WASHINGTON — Arctic sea ice this summer shrank to its second lowest level since scientists started to monitor it by satellite, with scientists saying it is another signal of global warming.

The National Snow and Ice Data Center in Colorado said the sea ice reached its summer low point on Saturday, extending 1.6 million square miles. That’s behind only the mark set in 2012, 1.31 million square miles.

Center director Mark Serreze said this year’s level technically was 3,800 square miles less than 2007, but that’s so close the two years are essentially tied.

“It’s a tremendous loss that we’re looking at here,” he said.

It was an unusual year for sea ice in the Arctic, Serreze said. In the winter, levels were among their lowest ever for the cold season, but then there were more storms than usual over the Arctic during the summer. Those storms normally keep the Arctic cloudy and cooler, but that didn’t keep the sea ice from melting this year, he said.

“Summer weather patterns don’t matter as much as they used to, so we’re kind of entering a new regime,” Serreze said.

“The trend is clear and ominous,” National Center for Atmospheric Research senior scientist Kevin Trenberth said in an email. “This is indeed why the polar bear is a poster child for human-induced climate change, but the effects are not just in the Arctic.”