Near Marion Island, The Roaring Forties, 46° 50′ S, 36°75′ E to The Great Ice Barrier, Antarctica, 66° 40′ S, 78° 22′ E

The voyage from Simonstown had not been without incident. By December 20 they were well south of the Cape and making a good 10 knots en route to the desolate chain of islands that stretches like a string of black volcanic pearls across the Southern Ocean, from Marion Island in the west to the remote and forbidding Heard Island far to the southeast. It was on that day, too, that the cook and his mate got themselves literally into hot water. “The cook and his mate were noticed sitting on the edge of a tub full of boiling water,” said Campbell, “a heavy lurch came, hot water swashed up and over, a dismal howl, and well I fancy the cook and his mate will be more careful in future!”

Dismal was the word for the weather, too, with “squalls, rain blowing fresh and a heavy swell behind us; ship rolling occasionally 30° each way, air becoming decidedly chillier, chairs dashing head-long about, breaking their own and everybody else’s legs.” But they took some solace from the hot grog that was served on the 21st to commemorate their first year at sea. In their laboratories, Wyville Thomson and John Murray labored over their paper on the nature of the deep-sea sediments and reflected on the successes that the expedition had amassed in only one year: manganese nodules and the transects of the Gulf Stream, the Sargasso Sea, and most especially the mid-Atlantic Plateau. It had been an excellent year and, as history would prove, of incalculable value to science.

The deteriorating weather had to be combated: “Every petty officer and seaman on board,” wrote Swire, “as well as certain of the marines, stokers and others, received gratis a thick pea jacket, a large worsted comforter, a pair of mitts for the hands, a knitted jersey, a pair of thick drawers and a sou’wester; he has moreover the choice of either a pair of sea boots or a pair of Flushing trousers, and a blanket is lent to each man, to be returned when called for.”

Challenger was now experiencing the “long swell” made famous by Captain Cook a hundred years before. As the corvette was pounded back and forth in seas that raced unhindered around the circumference of the planet, all on board wondered at the tenacity of that tireless navigator and how he had managed to navigate these waters in what was nothing more than, as Swire put it, “a little cockleshell. ”

On Christmas Eve, Campbell and some of the others amused themselves by trying to catch an albatross by flinging a baited line over the stern and waiting for the bird to swoop and catch it in its mouth. These were extraordinary creatures, with a wingspan that could reach 17 feet from tip to tip. The capture operation was delicate, because the bird’s bill was sharp enough to cut the line if it could get the angle right. This happened several times and the men’s efforts were unsuccessful.

The weather was now bitter and their memories of Simonstown and of having to throw water onto the deck hourly to prevent the pitch melting in the heat seemed a distant mockery. It was inconceivable that those memories were only a week old. Now hot cocoa was served regularly on the night watches, while those involved in the sounding and dredging operations received what Swire referred to as a “whack of wine.”

At lunchtime, 12 o’clock, on Christmas Day the crew assembled on the deck in the bitter weather and sang “The Roast Beef of Old England.” Lunch for the bluejackets was a basic affair, salt pork and pea soup. The officers and Scientifics as usual fared rather better, especially that evening when one of the Scientifics produced a large

bun together with several bottles of the Hibernian liqueur known as Mountain Dew. And so Christmas in those grim latitudes passed as pleasantly as possible, given the isolation of their situation. Swire wrote, “I bethought me of what the good people at home would be about at this time, and taking into account the two and a half hours difference in time, I came to the conclusion that whilst I was enjoying my whisky punch they were probably enjoying their dinner, which would be satisfactory for both parties. The toast of “Absent Friends” was drunk with enthusiasm here, as I have no doubt it was at home.”

