Glacier Temperature and Structure Variation Observed with Fiber-Optic Sensors on a Tibetan Plateau Glacier

Glacier temperature and structure can provide essential constraints for glacier change assessment. Traditional observed methods are mainly based on thermometers and ground penetrating radars, limited by sparse observations. We developed a kind of fiber-optic temperature sensor (Brillouin optical time domain analysis, BOTDA) and fiber-optic seismometer array (FOSA), which can realize high-resolution and multi-year continuous observations. We firstly conducted an experiment for the application of the fiber-optic sensors on the Kuoqionggangri glacier in the Tibetan Plateau. The BOTDA was buried in the ice and hang in the air to measure temperature changes, and successfully recording the ice surface temperature change. The FOSA was installed with seismic channel interval of 1 m buried in ice, and 10 m on ice surface, which clearly recorded the seismic wave signals of background noise, hammer hitting and people walking. Through analyzing the seismic waves induced by the hammer hitting, we obtained the ice-rock interface depth with a value of about 40 m. Moreover, there is a low-velocity layer with large S-wave velocity drop of 28% and thickness of about 7 m in depth of 30 m within the glacier interior. We inferred that the abnormally low velocity layer may be caused by stagnant water of the intergranular veins formed during the transition from snow to ice. This observation provides new evidence for the existence of the water-rich layer in the Tibetan Plateau, implying a new insight for evaluating glacier change.