Enlarge / Taku Glacier is one of many that begin in the Juneau Icefield. (credit: Mauricio Handler / Getty Images) The melting of one of North America’s largest ice fields has accelerated and could soon reach an irreversible tipping point. That’s the conclusion of new research colleagues and I have published on the Juneau Icefield, which straddles the Alaska-Canada border near the Alaskan capital of Juneau. In the summer of 2022, I skied across the flat, smooth, and white plateau of the icefield, accompanied by other researchers, sliding in the tracks of the person in front of me under a hot sun.