- Mark Kinver
- BBC Environmental Affairs Correspondent
“Our Planet’s Past and Present” series of special reports focus on the various impacts and changes brought about by climate warming on the earth. Update monthly before the UN Glasgow Climate Summit in November.
In the snow-covered Arctic Ocean, the warming of the earth causes the melting of sea ice to accelerate, and the shrinking of the ice sheet accelerates climate warming, because more solar heat is absorbed by the seawater instead of being reflected by the ice, which can be said to be mutually exclusive cause and effect.
Image source,Getty Images
Arctic sea ice functions as a natural thermostat and plays an important role in regulating the temperature of the earth. Therefore, changes in the area of the Arctic ice cover require close attention.
According to data from the National Aeronautics and Space Administration (NASA), from 1981 to 2010, the area of Arctic sea ice decreased by at least 13.1% every 10 years.
A research report published in 2007 revealed the relationship between the increase in the amount of greenhouse gases in the atmosphere and the melting of Arctic sea ice and the shrinking of the ice cover.
One of the main reasons for the increase in greenhouse gas emissions and the increase in the earth’s temperature is human activities.
The disappearance of Arctic sea ice, in turn, intensified the increase in the average surface temperature. According to calculations, sea ice can reflect 80% of the sunlight back into space, and this part of the sunlight will not cause the surface temperature to rise.
However, after the sea ice melts and the ice cover area shrinks, the sun hits the ocean directly, 90% of the heat is absorbed by the sea water, and the entire area becomes warmer.
This phenomenon is called albedo, and its principle is that light-colored surfaces reflect more solar radiation and heat than dark-colored surfaces.
NASA satellite images show massive loss of glaciers at the two poles of the earth
“critical point”
There is a seasonal cycle of freezing and melting of Arctic sea water. The freezing process reaches its peak in March each year, and the melting of sea ice reaches its peak in September each year.
However, ground and satellite data show that as the earth heats up, the area of sea ice in the Arctic is decreasing.
As the Arctic sea ice area shrinks and the sea water area expands, under the effect of albedo, the darker sea water absorbs more sunlight heat, and the heat reflected by the white ice surface decreases, which ultimately leads to the acceleration of the Arctic surface and sea water heating rate. .
Scientists worry that this trend will continue to the end, which may lead to the direct exposure of the surface of the snow and ice to the sun, and there will be a “critical point”-that is, manual intervention can no longer stop or reverse the temperature of the earth.
The world becomes smaller and warmer
A direct change brought about by the melting and reduction of Arctic ice is the smooth flow of the “Northwest Passage” (also translated as Northwest Passage, Northwest Passage). This is a maritime trade route connecting the North Atlantic and the North Pacific.
Since the 19th century, humans have been making continuous efforts to explore waterways and open routes in the waters between Greenland Island and the Arctic Ocean islands in Canada. Voyagers and explorers followed suit, and many people died in the Arctic Ocean.
Now, as the Arctic sea ice area shrinks in the summer, some experts predict that the Arctic Ocean route will have considerable commercial value in the near future.
Image source,Getty Images
Some people think that this will completely change the global shipping industry, while others think that this is a time bomb and a potential disaster.
Environmental protection groups worry that the opening of the Arctic Ocean shipping lines and the increasing traffic will surely bring devastating damage to the slow-growing and long-cycle Arctic marine biosphere.
What is particularly worrying is that once a freighter fails in the Arctic Ocean, it may cause huge pollution.
Image source,Getty Images
Food shortage
There is evidence that the melting of sea ice and thinning of the ice layer have already affected polar wildlife.
Even polar bears at the top of the food chain are not immune.
In more and more places, the ice layer is thinning and cannot bear the weight of polar bears. In order to find food, they either take a detour or swim in the sea.
In addition, polar bears foraging in places where humans settled in the Arctic Circle have become more frequent. Some people think that melting sea ice is an important reason-polar bears have become more and more difficult to find food in the natural environment in the original way.
After the glacier breaks and the ice tongue falls off, it becomes floating ice on the sea
Warm and cold ocean currents
Another issue that is drawing more attention from scientists is the Arctic Ocean Beaufort Vortex—a huge freshwater circulation formed by melting snow, rivers, and rainwater in the Arctic Ocean. Freshwater usually gradually flows into the North Atlantic Ocean.
If the fresh water of this vortex suddenly floods into the Atlantic Ocean in large quantities, it may weaken the strength of the Atlantic circulation, leading to major changes in the climate of Western Europe and North America.
The Atlantic Meridional Overturning Circulation (AMOC), which has a higher water temperature, encounters the ice water of the Arctic Ocean and then cools down, sinks, then advances southward, and then returns to the North Atlantic Ocean with warm currents from the tropics. This ocean current has a major impact on the climate of Western Europe and North America.
However, because fresh water has a lower density than sea water and lighter than sea water, it will float in the upper layer, which will reduce the strength of the Atlantic circulation and slow down the circulation of ocean currents.
Marine and climate experts believe that this situation will have an impact on the climate of the entire hemisphere, especially in Western Europe, and then affect the global climate.