Fig. 14

Location of the MGVC gravity point. a The satellite image of Mendenhall Glacier Visitor Center derived from Google Earth Pro. The red circle and green triangle indicate the MGVC gravity point and AB50 GNSS station, respectively. The white arrow indicates the direction of the photo (b). b The entrance of Mendenhall Glacier Visitor Center. MGVC is located about 25 m from the entrance. c The elevator lobby of the Mendenhall Glacier Visitor Center, where the AG point is located. The new AG point is located on the right side of the lobby when facing the elevators. The old AG point (Sun et al. 2010) was located at the left side of the lobby. However, in June 2012, we found that the old point was not available because of the illuminating exhibition. The white arrow indicates the photo direction of Figure A5 in Sun et al. (2010). d The FG5-111 absolute gravimeter on the new AG point. e The position of the new AG point. It is located at the tip of the pen and approximately 109.5 cm from the corner of the heater. The heater should not be activated during the AG measurement, because its vibration magnifies the scatter of the AG data. f The exact position of the new AG point. It is located at the center of a tile and approximately 63.5 cm from the corner of the pillar. Note that we failed to measure the gravity difference between two AG points using a relative gravimeter directly during the campaign AG measurement in 2012, due to the exhibit installed on the old point by the visitor center. Instead, we considered the gravity difference by adding a term of the step-like gravity change between 2008 and 2012 in reproducing the temporal gravity change at MGVC (Fig. 5)