On Boxing Day Challenger reached Marion Island, “cold, gloomy looking land, with snow reaching pretty low down,” wrote Campbell. Ashore they found the land spongy and boggy with nothing to relieve the eye but acres of moss, fur seals, and seabirds, principally albatross. Here, as elsewhere in the islands of the Southern Ocean, the Challenger men failed to distinguish themselves, killing many more animals than was necessary. In their defense we can only remember that they were the product of an age before wildlife conservation. Too, it was the era of descriptive biology par excellence, with the emphasis squarely on collecting specimens and returning them to British museums. Yet the slaughter outstripped even the demands of science and their stomachs. Within minutes of landing at Marion, Swire and the ship’s doctor killed a fur seal to no purpose, because they later discovered it was a sea elephant, the skin of which was worthless. Their slaughter of seabirds was even worse. Even Campbell found the harvesting excessive: “Does it not seem a shame to kill these glorious birds for the sake of their wing bones and feet?” he wrote. “Of the first pipe stems are made, and of the second tobacco pouches. . . .” Swire relates how he killed an albatross for a tobacco pouch but made a hash of skinning the feet. The wretched tobacco pouch’s value was now zero and the bird had been killed for no reason at all. We may well draw a veil over this more disagreeable aspect of Victorian culture.

The most notable vegetation on the island was the low green shrub, first discovered by Captain Cook, known as “kerguelen cabbage.” All agreed that when cooked it was every bit as good the ordinary cabbage they were used to. But by the 27th of December they were ready to leave Marion and, with the weather closing in, it was decided that the proposed visit to Prince Edward Island would be abandoned too. Instead, Challenger would head east immediately and seek the Crozet Islands.

Challenger arrived at the first of the Crozets, Hog Island, just before dawn on the last day of 1873. In such high latitudes dawn broke in the wee small hours and by 3:00 A.M. they could see that the island was completely wreathed in fog. All day they waited for the mist to clear, but when the day’s end came and it did not, Nares decided to move on for Possession Island, the largest of the Crozet group.

The weather here was better, and by 7:00 in the evening of January 3rd they were in the channel separating Possession and East Islands. It was “a lovely evening,” wrote Campbell, “blue-sky golden tinted towards the horizon, and the sun shining brilliantly over the heavy bank of yellow fog out of which we had sailed.” Ashore, beneath dark slopes and the black volcanic terraces, they spied a primitive encampment; just a hut, a boat, and some casks. They evidently belonged to sealers but no one was roused even by the firing of the ship’s cannon, the sound of which echoed forlornly among the island’s narrow valleys. Possession was deserted.

As at Prince Edward Island the unpredictable sub-Antarctic weather frustrated their plans to land. That night a gale blew up, and afterward the same heavy yellow fog came rolling in from the ocean. “We gave up all idea of landing on these abominable Crozets,” wrote Campbell, “and made sail for Kerguelen land, running before a strong westerly wind and a heavy swell the whole way.”

They arrived at Kerguelen on the morning of January 7, 1874, and could immediately see why Cook had renamed it “Desolation Island” during his visit 98 years before. “Kerguelen land is a gloomy

looking land,” wrote Campbell, “. . . with its high, black, fringing cliffs, patches of snow on the higher reaches of the dark colored mountains, and a gray sea, fretted with white horses surrounding it.”

The island of Kerguelen was discovered by the Frenchman Yves Joseph de Kerguelen-Tremarec in 1772. The news arrived in England in time to reach Cook before he set out on his last voyage, and he was directed by the Admiralty to “proceed in search of some islands said to have been lately discovered by the French in the latitude of 48° south, and in the meridian of Mauritius.” Cook found Kerguelen around Christmastime of 1776 and was so over-whelmingly unimpressed with the place that he immediately renamed it. The one redeeming feature of the island was its anchorage, quite the best in the Southern Ocean, which Cook named Christmas Harbor. “The general structure of Kerguelen island,” wrote Wyville Thomson, “very much resembles that of the volcanic district of Antrim, or of part of the west coast of Scotland. The coast presents a series of abrupt cliffs and headlands six to eight hundred feet high, terraced with horizontal beds of alternately softer and harder volcanic rocks. Long narrow inlets or fjords, bounded on either side by precipitous cliffs, run far into the land between the ranges of hills, cutting up the island in a singular way into a number of straggling peninsulas connected by narrow necks.”

It was indeed a desolate place but the wildlife was as abundant as at the Crozets and on Marion Island. Several parties went ashore exploring that first day and returned with various kinds of seabirds, sea elephants, and penguins. Once again the Kerguelen cabbage was found in abundance. William Spry had already commented on this strange vegetable at Marion Island, where he wrote, “a bountiful providence would seem to have placed it to keep away scurvy from any who might be so unfortunate as to be wrecked on its inhospitable shores.”

