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Prologue. The Berg

And now there came both mist and snow,

And it grew wondrous cold:

And ice, mast-high, came floating by,

As green as emerald.

The ice was here, the ice was there,

The ice was all around:

It cracked and growled, and roared and howled,

Like noises in a swound!

—Samuel T. Coleridge, The Rime of the Ancient Mariner (1798)

… the Southern half of the horizon was enlightened by the reflected rays of the Ice to considerable height. The Clouds near the horizon were of a perfect Snow whiteness and were difficult to be distinguished from the Ice hills whose lofty summits reached the Clouds. The Northern edge of this immense Ice field was composed of loose or broken ice so close packed together that nothing could enter it … we counted Ninety Seven Ice Hills or Mountains, many of them vastly large…. It was indeed my opinion as well as the opinion of most on board, that this Ice extended quite to the Pole or perhaps joins some land, to which it had been fixed from the creation….

—Capt. James Cook, Journals, Voyage of the Resolution and Adventure (1774)

SPECTER

It appears out of the fog and low clouds, like a white comet in the twilight.

To enter Greater Antarctica is to be drawn into a slow maelstrom of ice. Ice is the beginning of Antarctica and ice is its end. As one moves from perimeter to interior, the proportion of ice relentlessly increases. Ice creates more ice, and ice defines ice. Everything else is suppressed. This is a world derived from a single substance, water, in a single crystalline state, snow, transformed into a lithosphere composed of a single mineral, ice. This is earthscape transfigured into icescape. Here is a world informed by ice: ice that welds together a continent: ice on such a scale that it shapes and defines itself: ice that is both substance and style: ice that is both landscape and allegory. The berg is a microcosm of this world. It is the first and, paradoxically, the most complex materialization of The Ice. It is a fragment torn loose from the bottom of the globe, the icy underworld of the Earth; from the ends of the world, its past and future; from the Earth’s polar source, the end that makes possible the means. The berg is both substance and symbol. “Everything is in it,” as Conrad wrote of the human mind, “all the past as well as all the future.” The journey of the ice from core to margin, from polar plateau to open sea, narrates an allegory of mind and matter.

The great berg spins in a slow, counterclockwise gyre.

It is only another of a series of rotations that have characterized the berg’s fantastic journey. The continental plates that comprise the land form a lithospheric mosaic and spin with the infinitesimal patience of geologic time; the Southern Ocean courses around them, the gyre of the circumpolar current; storm cells swirl over the ocean, epicycles of the polar vortex; sea ice floes, like a belt of asteroids, circle endlessly, a life cycle of freezing and melting; icebergs, large and small, circle like comets around their peculiar icy sun. Superimposed over all these motions, the Earth itself rotates around its pole and revolves around the Sun. The ice terranes ring the core like concentric crystalline spheres. The ice mass that became the berg has passed from ice dome to sheet ice to glacier ice to shelf ice to pack ice to the diminutions of the bergs, cycle by cycle, like the gears of an ice orrery. The large bergs fragment into smaller bergs, the small bergs into bergy bits, the bits into growlers, the growlers into brash ice, the brash into chips and meltwater. With each outward frontier the pace of activity quickens.

Ice informs the geophysics and geography of Antarctica. It connects land to land, land to sea, sea to air, air to land, ice to ice. The Antarctic atmosphere consists of ice clouds and ice vapor. The hydrosphere exists as ice rivers and ice seas. The lithosphere is composed of ice plateaus and ice mountains. Even those features not completely saturated with ice are vastly reduced. The atmosphere is much thinner at the poles than elsewhere, in part because of the great height of the polar ice sheet. The hydrosphere is charged with bergs and coated with ice floes; during the polar night, its cover of sea ice effectively doubles the total ice field of Antarctica. The lithosphere is little more than a matrix for ice. Less than 3 percent of Antarctica consists of exposed rock, and the rock is profoundly influenced by periglacial processes, an indirect manifestation of ice.

Out of simple ice crystals is constructed a vast hierarchy of ice masses, ice terranes, and ice structures. These higher-order ice forms collectively compose the entire continent: the icebergs: tabular bergs, glacier bergs, ice islands, bergy bits, growlers, brash ice, white ice, blue ice, green ice, dirty ice; the sea ices: pack ice, ice floes, ice rinds, ice hummocks, ice ridges, ice flowers, ice stalactites, pancake ice, frazil ice, grease ice, congelation ice, infiltration ice, undersea ice, vuggy ice, new ice, old ice, brown ice, rotten ice; the coastal ices: fast ice, shore ice, glacial-ice tongues, ice piedmonts, ice fringes, ice cakes, ice foots, ice fronts, ice walls, floating ice, grounded ice, anchor ice, rime ice, ice ports, ice shelves, ice rises, ice bastions, ice haycocks, ice lobes, ice streams; the mountain ices: glacial ice, valley glaciers, cirque glaciers, piedmont glaciers, ice fjords, ice layers, ice pipes, ice falls, ice folds, ice faults, ice pinnacles, ice lenses, ice aprons, ice falls, ice fronts, ice slush; the ground ices: ice wedges, ice veins, permafrost; the polar plateau ices: ice sheets, ice caps, ice domes, ice streams, ice divides, ice saddles, ice rumples; the atmospheric ices: ice grains, ice crystals, ice dust, pencil ice, plate ice, bullet ice. The ice field is organized into a series of roughly concentric ice terranes, like the ordered rings comprising the hierarchy of Dante’s cosmology.

