Sea ice used to be the “armor” of the Arctic Ocean. Now the “armor” is becoming thinner and softer, and some of it has become “gauze”. Sea ice change is not an isolated event, but a fuse that can trigger a series of changes in the ocean and atmosphere. Cong Zhiyuan, a researcher and collaborator of the alpine environmental quality and safety team of the Institute of Qinghai Tibet Plateau, Chinese Academy of Sciences, found that the reduction of Arctic sea ice intensified the transportation of aerosols and other pollutants to the Qinghai Tibet Plateau. The relevant research results were published online in nature climate change on August 31. Recently, there have been bad news about the reduction of Arctic sea ice: the largest and most complete Milne ice shelf in Canada has collapsed; the Greenland ice sheet is melting faster and will no longer exist; some scientists even predict that the Arctic sea ice will disappear within 15 years. Will Arctic sea ice really become less and less or even disappear? What are the impacts of the reduction of Arctic sea ice? Therefore, the reporter interviewed relevant experts. < / P > < p > one of the most obvious signs of climate change is that the Arctic sea ice coverage – areas with more than 15% sea ice concentration are shrinking sharply. September is the month with the least sea ice coverage in the Arctic. Since the satellite observation records in 1979, the Arctic sea ice in September has been decreasing at a rate of 12.9% every 10 years. In fact, the Arctic sea ice coverage also shows a decreasing trend in other months. < / P > < p > “for the prediction of future Arctic sea ice, the mainstream international view is that before the middle of this century, the Arctic may appear ice free, that is, the sea ice coverage is less than 1 million square kilometers, but if greenhouse gas emissions are not limited, the occurrence time of Arctic ice free state will be advanced.” Dr. Song mirong, Institute of Atmospheric Physics, Chinese Academy of Sciences, told ScienceDaily. The warming rate of the Arctic is 2-3 times faster than that of the global warming, and the sea ice in the Arctic is decreasing. The sea ice with an ice age of more than 4 years is called “multi-year ice” by scientists. Research shows that in the 1980s, about one third of the sea ice in the Arctic region was multi-year ice. Now, the multi-year ice in the Arctic Ocean has almost completely disappeared. Instead, it will form and melt completely every year. It will be easier to melt in summer, which will aggravate the sea level rise and greenhouse effect. At the same time, the thickness of Arctic sea ice has also changed significantly. In the past, the average ice thickness in Arctic summer was 4.88 m, which was only 2.75 m by the end of the 20th century, a decrease of 43%. Since the beginning of the 21st century, the retreat speed of Arctic sea ice is far beyond people’s expectation. Recently, 33 major research institutions around the world submitted their outlook on Arctic sea ice coverage in September this year. Among them, the data submitted by the State Key Laboratory of atmospheric science and geohydrodynamics numerical simulation of Institute of Atmospheric Physics, Chinese Academy of Sciences (LASG) shows that the sea ice area will be reduced to 3.8 million square kilometers in September this year, which will be the second smallest value of sea ice area since the observation record, only larger than the record of 3.57 million square kilometers in 2012. Sea ice area is a measure of sea ice coverage area. Sea ice has a high reflectivity, which can reflect most of the solar radiation and maintain a cold source state in the polar region. The size of sea ice area can reflect the amount of solar radiation entering the earth system. The reason why scientists pay great attention to Arctic sea ice is that its change not only has a significant impact on local climate, but also has a sustained impact on the global atmosphere and ocean system. More importantly, polar sea ice and climate change have a significant impact on the climate of middle and high latitudes, especially in China. Liu Jiping, a researcher at the Institute of Atmospheric Physics, Chinese Academy of Sciences, said that at present, the prediction of Arctic sea ice is becoming more and more important, and it is very difficult to accurately predict sea ice based on existing prediction methods and technologies. < p > < p > Liu Jiping said that an important means is to establish a numerical model for prediction, which requires the use of historical sea ice, atmospheric and marine data to establish statistical models to predict the spatial distribution of sea ice density, sea ice thickness, etc. Liu Jiping’s research team has developed a numerical prediction system for Arctic sea ice. This system can use the fully coupled atmospheric sea ice ocean Arctic regional numerical prediction model to predict sea ice. The latest prediction result is that the minimum Arctic sea ice range in September this year is 4.36 million square kilometers. In addition, satellite observation is currently the most important means of Arctic sea ice monitoring. “When the satellite crosses the polar regions