By the beginning of February they had finished their survey of Kerguelen. It took three weeks to map the island, which was 100 miles long by 50 wide. Yet despite their best efforts, they had not

managed to penetrate more than 10 miles toward the center of the island. Joe Matkin wrote,

When the time came to depart nobody was unhappy. The sheer grinding desolation of the place was getting everybody down. Kerguelen presented all over the same dreary and desolate appearance, hills and more hills of volcanic pumice, all covered in snow and with a heavy fog that hung continually over the island so that the interior was always obscured.

However, the island’s desolation was offset by whalers who came aboard from the ships Emma Jane and Roswell King. The Emma Jane’s skipper dined with the Challenger officers almost every night, holding his audience enthralled with bloody tales of their grisly trade in these remote regions. The life endured by the whalers made that of the Challenger’s men seem a sinecure. The whalers joined up for four years and were paid according to their success, but their average wage was much less than even that of the Challenger’s bluejackets.

The whalers had been in the area around Kerguelen for three years and in all that time the only inhabited place that they landed on was Tristan da Cunha. Only once a year, when they rendezvoused with a support vessel that brought provisions and relieved them of their cargo of oil and skins, did they see a fresh face. It was an existence that none aboard Challenger envied even compared to what they contemplated on the next leg of their own journey, the

300-mile leg due south to the McDonald and Heard Islands and beyond that to the Great Ice Barrier of the Antarctic.

The seas around Antarctica are the moat that surrounds a fortress, and contribute to that vast continent’s isolation. Here in the deep south of the world there are no other continents to break the winds as they blow westward under the influence of Earth’s rotation. Consequently, the seas that these winds whip up are some of the most fearsome in the world. This terrible circumpolar storm track and associated westerly current together comprise what is today known as the west wind drift. The west wind drift with its attendant wind and waves, the Roaring Forties, are the barrier that isolates Antarctica from the rest of the world.

Antarctica is the southern edge of all three of the world’s major oceans—the Indian, Atlantic, and Pacific. Surface-water currents from these oceans interacting with the west wind drift make the Roaring Forties the world’s greatest natural blender, producing a water mass of such chemical and biological distinctiveness that the Southern Ocean qualifies as an ocean in its own right.

Warm surface waters from the tropics of the Atlantic, Pacific, and Indian Oceans move southward along their western margins and are deflected eastward when they encounter the circumpolar current. This interface is called the subtropical convergence and marks the point where the mixing of these different water masses starts. The mixing of warm tropical water with cold surface water from the Antarctic produces an intermediate water type that has its own special name: sub-Antarctic surface water. The Roaring Forties are bounded on their southern margin by another narrow zone where the sub-Antarctic waters of the Roaring Forties meet the truly cold waters that surround continental Antarctica. This is the Antarctic Convergence. But it is the subtropical convergence that is normally taken as the point where the Southern Ocean starts.

The Southern Ocean is characterized by markedly lower temperatures than waters on the northern side of the subtropical convergence, as well as by a much lower salinity, because it contains a substantial contribution of fresh water from melting icebergs. It is this water that, when it sinks, forms Antarctic Bottom Water (AABW) a vitally important component of the deep waters of the world and one that influences the world’s weather far beyond the boundaries of Antarctica itself.

AABW owes its unique composition to the fact that Antarctica produces more icebergs than any other continent. Only a minuscule proportion of Antarctic ice melts during the short summer. Virtually all of Antarctica’s ice loss is in the form of icebergs, which calve from the massive walls of the Ross and Wurm ice shelves and from isolated glaciers that penetrate to the ocean from the continental interior. Antarctic icebergs carry nutrients, continental sediments, and fresh water into and around the Southern Ocean. As the icebergs melt, this cold, fresh water is added to the maelstrom of the Roaring Forties, which is why the Southern Ocean is, on average, the coldest ocean in the world.

