Overview: Most people imagine dinosaurs lurking in warm locales with swamps and jungles, dining on vegetation and each other. But "Arctic Dinosaurs" reveals that many species also thrived in the harsh environments of the north and south polar regions. NOVA follows two high-stakes expeditions and the paleontologists who push the limits of science to unearth 70 million-year-old fossils buried in the vast Alaskan tundra.