(CNN)From year to year, the ice around the Arctic ebbs and flows, reaching a minimum and maximum as the temperature shifts through the seasons.
Watch as old sea ice vanishes
Scientists recently released time-lapse animation comparing Arctic sea ice since 1984 with now, and it is a little startling. The old sea ice -- the Arctic sea ice that lasts year after year -- is smaller than it has been in three decades.
You see, sea ice is kind of like plants. There are seasonal and perennial sea ice. The perennial sea ice lasts from one year to the next and represents the thickest ice. It can last for four, or even up to nine years or more without melting during the warmer summer months and can be at least 4 meters thick.
But lately, the thinner, younger sea ice -- less than a year -- has become the majority across the Arctic. Young ice struggles to reach 2 meters thick during winter months and then is more likely to melt during the summer.
In September, Arctic sea ice shrank to the second-lowest level since records began in 1979. The lowest sea ice extent was recorded on September 17, 2012, when it fell to just 1.31 million square miles (3.39 million square kilometers).
The polar sea ice has a direct influence on ocean circulation, weather and regional climate across the globe. Vanishing sea ice is an easy indicator that climate change is taking place.
According to NASA, many global climate models predict that the Arctic will be ice-free for at least part of the year before the end of the 21st century. Some models predict an ice-free Arctic by midcentury.
If this holds true, it would have a direct impact on weather patterns seen in the United States and around the world.