It is not merely the variety of ice that is overwhelming: the magnitude of ice is no less staggering. The Earth, the fabled water planet, is also an ice planet. More than 10 percent of the terrestrial Earth now lies under ice, with another 14 percent affected by periglacial environments and permafrost. Some 7 percent of the world ocean is covered by sea ice, and at any minute nearly 25 percent of the world ocean is affected by ice, especially icebergs. The vast proportion of the bergs inhabit the Southern Ocean, corralled by the Antarctic convergence. Of the Earth’s cryosphere, 99 percent is glacial ice, and 96 percent of that—over 60 percent of the world’s freshwater reserves—is in Antarctica. Within past geologic eras, the proportion of ice on the Earth has grown enormously. During the last glaciation in the Pleistocene, ice extended over 30 percent of the planet’s land surface and affected 50 percent of the world ocean. The immensity of the ice sheet even today is sufficient to deform the entire planet, so depressing the south polar region as to make the globe slightly pear-shaped.

Antarctica, showing major physiographic provinces. Redrawn, original courtesy National Science Foundation.

The Ice is, in turn, a constituent of an ice regime broadcast throughout the solar system. Pluto is an entire ice planet; the satellites of the outer planets are ice moons. On Mars and Earth, there are polar ice sheets; on some asteroids and amid the rings of Saturn, ice debris; and in the form of comets, interplanetary icebergs from the Oort cloud. The Earth’s cryosphere joins it to other worlds and other times—to the outer solar system and to vanished geologic pasts. It is a white warp in space and time. That the Earth’s ice consists not of ammonia or carbon dioxide or methane but of water, that it is crystalline rather than amorphous, and that the planet’s temperature range falls within the triple point of water account for the Earth’s uniqueness, and dynamism, as a member of the ice cosmos.

The berg contains a record of all this. Its travels have a mythic quality, a retrograde journey out of an underworld. It is a voyage that joins microcosm to macrocosm, that builds from a single substance—ice crystals—a vast, almost unbounded continent. Yet a descent to this underworld—from the ice-induced fog that shrouds the continent to the unblinking emptiness that commands its center—does not lead to more splendid scenes, as a trip through the gorge of the Grand Canyon does, or to richer displays of life, as a voyage to the interior of the Amazon does, or to more opulent civilizations, living or dead, as the excavation of Egypt’s Valley of the Kings or the cities of Troy does, or to greater knowledge, as the ultimately moral journeys of Odysseus, Aeneas, Dante, even Marlowe do. It leads only to more ice. Almost everything is there because almost nothing is there.

Antarctica is the Earth’s great sink, not only for water and heat but for information. Between core and margin there exist powerful gradients of energy and information. These gradients measure the alienness of The Ice as a geographic and cultural entity. The Ice is profoundly passive: it does not give, it takes. The Ice is a study in reductionism. Toward the interior everything is simplifed. The Ice absorbs and, an imperfect mirror, its ineffable whiteness reflects back what remains. Toward the perimeter, ice becomes more complex, its shapes multiply, and its motions accelerate. The ephemeral sample, the berg, is more interesting than the invariant whole, the plateau. The extraordinary isolation of Antarctica is not merely geophysical but metaphysical. Cultural understanding and assimilation demand more than the power to overcome the energy gradient that surrounds The Ice: they demand the capacity and desire to overcome the information gradient. Of all the ice masses in Greater Antarctica the berg is the most varied, the most informative, and the most accessible. The assimilation of The Ice begins with the assimilation of the iceberg.

The great berg hesitates.

A cloud passes before the sun. The berg glows blue amid a tar-black sea. Then almost imperceptibly it retreats, drawn back into the fog and pack ice, back into the first of the great veils of The Ice.

