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What happens when the Arctic’s ancient freezer starts to fail? Discover why thawing permafrost is a concerning global warming wildcard. Scientists have uncovered the truth behind giant sinkholes exploding from the frozen ground in Siberia, and a vast lake bubbling with methane in Alaska. They are pointing to a dramatic shift beneath our feet – one driven by thawing Arctic permafrost, the vast frozen layer that stores nearly twice as much carbon as the entire atmosphere. Learn why these geological curiosities reveal a dangerous climate wildcard – one powerful enough to accelerate global warming in ways current models don’t yet predict. To watch the full film, visit https://www.pbs.org/wgbh/nova/video/arctic-sinkholes/ 📰 Stay up to date on the latest science discoveries, full episodes, articles, videos, and more by signing up for NOVA's newsletter here: https://to.pbs.org/4brCC7Y ▶️ Stream NOVA documentaries & more with PBS Documentaries on Prime Video: https://amzn.to/4hXBlsu 🛍️ Shop official NOVA 50th anniversary merch: https://nova-shop.org/ Follow on social for more NOVA content Twitter: https://twitter.com/novapbs Instagram: https://www.instagram.com/novapbs TikTok: https://www.tiktok.com/@novapbs