The polar seas help regulate Earth’s climate, storing carbon, driving ocean currents and sustaining vast ecosystems. But as sea ice retreats and oceans warm, scientists are racing to understand what comes next. Above the Arctic, NASA investigates the complex relationship between sea ice and clouds. In Antarctica, researchers aboard the RRS David Attenborough track changes in the Southern Ocean and the krill that support extraordinary wildlife. In the High Arctic, WWF scientists monitor the underwater soundscape as increasing shipping threatens marine life. Meanwhile, in Nunavut, innovators and Inuit communities test ways to restore sea ice. Together, their discoveries reveal a planet in transition.