It is not only the extent of the sea ice that has changed, it is also the character. Arctic sea ice has become dramatically younger. As NOAA explains, age refers to thickness and durability when it comes to ice. Young ice is thinner and is more likely to melt in summer. Older ice – which is usually four years or older – is ice that survives all year round and thickens over time. Per die National Center for Snow and Iceold ice can become between 1.8 and 7.6 meters thick.
As you can see in the picture, older ice in the Arctic is a streak of what it once was. In 1985, 33% of ice in the Arctic was very old ice; in March 2020, only 4.4% of the sea ice was old.
According to NOAA, 20 to 30 years ago, the sea ice on the North Pole was dominated by ancient sea ice. Over time, old ice drifted through the Fram Sea Strait from the North Pole where it melted in the relatively warmer waters of the Atlantic Ocean. This was not a problem then, as new bundles of old ice were created in the Beaufort Gyre, which NOAA describes as a nursery for young ice to get thicker and stronger as it floats around for years. The agency says the summers in the southern branch of the Beaufort Gyre are too hot to survive ice.
To get a phrase out of the NSIDC, this ‘Benjamin Button ice’ is an element in a dangerous cycle, in which rising air and ocean temperatures more easily destroy the first-year ice and weaken older ice. If this cycle continues and older ice disappears from the Arctic Ocean, the world could see ice-free summers in the North Pole by 2030.