Tracking changes in massive ice sheets is key to understanding the effects of climate change. A new tool based on fiber optic sensing was demonstrated to provide detailed temperature measurements from the surface to the bottom of the Greenland Ice Sheet, generating a clearer picture of conditions in the world's second largest ice sheet.

The approach uses a mix of fiber optic cables and laser pulses to gain precise temperature readings from the surface to more than 1,000 m depth. The cable emits laser pulses along its entire length, stretching Installing fiber-optic cable on the Greenland Ice Sheet. Source: Poul Christoffersen/University of Cambridgefrom the surface of the sheet to its base a kilometer below. By analyzing the varying distortions in the scattered light as it encounters the surrounding ice, the system documents temperature profiles.

Previously recorded temperature distribution data were interpreted to resemble a smooth gradient, with the warmest points found at the top of the ice sheet exposed to sunlight and at the bottom due to geothermal heating and friction with the subglacial landscape. Measurements made with the new sensor system indicate temperature distribution to be more heterogenous, as indicated by localized hot spots at boundaries between ice of different ages and types, driven by deformations.

The research reported in Science Advances identified three layers of ice in the glacier, with the thickest consisting of cold, stiff ice formed over the last 10,000 years. Older ice from the last ice age, which is softer and more deformable due to dust trapped in the ice, lies beneath. The bottom layer is composed of warm ice more than 70 m thick.

Researchers from University of Cambridge (U.K.), Aberystwyth University (U.K.), Delft University of Technology (Netherlands) and University of Leeds (U.K.) contributed to this study.