This program explores Antarctica’s ever-changing icecap. Icebergs inch their way through hundreds of miles and thousands of years to be born as million-ton islands at the end of the sea. These vast platforms of ice are the source of life for seals and penguins, but they also have a life of their own. (Part 2 of 2)
[gentle music] - [Narrator] Winter at the end of the Earth.
For six months Antarctica lies in a frozen twilight zone.
The grip of winter has transformed the ocean into ice and a barren world above, yet underneath the waters are rich with life.
[gentle music] When the sun returns, the frozen ocean turns the liquid.
[dramatic music] Giant icebergs are released, plotting sculptures, which hold the mysteries of life.
[gentle upbeat music] [gentle upbeat music continues] - [Announcer] This program was made possible by contributions to your PBS Station from viewers like you.
Thank you.
[waves crashing] [gentle music] - [Narrator] Nowhere in the world is the pulse of the seasons more dramatic than in the waters surrounding Antarctica.
This is one of the great oceans, wrapping around the South of the planet like a giant, heaving monster.
But for all its power, every year this ocean succumbs to a greater force.
With summer's end a creeping chill descends upon these restless swells.
The ocean grows so cold that pancakes of floating ice appear.
Eventually this sea will freeze solid and, until summer's return, the South of the planet will be isolated within a vast white shell.
[gentle music] For eight months, the Southern Ocean will become a twilight zone, neither sea, nor land.
From late February, the ice front advances North to claim an extra two and a half miles of ocean every day.
In time these pancakes of ice will join to form a solid barrier around the Southern continent, impervious to any but the most specialized craft.
Even the most sophisticated, modern icebreaker cannot be assured of a path through.
This icebreaker is part of a pioneering bid to reveal the role of this annual freeze in the play of forces that governs life on Earth.
By the time the freezing stops, ice will have gripped almost 7 million square miles of ocean, an area equal to the land mass of South America.
It is the greatest annual event on the planet, in scale and sheer spectacle.
The South Pole ice cap, already the world's fifth largest continent, will double in size in just a few months.
But this vast drama is hidden in the Antarctic night behind an ice barrier riddled with hazards.
[gentle music] Although the main shell of ice is only six feet thick, it is studded with Antarctica's great offspring, giant icebergs.
To strike one would spell disaster, even for the reinforced icebreaker.
[gentle music] Towering 150 feet above the surface, these bergs were born into open water during the summer.
Now locked into the sea ice, they turn the Antarctic night into a giant minefield, to be crossed only with the utmost caution.
[gentle music] With the return of summer the ice will break up and release the bergs once more to wander the ocean currents.
But for now, like almost all life in this region, they lie in wait, trapped in winter's long pause.
[gentle music] At its peak, in late September, the sea ice will stretch fourteen hundred miles out from the Antarctic coast.
It is now the keeper of the Southern Ocean, a jailer, with the power to hold the very elements captive.
Water, air, and land all held apart at the whim of an unyielding force.
The once restless sea is now frozen into fractured ridges where ice floes have piled one upon another like wreckage from the conquest.
[penguin squawking] The creatures of the ocean are forced to cling to life in a world that's turned from liquid to solid.
Until the sun returns, it will be almost as if time itself has been put on hold, awaiting release only in a distant dawn.
[penguin squawking] But while life by any normal measure seems paused, there is an unseen process at work here.
[gentle music] This vast ice shell reveals signs that a force, as important as anything we have discovered in Antarctica so far, lies hidden in the long polar night.
[gentle music] Somewhere here, amidst the vastness and the jumbled ice floes, is now thought to lie the foundation of the world's weather cycles, ocean currents and much of the food supply that shapes life.
[gentle music] It gives these simple, crystalline structures an influence far beyond this stretch of sea ice.
[gentle music] Until the recent advent of icebreakers the secret remained out of reach.
Even now our attempts to unveil it are constrained.
[gentle music] This environment is more like the moon than the rest of Earth.
It's so hostile it can only be explored with elaborate life support systems, as if we were in fact exploring another planet.
[gentle music] The international research team will take samples of the sea ice every degree of latitude on their way South.
[drill spinning] The structure of the ice will tell of the precise mix of forces that formed it, the temperatures, how much snow there was, how much spray from the sea.
Unraveling the character of the ice has become the holy grail for the research team.
[gentle music] It had long been assumed life was dormant while this ice gripped the Southern Ocean, but that assumption has now been overturned.
