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TitleAbsolute gravity calibration of GPS velocities and glacial isostatic adjustment in mid-continent North America
AuthorMazzotti, SORCID logo; Lambert, AORCID logo; Henton, JORCID logo; James, T SORCID logo; Courtier, N
SourceGeophysical Research Letters vol. 38, L24311, 2011 p. 1-5, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20110195
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; Manitoba; Saskatchewan
NTS54L/16; 63K/13; 73B/02; 52L/04; 82J/16
AreaChurchill; Flin Flon; Pinawa; International Falls; Wausau; Iowa City; Saskatoon; Priddis; Minnesota; Wioming; Iowa
Lat/Long WENS-120.0000 -85.0000 60.0000 40.0000
Subjectsgeophysics; Nature and Environment; remote sensing; gravity; gravity interpretations; isostatic rebound
Illustrationslocation maps; plots
ProgramClimate Change Geoscience
Released2011 12 28
AbstractWe examine absolute gravity (AG) and vertical Global Positioning System (GPS) time series between 1995 and 2010 at eight collocated sites in mid-continent North America. The comparison of AG and GPS rates aligned to ITRF2005 yields a gravity/uplift ratio of -0.17 ± 0.01 uGal mm-1 (1 uGal = 10 nm s-2) and an intercept of -0.1 ± 0.5 mm yr-1. In contrast, aligning the GPS velocities to ITRF2000 results in a gravity/uplift intercept of -1.3 ±0.5 mm yr-1. The near-zero gravity/uplift offset for the ITRF2005 (or ITRF2008) results shows a good alignment of the GPS vertical velocities to Earth's center of mass, and confirms that GPS velocities in this reference frame can be compared to predictions of geodynamic processes such as glacial isostatic adjustment (GIA) or sea-level rise. The observed gravity/uplift ratio is consistent with GIA model predictions. The ratio remains constant in regions of fast and slow uplift, indicating that
GIA is the primary driving process and that additional processes such as local hydrology have a limited impact on a decadal time-scale. Combining AG and GPS measurements can provide significant constraints for geodetic, geodynamic, and hydrological studies.

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