The Arctic Ocean is likely to usher in its first "ice free summer" in 2034, according to a recent study published by US scientists in the academic journal climate.
The Arctic sea ice is not unchanging, and will change dynamically in a year: it will continue to melt in summer and reach the minimum area around September; it will continue to freeze in winter and reach the maximum area around March. In recent decades, due to the continuous increase of temperature in the Arctic, the area of sea ice in summer has continued to decrease.
These conclusions are supported by the observation and research of scientists through different technical means. Take the age of sea ice as an example. In 1988, about 25% of the Arctic sea ice remained frozen for more than four years. In 2013, the proportion dropped to 7%. In the past 60 years, the thickness of the Arctic sea ice has also been thinning. Through satellite observation, from 1979 to 2000, the average minimum sea ice range in summer in the Arctic was 6.7 million square kilometers. Since the beginning of the 21st century, this figure has reached the lowest level in 2012, only about 3.34 million square kilometers, which has been reduced by about half.
The decrease of Arctic sea ice has a direct impact on all kinds of organisms living on and under the sea ice. One of the main sources of food for polar bears is seals that breathe or rest on the Arctic sea ice, while their underwater activity is far less than that of seals. As a result, the reduction of sea ice has seriously affected the success rate of polar bear hunting, resulting in the sharp decline of its population in recent decades. In addition, although the effect of sea ice melting on sea water volume is smaller than that of land ice sheet melting, it directly affects the sea water salinity of sea ice area. The significant decrease of salinity will change the living state of some plankton and destroy the whole marine food chain network.
The reduction of Arctic sea ice will in turn affect the global climate. As the heat capacity of liquid water is greater than that of ice, once the Arctic Ocean loses the cover of sea ice in summer, it will absorb and store more heat, which will disturb the existing climate state from the current, atmospheric circulation and other aspects.
The extremely cold air mass over the Arctic is surrounded by a circle of polar high-speed circulation, which will not spread easily. It has been found that the disappearance of sea ice will weaken the high-speed circulation of the polar region and cause the low-temperature air mass in the Arctic to spread to the low latitude area. In recent years, extreme cold weather in North America and Europe is actually the result of global warming.
There is also a good side to the reduction of sea ice in the Arctic. For example, in terms of shipping, the Arctic sea route becomes possible, which will greatly shorten the distance from the Pacific coast to Western Europe and Northern Europe. However, the economic benefits can not offset the economic losses caused by meteorological disasters related to sea ice melting.
The decrease of Arctic sea ice is also related to the inclination of the earth and other factors. Since the earth's rotation axis was tilted more than it is now, resulting in more heat radiation to the poles, the Arctic is likely to have ice free summer 10000 years ago. However, the change of geological factors is very slow, at least in ten thousand years, so it can not explain the rapid change of sea ice area from this point of view.
According to the computer model simulation, the time point of ice free summer in the Arctic Ocean may be between 2030 and 2040, and 2034 is the most likely year. Because climate is a non-linear system, which is very sensitive to the establishment of models and the setting of conditions, scientists are generally cautious and conservative. In the past, the actual development will generally come earlier than predicted.
Human carbon emission is the most important factor affecting climate change in the past 200 years. If human beings do not make substantial changes in reducing carbon emissions, the global average temperature will rise by more than 1.5 ℃ by the end of this century. Without the leap forward development of science and technology, this temperature rise will have an irreversible impact. The ice free summer of the Arctic Ocean may just be the beginning.
Source: People's daily