It is ironic that Antarctic icebergs are such an important contributor to the formation of AABW, because the amount of precipitation that falls on the Antarctic continent is, in fact, very small. Indeed the interior of the continent is a cold desert, by far the largest and coldest on Earth. But the continent is so huge, and its storage capacity so voluminous, that even with the lack of precipitation Antarctica’s ice fields contain more than 60 percent of the world’s supply of fresh water, an amount equivalent to 60 years of global precipitation. Fresh water is Antarctica’s most abundant and accessible resource. Each year Antarctica produces some 5,000 icebergs, almost seven times as many as the Arctic and Greenland combined. Antarctic bergs are also much bigger than their northern cousins, each averaging about one million tons of pure fresh water.

Arctic and Antarctic icebergs differ in shape, too, a difference noted by Henry Moseley. The Challenger crew sighted their first

iceberg on February 10, 1874, after weathering a storm of such ferocity that the ship was forced to run under treble-reefed topsails. It was the worst gale that they had encountered since that first Christmas in the Channel. This time Challenger was damaged. The seas loosened the weather anchor, which swung free and staved in the hull by the sickbay. The ship’s carpenters were up all night repairing the damage; but by the 10th the ship crossed the 60th parallel and the weather lightened considerably.

At first the Scientifics had planned to log each iceberg and calculate a tally that would give some indication of their density in the austral summer. But they had to abandon that plan when they found that more than 40 were in sight at any one time. Moseley was fascinated by the bergs and noted that the typical Antarctic berg was table-shaped, with a thick dusting of snow on the flat upper surface and sides that were perpendicular cliffs. But this basic form extended only as far as the water line, beneath which the bergs spread out laterally, making it hazardous to approach them too closely.

Moseley noted that the above-sea aspect of the bergs showed many variations on the basic tabular form. Partly this was because of the channels around their bases, cut by wave action and contact with the warmer water. These “wash lines” undercut the cliffs at the edges and eventually the ice walls slipped free and crashed into the ocean, often leaving a surprisingly smooth and perpendicular surface behind. As the bergs melted and lost their mass in this way, they tended to roll over, eventually finding a new equilibrium position. When this happened the wash lines lifted away from the sea and ended up at an angle to the water’s surface. Moseley realized that it was possible to reconstruct the history of each berg by interpreting the complex interplay between the oldest and youngest wash lines. He noted, too, that even bergs with a complex wash-line history could eventually be categorized because they generally tilted in a regular fashion as their wash lines eroded. To the Challenger crew the feeling that Antarctic icebergs were built to a strict design by

unseen and little-comprehended forces added to the alien feel of the deep south.

What, then, is the reason for the limited variety of Antarctic icebergs? The difference between Arctic and Antarctic icebergs can be found by comparing the ways they form. Arctic bergs tend to calve from fast-moving glaciers and, therefore, tend to look like small mountains bobbing in the sea. In contrast, Antarctic bergs tend to calve from the more static ice shelves and glaciers that border the continent and protrude into the sea, making them not only larger, but also flatter, resembling the great tablelands of South Africa. Antarctic bergs can also reach immense sizes.

In the 1990s a berg the size of Oxfordshire broke off the Antarctic ice shelf and was widely hailed as proof of global warming. Another, the Trolltunga, began life as a separate ice tongue roughly the size of Belgium before breaking off and floating into the Southern Ocean. Such large bergs cluster near the shore where they chill the already super-cold air flowing from the Antarctic continent and produce huge banks of dense fog. Once beyond the icepack, however, they disintegrate rapidly and most are gone within two months, their melting contributing to the intense cold of the Southern Ocean. The outer boundary of the drifting bergs, where the melting is most intense, is the Antarctic Convergence. The water released by the melting of these bergs sinks rapidly and contributes to AABW.

But the deep waters produced at the Antarctic Convergence are not the only deep waters formed in these grim latitudes. Slightly further north, cold and northward flowing surface waters, sink to become sub-Antarctic intermediate water. Both Antarctic deep and intermediate waters spread north of the equator and both exchange with water from the northern hemisphere.

Mixing of water masses in the Southern Ocean is profound and continuous because the waters there are in a permanent state of flux; they never achieve thermal or density equilibrium. A stable surface layer never forms, partly because as icebergs form, salt is

concentrated in the seawater, increasing the density of surface water and causing it to sink.

