Keyhole Surgery: the moment when the bosun and crew retrieved the topmost floats of the Instrument Mooring #2 at the start of the morning watch aboard ship. By lunchtime, more than 2 and one half miles of equipment had up through this small hole. Note that, the rest of the Arctic Ocean is completely frozen-over, which means we now have to break ice with the ship everywhere we go. (photo by Chris German, Woods Hole Oceanographic Institution)

Today was the last day of summer in the Northern Hemisphere. With the sun directly over the Equator today, there would have been exactly 12 hours each when the sun was above or below the horizon at the North Pole. After today, the sun never reaches above the horizon now and, since we are pretty close to 90°N (about 200 miles at most), from this point on our days are going to get shorter and shorter (and darker and darker) and the temperature is predicted to drop accordingly as winter closes in.

Sunrise and sunset (red line) at the top of the world on the Autumnal Equinox, 2016.

So before conditions get too severe and the ice gets much thicker, today was time for the ship to complete its “chores” and recover the second of two long-term moorings from the seafloor. This one was truly enormous: 4,500 meters (14,800 feet) of instrument-studded cable had been strung out vertically at a depth of 4,800 meters (15,700 feet) a year ago on the axis of the Gakkel Ridge, which is also where we will be returning to hunt for black smoker vents in a few days.

The first task of the day was for the ship to send coded acoustic commands to the seafloor (equivalent to shouting “ping” at exactly the right pitch) so that mooring release would know that it was time to unhook from the anchor. Actually, just before that, the ship had to first break a hole in the ice (the ocean is now 100 percent frozen-over) so that there was a small, ice-filled lake directly above the mooring.

Once we could see the top of the mooring (some air-filled glass balls about 30 to 50 centimeters (12 to 20 inches) encased in bright yellow-and-orange plastic “hard hats) peeking out just below the ice, the ship moved up slowly and cautiously until the bosun and crew could snag the floats with grappling hooks and attach the top end of the complex string to the ship’s cranes and winches. Over the next 3 or 4 hours, the entire length of valuable equipment and even more valuable scientific information about the Arctic climate were brought safely on board—all through a hole in the ice smaller than a parking space in Woods Hole during the summer!