[gentle music] On board the mothership, cross-sections of the ice cores reveal that while this frigid world appears lifeless, in fact -- in spaces between the crystals, the ice shelters a thriving community.
[gentle music] These are microscopic algae.
Surviving temperatures of minus 18 degrees, they form a teeming community of simple, but plentiful life, even in mid-winter.
[gentle music] When this frozen expanse breaks up in summer, the hidden store of life in its depths will be released into the sea with dramatic effects.
Rather than being a preventer of life, the ice pack may be one of the driving mechanisms in the huge productivity for which the Southern Ocean is renown.
But we are barely beginning to probe its secrets.
[ice crashing] Human explorers did not sight the Southern ice until the middle of the 19th century.
It took the development of steam power in the early 20th century before anyone was able to breach the ice barrier, even in summer.
And the advances met with variable success, as evidenced by Shackleton's 1915 expedition here.
The makers of, 'The Endurance' woefully underestimated the challenge the ship would face.
It was crushed mercilessly by the ice, and its crew forced into an epic struggle for survival.
[wind gushing] [gentle music] It has taken the technology of the space age to allow us to venture here with any confidence.
[gentle music] In fact, the ship resembles a spacecraft more than a sailing vessel, with its minimal crew, its array of electronic monitoring and computerized guidance systems.
[gentle music] The once haphazard challenge of navigating this sea is now reduced to the touch of a hand on a single control.
[gentle music] For the first time we are able to penetrate to the dark heart of this crystallized ocean.
[gentle music] And then the final goal is at hand.
[gentle music] The ship has successfully penetrated 800 miles, all the way to the towering wall of the Ross Ice Shelf, that marks the edge of the permanent polar ice cap.
Directly ahead, the continent itself is still 500 miles away, but this is the furthest South any ship has been in winter, or can ever go.
[gentle music] It has taken two weeks of crashing through the ice, but the various measurements of the sea ice, that have been gathered along the way, provide the first portrait of the temporary continent from edge to edge.
However, it is only here the real story of the ice begins to unfold.
[gentle music] [wind gushing] With the deepening winter night, the temperature difference between the polar cap and the distant ice edge is growing.
Storms are ever more vigorous and winds stronger.
As the team completes the historic transect, 100 mile an hour Katabatic winds sweep out from the continent's heart sending the temperature plummeting to 40 degrees below freezing.
[wind gushing] [drill spinning] The winds go as quickly as they came, but they emphasize the harshness of the Southern winter.
[gentle music] And yet here on the outer edge of the Antarctic continent locked away 400 miles from the sea, an incongruous community has gathered.
With no females in sight, 25,000 male emperor penguins huddle together in a muted horde, unable to do anything but wait out three months of polar night.
The females have all left the remote cliffside colony weeks ago to feed at sea beyond the ice, leaving their eggs in the care of the males.
The region is so bitterly cold, the birds can only survive in the collective warmth of huddles such as this.
It seems the most improbable formula for survival.
[penguin squawking] [wind gushing] Conditions are so inhospitable they cannot even build nests.
Throughout the long winter night, the stoic males carry a single, precious egg perched between their bellies and their feet.
They will have no opportunity to leave or feed for three whole months.
But there is a reward locked in this icy realm that makes this bizarre ordeal worth enduring.
[penguins squawking] Indeed, this whole ritual is carefully timed to take advantage of one fleeting, but crucial event.
They are waiting for the dawn.
[gentle music] As if to herald the awaited end of the brutal winter, the sky lights up with spectacular flares of the Southern aurora.
[gentle music] Giant natural light shows created by magnetic storms, stirred in the atmosphere by currents of solar wind.
They provide eerie outriders for the moon's endless passage through the lingering night.
[gentle music] Then, the Earth tilts far enough at last for the sun to emerge above the horizon again for the first time in three months, bringing unfamiliar day light to this frozen world.
[gentle music] [penguin squawking] On cue in the Emperor colony, hatchlings begin to emerge to greet the new day.
The sun's return is the sign that the shell of ice that has held life in suspension has run out of time.
[wind gushing] Soon the sun's growing warmth will set off a chain of events that will provide the reward for the emperors' long winter ordeal.
Far away, above the center of the continent, 1,000 miles further South, the sun reveals drifting ice particles, known as diamond dust.
The particles form, as moisture carried in from the tropics, cools and descends over the South Pole.
