The Ice That Remains Is Younger

It’s not just the extent of the sea ice that has changed, it’s also the character. Arctic sea ice has gotten dramatically younger. As NOAA explains, when it comes to ice, age refers to thickness and durability. Young ice is thinner and more likely to melt in the summer. Older ice—which is typically four years or older—is ice that survives year-round and keeps thickening over time. Per the National Snow and Ice Data Center, old ice can grow to be between six and 25-feet (1.8 to 7.6 meters) thick.

As you can see in the graphic, older ice in the Arctic is a sliver 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 Arctic was dominated by old sea ice. As time went by though, old ice drifted out of the Arctic through the Fram Strait where it melted in the relatively warmer waters of the Atlantic. This wasn’t a problem then, as new batches of old ice were created in the Beaufort Gyre, which NOAA describes a “nursery” for young ice to grow thicker and stronger as it drifts around for many years. Today, summers in the southern branch of the Beaufort Gyre are often too warm for ice to survive, the agency said.

To use a phrase from the NSIDC, this “Benjamin Button ice” is an element in dangerous cycle, one in which increasing air and ocean temperatures more easily destroy first-year ice and weaken older ice. If this cycle continues and older ice disappears from the Arctic Ocean, the world may see ice-free summers in the Arctic as early as 2030.