Glaciology of the Berg

The berg synopsizes the natural history of Antarctic ice. The whole ice field derives from the recrystallization and rearrangement of a single substance, water, in a single state, the solid, under the influence of a single force, gravity. Its geology contains virtually an entire rock cycle based on a solitary mineral, ice. Its larger geography is organized into roughly concentric ice terranes: the berg, the pack, the shelf, the glacier, the sheet, and the source domes. Within its ice the berg contains a frozen record of these terranes and a history of movement through them. Thus the berg is by far the most complex ice mass, and its dazzling whiteness masks a dense fabric of acquired ices and shapes—of old materials, now reworked into new stuff; of old shapes, now subjected to new internal stresses and external sculpturings; of old motions, now propelled into new movements; of inherited appearances, now brilliantly illuminated by the contrasts of the berg’s new surroundings. Like the world-encompassing summas of medieval philosophy, in which a single principle of logic could endlessly ramify a limited body of texts, the berg evolves out of ice a grand synthesis of structure upon structure.

The process begins with the simple fall of ice crystals. In the interior of the continent, this involves little more than the settling of ice dust consisting of tiny prisms. Outward, along the coast, aggregates of prisms form snowflakes. The piling of crystal upon crystal leads to a process of ice lithification and metamorphosis. A stratigraphy of snow develops. Loose debris is transformed into structured layers. As snow builds up, compression and sintering round off individual crystals and reorganize the strata into a texture of toughened ice grains saturated with irregularly shaped bubbles of trapped air. Under further heat and pressure, the ice recrystallizes into ice slates, ice schists, and ice gneisses. Some air is squeezed out, other bubbles reshape into tiny globes, and swaths of bubbles form flow bands of white ice. Relentlessly, the density increases and firn becomes glacial ice—blue, hard, translucent. The speed of this metamorphosis varies with temperature and the thickness of the superimposed snow, both of which increase toward the perimeter of the ice field. With a density about one-third that of average rock and about 90 percent that of seawater, glacial ice floats. The heavy snowfall along the coast increases the proportion of snow and firn to glacial ice, with the result that Antarctic bergs can be relatively buoyant.

But there is more to the berg than its source ice. Chemically, Antarctic ice is the purest form of water on the planet. Yet from the beginning the ice fabric incorporates air, and glacial ice will typically show bands of blue ice and milky white bubbles. Other snows and other impurities will be acquired by the ice during its journey to the sea. Additional terrestrial dusts, nitrates, radioactive fallout, and extraterrestrial particulates all become embedded into the ice, often as nuclei for precipitants. Coastal glaciers may acquire rocky debris from adjacent mountains and eroding beds, while mountain glaciers may experience strong deformations that reconstitute their inherited ices, perhaps purging them of trapped air. Ice shelves pick up saline ice, which is frozen into bottom crevasses. The freezing of this saline ice can, in turn, capture organic material for the general ice matrix. Brine infiltrates firn and snow—blown as sea spray, insinuating along the permeability boundaries that segregate firn from glacial ice, and rising through vertical fissures in the glacial ice. Blue ice and white ice may be splotched with black (dirty) ice from morainal debris, or with green ice embedded within the ice fabric. The origin of the jade-green ice is uncertain. Green ice includes a mixture of contaminants, especially particulate protein-nitrogen, but its peculiar appearance seems to derive from a pure, bubble-free ice fabric that apparently originates in the vigorous shear zones found in mountain glaciers. This odd ice—like bottles wrapped in snow—may represent the optical effect of light on a highly oriented, clear ice.

The formation of the berg profoundly alters the composition of the ice. Liberated, the berg adds new materials, loses old ones, and rearranges its inherited constituents. More sea spray is absorbed and more brine infiltrates along the firn boundary. Additional saline ice may be acquired when the berg pauses in its journey, frozen amidst shore and fast ice. While the berg is at sea additional snow is added to the top, although more is also melted. This surface melting—the result of greater sunlight and higher ambient temperatures away from the ice field—percolates into the substratum and, in some cases, collects into snow swamps that drain off the sides of the berg. Meltwater percolation profoundly alters the internal ice structure, and seepage passes through the porous firn until it reaches a low enough temperature to refreeze. This change of state releases heat to the surrounding ice, with the result that the internal temperature of the iceberg rises to 6 degrees C. or higher. The recrystallized ice rearranges the stratigraphy of the inherited ice and adds new ice inclusions. This process of heat transfer by percolating meltwater—much more effective than heat conduction through ice—leads to rapid decay, a thermal rot. The disintegration of glacial ice releases the nitrates bound within the ice. The resulting nutrient bloom around the berg attracts algae and plankton. Other organisms are drawn to these primary producers, and a small marine biosphere encircles the berg, just as, for similar reasons, a marine biosphere encircles Antarctica.

