The comparison to the plastered ceiling of a room flashed into Keith’s mind. Surprisingly, despite the fact that his research into previous under-ice voyages had prepared him for it, the undersurface of the ice was far from smooth. Great rounded projections extended downward, reflecting additional thickness above. From his reading, Keith knew that such projections usually resulted from jamming together of the ice floes and the consequent rafting, or piling up, of broken segments of the once smooth surface when they did so.
One of the books had been written by survivors of a whaling ship which had been caught in the Arctic and had had to spend two horrible years there. It told how their ship had ventured into a wide lead at the edge of the ice pack, how it had unwisely gone too far between solid floes, how the lead began to close at the same time as the wind died, so that finally, in desperation, the crew had tried to tow her by getting out on the ice and pulling on hawsers.
Two or three times the lead reopened, bringing hope and causing renewed effort, but finally the ship was caught fast. Efforts to keep the ice broken up around her waterline were totally unavailing, and the squeeze began. Driven by far-distant winds and currents, the ice floes between which she was caught pushed inexorably together. Great blocks of ice popped up from the pressure, lying askew on top of those below. Many more were driven below the surface. A regular pressure ridge formed where the original lead of clear water had been, and the poor whaler was part of it, embedded in it.
The grinding pressure was slow, but irresistible. The ship’s wooden ribs bent, finally broke in a number of places. At the same time, by good fortune, she was heaved up, out of the worst of the pressure, so that her hull, though dangerously wounded, was still sound. Listing over heavily on top of the ice hummock created by the rafting together of the floes, she remained in this situation for two years, her crew suffering unbelievable privation from lack of food and the fierce cold. Ultimately this particular ship was fortunate. She had been stove in, but not excessively so. Her crew had been able to make the most critical repairs. When the ice floe released its pressure, which luckily for her it finally did, she was able to remain afloat and sail home. Most ships in her situation were not so fortunate and sank as soon as the ice opened up again.
The Norwegian explorer Fridtjof Nansen had deliberately taken advantage of these circumstances when he made his exploratory voyage across the Arctic Ocean in the last years of the nineteenth century. His ship was specially built, so designed that when frozen in the ice and subjected to the squeeze of the ice floes, she would rise up on top rather than be crushed. The little Fram endured a three-year freeze in the ice during which she actually did slowly progress across the Arctic Ocean, and finally, when the ice let her down once again into the free sea, sailed home to Norway, triumphant.
All of this was history; but now Keith was seeing the same situation from underneath. Although ocean currents and slow melting gnawed at the bottom side of the rafted ice floes and blunted their initially jagged edges, the hummocks nevertheless projected far deeper into the sea than their corresponding grinding edges extended above it. And in the water, as Keith well knew, the floes he was observing were teeming with life — primarily microscopic life — so that, even under the Cushing’s pair of powerful searchlights, the undersurface was dark.
But, though rafting was frequent, particularly in the area near the edge of the ice pack, it was by no means consistent. Most of the ice was a broad, thick sheet, solidly covering the surface of the sea. This was what Keith expected, having read all the accounts of the early under-ice explorations. As long as Cushing remained submerged in deep water, and barring the possibility of an iceberg frozen in the vast expanse of sea ice, he need fear no danger. In an apt analogy, one of the accounts had compared the Arctic Ocean to a huge room full of water, with a submarine the size of a matchstick suspended from the ceiling. On this basis the ice would be the thickness of the paint on the ceiling of the room, and the occasional rafting could be compared to carelessly laid or cracked plaster, bulging it downward.
Indeed, one could include polynyas in the metaphor by suggesting that the plaster had cracked open in several places — and icebergs by comparing them to occasional walnut shells, glued to it. In any case, in the deep Arctic Ocean basin, actually two basins, the only problems were those associated with its ceiling.
Next day, with the ice solid overhead, Keith ordered Cushing’s speed slowed to the minimum creeping speed and gently planed upward, raising a periscope long before there was danger of contact with the ice above. This permitted him to see the ice directly, from a much closer range, to confirm the reports he had read and the visual impressions given by the television transmitter. There was danger to the periscope, of course, should Cushing inadvertently come too close to a hummock. In one of the early explorations Nautilus had bent both of hers in such an accident.
To maneuver the ship into the shallowest portion of the ice floe, however, to find a polynya (inevitably frozen over in winter) and surface through it, or fire missiles through it, use of the periscope was imperative. It was as much for drill as for anything else, but it was nevertheless with extreme curiosity that Keith followed his periscope up from the floor. He put his eye to it as soon as the eyepiece came out of the periscope well, almost as though he were making an observation during a wartime approach on an enemy ship.
By careful calculation, the top of the ’scope was no closer than twenty-five feet from the bottom of the ice floe. Nevertheless, Keith had momentarily forgotten that even in low power it had a magnification of one and a half times, and his first reaction was alarm as the huge menacing cover filled the delicate lens. He had deliberately chosen the time of maximum daylight, and there was a moderate lighting of the nearly impervious ice. Except for color, it looked much like the frosted glass viewer upon which people spread their colored slide transparencies for comparison. Training the periscope forward he could see the powerful rays from the searchlights of the television set beaming upward through the water and reflecting upon the bottom of the ice, giving it an eerie surreal effect. To either side, with less benefit from the searchlights, the ice appeared like heavy green-tinged rain clouds, except much closer and more menacing. The best view was dead ahead, where he had the most light, and he could see, as the television had shown from farther below and with less resolution, that while it contained many small bumps and a few large ones from rafting, the undersurface of the ice was relatively free of jagged edges. He would never dare run at more than creeping speed this close to it, however. An unseen hummock of deep rafted ice, detected too late by the upward-beamed fathometer, could easily destroy a periscope and even damage the tough steel of Cushing’s sail.
Cushing had only just entered the ice pack. Perhaps there were thinner patches of ice ahead. Perhaps a polynya, or a lead, more thinly frozen over than the main floes. But already the vista was discouraging. Fifteen or twenty feet of ice were far too much to shoot a missile through, no matter what stratagems were employed. Cushing would have to break through and launch her test missiles in the surface mode. And, so far, the ice detector had found no areas of thin ice at all. Thoughtfully, Keith motioned for the periscope to be lowered. The entire time it was up had been one of tension. He was afraid of damaging the delicate instrument, but mainly his tension was due to the menace of the ice cover.