around, that is, from inland to coastal.
With good topographic conditions, it is not enough to move the huge Antarctic ice sheet. Because there is great friction between the bottom of the ice sheet and the ground, it will prevent the ice sheet from sliding down. We can do a small experiment by placing an iron block on a slightly inclined board. Due to the friction between the iron block and the board, the iron block is prevented from sliding downward. At this time, the iron block is stationary. But if the bottom of the iron block is coated with a thin layer of lubricating oil, the situation is completely different. Since the lubricating oil reduces the friction between the iron block and the board, the iron block will slide down the inclined plane under the action of gravity.
The movement of the Antarctic ice sheet is also completed with the help of such "lubricant". The ice water produced by the melting of ice at the bottom of Antarctica is a good "lubricant". At the bottom of the ice sheet, due to the influence of geothermal, the base temperature is usually high, which is conducive to the melting of ice at the bottom of the ice sheet. In addition, the bottom of the ice sheet bears the pressure caused by the weight of the huge ice layer, which leads to the corresponding reduction of the melting point of the ice and the melting of the ice at the bottom of the ice sheet. Under the combined action of these factors, the bottom of the Antarctic ice sheet will melt locally, forming a unique "lubricating layer", so that the huge ice sheet can slide. If you carefully observe the ice profile, you will find that the ice base is more transparent than the upper layer, which is the result of local melting.
There are great differences in the movement speed of the Antarctic ice sheet in different regions, which is mainly affected by factors such as substrate temperature, substrate strength, ice thickness and substrate inclination. Generally, the movement speed of the inland part is slow and that of the coastal edge part is fast. Because the ice sheet moves from inland to coastal, it forms an ice shelf protruding to the ocean in the coastal area of Antarctica. The ice shelf will collapse at a certain stage, forming hundreds of millions of icebergs of different sizes and shapes floating to the sea. Some of these moving icebergs even stretch for hundreds of kilometers, like giant islands floating on the sea, which will not completely melt until more than 10 years later!