Arctic sea ice keeps declining

Arctic sea ice keeps declining

By Elisa Jiménez Alonso

The extent of sea ice in the Arctic Ocean fluctuates naturally. Usually it reaches its maximum in March and its minimum in September of each year. Winter and summer extent trends, however, have been declining.

That is also true this year. As reported by the Met Office, measurements of the extent of summer Arctic sea ice show that 2016 is jointly the second lowest year on record at 4.14 million square km. The lowest extent recorded since satellite monitoring began in 1979, was in 2012 at 3.39 million square km.

It is important to add, that the 10 years with the lowest Arctic sea ice extent have been within the last decade, showing an alarming trend. Dr Ed Blockley, who leads the Met Office Polar Climate Group, says, “the current rate of loss of Arctic summer sea ice of 13% per decade is equivalent to an annual loss greater than the size of Scotland.”

Image: Arctic sea ice minima from 1979 to 2016 according to the NSIDC Sea Ice Index. Source: Met Office UK.
 

NASA points out that, “cycles of natural variability such as the Arctic Oscillation are known to play a role in Arctic sea ice extent, but the sharp decline cannot be explained by natural variability alone. Natural variability and rising global temperatures have worked together to melt greater amounts of Arctic sea ice.” Some climate models even suggest we might see an ice-free Arctic for part of the year before 2100.

Sea ice is much brighter than the ocean surface, which means it reflects more of the Sun’s energy back. The darker ocean surface, however, becoming more exposed now, absorbs more energy, which heats the water up, causes even more ice to melt, and warms the Arctic climate.

Video: This NASA animation shows the Arctic sea ice age for the week of the minimum ice extent for each year, depicting the age in different colors. Younger sea ice, or first-year ice, is shown in a dark shade of blue while the ice that is 5 or more years old is shown as white. A color scale identifies the age of the intermediary years. A bar graph displayed in the lower right corner quantifies the area covered by the ice in each age category on the day of the annual minimum. In addition, memory bars shown in green portray the maximum annual value for each age range seen since Jan. 1, 1984, on the day of the annual minimum.


Cover photo by Barni1/Pixabay (Public Domain)

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