The dusting of crystals has accumulated in fractions of an inch, over hundreds of thousands of years to form a solid ice dome two miles high.
[gentle music] Under its own weight and gravity's pull, ice begins to flow slowly down the flanks of the dome in vast frozen rivers radiating outwards from the pole.
The rivers move faster as they spill over mountains nearer the coast and reach towards the sea.
[gentle music] It's a creeping torrent of frozen water, 46,000 times the annual flow of the Mississippi River.
It never melts.
It simply pushes out beyond the edge of the continent to form an immense shelf of ice 300 feet high around Antarctica's rim.
[gentle music] For half a million years it has moved almost imperceptibly.
Now it is about to take a quantum leap.
The towering cliff is highly unstable.
The push from behind is relentless and irresistible.
The outward movement of ice that began at the pole 1,000 miles away, will not be stopped.
This ice mass, the size of a continent that has persisted through aeons, now fragments, and dissipates in a matter of moments.
[ice crashing] [gentle music] The evolutionary pace that held it captive was the ice's protection.
Now, even the largest sections that break free of the pole's lingering grip only hasten their demise.
They may be 100 miles long and 60 miles wide, but few will last a dozen years past this point.
[gentle music] This is the outpouring of the continent and the seed of the great winter freeze.
Where the other great continents have huge rivers, the runoff from Antarctica scatters into the sea in a mosaic of icebergs.
It chills the air and sea surrounding the continent.
And when the sun vanishes the region becomes so cold the sea locks solid.
About 5,000 bergs are born every summer, more than six times the number from the Arctic, 400 cubic miles of ice, launched into the sea around the continent every year.
[gentle music] Million ton ice cubes that tower above the sea.
[gentle music] But that's nothing compared to their bulk beneath the surface where they can stretch 1500 feet down toward the sea floor.
The ice has about 90% of the density of the surrounding sea water.
It is enough to keep it floating, but only just.
9/10ths of the berg is submerged and it is down here they have their most dramatic effects.
While the ice chills the ocean, the relative warmth of the sea begins to work on them as well.
[gentle music] It creates a world like no other.
[gentle music] Weddell seals dive deeper, and longer than any species on the planet.
They are the only mammals that are at home here in the deep blackness beneath the bergs frozen underbellies.
Throughout winter, light levels have been up to 1,000 times less than those in open water.
Temperatures have been as low as minus 20 degrees, and with so much water taken up as ice, the sea becomes highly concentrated brine.
[gentle music] It's remarkable that life survives here at all.
[gentle music] But this is also a sheltered world.
With no flowing rivers and no disturbance from wind, the sea is so clear that to dive here is more like swimming through deep space than water.
[gentle music] In fact it is these exceptional conditions that set the scene for the astounding events which will soon take place in the wake of the sun's return and for which all life now waits.
[gentle music] Among the vast ice sheets traveling down from the polar ice cap are huge fingers of glacial ice that have gouged their way through the inland mountains.
In their passage they have gathered finely ground dust, minerals, and microscopic plants and animals, now all suspended in the ice.
Wherever the ice meets and is melted by the ocean, its great burden is released.
So effective is this icy conveyor belt that the Antarctic debris can be readily identified in deposits left by melting ice bergs thousands of miles to the North.
The seas around Antarctica are constantly deluged with an unending flow of nutrients that make these waters among the richest in the world.
As the melting bergs flood the sea with nutrients, salt is leaching out of the sea ice surrounding them.
It forms brine so concentrated that it stays liquid well below normal freezing temperatures.
[gentle music] In fact, it is so cold it freezes the sea on contact, forming icy stalactites where it emerges.
But the brine is also so heavy it sinks to the bottom creating tiny currents that carry the nutrients up to the microscopic life amidst the ice crystals above.
When the new spring sun adds constant light to this cocktail, it sparks an explosion of life.
[gentle music] The algae in the ice reproduces rapidly, plant growth that is hundreds of times the levels in the surrounding ocean.
[gentle music] Suddenly the underside of the sea ice becomes a vast continent-sized pasture, growing 24 hours a day for three months on end.
[gentle music] The sudden abundance of plant life sparks an explosion of tiny grazing animals.
The shrimp-like, Antarctic krill are, by far, the most obvious.
Within weeks they multiply into vast drifting swarms measurable in the hundreds of thousands of tons.
