The extent of sea ice blanketing the Arctic this winter fell to the lowest level on record, researchers announced this week, an ominous signal about the effects of climate change in the world’s fastest-warming region.

The Arctic reaches its maximum sea ice in March each year and then starts a six-month melt season. The National Snow and Ice Data Center said the peak measurement taken Saturday was 5.53 million square miles (14.33 million square kilometers) — about 30,000 square miles (80,000 square kilometers) smaller than the lowest previous peak in 2017.

Sea ice plays many important roles for the global climate: Its white surface can reflect energy back into space, helping the planet cool. It also acts like a blanket for the ocean, insulating it and preventing ocean heat from reaching the atmosphere. Less sea ice means more heat goes in Earth’s systems, warming the atmosphere and the oceans.