High above a meltwater lake in Greenland, 3,000 or so feet from the ground, the plane tipped so that Tom Hegen could shoot straight down. The plane circled the lake to find the right angle and the right light, and then did it again

This past June, late one night, a team of scientists camped out on a fjord in Greenland heard a roar. When icebergs are born, they fill the ocean with noise, and the Helheim Glacier was cracking.

This story starts more than 18 years ago, in March 2000, when a piece of the Ross Ice Shelf broke off and floated free on Antarctic waters. The crack of that iceberg forming filled the ocean with noise. Since scientists started documenting the size of icebergs, they had never seen one larger.