Icebergs are fundamental to the energy budget and hydrologic cycle of the ice field—and of the Earth. Only a minuscule portion of Antarctic snow melts, and that is restricted to intermittent streams of glacial meltwater confined to rocky oases. A much greater proportion of snow sublimates, vaporized by katabatic winds warming as they pour down from the polar plateau. Some snow is blown to sea by powerful offshore winds. But virtually all the ice on the continent ablates in the form of icebergs, calved from vast ice shelves and isolated outlet glaciers—the Amazons and Mississippis of Antarctica. The discharge of nutrients, water, and eroded earth from Antarctica is thus dissipated around the Southern Ocean by wandering icebergs. In places the deposition of debris by icebergs, “drift,” is considerable. Off the coast of South Africa more than a meter of glacial till has accumulated, evidently the product of iceberg rafting from Antarctica during the past glaciation. Similarly, icebergs affect the distribution of fresh waters around the Southern Ocean. Instead of entering the sea in relatively concentrated streams, there is a slow leaching of fresh water from a wandering mosaic of thaw-points. Since major melting does not occur until the berg leaves the near-shore environment, and usually not until the pack ice is breached, discharge by icebergs is diffuse and far-flung. This, in turn, affects the salinity, density profile, and thermodynamics of the outer Southern Ocean. It requires almost as much energy to melt ice as to raise the temperature of the resulting water to its boiling point. This energy must come from the sea.

Similarly, the amount of water and heat drained into the Antarctic sink has global consequences. The Ice is the cold core of the planet. The amount of precipitation that falls on Antarctica is small by tropical standards, and only in selected areas does it approach the rates typical of temperate zones. The interior is a cold desert, the most total desert on Earth. But the continent is so huge and its storage capacity so enormous that the quantity of fresh water it contains dominates the global water budget. Over 60 percent of the world’s fresh water resides in the ice of Antarctica, an amount equivalent to sixty years of global precipitation or forty-six thousand years of flow by the Mississippi River. Its fresh water is the largest and most accessible of Antarctica’s mineral resources, and it is all discharged in quantum bits, as bergs.

Annually, Antarctica produces some five thousand bergs, about 6.5 times the production of the Arctic. The average size of Antarctic bergs is much greater than that of Arctic bergs, each Antarctic berg averaging about one million tons of pure fresh water. Total production equals nearly 690 cubic kilometers of ice. Unlike Greenland bergs, calving off fast-moving glaciers, Antarctic bergs tend to calve from ice shelves or from the tongues of outlet glaciers protruding into the sea. The Greenland bergs, accordingly, resemble small peaks, while the Antarctic bergs resemble great tabular plateaus. On the average, Antarctic bergs are 100–400 meters long, with 12–40 meters of exposed freeboard. The ratio of length to width varies between 1: 1 and 4: 1, with an average of 1.6: 1. Similarly, the ratio of sail to keel, or the exposed freeboard to the submerged stratum, varies widely. For freshly calved tabular bergs, the ratio is 1: 10. The actual value will depend on the source and the character of the ablation process—in particular, the thickness of the firn layer and the vitality of fresh snowfalls, and the relative vigor of bottom melting compared to surface erosion. For domed bergs, the ratio is closer to 1:6; for blocky bergs, 1:4; for drydock bergs, with their much-eroded spindly pinnacles, 1:2.5. Both ratios—of sail to keel and length to width—are influential in determining how responsive the berg is to wind and wave, how it erodes, and how likely it is to overturn.

Antarctic bergs may reach immense sizes. One sighted in 1927 was reported as 160 kilometers long, with a freeboard height of 35 meters. Others have been measured at 140 × 60 kilometers, 100 × 70 kilometers, and 100 × 43 kilometers. The greatest, tracked in 1965, was 140 kilometers long and featured a surface area of 7,000 square kilometers. One colossal berg, the Trolltunga, began as a severed ice tongue roughly the size of Belgium. The larger bergs cluster near the shore, where they contribute to a chilling of air and sea and to the production of an insulating fog, but once beyond the pack they risk rapid disintegration. In fact, some sort of fragmentation may be necessary to move a berg through the pack. Most bergs will not survive two months, or less than a single summer season, in the open sea.

The berg is a record of Antarctic ice shapes no less than of ice substances. Its structural cryology chronicles ice deformation, much as its stratigraphy chronicles ice deposition. Berg structure is internal as well as external: it records ice deformations and ice movements experienced while the ice mass existed within the confines of the ice field, and it documents the free-floating behavior of the ice mass in its reincarnation as a berg. Together these two forms of movement—internal flow and external displacement—generate a hierarchy of shapes, extending from the microcosm of ice crystals to the macrocosm of ice sheets. As ice masses respond to new stress fields, their shapes reform. The shape of the berg itself is only a fleeting phase in this history.

