Exploring the human and natural histories of Antarctica’s sea ice
Presentation by Dr Joy McCann to ANU Research Roadshow, November 2020
I am mesmerised by sea ice. It is neither land nor sea, but something else entirely. Below me, invisible currents stir delicate white crystals of ice, pushing them together until they curl up at the edges. The ice is blooming like lotus flowers on the cobalt blue sea. Our ship moves slowly in this ice garden. Now and then the steel hull screeches like a banshee, and the frozen surface buckles and cracks. We pass giant tabular icebergs. All eyes are on them, but it is the enveloping sea ice that takes my breath away.
Antarctica is surrounded by the vast Southern Ocean. In winter, sea ice covers up to 20 million square kilometres – more than half of its surface. In summer, the sea ice all but melts away, leaving pockets trapped within Antarctica’s curving coastline. This seasonal freeze and thaw has been described as the ‘largest seasonal physical process in the world’. It dictates everything here – movement, temperature, colour, life and death.
I am beguiled by sea ice. It seems to be a living thing – moving and shapeshifting – drawing stories to the surface from the deep, powerful currents below. Many others have been beguiled before me. The Australian physicist, Louis Bernacchi wrote in 1898 that the sea ice encircled Antarctica like a ‘mighty spell … as if to guard the treasures locked up within its bosom … Lonesome, and unspeakably desolate it is, but with a character and a fascination all its own’. In my book Wild Sea, I experimented by putting the Southern Ocean at the centre of my narrative. This time, I am casting sea ice as the central character. The sea ice seems an ideal place to sift through the entangled histories of humans and marine life above and below its surface.
In contrast to the barren conditions on the polar ice sheet, the waters around the sea ice are brimming with life. For the ocean around Antarctica is one of the largest ecosystems on Earth, thanks to Antarctic krill which congregate here to feed on the rich nutrients that grow on the underside of the ice. They breed here in massive numbers. There are so many that their biomass is estimated to weigh more than the entire human population of the planet. Krill are the main source of food for whales, seals, penguins, squid and fish. And so, in the human quest for new sources of wealth, the sea ice became an arena of violence from the earliest voyages into the high southern latitudes.
Commercial sealers converged in pursuit of their prey after James Cook’s reports of the region’s prolific marine life filtered back to England in the late 18th century. Operating in secrecy, sealing gangs would spend months on the remote islands of the Southern Ocean, butchering seals with impunity until the beaches were silent. When the Chanticleer, a Royal Navy survey ship, visited the South Shetland islands during a British expedition in the 1820s, the ship surgeon noted that the fur seals had all but disappeared there. ‘Such is the havoc made by sealers among them, that they are now scarce and seldom seen. The shores of this basin must have formed a delightful retreat for these persecuted creatures before it was found out by man.’ When James Clark Ross published his account of a four-year voyage in 1847, he counted 30 large whales around the vessel at any one time. ‘Hitherto,’ he wrote, ‘beyond the reach of their persecutors, they have here enjoyed a life of tranquillity and security; but will now, no doubt, be made to contribute to the wealth of our country, in exact proportion to the energy and perseverance of our merchants.’
By the early twentieth century, commercial whalers were fulfilling that prophesy, venturing into the Southern Ocean to hunt the large baleen whales on their summer migration to the cold Antarctic waters to feed as the sea ice receded. The whalers were after the oil-rich blubber, and the whales were hunted without mercy. Some estimate that 300 000 blue whales alone were slaughtered between 1900 and the 1960s. By the early 20th century, in the period often called the heroic era of Antarctic exploration, sea ice played a starring role in stories of human survival. But it also became the setting for close encounters between humans and marine life.
At the edge of every icefloe in summer, there is always an assortment of crabeater seals, snow petrels and penguins feasting on a banquet of krill. Nearer the coastline, the occasional orca or leopard seal patrols for an easy meal on ice. During Ernest Shackleton’s Nimrod expedition in 1907, the Adélies won over everyone with their human-like antics. The expedition’s chief scientific officer, Edgeworth David, thought them ‘the dearest, quaintest, and most winsome birds imaginable.’ They would come running up to the men, waving their flippers as if to signal for them to wait, occasionally tripping over in their haste. Aboard the Terra Nova in 1910, Robert Scott too was charmed by the Adelies.
Sea ice is notoriously fickle. The ship might enter thin ice that gave way easily, only to be brought to a halt by a small floe that seemed to Scott to be ‘possessed of an evil spirit’. Caught between two floes, the Terra Nova would swing around and fall away, then drift to leeward before the next assault on the ice. Each manoeuvre could take up to half an hour, and Scott found himself entertained by groups of Adélie penguins diving for food under the ship. He thought them ‘wholly ludicrous’ on the ice, but underwater their agility and speed were astonishing. Such interactions may have been heart-warming in any other context, but during these expeditions they invariably ended with animals being slaughtered for fresh meat or preserved as specimens for display in museums far from home. Scott wrote in his diary: ‘It seems a terrible desecration to come to this quiet spot only to murder its innocent inhabitants and stain the white snow with blood; but necessities are often hideous’.