Challenger’s Scientifics noted the complexity of the surface and deep-water currents around Antarctica when, on February 11, 1874, at a latitude of 65° S, a detailed analysis of the vertical temperature structure of the ocean showed a layer of deep water (between 300 and 1,800 feet) that was warmer than either the overlying or underlying waters. This, almost certainly, was a localized eddy of tropical water trapped between the AABW and the cold surface water formed by the melting icebergs that surrounded the ship. The thermal inversion caused much consternation among the Scientifics, or as William Spry put it, “. . . first a cold stratum to 50 fathoms, and then warmer to 300 fathoms, to the great surprise of our ‘Philos,’ thus putting their whole theory out of gear. . . .”

The tempestuous whirl of circum-Antarctic waters is also responsible for their being among the most fertile in the world. Upwelling caused by the water racing around the coast of Antarctica brings to the surface nutrients such as nitrates and phosphates, which fuel the extraordinary biological fecundity of the seas there.

Not only does Antarctica transform the waters that circulate around it, but those same waters also transform the continent itself, being largely responsible for the land’s extreme cold by maintaining its thermal isolation from the rest of the planet. Water and land are mutually and eternally interdependent and by controlling the formation of the greatest mass of cold deep water on the planet, Antarctica and the Southern Ocean in turn control the world’s weather. This phenomenon started when Antarctica separated from South America sometime in the early Cenozoic (or Tertiary era). The single crucial change that ceded control of the planet’s weather to this region was its suddenly acquired ability to form cold deep waters, and that was an accident of plate tectonics.

It seems that at the end of the Cretaceous period, just before the dinosaurs and so many other creatures and plants got snuffed, deep waters were formed in the tropics, just about as far as it is

possible to get from the poles. The world was still girdled by a super ocean we call Tethys and the planet’s surface waters basked in the heat of a sun that was already augmented by greenhouse-gas concentrations several times higher than those of today.

Under these conditions the surface waters of the Tethys started to sink. As they heated up, water evaporated into the atmosphere, concentrating the salt, and the density of the remaining water increased. This deep water then passed out of Tethys into the other oceans of the world and eventually circulated as far as the high northern and southern latitudes. But there is good evidence to suggest that by the end of the Paleocene period—only 10 million years later (55 million years before present)—cold waters were also being formed somewhere in the high southern latitudes. The most likely explanation is that in the Paleocene, when it separated from South America, Antarctica’s thermal isolation began.

As Antarctica drifted farther south it became more and more isolated from the rest of the world and the oceans around it widened, initiating the complex system of currents that characterize the Southern Ocean. In a positive feedback loop of progressive cooling, Antarctica became more and more thermally isolated from the rest of the world and cooled still further. The “ice-house Earth” had begun with a vengeance. By the time Antarctica drifted as far as the South Pole, it was the coldest continent on Earth. As early as the Early Eocene the glaciers, which were spreading across the surface of the continent, reached the sea and began cooling the water there. As these waters cooled, they increased in density and began to sink, traveling off into the world ocean carrying oxygenated cold water with them and replacing the warm, saline, deep waters—formed in Tethys—that were previously the dominant type of deep water.

Yet not only is Antarctica heavily responsible for the control of global climates through its production of cold deep water, it is also one of the best places in the world to examine the record of past climate, particularly over the last several glacial cycles. These comparatively recent cycles are particularly important to us because

they ushered in the era of humankind. And the singular property that makes Antarctica so useful as a monitor of past climatic change is one that Henry Moseley, too, found intriguing. Because by the end of the third week of February 1874, as Challenger moved among the icebergs only a handful of miles from the Great Ice Barrier, Moseley observed that the ice of the bergs showed layers of compaction. He wrote, “The entire mass shows a well marked stratification, being composed of alternate layers of white opaque looking, and blue, more compact and transparent ice . . . the color depending on the greater or less number and size of the air-cells in the ice.”

It was a clue that in the same way that the sediments of the ocean floor are the library of time, the ice of the Antarctic also preserves a record of climate change.