The berg, nonetheless, displays by far the greatest variety of structures. On the microscopic level, there are ice fabrics—mosaics of ice crystals and inclusions like air—that hark back to the origin of the ice mass and that all glacial ices exhibit. As more snow accumulates and as the entire ice matrix flows, the fabrics constantly reform, recrystallize, and reorganize. On a larger scale, other structures become visible—ice fissures and ice faults, crevasses torn by moving ice and icequake; ice strata, the product of the inexorable compression that transforms snow into firn, firn into ice, and glacial ice into metamorphic ice schists and ice gneisses; ice folds, the buckling of ice as it meets earth or more ice; long-wave flexures of ice, undulations of large-scale ice bodies. On the macroscopic level, structures are defined as the ice mass encounters distinct boundaries to its spread—sea, land, other ice. Ice masses become ice terranes. Some of these structures will vanish as new stresses reshape the ice mass. Some will persist for a time, surviving as ghostly sutures or relic fabrics. Some—those that lead to the rupture which finally releases the ice mass from its ice field—will shape the iceberg.

The berg takes its gross shape from the properties of the ice shelf or ice tongue from which it derived and the deformations that liberated it as a distinct ice mass from those terranes. The floating ice sheets come under the influence of waves, tides, and the internal flow that results from thinning as land-based ice spreads out across the sea. Infinitesimal cracks preserved in the ice fabric propagate, and large inherited fissures persist. New stresses, particularly near the exposed terminus, develop into new fractures. Seawater etches along crystal boundaries, and brine infiltration along cracks and within the firn lowers the strength of the ice dramatically. The processes involved may be complex and competitive, but the composite mechanical effects of wind, tide, and wave cause exposed ice to bend and fracture, fatigue and fail. The calved ice mass becomes an iceberg.

The iceberg accelerates the motions, and the shaping, of its ice terrane. The ice mass is subjected to a new range of external stresses from wind and wave, as well as new internal stresses resulting from its recent liberation from a confining ice field. Its inherited structures are quickly reworked. Previously, the ice mass slowly accumulated or, at the least, it was conserved. Changes in form resulted from the rearrangement of ice. Now the ice is shed. Processes other than those characteristic of confining ice begin to operate, and the berg breaks up and melts. The entire mass, not only its internal fabric, is restructured. The shapes become more visible and vastly more exotic, the rate of change accelerates, and the ice reverts to water. The most interesting period in the ice shaping is also the most transient. In Antarctica, ice begets ice. The ice—its composition, shape, movements—exists because of its informing ice field. When the ice field breaks up, the ice mass loses its identity as ice.

The process of disintegration is both mechanical and thermal. Each aids the other. Melting begins while the ice mass remains within an ice shelf or glacial tongue. Some melting scours the exposed ice front, some scours the top, and some scours the floating bottom. Along the bottom there will be both melting and freezing. But if the freezing predominates before the ice mass calves, it will soon be superseded by melting once the berg takes to sea. Top melting will result in the percolation of meltwater through the porous firn. Side melting, especially active when accompanied by waves, carves out the flanks, and the berg acquires a scalloped texture. Small convective cells eat away at the sides; the released fresh water and air bubbles form a turbulent boundary layer along both ice and seawater and rise through a series of thermal terraces. These carved subsurface facets expose yet more ice surfaces and encourage still faster melting. If sufficient meltwaters accumulate on the top, they may flow down the sides to give the berg a fluted appearance. But the roughened bottom, gouged by large crevasses, disintegrates most rapidly. The fissures widen and rise; the berg thins, making it more susceptible to wave-induced flexing; and the berg itself calves.

Of the two processes, melting ultimately triumphs over mechanical disintegration. Melting prepares the ice mass for ruptures, large and small, and unlike breakage it reduces the volume of the ice. Melting is the final solution: ice is no longer reformed into ice but transformed into water, a change of state that will remove it from the ice field completely. Yet the mechanical processes assist melting by increasing the proportion of the total ice that is exposed to thermal activity. Some ice spalls off the sides. Some is mechanically eroded by waves—melting into exposed pinnacles that quickly rot and into terraces that, as overhanging cliffs, soon fail and drop. The thinning of the berg encourages rupture by allowing the ice mass to flex amidst long ocean swells. Some disintegration follows from simple collision, especially where a grounded berg is struck by a free-floating one. Grounded bergs, in fact, are a prominent source of brash ice. Differential heating—the sharp contrast between cold ice and warmer sea—can lead to thermal spalling, with chunks and slabs of ice breaking free like exfoliating granite and sandstone. The permeability boundary between firn and glacial ice, a zone of potential penetration by brine, may lead to the large-scale slumping of firn, a process of mass wasting.

