South Georgia Island: A Sentinel for Climate Change

South Georgia was covered by a massive ice cap during the last ice age, researchers have discovered.

Today South Georgia is home to over 100 glaciers, juxtaposed with green grass and abundant wildlife. But this wasn’t always the case. Twenty thousand years ago ice extended tens of kilometres out into the ocean from the island, with life only existing at the ice margin and beyond. Associate Professor Duanne White worked with a team of international researchers to discover that ice on South Georgia is sensitive to short-lived cooling and warming, growing and shrinking dramatically as the climate changed after the last ice age.

While the island is small compared to Antarctica and its ice caps, this is an important result. South Georgia is located in a part of the sub Antarctic that is particularly sensitive to changes in climate, and can be considered a “sentinel” to climate change.

“Glaciers in the sub-Antarctic are retreating dramatically today, in response to an ever-warming atmosphere and ocean,” says White. “It is perhaps unsurprising that South Georgia’s glaciers were sensitive to climate change in the past, but our work has really shown that they were dynamic and underwent big changes in response to past warming.”

“Improving the history of glacier behaviour on South Georgia even further is now essential so that we have a long-term context for the alarming recession we are witnessing right now.”

A team of researchers from the UK, Germany and Australia visited the island twice and used sophisticated sonar technology mounted to the hulls of ice-breaking vessels to reveal patterns of glacier growth and retreat. They discovered clear patterns of past glacier extent, with moraine ridges bulldozed into the seabed. This proved that, in contrary to previous estimates, the ice shelf extended many kilometres across the continental shelf. They also used weighted gravity corers to retrieve samples of ancient sediment from the ice-carved troughs that radiate from the island.

The paper, “Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation” is published in Nature Communications. You can read the full article here.

The research was led by the University of Exeter, UK, and funded by Natural Environment Research Council.