We've all heard that the Arctic ice is disappearing, surefire proof that global warming will kill us all. But isn't it also true that Antarctica's ice is growing by leaps and bounds? Doesn't that mean we're getting into a lather over nothing?
The area covered by Antarctica's sea ice has indeed expanded over the past two decades. So in the most literal sense, yes, you're right. But it's a fallacious leap of logic to argue that this trend bodes well for the planet's health. The increase in sea ice around the South Pole may actually be bad news—an indicator that steadily rising temperatures are already wreaking havoc.
It's important to keep in mind that the Arctic and Antarctic are geographically dissimilar, so it's not too surprising that their sea-ice situations would vary. The Arctic consists of a largely frozen ocean surrounded by such land masses as Canada, Alaska, and Russia. Its southern cousin, meanwhile, is almost the exact opposite—a land mass surrounded by ocean on all sides.
Because it's semi-landlocked, and thus less buffeted by ocean currents and winds, the Arctic tends to have more moderate seasonal swings in sea ice coverage. While Arctic sea ice can persist for many years, much of Antarctica's sea ice tends to form and disappear quickly—and somewhat unpredictably.
Satellite monitoring of Antarctica's sea ice began in 1972, and for the first six years there was an alarming reduction in coverage every year. But to the bemusement of scientists, the trend began to reverse itself in 1978. Since then, the surface area covered by the continent's sea ice has expanded by an average of 0.5 percent annually; however, it's a matter of debate whether sea ice covers as much territory today as it once did in the early 1970s.
No one's entirely sure what's causing the expansion of sea ice in Antarctica, but the likeliest explanation is a disturbing one. According to a 2005 NASA-funded study, warmer temperatures have caused greater snowfall around the continent's edges, where the open oceans provide plenty of raw material for precipitation. (Warmer air absorbs moisture more readily.) The weight of that excess snow pushes sheets of sea ice down into the water, causing more water to freeze.
The incremental expansion of Antarctica's sea ice has coincided with some more troubling changes. Four of the continent's largest glaciers (whose fates are largely unrelated to that of sea ice) are retreating rapidly, and researchers blame increases in ocean temperature. The diminishment of such massive glaciers means that, despite the slow creep forward of the continent's sea ice, the total mass of all Antarctic ice—which includes inland ice—has experienced a marked decrease. And a continuation of that trend could lead to significant rises in global sea levels. Furthermore, snow is melting much farther inland than ever, as well as high up in the Transantarctic Mountains.
Some of these events might be due to causes that aren't necessarily related to human activity; it's been well-established, for example, that the Antarctic is heavily affected by naturally occurring El Niño/La Niña cycles in ways that scientists have yet to fully comprehend. But the Lantern remains convinced that our species' carbon output is changing things for the worse down in the land of penguins.
Ultimately, though, it's the Arctic that should be of greater concern at the moment. The situation on the globe's roof seems truly dire; despite the fact that last year's Arctic winter was unusually frigid, the region's sea ice continues to deteriorate. While there was a slight increase in seasonal sea ice last winter, the oldest sea ice continues to vanish at a rapid clip. This so-called perennial sea ice used to cover up to 60 percent of the Arctic; now that figure has been halved. According to NASA's Jet Propulsion Laboratory, which analyzes data from the QuickSCAT satellite, the Arctic lost a Texas-size chunk of perennial sea ice between 2005 and 2007.
That might be bad news for star-crossed polar bears, but don't think they're the only ones who will suffer. Weather at the poles plays a big role in conditions here in the United States. For example, milder Arctic cold fronts can reduce snowfall in Western mountains, which in turn can affect the water supply in thirsty Western states.
Is there an environmental quandary that's been keeping you up at night? Send it to firstname.lastname@example.org, and check this space every Tuesday.
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