The marks of the strain that produced calving will persist for a time, although fissures will slowly heal shut, and some of the fractures may become zones of weakness for further mechanical disintegration as the berg experiences a new set of stresses. The intensity of this activity will vary with the size of the berg, and it will be reflected in the berg’s shape. Gigantic bergs—with dimensions measured by tens of kilometers—will not undergo much internal change. Only the edges of the berg will be affected. Smaller bergs, with higher proportions of newly exposed edges, will show proportionately greater change. No longer subjected to a high confining pressure and no longer protected by an enveloping shield of ice, the sides of the ice mass will ablate rapidly.

The berg’s motions, too, are a curious amalgamation of its history and its present state. All the movements that have characterized the ice mass on its journey are present. Past motions are preserved in the internal ice fabric. Current motions are revealed by the gross movement of the berg, as many former stresses vanish and new stresses appear. Its free-floating motions give the berg many of its distinctive characteristics. Unlike other ice masses, the berg will not merely flow internally, within the confines of the rigid ice field, but will respond more or less freely to its new environment of fluids, the sea and the air. The berg will drift in ocean currents and wind fields. It will bob, rock, and spin. It will tilt or even overturn as erosion modifies its density profile. From the simplest of motions, that which governs the settling and compression of snow, the iceberg has acquired an almost limitless mobility. The price paid for this mobility is disintegration. Time itself accelerates; events crowd one upon the other; the more rapidly the berg moves, the more swiftly it decays. The ice began in a nearly timeless state, 15 prolonged over centuries, even millennia, because the extreme cold of the source region slowed movement to a vanishing point. But as the ice acquires composition, shape, movement, variety on its journey outward, it correspondingly wastes away. The smaller the berg, the greater its mobility and the faster its disintegration.

Very large tabular bergs are the least mobile and show the greatest persistence. They cling to the shore, grounded or entrapped in pack ice. The heavy concentration of large bergs near the coast contributes to the preservation of a wide belt of fast ice and shore ice even during the summer. Only when they break up into smaller units and proceed through the pack do bergs respond freely to wind and wave. In broad terms, their drift is set by ocean currents. Because of its large draught, its keel, the berg behaves as a current integrator, sailing roughly eastward with the nearshore flow of the Antarctic circumpolar current and ultimately breaking free of shore influences to enter the broad west wind drift out to the Antarctic convergence. There are considerable variations, however.

The act of breaking loose from the coast is typically not a single event. Several years may pass before the berg actually becomes a free-floating vessel. Frequently, the berg grounds as it attempts to sail from the continental shelf or to pass around peninsulas of ice or land, or as it encounters eddies within the current that trap it temporarily in a frozen gyre of bergs and pack ice. From its first calving the berg may be recaptured several times by the ice field—to be refrozen, reincorporated, then liberated again. The vast majority of large bergs hug the coast, and most of the bergs that survive many years do so because they move ponderously out from the ice shore. The average longevity of an Antarctic iceberg is four to six years. The colossal Trolltunga berg, however, was tracked for over eleven years, slowly creeping along the frozen shoreline of Queen Maud Land before it was absorbed within the Weddell gyre, where it spent more than two years before being catapulted into the South Atlantic. Once it enters more or less open ocean, a berg advances an average of 8–13 kilometers a day.

Other influences shape the actual drift track of the berg. The Coriolis force, pronounced at high latitudes, gives a small northward component to the berg’s circumpolar drift. Tides work to lift grounded bergs and to move others, while winds shape considerably the local pattern of drift. How influential winds become depends on the strength of the wind, the size of the berg, and the proportion of sail to keel. High winds (over 50 kilometers per hour), small bergs, and large sails make for responsive ice. Even large bergs will be sensitive to very high winds and the waves they generate. But the storm cells that orbit the continent follow the general trend of the Antarctic circumpolar current. While, in the short term, wind and current may compete, in the larger scale of things they complement each other. The bergs circle the continent like ice debris in the rings of Saturn.

The perimeter of ice varies with the ebb and flow of the circumpolar current and the general climate. The pack ice remains frozen much of the year, retarding the movement of trapped bergs. At other times, the perimeter of the circumpolar current swells outward and icebergs range widely over the Southern Ocean. Occasionally, very large bergs encounter favorable circumstances that fling them outward well beyond the Antarctic convergence altogether. Bergs have been sighted from South Africa after being hurled out of the Weddell Sea gyre, as well as off the coast of Peru, embedded in the cold Humboldt current.

