Coastal Antarctic Ice at Risk: Permafrost Melting Faster Than Expected

For years we've known that the permafrost in the Antarctic is at risk of melting. Warmer temperatures have helped encourage areas that have been frozen for years to slowly thaw. Now, scientists have documented an acceleration in the melt rate of permafrost for the first time in a section of Antarctica that was once thought to be stable. The findings are worrisome for the future of these northern areas, which rely on the stability of ice.

Permafrost is an important part of northern climates. Unlike glaciers and ice sheets, which sit on the ground, permafrost is a mixture of frozen soil and ice and is usually buried under layers of sediment. When it melts, the ground can become unstable and sink, causing the entire environment to change.

In order to examine the melt rate of permafrost in the Antarctic, the researchers tracked data from Garwood Valley in the McMurdo Dry Valleys region of Antarctica. This region contains one of the largest stretches of permafrost on the continent. Although the ice was once thought to be in equilibrium in this region, LIDAR and time-lapse photography seemed to indicate otherwise. In fact, the researchers found a rapid retreat of ground ice, similar to what is currently being found in the coastal Arctic and Tibet.

"The big tell here is that the ice is vanishing--it's melting faster each time we measure," said Joseph Levy of the University of Texas at Austin, one of the researchers, in a news release. "This is a dramatic shift from recent history."

Surprisingly, though, rising temperatures do not account for the increased melting in Garwood Valley. In fact, the Drys Valleys experienced a cooling trend from 1986 to 2000, followed by stabilized temperatures to the present. Instead, the melting can be attributed to an increased amount of sunlight reaching the ground.

Sunlight bounces off of white surfaces, such as what can be found on the reflective surfaces of glaciers and ice sheets. Darker surfaces, such as dirty ground ice, absorb greater amount of solar radiation. While thick layers of sediment usually insulate deeply buried permafrost, some sediment is thinner. This thin sediment actually helps "cook" the nearby ice and accelerate melt rates.

What is more worrisome, though, is the fact that Antarctica is expected to warm in the coming century. This could exacerbate the current melting and could cause slumping conditions, which is when the frozen landscape sinks and buckles.

"There's a lot of buried ice in these low-elevation coastal regions, and it's primed to melt," said Levy.

The findings are published in the journal Scientific Reports.