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On the final day of my expedition to Antarctica last year, ten of us set out on a Zodiac to tour dozens of icebergs in nature’s wondrous ocean museum. The frozen sculptures glistened in exquisite hues of blue and cyan; iceberg colors vary by the density of air bubbles. Each was formed after snapping off an ancient glacier. The iceberg that sank the Titanic in the Atlantic, in 1912, was considered a mere “bergy bit,” or a smaller piece of floating ice; it melted within a couple of years. The ones we saw around Antarctica were massive. Occasionally, we spotted blubbery elephant seals (which can weigh more than four tons) napping on icebergs, or Adélie penguins (so named by a French explorer, for his wife) leaping among them, or a Humpback whale’s blow unnervingly nearby. As we headed back to the ship, the naturalist steering the Zodiac suddenly turned off the motor. “Listen,” he said. Antarctica is usually a powerfully silent continent except for the gusting winds or the lapping waves on its coastline. He put his finger up, signalling to wait for it. We sat motionless. A thundering crack then ripped through the air, echoing across the water until it felt like it was going off inside my head. We watched a towering slice of the continent break off and crash into the Southern Ocean. It felt cataclysmic.

For almost a half century, I’ve covered wars, revolutions and uprisings on four continents, many for years on end. I’ve always been an outside observer watching as others killed each other. I lamented the loss of human life—and the warring parties’ self-destructive practices—from an emotional distance. In Antarctica, I saw war through a different prism. And I was the enemy. “Humans will be but a blip in the span of Earth’s history,” Wayne Ranney, a naturalist and geologist on the expedition, told me. “The only question is how long the blip will be.”

Last week, the temperature in Antarctica hit almost seventy degrees—the hottest in recorded history. It wasn’t a one-day fluke. Famed for its snowscapes, the Earth’s coldest, wildest, windiest, highest, and most mysterious continent has been experiencing a heat wave. A few days earlier, an Antarctic weather station recorded temperatures in the mid-sixties. It was colder in Washington, D.C., where I live. Images of northern Antarctica captured vast swaths of barren brown terrain devoid of ice and with only small puddle-like patches of snow.

The problem is not whether a new record was set, “it’s the longer-term trend that makes those records more likely to happen more often,” John Nielsen-Gammon, the director of the Texas Center for Climate Studies at Texas A. & M. University, told me this week. “It’s sort of like a forest where trees are constantly growing and trees are dying, but if they start dying faster than they can grow back, then you eventually lose the forest,” he said. “The same thing applies to glaciers. Glaciers flow out to the ocean and break off, but if they break off faster then the glacier retreats and you lose ice—and then the sea level goes up around the world.”

The iceberg that I watched break off from Antarctica was part of a process called calving. It’s normal and a necessary step in nature’s cycle, except that it’s now happening a lot faster and in larger chunks—with existential stakes. The ice in Antarctica is now melting six times faster than it did forty years ago, Eric Rignot, an Earth scientist at the University of California, Irvine, and a co-author of a major study of the continent’s ice health, told me.

This month, an iceberg measuring more than a hundred square miles—the size of the Mediterranean island of Malta, or twice the size of Washington, D.C.—broke off the Pine Island Glacier (lovingly known as PIG, for short) in West Antarctica. It then broke up into smaller “pig-lets,” according to the European Space Agency, which tracked them by satellite. The largest piglet was almost forty square miles.

The frozen continent is divided into West Antarctica and East Antarctica. (The South Pole is in East Antarctica.) Most of the melting and much of the big calving has happened in the West and along its eight hundred-mile peninsula. But, in September, an iceberg measuring more than six hundred square miles—or twenty-seven times the size of Manhattan—calved off the Amery Ice Shelf, in East Antarctica. Calving has accelerated in startling style. Two other huge soon-to-be bergs are being tracked as their crevices and cracks become visible from space. One is from PIG in the West, the other is forming off the Brunt Ice Shelf in the East.

The world’s largest iceberg—a colossus measuring more than two thousand square miles, or about the size of Delaware—broke off West Antarctica, in 2017. It was so big that maps of the continent had to be redrawn. It’s now slowly making its way around the Antarctic Peninsula, headed toward the Atlantic Ocean on a path known as “iceberg alley.”

The amount of ice on Earth was pivotal in the creation of human civilization ten thousand years ago, a fact that paleo-climatologists only discovered in the late twentieth century. Scientists now say that ice is the key to peace among civilizations for millennia to come, too. “The stability and size and mass of Antarctica is not a bad proxy for how violent the world could become, in that human civilization was built on a stable climate,” Spencer Glendon, a senior fellow at the Woods Hole Research Center, explained to me. “For the first hundred and ninety thousand years that they were on the planet, humans moved from place to place to find temperate weather, as ice and deserts shifted and temperatures moved in wild swings. About 10,000 B.C., the climate stabilized. When it stabilized, the nice places stayed nice. A stable climate helped humans stop being nomads. And that’s why people settled,” creating time and space to create humankind’s first civilizations.

In physics terms, the climate stabilized because there was just the right percentage of ice on the planet, Glendon explained. Ice reflects, so sunlight bounces off it back into space and doesn’t overheat Earth or its inhabitants. That’s now changing, as Antarctica (and Greenland) shrink. For the past ten thousand years or so, glaciers shrank in summer and grew in winter, but they had a mean or average size that was stable over time, he said. “Now, all the glaciers are receding. And that’s because it’s warmer, so they shrink more in the summer and expand less in the winter—and there’s less and less ice.”

At least eighty per cent of the planet’s fresh water is also contained in Antarctica’s ice. Icebergs that melt help replenish supplies. Again, the issue is balance. If Antarctica were to completely melt, the oceans would rise around the world by up to two hundred feet, an apocalyptic event that would reconfigure the globe’s geography. The might and majesty of Antarctica—in its huge spiny peaks and frigidly uninhabitable plateaus—makes that prospect seem impossible. In winter, the temperature has reached as low as a hundred and forty-eight degrees below zero Fahrenheit. Yet the process has begun. In 2018, a survey published in Nature reported that Antarctica lost more than three trillion tons of ice between 1992 and 2017. That’s enough to fill Lake Erie twelve times over, according to Earther. A quarter of the glacier ice in West Antarctica is now unstable due to melting over the same period, a second report, by scientists at the Centre for Polar Observation and Modelling in Britain, concluded last year. New snowfall can no longer compensate for the losses.