A new observation from NASA revealed that the oldest and thickest ice in the arctic has either melted or thinned away due to warming summers, leaving the sea ice cap more vulnerable to the increasing temperature of the ocean and atmosphere.
According to NASA, the Arctic sea ice is in constant process of expanding and shrinking. Sea ice forms during winter and melts during summer. As the sea ice survives the melting season, it thickens by three to seven feet by the first year. Multi-year sea ice, or those that survived multiple melting seasons, can expand about 10 to 13 feet thick, making it more resistant to melting.
However, warming temperature during the melting season is weakening the older sea ice, making it brittle and more prone to melting and breaking up. Furthermore, the Arctic sea ice is melting way faster in previous years, making it difficult for the sea ice to expand during winters.
"What we've seen over the years is that the older ice is disappearing," said Walt Meier, a sea ice researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a press release. "This older, thicker ice is like the bulwark of sea ice: a warm summer will melt all the young, thin ice away but it can't completely get rid of the older ice. But this older ice is becoming weaker because there's less of it and the remaining old ice is more broken up and thinner, so that bulwark is not as good as it used to be."
In order to keep track of the changes of the Arctic sea ice, scientists have been using data from a variety of sources, primarily satellite passive microwave instruments. This method of monitoring the sea ice movement and evolution of its age was developed by scientists at the University of Colorado in the early 2000s.
The instruments being used in this method measure the brightness temperature of the sea ice. Sea ice emits microwave energy depending on multiple factors, such as the ice's temperature, salinity, surface texture and the layer of snow on top of the sea ice. Each floe of sea ice has a unique brightness temperature. Using this unique feature of each sea ice, scientists were able to identify and track each floe of sea ice as they move in the Arctic.