How does ice in the Arctic melts?

Every year in the Arctic, the same process occurs: the cap of sea ice in the Arctic Ocean melts and throughout the spring and summer recedes until it reaches the annual minimum. When the ocean and air cool with the advent of autumn, the ice cover grows again, and the cycle continues. But if you look at the smaller regions of the Arctic, you can get a more detailed picture of what is happening.

The map above shows the territory covered by arctic sea ice on September 13, when the ice reached its minimum for the year. The extent of sea ice is the place where the ice concentration is at least 15%. The map was compiled on the basis of observations of the Global Change Observation Mission 1st-Water satellite operated by the Japan Aerospace Exploration Agency. The yellow outline shows the median sea ice area, which was observed in September from 1981 to 2010.

According to the National Snow and Ice Data Center, the Arctic ice cover in 2017 decreased to 4.64 million square kilometers, and this is the eighth poorest indicator for 39 years of satellite observations. Having compiled graphs of these annual minimums and maximums, scientists found a steep decline in the total volume of Arctic sea ice in the satellite era. But the decline in different regions of the Arctic Ocean is different. The Beaufort Sea north of Alaska, for example, is the region where sea ice is declining the fastest.

This year the ice in the Chukchi Sea and the Beaufort Sea reached a minimum by the end of September, later than the Arctic as a whole. The graph above shows that the ice in these two seas is still decreasing, although in other regions it began to freeze. Melting lasted longer in the Beaufort Sea, which eventually began to freeze again after it reached the ice low on September 27.

The loss of ice in the Beaufort Sea and the Chukchi Sea was not a record this year, but the scale was much lower than usual. Notice, on the map the edge of the ice in these seas was spread much farther to the north than on average. According to Walt Meyer, a scientist from the National Snow and Ice Data Center, the Chukchi Sea and the Beaufort Sea entered the thawing season with a huge volume of first-year ice. This type of ice is thinner than the perennial ice (which survived the previous melting seasons), and melts much faster.

Meyer also notes that low-pressure weather systems have remained near the North Pole for most of the summer. “Low pressure keeps the weather colder overall and leads to a relatively higher ice area in general,” says Meyer. “However, the location of the low this year has led to the formation of winds blowing from the south and west. They help move ice from these regions. Also, winds could bring warm ocean waters from the Bering Strait region. “