Ocean swells cause the berg to oscillate (if the ice is rigid) or vibrate (if the ice is elastic). Some of the movement is linear, making the berg bob up and down like a glacial cork. Some is angular, encouraging the berg to rock back and forth. Both oscillations and vibrations, however, set up stress fields within the ice. How the berg responds depends on the wavelength of the swell, the thickness of the berg, and the presence of internal fissures. Very large, thick bergs absorb the vibrations with little effect; the entire berg may slowly bob or rock but there will be little internal deformation. Thinner bergs or ice shelves may simply bend elastically without rupture. But under the proper circumstances—if the wavelength of the swell and the ratio of thickness to width in the berg are in the right proportion—rupture may occur. Should the berg vibrate near its natural frequency, it will shake into large pieces. Flexure and fatigue failure seem to be important processes in the calving of bergs from shelves. For large bergs, especially those with residual cracks that may propagate under the proper stresses, the process of stress failure continues to operate.

The berg even rotates. One rotation is slight but constant, the product of a sheath of meltwater that surrounds the berg as it ablates. This liberated freshwater has a lower density than the surrounding seawater and accordingly it rises. At lower levels, the pressure differential is sufficient to have an impact. Seawater enters the sheath, but under the impress of the Coriolis force, the flow deflects to the left; the berg spins. More dramatic are those rotations from top to bottom of the berg. The density profile of an Antarctic iceberg shows a lighter top of snow and firn riding above a much denser ice substratum. But as the top erodes, as side disintegration results from thermal ablation and the mechanical response to the new stress field, and as the bottom reshapes from crevasse erosion and thermal convection along the sides, the berg can become unstable. The top may roll over. The critical variable seems to be the ratio of berg length to width. For a berg 200 meters thick, the minimum width should be 220 meters to prevent roll instability.

Only occasionally does the process get this far. More common is an adjustment of shape to density that causes the berg to tilt perpetually one way and then another. The berg will list more often than it will capsize. The lighter snow and firn are particularly susceptible to wave erosion, brine infiltration, meltwater percolation. A drifting berg will experience a wave-cut underwater terrace to its rear, and the removal of this material causes the rear to rise and the front to lower. This tilting affects the way the berg intercepts current and wind, and the berg rotates. The newly exposed top will, in turn, be subjected to more vigorous wave erosion. In theory the process can continue indefinitely. But before an ice peneplain can result, the berg will most likely dissolve into a kaleidoscope of exotic forms, a happy entropy of particles and motions.

A Plastic Art: The Esthetics of Icebergs

Ice is a plastic art. No other object more fully challenges the theory and practice of esthetics. The journey of the ice from crystal to berg is not simply a story of matter and motion: it is an esthetic journey of the first magnitude. And of all Antarctic ices the berg is the most artful. It contains all the stuff, the shapes, and the motions of other Antarctic ice, yet it combines them uniquely and it mounts them, like a set jewel, in an environment that enhances their effects. To James Eights, first naturalist to land on the continent, the icebergs were “in a peculiar manner, adapted to create feelings of awe and admiration in the bosom of the beholder, not alone from the majesty of their size, but likewise, by the variety of the forms and ever changing hues that they assume.”¹ To veteran Antarctic explorer and scholar Frank Debenham, the bergs were “of all the natural features of the Antarctic the most strange and impressive.”²

No other ice mass displays such a range of sculptural forms. Though the largest bergs are impressive by virtue of their sheer monotonous size, the smaller bergs take the shapes of white earthscapes. Erosion weathers them and instabilities tilt them into exotic spires, castellated facades, and ice sphinxes. Others assume the lumpish mass and abstract blocky forms of modernist sculpture. The ice terrane as a whole presents a sculpture garden of kinetic art.

No other ice mass plays with light so effectively. The berg’s appearance changes constantly, with the orientation of berg to sun and to the surrounding environs of sea ice, fog, and cloud. The berg’s translucent blue and green ices, its dull luminous firn, and its brilliant reflective snow make the berg into a virtual prism. In purest forms, glacial ice glows with a bluish tint. Occasionally absorbing impurities or acquiring glasslike properties of sheared ice, it takes on a greenish lustre, like dull jade. In still other circumstances, its bottom strata are charged with rocky, brownish debris which may rise to the surface should the berg overturn. With bands of whitish bubbles swirling through it and fresh snow lacing its fabric of fractures, the blue ice resembles a patch of sky streaked with ice clouds—a bizarre reification of its source in the polar plateau.

Immersed in direct sunlight, the snowy berg hurls the light back with dazzling intensity. The berg sparkles amid its surroundings, an undifferentiated, unearthly presence. Nothing of the berg itself is revealed. Better understanding requires more subtle lights. In oblique sunlight the berg appears like ivory, dull and opaque. In fog the berg is highlighted by shadow, a grey outline amidst a whitish mist. In stronger sunlight, it emits a ghostly translucence, becoming a kind of ice opal. Under an overcast sky, white light cannot penetrate. But other wavelengths act on the ice and snow to produce an eerie, bluish-white phosphorescence, a luminous glow that accents the internal structure of the berg and contrasts weirdly with the ivory-colored sea ice and the navy-blue sea.

