ESS EARTH SCIENCESSECTOR SECTEUR DES SCIENCES

• Main Authors: De La Terresst, A. Lambert J. Henton, J. Huang, N. Courtier, J. Liard
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Hudson; Hudson Bay
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.643.3659; http://www.ngs.noaa.gov/GRAV-D/2009Workshop/Presentations/Henton_graceAG_09.pdf

GRACE monthly gravity estimates have been compared with annual surface gravity measurements at mid-continent North American sites to examine similarities and differences in observed trends and inter-annual variations. At some sites the GRACE trends are significantly different from the surface absolute gravity trends corrected for vertical movement, probably as a result of different spatial averaging of the dominant postglacial rebound signal. However, at sites where inter-annual variations are significant, there are strong similarities between GRACE and surface gravity data, indicating the presence of large-scale changes in groundwater storage. • Monthly GRACE gravity values were derived from the CSR-RL04 spherical harmonic monthly models for the period of April 2002 to January 2009. • Surface gravity observations have been carried out annually at mid-continent sites for well over a decade. The surface gravity values reported here are based on at least 24 hours of gravity observations using free-fall absolute gravimeters. • GRACE and surface gravity trends at mid-continent North American sites are in agreement at some sites but not in others. At Churchill the trend from surface measurements is expected to be higher than the GRACE trend as a result of Hudson Bay outflow, which should reduce the GRACE trend and increase the surface gravity trend. At other sites, such as Flin Flon and