The vast white expanse of Antarctica is almost like a blank screen that shows us Sym's inner life. Its desolate and removed landscape mirrors her loneliness, while the cold climate reflects her sexual frigidity—something Sym worries about constantly because she's so uninterested in sex. "That's when I sealed myself inside," Sym says after being teased by her sexually active friend Maxine. "Laced up the tent, so to speak. Filled the locks with water so that they would freeze" (1.18). Just like Antarctica, then, Sym is isolated and frozen.
Even Symmes Hole, the hollow portal to the center of the world that supposedly lies somewhere in Antarctica, represents Sym's interior landscape. She feels empty after her father dies, unlovable and socially worthless.
The continent's quiet aural landscape matches Sym's as well since she is partially deaf. "At home there is nowhere you can stand—the playground, the garden, the high street—and not hear the drone of an airplane," she observes. "But here in Antarctica it is the rarest of sounds" (11.68).
The isolation seems to make other people on the trip uneasy, but Sym is totally in her element. She says:
The clamor of silence was so loud that it herded the other visitors into a nervous huddle […] Didn't worry me! […] Me, I do silence. (6.48-49)
Sonically, then, Sym is in her element. Add in the fact that she has a pseudo-romance with an Antarctic explorer inside her head and that she's always wanted to go to Antarctica, and it's clear this place is far more than an icy and isolated landscape: It's a geographic and environmental symbol for our main girl.
To dig a little deeper into this symbol, swing by the "Setting" page.