'Tiger Stripes' Act As Glacier Speed Bumps
Nature’s No-Slip Grips Slow Down Glacial Paths Towards The Sea
Scientists at Princeton University and the British Antarctic Survey have finally solved the riddle of why Antarctic glaciers don't speedily race their way to the open sea. The reason why is friction.
Much like non-slip strips on floors prevent people from slipping on wet and slick surfaces, similar geological ribs, called ribs because of their slightly curved shape, create enough friction to inhibit glaciers from slipping along the underlying bed of rock and sediment.
The ribs, also nicknamed "tiger stripes" as a nod to Princeton's tiger mascot, lie at roughly 30-degree angles to the direction of the glacier's movement. The angle serves to curb a glacier's tendency to slip along the otherwise smooth bedrock halting its movements from a dash to a crawl. The ribs are formed due to natural processes occurring over 50 to 100 years that are strongly affected by how water from melting ice infiltrates the space between the ice sheet and the bedrock.
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Direct study of the bottom of these glaciers is nearly impossible. The glacier ice is over a mile and half thick obscuring visibility of the ground below. Instead, researchers used a combination of satellite measurements of ice velocity, ground penetrating radar collected from airplanes, field observations, and also mathematical modeling based on data from the National Snow and Ice Data Center and the British Antarctic Survey. They focused their study on two glaciers: the Pine Island Glacier and the Thwaites Glacier in West Antarctica, which together account for roughly 10 percent of the observed sea level rise over the past 20 years despite their relatively small areas.
Although more research is needed to verify the scientists' findings, their discovery is not without precedence.
"Our guess is that these ribs are related to typical landforms that exist in the formerly glaciated areas of North America and Europe," said British Antarctic Scientist Richard Marsh who worked on the project. "A great example is the drumlins — raised areas of soil and rock — that make the hills in Seattle or Glasgow."
The research also suggests that the ribs have serious implications for buffering the effects of a warming climate: they delay the movement of ice that reaches the ocean and contributes to rising sea levels.
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