Arctic sea ice shrank to a tie for the lowest measured winter level, a development announced as temperatures broke March records across the United States, Mexico and parts of Europe, the Associated Press reported. The winter maximum — the time of year when sea ice normally grows — is one of the key points in the seasonal cycle because it sets how much ice is available going into the summer melt season.
The AP reported that Arctic sea ice levels are crucial to the region’s climate. With less reflective ice, more heat energy can move into the ocean rather than being bounced back to space, and the lack of sea ice also affects wildlife such as polar bears and seals that rely on the seasonal ice. The ice changes can also affect human activity, including shipping routes, which can have broader geopolitical ripple effects.
The Associated Press said the National Snow and Ice Data Center measured this year’s winter peak at 5.52 million square miles (14.29 million square kilometers), slightly below last year’s 5.53 million square miles (14.31 million square kilometers). The center considered the two values so close that the result effectively ties for the winter record, rather than establishing a single new low.
According to the reporting, the year’s winter sea ice area was about 525,000 square miles (1.36 million square kilometers) lower than the 1981 to 2010 winter average peak. Walt Meier, a senior scientist at the data center, said warming has reduced the opportunity for ice to grow during the winter and leaves the Arctic with a “head start on the summer melt season,” because conditions start the melt from a lower baseline.
Meier told the AP that the pattern is more consistent with a steady decline than a sudden shift to a new “regime.” He said the winter maximum was interesting as a sign of a warming climate, and he contrasted the winter sea ice’s record with how variable growth can be from year to year due to weather.
The Associated Press also tied the Arctic report to extreme heat elsewhere. Climatologist and weather historian Maximiliano Herrera, who tracks extreme temperatures, described the March heat as “by far the most extreme heat event in world climatic history” and warned on social media that the next few days would be “much worse,” the AP reported.
Christ Burt, a weather historian, told the AP that sixteen states broke March temperature records in the past week or so. The AP reported that twenty-seven locations had temperatures in the past week high enough to tie or surpass the hottest April day on record, and Herrera said that, in Asia, “dozens of thousands of monthly records” were smashed with margins of 30 to 35 degrees (17 to 19 degrees Celsius).
At the same time, the AP reported that Antarctica set a record for the coldest March day anywhere on Earth, at minus 105.5 degrees (minus 76.4 degrees Celsius), citing Herrera and Burt. The AP said Meier pointed to local weather and ocean factors as reasons Antarctica’s sea ice can behave differently than the Arctic.
Meier told the AP that summer melt is the “really the critical time,” because with less white ice reflecting strong summer sunlight, oceans absorb more heat. He said that the Arctic warms closer to temperatures further south and that atmospheric pressure changes as a result, and he described a leading theory — still controversial — that the resulting Arctic changes can affect the movement and shape of the jet stream, which contributes to bursts of extreme weather.