several times a day, the advanced microwave scanning radiometer and special sensor Microwave Imager on the satellite collect data. Through the analysis and inversion of the image formed by the data, the distribution of polar sea ice density can be obtained, and then the sea ice area can be calculated.” Song mirong said. According to Liu Jiping, satellite remote sensing has the characteristics of large-scale, real-time and continuous observation. The resolution of high-resolution satellites can reach hundreds of meters, which can help researchers to see the evolution of sea ice morphology, provide more accurate and reasonable initial conditions of sea ice for numerical models, thus reducing the simulation deviation of numerical models and improving the Arctic The prediction ability of sea ice. However, at the same time, high-resolution satellite remote sensing can only better observe the sea ice cover in the polar region, and the cloud cover greatly reduces the high-resolution visible and near-infrared satellite remote sensing, and has a large error in the estimation of sea ice thickness and other states. Global warming undoubtedly plays an important role in the reduction of Arctic sea ice. However, in addition to global warming, the causes of Arctic sea ice change include the following factors: the melting of Arctic land glaciers leads to the increase of runoff, which significantly affects the amount of Arctic ice; the change of temperature and flow of warm water from the Atlantic Ocean has a great impact on the Arctic sea ice; the high temperature of sea water from the Pacific Ocean affects the melting of sea ice in summer in the Arctic; and some regions of the Arctic The wind power tends to weaken, which significantly affects the sea ice output, and has an impact on the total ice amount in the Arctic Ocean. < p > < p > sea ice used to be the “armor” of the Arctic Ocean, but now the “armor” is becoming thinner and softer, and some of it has become “gauze”. Sea ice change is not an isolated event, but a fuse. It can cause a series of changes in the ocean and atmosphere, which will have a profound impact on the ecosystem, coastal stability and human settlements in alpine regions. At the same time, it will further affect the global climate system and affect the intensity and frequency of extreme events. In Song mirong’s opinion, the reduction of Arctic sea ice will directly affect the polar ecological environment. At the bottom of the sea ice, specific algae and bacteria grow to provide food for plankton, which in turn feeds larger animals. The reduction of sea ice, especially the appearance of more open waters in summer, will result in a significant reduction of plankton, which will affect the zooplankton feeding animals. In addition, polar bears, seals and walruses are losing their habitat and are forced to move northward, while some new species, such as North Atlantic cod and top predator whales, are moving in because there is no sea ice cover, which changes the ecological environment in the polar region. < p > < p > if the Arctic sea ice disappears completely, in addition to the polar ecological environment will be changed, the global ocean circulation will be destroyed, and the polar and global weather and climate system will be affected. The frozen greenhouse gases in the Arctic permafrost may be released, which will aggravate the Arctic warming. The study shows that the Arctic change is closely related to the extreme high temperature, extreme low temperature, heavy precipitation, heavy snow and haze days in China, high temperature and heat wave in Europe, cold trend in northern Eurasia in winter, and snowstorm in Northeast America. For example, during the accelerated warming phase of the Arctic, the number of cities in the northeast of the United States experiencing violent snowstorms has increased significantly. In addition, the accelerated warming of the Arctic will lead to further melting of Greenland ice sheet, resulting in sea-level rise, seawater will flow inland, and saline soil will expand inland, which will lead to land salinization and swamping, and the planting area close to the coastal areas will be sharply reduced, resulting in the decline of food production. Therefore, more and more frequent extreme weather and climate events will pose a direct challenge to the safety of human life and property in the densely populated middle and low latitudes of the northern hemisphere. < / P > < p > the possible upside is that routes between the Pacific and the Atlantic through the Arctic Ocean will become more frequent. With the global warming, the Arctic sea ice is melting, which makes the Arctic waterway gradually navigable. The Arctic channel mainly includes the Northeast channel along the Russian coast, the central channel crossing the central high seas of the Arctic Ocean, and the northwest channel passing through the Arctic islands in northern Canada. The Northeast channel is the main navigable route at present. In recent years, China’s container ships which have been successfully piloted go through the Northeast channel. After 12 years, “world class Super project” Shantou Bay Tunnel ushers in a historic breakthrough today