As a numerical modeler within the Seamstress team, my role is to simulate the effect of natural processes that could affects the regional stress field, by using advanced computational methods. The model presented here is a simulation of the Earth’s response to glaciation and deglaciation cycles, a physical process that is known as glacial isostatic adjustment (GIA). In other words, the Earth’s most outward layer, the lithosphere, falls or rises in reaction to its ice-age burden. In return, the deformation of the lithosphere results in the perturbation of the Earth’s stress field over regions affected by the glaciation and melting of the ice-sheet.
The following animation shows the magnitude of the maximum horizontal stress (SH) induced by GIA and calculated from the model for the last 122.8 kyrs. This period of time includes three episodes of glaciation and deglaciation that covers Greenland (Lecavalier et al., 2016), Fennoscandia, Svalbard and the Barents Sea (Patton et al., 2020). The ice models are applied at the surface of a spherical earth defined by a Maxwell viscoelastic rheology and includes every layers of the Earth from its surface to 2000 km depth.
Results show that the maximum horizontal stresses are compressive in regions covered by ice and tensile off the edge of the ice-sheet. The local maximum of the horizontal stresses (around 30 MPa at the last glacial maximum for SH) matches with the ice thickness’s local maximum (around 3000 m at the last glacial maximum over Northern Sweden, Greenland and East of Svalbard). The tensile region located around the ice-sheet extent, results from the formation of a bulge that surrounds the subsidence zones formed by the weight of the ice cover on the Earth’s lithosphere. The pockmarks of Vestnesa ridge are located is a region where the forcing from the ice-sheet have probably influenced sediment fracturing as well as the gas hydrate and free gas reservoir dynamics in this region.
Figure: Map of maximum horizontal forcing (SH) derived from crustal adjustment following the retreat of the ice. Blue areas are subjected to a tensile stress regime whilst red areas are in a compressive stress regime. The black vectors indicate the orientation of the maximum horizontal stress.
Text and illustration Rémi Vachon