The berg synopsizes the esthetics as much as the glaciology and geography of Antarctica. Yet it does so by virtue of a paradox. The simplicity of The Ice is staggering, and embedded within the ice field an ice mass is flat, opaque, almost featureless. It only reflects those perceptions brought to it, or refracts that information extracted from it. The ice field from which the berg emerges is an esthetic sink. The character of The Ice is derived and its brilliance secondary. The Ice adds by removing, transforms without creating, informs by obscuring. Its meaning does not reside within Antarctica, awaiting revelation, but derives from the illumination brought to it from outside. Ice does not merely reflect mind: it absorbs it. The more it absorbs, the larger it becomes; the more light brought to it, the more powerful its reflection.

The special properties and meaning of the berg both as a natural phenomenon and as an esthetic object derive instead from its surroundings, from the fact that this ice mass has been removed from its confining ice field. There are contrasts—ice and ocean, ice and the esthetic canons brought to bear on it. The berg is the most revealing, and most pleasing, of Antarctic ices because it is the least typical. It is the most intellectually and emotionally accessible of Antarctic ices because it is the most complex. In this, too, the berg symbolizes Antarctica—the least known and least knowable of continents, not because it is the most complex but because it is the most simple. This is a looking-glass landscape where things may be less, not more, than they seem.

Its simplicity is stupefying. Contrasts, comparisons, analogies, metaphors—all vanish before the pure immensity of the ice monolith. Antarctica mocks the belief that the essence of art—or of life or of civilization—is simplicity. This is a minimalist landscape that requires a high order of esthetics to be appreciated. Where the ice is ensconced within ice within more ice, art finds itself without information; the senses are stripped; perception vanishes into a white nirvana. At its source, The Ice is a world in a state that approximates frozen invariance. The Ice is nature as modernist.

But the iceberg escapes this condition. The berg was accessible to traditions of representational art and, almost alone among Antarctic ices, it was painted and photographed by pre-modernists. It is easy to value the berg because one can contrast its ice mass to non-ice surroundings. Broken out of the ice field, the berg acquires new properties, new motions, new structures. It offers contrasts, often brilliant, with its new environs. It does not match ice with ice but ice with sky, sea, earth. Were the ice still embedded in the polar plateau or the ice shelf, the appearance of the berg would be far less dramatic; it would not even have an identity in any meaningful sense. But amidst the Southern Ocean—surrounded with chunks of glacial ice, pack-ice floes, ocean waves, storms, mixed clouds, changing skies, aquatic life—the berg acquires immediate esthetic appeal. There is even sound: the cries of birds, the slap of waves and whitecaps, the hissing of air bubbles rupturing from glacial ice. The berg breaks, at last, the enormous silence of The Ice.

So it is with the ice field of Antarctica. Were the Earth truly an ice planet, the Antarctic would hold little interest. It is the contrast of ice to Earth, and of Ice to Idea, that makes it fascinating. The whiteness of the berg would be oppressive—meaningless—without its surrounding environment of sea and civilization. The berg is the most revealing of Antarctic ices because, in departing the ice field, it is the least typical. It is the most accessible of Antarctic ices because, in its many contrasts, it is the most complex. The berg is rich in information and knowable; its appearance can be quickly appreciated and assimilated. In Antarctica, the complicated is easy, the simple baffling.

VANISHING POINT

The iceberg, much reduced, drifts and disintegrates.

As it nears the boundary of the convergence, it breaks and ablates rapidly. It spins ponderously in its sheath of meltwater. Those waters vanish into the bottom circulation of the world ocean and the ambient humidity of the global atmosphere. They are part of the hydrologic cycle, the final cycle The Ice will know. The berg has lived within a great series of vortices, a geophysical field shaped by ice. At their source is a profound stillness, as close as the Earth can get to a condition of absolute zero, a cold so intense as to seemingly halt all motion. Outward from this origin the ice accelerates, the cycles multiply. The Antarctic convergence is the final perimeter. Once the berg crosses that frontier it is outside the ice field and soon expires. Its disintegration is rapid and inevitable. Slowly it spins its final rotations. Its bobbing causes a patch of green ice within it to flash like a semaphore from a field of white, a bottle in a message. The berg blinks like a dying pulsar, then disappears.

For a while its particles fly free from the ice, like the tedious outward burst of a frozen big bang. But none will ever escape that influence entirely. And over geologic time some will return. Once again they will be reduced from complexity to simplicity, reshaped to unearthly minima, and drawn back into the great polar vortex—back to the ends of the world, back to the spiraling nebula of Ice that is Antarctica, sweeping everything within its field into the heart of an immense whiteness.