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Godzilla Ice
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| Photo by Jaime Ramos for National Science Foundation |
I had come to the Antarctic at the invitation of the National Science Foundation to learn about ice, and from the day I landed at its base at McMurdo I had been hearing Marchant’s name. But his tiny encampment is one of the more remote field camps the NSF supports, and the only way to get there is by helicopter. During the austral summer, the NSF maintains a fleet of choppers for ferrying scientists and their equipment to and from the field camps; they would try to fit me into their schedule, I was told, but no guarantees.
Logistics in the Antarctic have been particularly difficult this season. Four years ago, a humongous iceberg known as B15 broke off from the Ross Ice Shelf north of McMurdo and started drifting into McMurdo Sound. Soon after its secession, the initial berg broke up into several pieces, but its largest fragment, B15-A, is still 80 miles long and has a total area of 1,200 square miles, almost the size of Long Island. The presence of this behemoth has interrupted the normal patterns of wind and ocean currents, and because of this disturbance the entire surface of the sound is frozen solid.
B15-A has been making life hell for Antarctica’s humans and also for the region’s penguins. During November, penguins should be nesting, the males sitting on the eggs while the females go to the sea to feed. In normal years there is usually about 10 miles of ice from the coastline where the rookeries are located out to the open water, and the birds can make that trek without much trouble, Dr. Steve Alexander told me. An affable, laconic English biologist, Alexander is the manager of McMurdo’s Crary Science Laboratory, the logistical hub for Antarctic science. This year, however, the penguins must cross nearly 80 miles of ice, “which is too far to make it worth their while,” Alexander said. The birds have been abandoning their rookeries, leaving their eggs and waddling away.
The Physiology of Freezing
It is no coincidence that the local term for being in Antarctica is “on the ice” — as in the oft-asked question “How many seasons have you been on the ice?” As a newbie, I signaled my neophyte status in myriad ways, from my ignorance of the argot to my wimpy need to bundle up in four layers of clothing every time I set foot out the door. Even in summer, the average temperature on the Antarctic coast (where McMurdo lies) is around -15°C. In winter it drops to -30°C. Inland, the summer average is around -40°C and the winter average -70°C. The coldest temperature ever recorded on Earth, -89.2°C, was at the Russian Vostok Station. All this is without considering the wind-chill factor, which can easily shave off another 20 to 30 degrees. The day I spent at the South Pole I felt as if my mind had crystallized — the chill penetrated so deep, I could barely breathe, let alone think. And that was in the middle of summer.
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Ice crystals are not only sharp; they also have the unusual property of taking up more space than the water from which they were formed. Water is one of the very rare substances that expands when it freezes — ice is 8 percent less dense than liquid H20, which is the reason why ice floats, and this singular fact has made life on Earth possible. If, like most liquids, water contracted when it froze, the denser, heavier ice would drop to the bottom of the sea, and the world’s oceans would long ago have solidified into an unmeltable mass.
But if ice is physically necessary for Life as a whole, for individual lives it is almost universally lethal. (Anyone cryogenically frozen today would be so badly cell-damaged, if they were ever reanimated it is hard to see how life would be tolerable.) In order to preserve flesh below 0°C, you need to replace the water with a fluid that remains liquid — in effect, antifreeze. Scientists have been trying to invent a suitable substance for years; aside from cryogenicists, surgeons would like to use such a fluid for preserving transplant organs. So far they have met with limited success, yet within the Antarctic seas, aquatic creatures have long ago solved the problem and happily swim in water at a perpetual subzero chill.
On the bottom level of the Crary Lab, communities of sea stars, sea urchins and giant flealike isopods splash about in tanks cooled to a crisp -2°C. Alexander, who began his career in the Antarctic studying benthic (or deep-sea) ecology, explained that these invertebrates resolve the problem of living below freezing by the simple expedient of “maintaining their internal salinity at close to that of the sea itself.” Just as salt is used to de-ice roads in Boston and Manhattan, so it staves off freezing in the polar oceans. Call it the saline solution.
But vertebrates such as fish have evolved over millions of years with a physiology that would not tolerate such increased saltiness. “Antarctic fish have a little more salt in their bodies than you and I, but not a lot more,” Alexander explained. And yet in the Crary Lab tanks, schools of small perchlike fish are happily defying the subzero barrier. “They actually don’t survive if you raise the temperature,” Alexander noted. They belong to the suborder of notothenioidei, a group of Antarctic species that have evolved the ability to manufacture within their bodies a truly bizarre variety of antifreeze. Utterly banal to look at, each fish was quietly performing a miracle.
The man responsible for resolving the notothenioid puzzle is Dr. Arthur (Art) DeVries, one of the legends of Antarctic science. A great gruff bear of a fellow with a rumbling baritone and a distracted air, DeVries is a molecular biologist and physiologist at the University of Illinois, Urbana, who has devoted three decades of his life to the unorthodox biology of polar fish. Yet even he seems amazed by how notothenioids deal with ice. Although the Antarctic seas are liquid, DeVries explained that ice crystals are constantly forming at the bottom and floating up to the surface. Notothenioids breathe in these fragments through their gills and ingest them as they eat. Since their bodies are in thermal equilibrium with the seawater (and hence also at several degrees below zero), these crystals ought to nucleate immediate freezing in the surrounding fish flesh — but that is not occurring.
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