They'll become the largest known biomass of any single species on the planet, five times the total mass of humanity.
[gentle music] This is the time all other life on the sea ice has been waiting for.
[gentle music] After their punishing winter fast, the Emperor penguins begin a round of constant shuttling between the ice edges and the ocean depths.
[gentle music] [penguins squawking] From the sun's first light they search out whatever small breaks in the sea ice allow them access.
[penguins squawking] A single dive may take them to depths of 600 feet in search of fish drawn to the sudden abundance.
These are the world's largest penguins.
They can stay down here for seven minutes at a time and maintain the activity for hours on end.
[gentle music] After three months of inactivity, they'll now take only three or four minutes rest between dives.
The Antarctic summer is so short, the demands of winter breeding so great, that they must consume enough in this brief frenzy to both restore their condition, and prepare for the next long winter's night only a few months away.
[gentle music] Soon access to the bonanza will be made easier.
[gentle upbeat music] As summer progresses, the winds sweeping down from the South Pole will join with rising temperatures to finally loosen winter's icy grip on the Antarctic shore.
[gentle music] With the wind driving from above, and the pulsing of tide and current beneath, the great ice shell begins to fragment.
[gentle music] The bergs of previous summers that have lain trapped in the ice's embrace are at last free again and the slow outward journey that began at the pole so long ago resumes.
[gentle music] Although free, the biggest will not get far.
[gentle music] Their bulk greatly reduces their movement, their keels grounding on the bottom, keeping them close to the shore.
[gentle music] In the process they keep the surrounding environment cool, block wind and waves, and prevent warmer water from reaching the shore and bays, helping refrigerate the Antarctic coast even in summer.
[gentle music] [water flowing] [gentle music] But from the moment they are created, these monsters of the sea are already dying, each new form a celebration of the process of decay.
[gentle music] However, while they persist, the bergs and the ice floes open the region's huge spring banquet to other creatures for which the Antarctic is renowned.
The ice provides vital breeding grounds in a region where little of the coastline has exposed rock.
[gentle music] [water flowing] Better still, the floating platforms mean that even for pups, and nursing mothers unable to travel far, the pantry is never far away.
[seal barking] Leopard seals are among the dominant predators of these waters.
The icy crags and passageways amongst the drifting bergs create a unique hunting ground of inverted reefs in the open ocean, and for which the seal is ideally suited.
[gentle upbeat music] The threat of seal attack is such that only the protection of numbers gives penguins the confidence to enter the water at all.
[water splashing] [gentle upbeat music] In a one to one contest between penguin and seal, the penguin would have no chance.
[water splashing] [gentle music] The only place a penguin is safe is on the ice.
And here on the Northern margins of the ice fringe, other penguins are now common.
[penguin squawking] These are chinstraps and gentoos.
The ice provides them a retreat and a refuge.
Without it, they couldn't join in this summer harvest.
[penguin squawking] As the summer advances, the range available to life increases.
Even the Northern reaches of the continent itself are now ice free.
[gentle upbeat music] But the offshore waters right around the continent remain dotted with floating islands of ice that prolong the conditions that began with the sunrise.
[gentle upbeat music] It allows these latecomers that couldn't withstand the full rigors of winter to still share in the bonanza.
But the summer is well advanced before the ice breaks up this much, and as it does the krill swarms that had formed under it also dissipate.
[gentle music] [penguins squawking] It means the new arrivals must hold their breeding until later in the season, and complete it in a shorter time.
[penguins squawking] It's now thought that the breeding success of many penguin colonies is directly related to the persistence of the sea ice around the shoreline.
If the ice stays too long, the chicks will not have time to mature.
If it disappears too quickly, they may face starvation.
It seems there is no escaping the hold of the ice, even at the height of summer.
[gentle upbeat music] But for now the ocean is all but free of the force that was holding it in check, and the world has returned to its more usual order.
The ocean warming the air, the wind stirring waves and currents, the two in concert seem certain to vanquish the ice completely.
Their united battering dramatically increases the bergs' rate of decay.
Many of the smaller bergs will not survive the assault.
[gentle music] [waves crashing] Even the largest are now driven according to the whim of wind and tide.
[gentle music] [waves crashing] They're pushed back against the shores from which they had just escaped.
[gentle music] [waves crashing] [gentle music] The unfamiliar battling of elemental forces on the surface will reach down to affect even those far below.
