Rising oceanic and atmospheric temperatures have been causing the volume of sea ice to decrease steadily since the industrial revolution. Now, in 2018, that number is leveling out as the amount of old sea ice has been well overtaken by new ice.
Two kinds of ice can be found in the Arctic: Annual sea ice, which melts and reforms over the course of a year, and perennial sea ice, which stays frozen for many years and gets thicker each winter. Since 1958, perennial sea ice in the Arctic has decreased in thickness by about 67% and 800,000 square miles. Now, the ice in the northern ocean is made up of roughly 70% annual ice.
Unlike perennial ice, annual ice is less at the mercy of global warming. As a result, the variation in Arctic ice volume from winter to winter is fluctuating less than it has in the recent past.
Pros and cons
Steadying numbers might seem initially like cause for celebration, but all is not as happy as it looks. While perennial sea ice is more prone to the effects of global warming, that ice is much thicker than the annual ice that forms. The thinner seasonal ice is more susceptible to the elements, but one advantage it has over old ice is that it grows more quickly.
As temperatures continue to rise, older ice will continue to melt, leaving a greater and greater percentage of annual ice to fill in the gaps. What happens then?
A warmer future
One of the significant concerns that come with melting sea ice is rising ocean levels. Another issue has to do with species mobility. Polar bears exist only within the Arctic circle (the word “arctic” is derived from the Greek word for “bear,” which makes the Antarctic, “without bears”). As the amount of sea ice present year-round disappears, it becomes more difficult for the bears to hunt over vast areas.
Ice also reflects the sun’s rays much better than the surface of the ocean does. Less ice means less radiation being reflected and more is absorbed. The more radiation is absorbed, the warmer the water gets. Warmer water leads to potentially-lethal trouble for cold-water animals.