The Arctic, an ocean surrounded by land, responds much more directly to changes in air and sea-surface temperatures than Antarctica, Serreze explained. The climate of Antarctica, land surrounded by ocean, is governed much more by wind and ocean currents. Some studies indicate climate change has strengthened westerly winds in the Southern Hemisphere, and because wind has a cooling effect, scientists say this partly accounts for the marginal increase in sea ice levels that have been observed in the Antarctic in recent decades.<quoted text>
And what about the Antarctic ice increasing?
“Another reason why the sea-ice extent in the Antarctic is remaining fairly high is, interestingly, the ozone hole,” Serreze told Life’s Little Mysteries. This hole was carved out over time by chlorofluorocarbons, toxic chemicals formerly that were used in air conditioners and solvents before being banned.“The ozone hole affects the circulation of the atmosphere down there. Because of the ozone hole, the stratosphere above Antarctica is quite cold. Ozone in the stratosphere absorbs UV light, and less absorption [by] ozone makes the stratosphere really cold. This cold air propagates down to the surface by influencing the atmospheric circulation in the Antarctic, and that keeps the sea ice extensive.”
But these effects are very small, and Antarctic sea-ice levels have increased only marginally. In the coming decades, climate models suggest rising global temperatures will overwhelm the other influences and cause Antarctic sea ice to scale back, too.
The extent of Arctic sea ice at its summertime low point has dropped 40 percent in the past three decades. The idea that a tiny Antarctic ice expansion makes up for this — that heat is merely shifting from the the Southern Hemisphere to the Northern and therefore global warming must not be happening — is “just nonsense,” Serreze said.
Antarctic land ice mass is of course melting.