A fjord is a deep valley carved by glaciers. Most famously, fjords were cut into the land by ice melt during Norway's summers, when fast-moving rivers flow between stunningly tall cliffs. Now a group of researchers have discovered that the fjord was also common to Antarctica, back when its eastern ice sheet grew and shrank rapidly every year.
Above, you can see a fjord in Alaska, whose steep, green walls resemble what you might have seen millions of years ago in the eastern mountains of Antarctica, before the Aurora Subglacial Basin was buried beneath kilometers of ice. And if ice sheets on this southernmost continent keep melting, you may yet see them again.
A team of researchers used satellite radar images to peek beneath the continent's thick eastern ice sheet. Though 98 percent of Antarctica is buried under ice, parts of its western ice sheet are thinning and breaking off. Not so with the eastern sheet, which many scientists believe to be far more stable. New research reveals that roughly 16 million years ago, however, the eastern ice sheet was much more variable. It covered less of the continent, and melted enough every year to cut dramatic fjords into the landscape.
According to geologist Sandra Passchier, who writes about this new research in Nature:
[The research team] surveyed the preserved topography under thick ice in the Aurora Subglacial Basin. Their studies reveal a previously unknown subglacial mountain range dissected by a series of parallel valleys; these valleys have U-shaped cross-sections and are some 50 kilometres wide. Rock uplands form barriers to ice flow (see photo at left), and knowing their location sets an important boundary condition for ice-sheet models. The newly discovered subglacial mountains, at one time positioned at the edge of the ice sheet, would have restricted the outflow of ice, and outlet glaciers with steep gradients carved deep into the rock. A fjord landscape resulted - perhaps similar to that seen in East Greenland or Norway today - in which glacial valleys were carved over several glacial periods and, at times, were flooded by the sea.
The more geologists learn about the landscape of Antarctica, the more obvious it seems that climate changes are the norm, rather than the exception, in Earth's history.
Read the full scientific study via Nature.
Top photograph by Lee Prince/Shutterstock;