Touching the inside surface of the acrylic pod, I could feel the penetrating cold held at bay by technology. Listening to the sea, we heard strange chirping sounds, the mating calls of Weddell seals mixed with the rumblings of grounded icebergs. In the coming weeks the sea ice would crack open and release these masses from a winter’s purgatory, and their roots would plow the bottom as they flowed out of Prydz Bay, ripping out long gashes that would create new havens for marine life.

Leaving the bay, we headed out to the open ocean. The sea ice dissipated, and our surroundings became liquid blue. Pinging the area, I detected something immense floating on the surface a mile to the east. It was a tabular berg, the largest type of iceberg. Formed when large portions of an ice shelf break off and drift free, these glacier-like ice sheets can span several square miles, their sheer white cliffs towering hundreds of feet above the surface and reaching a thousand feet below.

Ben surfaced the sub so that we could take a look. The berg was a plateau of ice as big as three aircraft carriers, its waterline ringed by a turquoise lagoon, an effect created by its submerged alabaster mass. A twenty-foot ledge, forged by lapping waves, hung over the surface.

The face of the berg was mesmerizing—a two-hundred-foot-high curl that resembled a tidal wave frozen in time. Dark blue ice rose from the sea to form its textured vortex, melding into glistening clear ice capped by its snow-covered lip.

Antarctic clear ice was the oldest ice on the continent, its presence on the tabular berg tracing back to the glacier that calved it into Prydz Bay. Over eons, tons of snowfall had accumulated and had been compressed on the glacier. Air bubbles trapped in the ice were squeezed out, rendering the ice as clear as crystal and as old as half a million years.

The blue ice was a phenomenon associated with melting and re-freezing, a process that forced out trapped air, allowing the blue color in the visible light spectrum to pass through while blocking the red color.

Circling the tabular berg, we came upon a third color: green.

As glaciers cross the Antarctic continent, their roots crush and absorb minerals from the underlying bedrock. When the ice melts, phytoplankton feeds off the minerals and grows. In turn, krill feed on the phytoplankton, and penguins, seals, and whales feed on the krill.

The Antarctic food chain would not exist without its glaciers.

Hours later, we came across the top of that food chain.

We had been following a pair of minke whales. Thirty feet long, these ten-ton baleen mini-giants were less than half the girth of their rorqual cousins, the humpback and fin whales, and were quite plentiful in Antarctic waters. Ben was keeping us within visual distance of their white underbellies when a dozen blips suddenly popped onto my sonar screen.

Orca.