Invited by State Key Laboratory of Geodesy and Earth’s Dynamics (SKLGED), assistant professor Liu Lin from The Chinese University of Hong Kong(CUHK) visited Institute of Geodesy and Geophysics(IGG) and gave an academic report in title “One’s Trash, Another’s Treasure: The Use of Reflected GPS Signals for Permafrost Studies” on May 3.
The report firstly introduced the basic principle of using GNSS reflection signals to measure the thickness variation of the active layer of permafrost, and demonstrated the successful cases of monitoring the annual and seasonal changes of the active layer of permafrost in the Barraw area of Alaska. He found the permafrost occurred the sedimentation at a rate of 1.4 cm/yr between 2004 and 2010 near the GNSS site of SG27 in the area, and it increased at a rate of 1.4 cm/yr between 2011 and 2014. The reason for this variation was mainly the variation in the overlying layer of underground ice. The report also introduced a periodic deformation composite model of permafrost active layer in freezing-thawing state. This model can better explain the cyclic deformation of the active layer caused by the periodic variation of freeze-thaw status of permafrost. After the report, the participants discussed with professor Liu on GPS reflected signal processing, permafrost calculation methods, and 2017 joint scientific research results, and exchanged opinions on the joint scientific research issues to be carried out in 2018. The report achieved good communication results.
Assistant professor Liu received his Ph.D. degree from University of Colorado in 2011 and then worked as a postdoctoral researcher at Stanford University. He is mainly engaged in permafrost, glacier geodesy and geophysical research.

                                                                              Professor Liu was giving his report.