Young Ice: Too Little Time to Get Old

Young ice breaks apart easier than old ice, and breakup of large areas of sea ice has become increasingly more common.

In March and February 2013 an area of sea ice north of Alaska broke up over a period of two to three weeks. Strong winds drove large ice floes from the Beaufort Sea toward the Bering Strait. Because the ice had formed during the same winter, it was more fragile and dissolved more easily than older ice would have done.

"We are moving from thicker, multi-year ice to thinner, newly formed ice," says Jonathan Rheinl?nder, researcher at the Nansen Environmental and Remote Sensing Center and the Bjerknes Centre.

"There are more leads."

Rheinl?nder investigates rapid breakup events. The ice pack transforms from a continuous surface into a cluster of floes that are easily moved by currents and winds.

Young ice is weaker

The Arctic sea ice cover reaches its minimum in September, after the summer melt season. 2024 is unlikely to be among the years with lowest sea ice extent, however there is considerably less ice than in any year before 2007.

The smallest sea ice extent recorded occurred in 2012. The rapid breakup event in the Beaufort Sea in late winter 2013 followed that summer.

Simulations Jonathan and his colleagues have run with an ice model, indicate that the ice cover in the Beaufort Sea breaks more easily now than in the past. Rapid events with large areas dissolving during storms occur more often than before.

"One could think that the increase in leads were caused by stronger winds," he says. "But that is not the case. We can only explain this with changes within the ice."

Storms have not become more frequent. The fact that the ice cover breaks up more often is because the ice is thinner and more fragile.

"If the melting season starts with a thin ice cover, it may break down earlier. At the same time, there is also a lot of other things that come into play."

The temperature and wind conditions during the summer largely determine the extent of sea ice melt.

No time to get old

Open water increases the transport of heat from the ocean and into the cold, Arctic winter night. Leads can cause the sea to cool down more than if it had been protected by ice.

"Previously, it was thought that leads increase the production of new ice," says Jonathan Rheinl?nder. "But we must consider both sides of the equation."

When the ice breaks up, it is more easily moved. In years with a lot of cracking more ice is also transported out of the Beaufort Sea. In total, simulations and satellite data show that breakups cause reductions in winter sea ice.

In the past ice from the western coast of Greenland remained in the Beaufort Sea for several years before being transported out. Now it rarely gets old.

"After 2007 the Beaufort Sea has gone from nursery to graveyard."