In particular, the Bering Sea, site of some of the largest commercial fisheries in the United States, saw unprecedented reductions in sea ice for the second winter in a row. What sea ice does exist tends to be younger, thinner and more susceptible to melting.

“The very old ice that’s been around for more than four years used to be 33 percent of the ice cover and now it’s 1 percent,” Dr. Perovich said. “One way to think about that is, when we look at the area that the old ice covered back in 1985 it was a little bit bigger than the United States east of the Mississippi River. And all that’s left now is Maine.”

The loss of sea ice changes how much heat is in the ocean, which in turn affects fisheries and ecosystems, creating cascading effects within this interconnected system. Among those affected are the more than 70 Indigenous communities in Alaska including the Inupiat, Central Yupik, Cupik, St. Lawrence Island Yupik and Unangan peoples. For the first time in the report’s 14-year history, it included input from some of these communities.

They said that the warming Arctic was shrinking their access to the food resources that have long provided the basis for their communities’ resilience.

The delayed and more drawn-out autumn freeze leaves communities isolated during a growing part of the year. That’s because they can’t use boats to travel to neighboring communities during this time but also can’t safely travel on top of the ice. At the same time, changing ocean temperatures are shifting food seasons. In Wales, Alaska, an Inupiat community that is the westernmost settlement in the United States, clams that once used to be harvested in the fall are now ready in summer.

“The way that the lower 48 relies on, say, citrus or grapes or the potato as garden food sources, the Bering Sea, when the sea ice comes, it is our garden,” said Mellisa Johnson, a guest editor on the report and a member of the Bering Sea Elders Group, which is made up of 38 tribal elders from the region. “It is our way of life.”

Similarly, whole Arctic communities have been built on permafrost. Because of climate change, that ground is now thawing. As it does, it causes roads to slump and houses to collapse.