Midway Evaluation in Geophysics - Greta Bellagamba

Student:
Greta Bellagamba

Doctoral committee:
Dr. Halldór Geirsson, Associate Professor, Faculty of Earth Sciences, University of Iceland
Dr. Michelle Maree Parks, research specialist, Icelandic Meteorological Office
Dr. Peter Schmidt, researcher, Swedish National Seismological Network, Uppsala University, Sweden

AbstractThe Earth response to glacial load change is called Glacial Isostatic Adjustment (GIA). Approximately 10% of Iceland is covered by glaciers which are melting as a result of global warming. Iceland is situated on a plate boundary and above a mantle plume, therefore geological conditions are different from most places where GIA is studied. The aim of this project is to investigate GIA in Iceland through a model with a new glacial load history and constraints from updated geodetic data, using the Finite Element Method (FEM). A GIA model is made of two parts: an Earth model and a glacial load history. I use a flat-Earth approximation for the Earth model, with a structure of two elastic layers on top of a viscoelastic half-space. The rheology is linear, and earth model parameters vary only with depth. The glacial load history comes from mass balance calculations, and is imposed as a boundary load on the Earth model. We run the model with different values of viscosity and lithospheric thickness, comparing the calculated displacements to GNSS time series, to find the best parameters to represent Iceland. Preliminary results are a viscosity of 3x1018 Pa s and an elastic thickness of 35 km. There is also emphasis on correct calculation of horizontal GIA deformation in order to better understand GIA-induced stress changes on e.g. volcanic systems and mantle melt production. Eventually, the goal is to evaluate how GIA affects volcanic systems (such as Grímsvötn) and whether eruptions frequency and volume may be affected by climate change.