'Tiger Stripes' Located Beneath Antarctic Glaciers Act Like Speed Bumps

"Tiger stripes" of dirt and rock found far beneath Antarctic glaciers create zones of increased friction that act like speed bumps on the ice's otherwise steady march toward the sea.

These were the findings of an international team of researchers who believe that by identifying how these high-friction regions form and dissipate, they may be able to come to a better understanding of how global warming affects the glaciers' flow.

In particular, the researchers studied two glaciers, the Pine Island Glacier and Thwaites Glacier in West Antarctica, which together are believed to have contributed to about 10 percent of the observed sea-level rise of the past 20 years.

The discovery of the tiger stripes was done using mathematical modeling based on data from the National Snow and Ice Data center and the British Antarctic Survey (BAS). Conducted by Olga Sergienko of Princeton University's Program in Atmospheric and Oceanic Sciences, the model predicted the stripes, or ribs, which had been theorized some time prior by BAS scientist Richard Hindmarsh.

According to Sergienko, the stripes put the brakes on the glaciers whenever friction is high. In the case of low friction, such as when melting ice coats the bedrock, the glaciers slide along much faster.

"The ribs may play an important role in buffering the effects of a warming climate, since they slow the movement of ice that reaches the ocean and contributes to sea-level rise," Sergienko said, noting, "These changes can happen independently of climate change, too."

Though more research is needed to verify their findings, the scientists said there is possible precedence for the discovery.

"Our guess is that these ribs are related to typical landforms that exist in the formerly glaciated areas of North America and Europe," Hindmarsh said. "A great example are the drumlins -- raised areas of soil and rock -- that make the hills in Seattle or Glasgow."

Though not involved with the work, Douglas MacAyeal, a professor of glaciology at the University of Chicago, said the research will likely have significant repercussions for future studies on the region.

"This is strongly suggestive of a new style of physical controls over friction, like water flow in the thin zone between the rock of the bed and the ice," he said. "The results of this study will drive new theoretical and observational efforts to understand what causes this pattern."