Scientists have used fibre-optic sensing to obtain the most detailed measurements of ice properties ever taken on the Greenland Ice Sheet. Their findings will be used to make more accurate models of the future movement of the world’s second-largest ice sheet, as the effects of climate change continue to accelerate.
The research team, led by the University of Cambridge, used a new technique in which laser pulses are transmitted in a fibre-optic cable to obtain highly detailed temperature measurements from the surface of the ice sheet all the way to the base, more than 1,000 metres below.
In contrast to previous studies, which measured temperature from separate sensors located tens or even hundreds of metres apart, the new approach allows temperature to be measured along the entire length of a fibre-optic cable installed in a deep borehole. The result is a highly detailed profile of temperature, which controls how fast ice deforms and ultimately how fast the ice sheet flows.
The temperature of ice sheets was thought to vary as a smooth gradient, with the warmest sections on the surface where the sun hits, and at the base where it’s warmed by geothermal energy and friction as the ice sheet grinds across the subglacial landscape toward the ocean.
The new study found instead that the temperature distribution is far more heterogenous, with areas of highly localised deformation warming the ice further. This deformation is concentrated at the boundaries between ice of different ages and types. Although the exact cause of this deformation remains unknown, it may be due to dust in the ice from past volcanic eruptions or large fractures which penetrate several hundred metres below the surface of the ice. The results are reported in the journal Science Advances.