Atop Earth,sex loan luan han ice is vanishing.

The National Snow and Ice Data Center announced Monday that Arctic sea ice, which has historically blanketed the expansive Arctic ocean, fell to its lowest extent for the year. Called the "Arctic sea ice minimum," the event occurs annually near the end of summer. 2020, however, met a grim benchmark. For only the second time in the satellite record, sea ice fell below 4 million square kilometers, or about 1.5 million square miles. Only 2012, which holds the record for the lowest ice extent, had less ice.

The diminished sea ice this year is part of a declining trend in the now 42-year Arctic satellite record. It's a consequence of a rapidly heating planet.

"The last 14 years (2007-2020) are the 14 lowest years in the record," said Walt Meier, a senior research scientist at the National Snow and Ice Data Center. "In other words, we are in a changed Arctic from the 1980s and 1990s and earlier."

The 2020 minimum is 969,000 square milesbelow the average minimum observed between 1981 to 2010, the National Snow and Ice Data center noted. That's about the size of Alaska, Montana, and Texas put together.

Although the satellite record is the modern gold standard in reliable Earth observation, century-old shipping logs, meticulously kept by mariners, reveal the Arctic's over 40-year-long sea ice slide is extreme, even compared to past, natural declines.

"From Siberian heatwaves to near-record low sea ice, we are already witnessing the effects of climate change in the Arctic," said Zachary Labe, a climate scientist at Colorado State University's Department of Atmospheric Science.

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As the graphic above reveals, Arctic sea ice is a shell of its former self: The orange line shows the typical ice extent for mid-September between 1981 and 2010. What's more, nearly all Arctic sea ice is now young and thin, meaning it's easier to melt. In 1985, one-third of sea ice was old (meaning over four years old). By March 2019, just 1.2 percentof the ice was considered old.

The blanket of ice atop Earth is crucial for a number of reasons, even if you live thousands of miles away.

• Less sea ice means a warmer Arctic, as open water soaks up more sunlight (sea ice reflects about 80 percent of sunlight back into space). There's mounting evidence that a heating Arctic results in more persistent global weather patterns, creating stagnant weather events like longer heat waves in the U.S., Europe, and elsewhere. (A warmer Arctic is linked to a wavier or amplified jet stream, which can allow an extreme weather pattern, like a heat wave or cold spell, to stall over a region.)

• Sea ice is polar bear habitat. The loss of ice, consequently, extends the period of time these marine mammals must fast as they wait for their feeding grounds to freeze up. As ice continues to dwindle, biologists expect many polar bear populations to fail this century.

• In part due to diminished sea ice, the Arctic is warming about three times faster than the rest of the globe, and this warming makes wildfires more extreme during the summer, particularly in Siberia and the Arctic Circle. The last two summers have seen unprecedented burning in the Arctic, as persistent, record-breaking heat settled over the region. This could be the start of a new Arctic fire regime.

• Permafrost, ground that typically stays frozen, is thawing. Infrastructure like roads, buildings, and oil tanks, is beginning to fail.

Sea ice in the central Arctic has been particularly diminished this year, as warmer temperatures and winds decimated the ice pack. "2020 has the most open ocean water ever observed in the Central Arctic region," said Labe. "This is really striking, but unfortunately, not surprising. Climate models continue to project further Arctic amplification and losses of sea ice if we do not have a systematic reduction in greenhouse gas emissions."

When sea ice melts in the Arctic, it feeds, or amplifies, more melting. Though a complicated nexus of climate and weather (storms, ocean currents, etc.) impacts the sea ice each year, one impact, called the Arctic ice-albedo feedback, is critical, said Meier. As described above, sea ice is excellent at reflecting sunlight back into space, but melted ice means that darker, open water now soaks up more heat. Meier has observed an earlier onset of melting ice each year, which means more ocean is open during June and July when the most sunlight is shining. This ocean heat build-up then delays the autumn freeze, resulting in a pattern of less ice.

Sure, 2020 had the second-lowest ice extent on record. But in a decade or two from now, as the planet relentlessly warms, 2020 may seem like a relatively "good year" for the Arctic.