The Earth’s north and south polar regions are responding quite differently to climate change
The Arctic and Antarctic are the two coldest regions on Earth. Sitting at opposite poles, they might seem like mirror images of each other. But their environments are shaped by very different forces. And that’s why global warming is affecting them in very different ways.
These differences also help explain their effects on the rest of the planet.
At the north end of the world, the Arctic consists of an ocean enclosed by several large blocks of land: North America, Greenland, Europe and Asia.
Much of the Arctic Ocean is covered by a thin crust of sea ice, most of it 1 to 4 meters (3 to 13 feet) thick. It forms as the surface of the ocean freezes during winter. Some of this ice melts during the warm months. Arctic sea ice reaches its smallest area at the end of summer, in September, before it starts growing again.
Arctic sea ice has shrunken dramatically in recent years. The area of ice left at the end of summer is now about 40 percent less than it was in the early 1980s. Each year, on average, it decreases by another 82,000 square kilometers (32,000 square miles) — an area about the size of the state of Maine. The pace of sea-ice loss has “surprised a lot of people,” says Julienne Stroeve. She’s a polar scientist at the University of Manitoba in Canada. And she predicts that by 2040 the Arctic Ocean could be mostly ice free during summer.
The situation in Antarctica, at the south end of the world, is quite different. The sea ice here actually has increased a bit since 1980. This often confuses people. And climate skeptics sometimes take advantage of this confusion to mislead people. Those skeptics argue that the world is not actually getting warmer. They cite expanding Antarctic sea ice as evidence of this. But if you understand how the Arctic and Antarctic are different, then what’s happening down south makes sense.
Antarctica is in some ways the opposite of the Arctic. Rather than water surrounded by land, it is land surrounded by water. And that difference has shaped the climate of Antarctica in major ways.
The Southern Ocean, which surrounds Antarctica, is the only place where a ring of ocean, unbroken by land, circles the planet. If you’ve ever crossed the Southern Ocean by ship, you will know it is some of the roughest water on Earth. The wind constantly whips the water into waves that can tower 10 to 12 meters (33 to 39 feet) — as tall as a three-story building. That wind always pushes the water eastward. It creates an ocean current that circles Antarctica. Such a current is known as circumpolar.
The Antarctic Circumpolar Current is the most powerful ocean current on the planet. It, and the winds that drive it, isolate Antarctica from the rest of the world. They keep Antarctica far colder than the Arctic.
The Arctic and parts of Antarctica are among the fastest-warming places on Earth. They are warming up to five times as quickly as the rest of the planet. But because these two regions start out at different temperatures, the same amount of warming has very different effects.
Much of the Arctic is only a little bit below freezing in summer, so just a couple degrees of warming means that much more of its sea ice will melt.