Once the ceiling of ice overhead made this a sheltered environment.
As the giant berg is driven back towards the shore, its icy bulk now becomes a threat.
200 feet of solid ice being driven by wind and sea, ploughs across the seabed like a skyscraper on a rampage.
[ice crashing] But even now it provides opportunity for life, as starfish move in to feed on sea urchins laid waste in its wake.
[gentle music] In the end, the sea will win the summer battle of the elements.
The great underwater bulk of the ice bergs is such an effective keel it keeps them following the coastal sea currents regardless of the wind's variations.
They track Eastwards close to shore from time to time catching in coastal eddies, so instead of drifting ever further away, they gather in backwaters and bays.
[gentle music] For a short time now, visitors are tempted to venture into the once impenetrable ice.
[gentle music] Awaiting them is a gallery of fantastic sculptures.
[gentle music] The clustering of bergs chills the waters cold enough to slow the bergs decay.
Protected here, they may remain for two years or more before finally escaping to the open sea and their final demise.
[gentle music] In the meantime, they continue to impose their pace on life, prolonging the exceptional ecosystem that has evolved around and beneath them.
[gentle music] Their continued shelter still offers grazing for lingering swarms of krill, also for crabeater seals that feed on them.
The crabeaters emphasize the central role of this ice world in the web of ocean life.
Numbering some 70 million, they're the most numerous seals in the world.
Childhood scars signify that they in turn are prey for large ocean predators like orca and leopard seals.
But the crabeater seals feed exclusively on krill.
And so a vast and far reaching food chain is wholly dependent on the seasonal bounty brought by the ice.
[water splashing] The sheltered bays also show another side of the bergs.
[gentle music] The still waters reveal the slow release of air trapped when the ice formed hundreds of thousands of years ago, and only now freed again as the berg melts.
[gentle music] Other bergs have calved from ice that has been under such pressure it contains no air bubbles at all and is literally crystal clear.
[gentle music] The gathering of krill in these sheltered bays has now also attracted others.
Humpbacks are one of several whale species that depend on krill and must come here annually.
[water spraying] Even so, whales and seals combined devour only about 20% of the outpouring of life that flows from the ice field.
[gentle music] [whales whistling] But now this summer of abundance is almost done.
The driving Katabatic wind that rules the continent, again pours out from its heart to drive the remaining ice from its shores.
[gentle upbeat music] The platforms that have been the nursery to Antarctic life are suddenly fractured and dispersed.
[waves crashing] This is the first swim these chicks have had, and they're swimming for their lives.
[penguins squawking] Their desperate efforts are largely futile.
But these chicks are not developed enough to survive the open sea.
The break-up of the family home has simply come too soon and most will perish with the pack ice.
[gentle music] The enclosing ice pack gone, ocean currents can now carry bergs far offshore and the influence of Antarctica is extended beyond the reach even of the winter's sea ice.
Some will make it as far as 2,000 miles to the North.
In fact it's here, on the outer limits of the Southern Ocean, that most of the ice spawned at the ice cap, countless millennia before, finally merges with the sea.
Meltwater from the berg's surface percolates deep into the ice, raising the internal temperature to six degrees or more, effectively rotting the berg from the inside.
It is far more effective than heat conducted directly from air or sea.
Top heavy and weakened internally, the berg goes into an agonized death roll.
[gentle music] [ice crashing] The berg will roll many more times, breaking into ever smaller pieces, until its ice, its coldness, and its burden, finally merge with the sea.
The ice continent's progeny, now spread across a fifth of the planet, carries its influence into all the major oceans of the world.
[gentle music] The sun is setting on another Antarctic summer.
As the temperatures drop steadily from minus five to minus 25, the sea begins to generate an eerie steam.
[gentle music] The Southern ocean's long dusk has begun anew.
[gentle music] And as winter's endless night returns, threads of crystalline ice again begin to spread their veil across the restless sea.
[gentle music] Within a month ocean and sky are once again separated by an icy shell.
The life that once flourished here, held once more, to await a distant spring.
[gentle music] Only the occasional straggler left to trudge across the vastness.
[gentle music] [penguin squawking] [gentle music] And on the Southern ocean beyond, a lonely berg that has escaped the grip of the freezing sea, drifts for perhaps one winter more.
[gentle music] - [Announcer] This program was made possible by contributions to your PBS Station from viewers like you.
Thank you.
[gentle upbeat music]
