Constant warmth punctuated by repeated winter heatwaves stymied Arctic sea ice growth this winter, leaving the winter sea ice cover missing an area the size of California and Texas combined, and setting a record-low maximum for the third year in a row.

Even in the context of the decades of greenhouse gas–driven warming, and subsequent ice loss in the Arctic, this winter’s weather stood out.

Arctic sea ice extent as of March 20, 2017, compared to the previous record low year and the 1981–2010 average.

“I have been looking at Arctic weather patterns for 35 years and have never seen anything close to what we’ve experienced these past two winters,” Mark Serreze, director of the National Snow and Ice Data Center, which keeps track of sea ice levels, said in a statement.

The sea ice fringing Antarctica also set a record low for its annual summer minimum (with the seasons opposite in the Southern Hemisphere), though this was in sharp contrast to the record highs racked up in recent years. Researchers are still investigating what forces, including global warming, are driving Antarctic sea ice trends.

Sea ice is a crucial part of the ecosystems at both poles, providing habitat and influencing food availability for penguins, polar bears, and other native species. Arctic sea ice melt fueled by ever-rising global temperatures is also opening the already fragile region to increased shipping traffic and may be affecting weather patterns over Europe, Asia, and North America.

Arctic air temperature differences about 2,500 feet above sea level in degrees Celsius from Oct. 1, 2016, to Feb. 28, 2017. Yellows and reds indicate temperatures higher than the 1981 to 2010 average; blues and purples indicate temperatures lower than the 1981 to 2010 average. NSIDC

The area of the Arctic Ocean covered by sea ice usually hits its winter peak in early to mid-March, as the freeze season ends with the reemergence of the sun above the horizon.

This year’s maximum was likely reached on March 7, the NSIDC said Wednesday, when sea ice covered 5.57 million square miles, the lowest in 38 years of satellite records. This area came in just under 2015’s maximum of 5.605 million square miles (the NSIDC slightly revised its numbers for last summer, so 2015’s maximum actually ranks lower than 2016) and 471,000 square miles below the 1981–2010 average, an area larger than California and Texas combined.