Geodesy & Crustal Deformation Geology 6690/7690 Geodesy & Crustal Deformation 30 Aug 2017 Geodesy is the measurement and representation of the shape of the Earth and its gravity field Motivation: Most active processes that are of interest to Earth scientists change the shape of the planetary surface and change the gravity field. Applications of geodesy include legal & construction industry (“surveying”), navigation & many other… Research applications include studies of tectonics & the earthquake cycle, hazard analyses/modeling (landslide & mass wasting, volcano studies & monitoring), climate studies (sea level, water & ice mass), and water monitoring Read for Fri 1 Sep: Wahr §1 (1-3); §2.5 24-75 © A.R. Lowry 2017

Geodesy is the study of the shape of the Earth’s surface, and its gravitational field…

Example: The Geoid Satellite altimeter measurements of sea surface height used to estimate the geoid have greatly aided study of seafloor tectonics

Example: Gravity Studies “Mascons” (mass concentrations) within annular rings have long been recognized as evidence of impact structures in planetary science… Recognition of a signal consistent with a mascon near Chicxulub (Yucatan) MX prompted a closer look…

Example: Landslide Monitoring Velocities of “permanent scatterers” in the Arno basin, Tuscany, from multiple Interfero- metric Synthetic Aperture Radar (InSAR) images.

Example: Surface Hydrology River height changes can be difficult to measure accurately using surface gauges because “dynamic” water heights on different channels and different parts of channels can vary by > 1 m in height… Amazon heights are found to change by about 10 meters peak-to-peak annually using satellite Synthetic Aperture Radar altimetry. Can use similar altimetry for rivers, lakes and oceans

Example: Sea Level Change Climatological models of sea level rise used in 2007 IPCC reports predicted a likely rise of 30 cm from 1990 to 2100, with envelope from 10 to 90 cm. Laser altimetry from TOPEX and Jason satellite measurements show rise of 3.4 mm/yr from 1993 to 2016, or ~ around 8 cm from 1990-2016… Near the upper 2 envelope for that period from IPCC models.

Example: Sea Level Change Regional rates of altimetric height change show evidence of both dynamical effects (ENSO) and geoid change.

Measurements of sea level change show a sharp drop in global levels starting ~mid 2011, coincident with a switch from El Nino to La Nina ocean current conditions… Time-variable gravity measurements showed the water temporarily moved to land-surface via precipitation!

Example: Groundwater Hydrology Gravity And Climate Experiment (GRACE) measurements of surface mass change in the Amazon basin indicate ~100% greater amplitude and a phase delay in annual storage of water mass relative to hydrological models based on surface measurements of precipitation and river outflow

Example: Cryosphere (Greenland) Barletta et al., Cryosphere, 2013 (via polarportal.dk) GRACE shows ~200 km3/yr decrease in ice mass from 2002 to 2017, mostly from coastal areas 0.6 mm/yr of sea level change

Example: Cryosphere (Antarctica) GRACE measurements of mass change in Antarctica indicate –165±71 km3/year 2002 to 2010 (from W Ant)