In 1994, Dr Barbara Wienecke embarked on her first midwinter journey for the Australian National Antarctic Research Expedition. By then, the sea ice had become a scientific laboratory. A seabird ecologist, she was there to study the Emperor penguin rookery near Australia’s Mawson station, tracking their journeys to forage for food, and taking samples and measurements to determine their physical condition and food sources. Barbara created a mental map to help her navigate between the field hut and the rookery out on the sea ice, christening the distinctive icebergs trapped in the frozen ocean with names like ‘Pig’, and ‘Amphitheatre’ and the ‘Mother of all Bum Slides’, and finally the ‘Big Window’. On her first journey to the rookery, the icebergs muffled all sound and she saw only the odd stray bird. ‘Then at the end of this huge, tabular iceberg’, she recalls: ‘… suddenly there they were…there was just this mass of black bodies and the noise was phenomenal.’  There were around 11,000 breeding pairs, courting or promenading with their partners. She fell on her knees at the sight, and she told me that, despite her years of research, ‘Nothing prepares you for something like that.’ Her tracking devices showed that, during the dark winter months, the females would travel up to 3,000 kilometres in search of food before returning to the colony – fat and glossy – to reunite with their partners.
The males remained in the colony on the sea ice, huddled together for protection and warmth, all the while balancing their precious single egg on top of their feet. They do not eat for around 115 days, and they lose almost half of their total body mass. When the females returned in July, Barbara described how the subdued colony would erupt in an explosion of noise as the females bumped their way through the throng to find their mates. By December, the entire colony would return to the sea for the brief summer months.
Over the years, Barbara and her colleagues have observed disturbing changes in the Emperors’ behaviour. During an aerial reconnaissance in 2010, she was shocked to see a colony located on the top of a grounded iceberg. The surrounding sea ice that year was simply too weak to support the heavy birds. This location was not only unstable. It also exposed the chicks to crevasses and strong winds. Four years later, aerial photographs and satellite imagery revealed four separate colonies rearing their chicks on ice shelves rather than on sea ice. Recent climate modelling shows that, without changes to our greenhouse gas emissions, Emperor penguins could virtually disappear by the end of the century due to the loss of sea ice.
As the Emperors’ courageous and fragile existence on the fickle sea ice shows, the environmental violence of climate change has already reached this most remote and ephemeral place on Earth. The wider significance of these changes in sea ice is chilling. As the ice forms, it expels salt into the surrounding water, making it heavy. This dense, cold water sinks to the seabed and flows over the continental shelf and into the world’s oceans. The seasonal heartbeat of freeze and thaw, and the slow circulation of Antarctic Bottom Water, is the driver of global weather patterns. It is also plays a crucial role in drawing heat and carbon dioxide from the atmosphere into the ocean depths.
First, there was the violence of sealing and whaling, then industrial-scale fishing and krill harvesting, and now the slow violence of global warming. The ocean off the West Antarctic Peninsula is one of the fastest-warming places on Earth, threatening the massive shoals of krill that support the entire Antarctic ecosystem. Even in this remote, ephemeral environment, humans have left their mark.
There is a great risk in thinking that Antarctica’s realm of sea ice has no history. That its seasonal freeze and thaw is timeless, and holds no memory of past violations. Or that our newfound appreciation of the resilience and beauty of its creatures renders it immune from further catastrophe. But the sea ice and the creatures that inhabit it have their own stories to tell. And we are part of those stories, just as they are part of ours. Through the prism of sea ice, perhaps we can shift the focus away from our human-centred narratives to acknowledging the agency of the creatures and the ocean itself. The seasonal heartbeat of freeze and thaw might reassure us that all is well, but the precarious existence of its inhabitants, like the polar bears in the Arctic, is a clarion call from the furthermost ends of the planet.
 Richard M Laws, Large Animals and Wide Horizons: Adventures of a Biologist; The Autobiography of Richard M. Laws, pt 3, Antarctica and Academe, ed. Arnoldus Schytte Blix, Scott Polar Research Institute, Cambridge, 2012, p. 266.
 Louis Bernacchi, To the South Polar Regions: Expedition of 1898–1900, Bluntisham, Denton, 1991 (1901), pp. 31-2.
 William Henry Bayley Webster, Narrative of a Voyage to the Southern Atlantic Ocean, in the Years 1828, 29, 30, Performed in H.M. Sloop Chanticleer, under the Command of the Late Captain Henry Foster, F.R.S. &c., R Bentley, London, 1834, p. 157.
 James Clark Ross, A Voyage of Discovery and Research in the Southern and Antarctic Regions, During the Years 1839–43, vol. 1, J Murray, London, 1847, pp. 191–92.
 Robert Falcon Scott cited in Edward J Larson, An Empire of Ice: Scott, Shackleton, and the Heroic Age of Antarctic Science, Yale University Press, New Haven, 2011, p. 180.
 Barbara Wienecke, interview with author, 30 September 2019.
 Wienecke interview, 30 September 2019.
 Wienecke interview, 30 September 2019.
 Stephanie Jenouvrier, ‘Emperor penguins could march to extinction if nations fail to halt climate change’, The Conversation, 8 November 2019.
 Cassandra M Brooks et al, ‘Antarctic fisheries: factor climate change into their management’, Nature, 13 June 2018.