Large-scale glacial melt is one of the realities that is being addressed by researchers in regards to global warming, as these systems of ice are the chief source of water contributing to sea level rise as global temperatures increase. There is a great deal of concern over the ice sheets covering Greenland, melting due to the nature of ocean currents in the region, and the ice shelves in West Antarctica, vulnerable from melt caused by warm water from below, as well as increasingly warm air from above. In contrast, the much more massive ice sheet that covers East Antarctica has historically been considered stable, and has been recorded as gaining ice in recent years, as opposed to the losses seen by Greenland and West Antarctica. However, a new study of the Totten Glacier in East Antarctica has shown that the world’s largest volume of ice has collapsed many times in the past — sometimes catastrophically so — and is in danger of dosing so again.
Antarctica’s Totten Glacier is the continent’s largest glacier, a massive ice field roughly the size of California, and is approximately 2.5 miles (4 km) thick. The glacier itself is comparatively stable as it now stands, but this new study, conducted by an international team from Australia, New Zealand, the United Kingdom and the United States, warns of potential key vulnerabilities in the Totten ice system that could trigger a domino effect collapse along the length of the glacier.
The end of the glacier itself extends out over the ocean in a large ice shelf that covers an area 90 miles by 22 miles (145 km by 35 km), with roughly 40 percent of its height extending a mile below the surface of the ocean. It’s the inherent stability of this ice shelf that keeps the rest of the Totten Glacier from sliding off into the ocean, but as the oceans heat up, that stability is threatened: much like its Western Antarctic counterparts, warm ocean waters are eroding the ice shelf’s base from below, and its grounding line, the point where the ice shelf meets the seafloor, has already retreated inland by 3 km (1.9 miles) between 1996 and 2013.
Their research also found that the glacier has been prone to rapid retreats in the past, as evidenced by sedimentary deposits under the glacier — it may remain stable for a long time, but when it goes, it collapses quickly. Under the ice, Antarctica has a vast system of sub-glacial lakes and rivers that allow portions of the miles-deep ice sheet to flow more freely, and the Totten Glacier in particular flows over top of a large number of these bodies of water. If the more stable region of ice near the coast that currently acts like a slow-moving dam were to give way, that would allow a massive amount of ice from the glacier to flow into the ocean — and this would also affect the stability of Totten’s neighboring glaciers.
The last major retreat seen by the Totten ice sheet was roughly 3 million years ago, when ocean levels were 30 feet (10 meters) higher than they are today, average global temperatures were 2ºC (3.6ºF) higher, and the atmosphere’s carbon dioxide level was at 400 parts per million. "We are at 400 ppm right now, and if we do nothing about climate change we’re going to get 2 degrees Celsius more warming, too," warns study senior author Martin Siegert, of Imperial College in London.