Antarctica

Antarctica

The coast of Antarctica was rather like the West Coast. It had Southern Beech, ferns and even things that looked like nīkau. During interglacial periods it was a climate that allowed a woodland forest. During glacial periods the ice was as extensive as it is today, flowing through the mountains and out onto the coast.

Peter Barrett describing the dynamic nature of Antarctica’s ice sheets, in an interview broadcast on National Radio, 2 March 2006

A fascination with Antarctica brought the young English geophysicist Trevor Hatherton (1924-1992) to New Zealand in 1950. He took a job with the DSIR, investigating the magnetic properties of volcanic rocks in the central North Island. But by December of 1955, he was in Antarctica for a reconnaissance on foot over sea ice to select a site for New Zealand’s base. Construction of Scott Base began the following year and, as chief scientist to the New Zealand International Geophysical Year Antarctic programme, Hatherton headed the team until 1958.

He left New Zealand twice, temporarily, to take up fellowships at the California Institute of Technology and Stanford University, but returned in 1967 to become the director of the Geophysics Division, DSIR, a position he held for 18 years.

It was to take nearly 30 years before Hatherton revisited Antarctica as the chairman of the Ross Dependency Research Committee, which was organising the science programme on ice, and he was invited to take part in a workshop on the Antarctic Treaty.

Frozen extremes

Antarctica is the world’s largest desert, receiving less than 50mm precipitation a year in some places. The icy continent also holds the record for being the windiest, coldest and most hostile place on Earth. However, when Antarctica was still part of the supercontinent Gondwana more than 180 million years ago, it was a green land with rivers, forests, reptiles and even dinosaurs. The evidence is still preserved in the layers of rock in the Transantarctic Mountains, where scientists find river sands that tell them which way rivers once flowed, tree stumps and the bones of reptiles and amphibians.

When Gondwana broke up, Antarctica eventually settled over the South Pole, and today it is wrapped in an ice cap up to 4km thick, more than 4000km across and with almost three-quarters of the world’s fresh water trapped in it. Because of its remoteness, Antarctica provides a baseline for scientists and acts as a sensitive barometer for global change.

Climate secrets

As a graduate student Peter Barrett made a ‘missing link’ discovery of the first tetrapod fossil, thereby clinching the land connection between Antarctica and other Gondwana continents. A few years later, in 1973, he was one of three ‘lucky Kiwis’ to take part in an expedition aboard the Glomar Challenger, the first research vessel equipped for deep-sea drilling. The team drilled in the Ross Sea and brought up sediment cores whose layers of glacial deposits and mud showed that Antarctic glaciation had begun more than 20 million years earlier than previously thought. A few months later, another cruise led by New Zealander Jim Kennett obtained the first isotope records of climate from the deep sea, confirming the results.

These early projects eventually led to the multi-national Cape Roberts Project, headed by Barrett, now the director of the Antarctic Research Centre at Victoria University. During the late 1990s, three holes drilled near the edge of the mountains recovered a remarkable ‘sedimentary tape recorder’, confirming that massive ice sheets have covered Antarctica since around 34 million years ago. However, the ice cover was highly dynamic, coming and going in response to perturbations in the Earth’s orbit, known as Milankovitch cycles, which affect the amount of radiation the planet receives. For the past 15 million years, the size of the ice cap has been relatively stable.

Beginning in the 2006/2007 summer, the Andrill project will continue the quest to unravel the climate history of the Ross Ice Shelf by drilling through 100m of ice, 900m of water and up to 1200m into the sea floor near Scott Base.

Window into the past

Nancy Bertler is New Zealand’s representative at the International Transantarctic Scientific Expedition, which aims to gauge climate variability in more recent times (the last few thousand years) by studying ice cores. Ice delivers information about the past in different ways. The ice itself, via the isotopic ratio in the water, records past temperatures, precipitation levels and even carries information on the origins of the air mass that precipitated the snow. Dust caught in the ice is a measure of how vigorous past storms were and the gas trapped in tiny bubbles provides a sample of an ancient atmosphere from thousands of years ago.

Hole in the sky

Every spring since the early 1980s, a hole has been opening in the ozone layer above Antarctica. It forms because strong circumpolar winds create a polar vortex during winter and, in spring, a combination of sunlight, low temperatures and chlorine from human-made chemicals triggers a chemical reaction that destroys more than half of the ozone inside the polar vortex. The National Institute of Water and Atmospheric Research runs an extensive programme of measuring trace gases that play a role in ozone depletion or are useful as tracers of atmospheric motion.

By Veronika Meduna

Medals and awards

Trevor Hatherton: FRSNZ, Hector Medal

Peter Barrett: FRSNZ, Premio Internazionale Felice Ippolito, Marsden Medal, SCAR President’s Medal

Further reading and websites

Antarctica New Zealand website

Antarctic Research Centre website

Trevor Hatherton (ed), Antarctica, A H & Reed, 1965

Warren Herrick, A Year on Ice, living and working in Antarctica, Shoal Bay Press, 1997

Image courtesy Antarctica New Zealand Pictorial Collection

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