Exploring the frozen continent
How Edinburgh's expertise in Antarctica is revealing secrets of the Earth's past and future.
Our understanding of the Antarctic continent has always been subject to mystery. That vast, inaccessible, human-less wilderness can seem to have more in common with the Moon than Earth’s lush forests and mountainous terrains. Lagging well behind our vast knowledge of the planet’s other expanses – not to mention the Moon itself - until the heroic expeditions of the 20th Century our singular guide to the icy region was J. Murray’s vague map, published in the Scottish Geographical Magazine in 1886, and including only peripheral indications of a coastline and a tantalisingly imaginary line that indicated the “supposed outline of Antarctic Continent”. We knew nothing of the interior.
But exploration of the interior and the plate tectonic revolution of the mid-twentieth century changed all that. Finally, the science community had roundly accepted the theory that the outer rigid layer of the earth (the lithosphere) is divided into a couple of dozen "plates" that move across the Earth's surface, relative to each other. This led to a surge of research into the Antarctic region, including depth-sounding of the ice sheet that revealed that what lay beneath was part of the ancient Gondwana supercontinent that began to break up about 180 million years ago. It split into parts of present-day Africa, South America, Australia, the Indian subcontinent, Madagascar, and Antarctica. Suddenly the frozen continent had become part of the world as we knew it.
Fluvial in origin
David Sugden is Emeritus Professor in the University’s School of GeoSciences and an eminent glaciologist, and he regards this period as pivotal in the progress of our understanding of Antarctica.
“As knowledge of ice sheet history emerged from these new studies, it became clear that the Antarctic sheet had been in existence for some 34 million years,” he says. “That’s much longer than the two to three million years of the northern hemisphere. So when researchers considered how much change had occurred in the landscapes of places like Scotland, it became reasonable to assume that Antarctica’s underlying bed, having been exposed to glacial erosion for ten times as long as the north, had been modified even more.”
David began to test this theory further when his own personal experience of the region began. He was working as a researcher, alongside the University of Maine’s George Denton, in the McMurdo Dry Valleys – Antarctica’s largest ice-free area. There they discovered that much of the continent’s frozen landscape did, in fact, pre-date the ice sheet.
“We found that areas like mountain escarpments and valleys, were fluvial in origin,” says David. “The ice sheet had covered the area, but had been selective about where it deepened a river valley to form a trough, and instead protected some valleys when its base was below the melting point. The landscape of these escarpments reminded us of South Africa, especially the Drakensberg Mountains and Namibia, which we then duly visited. The similarity with the Dry Valleys was remarkable.”
David then began researching the subglacial landscape of Antarctica with Stewart Jamieson, a former PhD student and researcher at Edinburgh who is now based at the University of Durham. Stewart helped to create a reconstruction of the landscape, and this provided the pair with the inspiration for their latest study.
“It looked just like South Africa,” says David. “Moreover, the uplands beneath the West Antarctic Ice Sheet looked like Madagascar. This helped us form the idea that the main landscape features in Antarctica are similar to those of our southern continents, and so had to have been formed by similar river processes.”
David and Stewart have published their findings in the Scottish Geographical Journal, a move that seeks to quantify and test their ideas among their peers, and also to consider the implications for future research.
“Our work reinforces the view that the landscape of Antarctica is extremely old - much, much older than originally thought,” says David. “Just as the tors on the Cairngorm plateau in Scotland are thought to be on an ancient land surface that has largely survived beneath ice sheets, now in Antarctica we can actually see very similar landscapes under ice that has protected it.”
Oldest ice on Earth
David says that the new research could bring the very distant past into the future, too: “The sheer age of the Antarctic ice sheet and its persistence for millions of years means that the mountains that rise above it have been subject to those freezing polar conditions for the same length of time. So the oldest ice on Earth is there, buried beneath a thin cover of rock fragments. And air bubbles within that ice can hold traces of the atmosphere from millions of years ago – that’s an enticing prospect… what could those traces tell us?”
With research into climate change at the heart of the School of GeoSciences’ priorities, David’s work also holds the potential to help us understand the planet as it warms.
“The stability of the ice sheet is influenced by the way it flows across the underlying landscape”, he says. “A discovery from our work is that the ice sheet has eroded deep troughs up to 2 km below sea level - one is 50 km wide, and extends 1000 km inland. These troughs can threaten the sheet’s stability if warm coastal water seeps beneath the glaciers, causing them to thin and their bottoms to melt. This in turn means they will flow faster and discharge more ice from their basins, potentially contributing an additional one or two metres to the global sea-level. So it’s vital that we continue to study, monitor and find solutions for this.”
And, says David, the University of Edinburgh, and Scotland as a whole, are best placed to do this: “The Royal Scottish Geographical Society was heavily involved in early Antarctic research at the turn of the twentieth century, and the University has been linked to several expeditions to the region. Scotland really has pushed forward our understanding of the Antarctic continent. It’s only right that the School of GeoSciences keeps this work going.”
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All photos courtesy of David Sugden.