Here’s one more reason to work to halt climate change: the Arctic Ocean has lost 95% of its oldest, thickest ice since 1985.

Two kinds of Arctic sea ice have been a defining feature of our northern ocean for hundreds of thousands of years. Multiyear ice persists during the summer melting season. Seasonal ice forms anew during the long winter months in the Arctic’s open water. This pattern of sea ice and open water changes each year depending on temperatures, tides, winds and other events. But the general pattern has persisted so that ecosystems, animals and people have been able to thrive in the Arctic largely by depending on sea ice and its predictable, seasonal change.

The most recent Arctic report card from the U.S. government’s leading ocean scientists documents the precipitous loss of multiyear sea ice. When they began measurements in 1985, government scientists calculated that multiyear ice made up 16% of the total. This year, that had dropped to only 1% of Arctic sea ice—a 95% reduction in multiyear ice over the last 33 years.

This finding matches the trend from a recent Ocean Conservancy analysis of sea ice. Our scientists looked at sea ice data for the Central Arctic Ocean by decade since satellite measurements began in the 1980s. We found that during the 1980s only 1% of this area was open water at the height of the Arctic summer in September. In our current decade (2010 to 2017), open water increased to an average of 22%. The same comparison found that sea ice thickness decreased by 60%, from an average of 2.2 meters to less than a meter of thickness.

These clear trends validate what many scientists and communities in the Arctic are observing:  an ocean that is emerging from the persistent sea ice that has characterized it for all of human history. How will organisms adapt, migrate, increase or decrease? How will ecosystems re-assemble with different or changing components? And how will humans, whether those who live in Arctic communities or who participate in global economic sectors, change and adapt?

The honest answer is that no one knows because we’ve never faced this level of change in the Arctic. We should go slow by adopting precautionary policies for increased industrial access for commercial fishing, shipping, and offshore oil and gas. We should do more scientific research, like the studies summarized in the Arctic Report Card, so that we can better understand how the Arctic works and how changes are rippling through ecosystems. We should listen to and help Arctic communities adapting to changing circumstances.

Most fundamentally, we should work to reverse climate change. In the long run, getting our greenhouse gas emissions under control could actually reverse melting trends and restore Arctic sea ice. Indeed, because Arctic sea ice plays such an important role in global temperature regulation, restoration of Arctic ice may be vital not just for the Arctic, but for the world.