Kulusuk, GreenlandA thousand feet above the glistening, iceberg-dotted water of the ocean off of East Greenland, oceanographer Josh Willis braces for balance, his feet spread wide on the metal floor of a specially-outfitted airplane. He grips a wide grey cylinder, hovering it over a 6-inch-wide bottomless tube.

The pilot’s voice crackles over the intercom: “3, 2, 1, zero, DROP.”

Willis lets the cylinder go. With a whoosh, it slips down the tube and into the wide-open air.

The plane banks hard to the right and everyone on board rushes to a window. “I see it!” yells Ian Fenty, another oceanographer on the project, as the probe—designed to sink to the seafloor and record the properties there—splashes down.

Willis, Fenty, and a crew of