Since the early 20th century, nearly all of Earth’s glaciers have been retreating or melting. Glaciers cover 10% of the planet’s land area and contain 75% of our fresh water. Moreover, the water from melting glaciers accounts for nearly two-thirds of the observed rise in global sea levels. Despite the looming ecological consequences, glacier motion remains poorly understood because of a lack of research on how large ice masses sheer and flow in contact with bedrock.
The roughness of bedrock, the temperature of the ice-bed interface and the presence of water-filled cavities all affect friction and influence how the ice will flow. Studying these factors poses unique challenges—remote radar sensing by satellites and aircraft can track glacial movement, but it can’t peer through thousands of feet of ice to measure detailed properties of the ice and rock.
In a new paper in The Journal of Chemical Physics, theoretical physicist Bo Persson of the Jülich Research Center in Germany describes a new model of ice friction that offers crucial insight into glacier flows.
Persson turned to previous studies of rubber surfaces that are either in stationary contact or sliding past each other. For glaciers, he examined factors such as bedrock and ice roughness, and the effect of regelation—melting and freezing caused by local pressure fluctuations.
For most thick glaciers—like the polar ice caps—the temperature between ice and the bedrock is close to the melting temperature of ice due to geothermal heating and frictional. As a result, the cavities are almost always filled by pressurized water.
Angelike Humbert works on ice-sheet modelling and the remote sensing of ice sheets and glaciers using satellites.