GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 HOW ELASTIC IS ELASTIC DEFORMATION (IN GREENLAND)? A. Consorzi, D. Melini, G. Spada Glacial Isostatc Adjustment (GIA) is the tme-dependent response of the Earth to spato-temporal variatons of surface loads. Since the seminal work of Wu and Pelter (1982), the GIA community has customarily adopted rheological models including a fuid core, a viscoelastc mantle and an elastc lithosphere. As a mater of fact, the focus of GIA modelling has always been the mantle viscoelastc rheology, that is the main driver of the deformaton on the millennial tmescale. This is motvated by the large size of the Late-Pleistocene ice sheets, which induce deformatons that are mainly sensitve to the Earth’s bulk propertes. Presently, the highest rates of GIA deformaton are measured in locatons like Greenland, North America and Antarctca (Kremeer et al. 2018, Khan et al. 2016), where glaciers or ice sheets are stll present. These ice masses are experiencing, in additon to the regular cycle of seasonal accumulaton and ablaton, a net loss caused by climate change (Osatoka et al. 2022). For this reason, GNSS statons located in the proximity of these glaciers are sensitve not only to the GIA-induced displacement but also to the elastc response of the lithosphere. Relatvely small ice loads are expected to drive deformatons that sense the fne structure of the Earth’s outermost layers. Even though it is undeniable that the lithosphere presents an elastc behaviour with respect to the underlying mantle, it is also true that elastcity is an ideal concept. In fact, rheology is a mater of tme scales and, if we focus on those of GIA, the assumpton of a purely elastc lithosphere is certainly unquestonable. Nevertheless, since we now dispose of high-quality geodetc records through the GNET (Bevis et al. 2009), it should be possible to identfy lags between the load tme evoluton and the surface response. This becomes even more important when we perform local studies: especially nearby glaciers, the contributon of local processes such as underground water drainage, porosity or permafrost variatons become more important and contribute to the inelastcity of the frst lithospheric layers (Durkin et al. 2019, Mordret et al. 2016). Few other works in the literature have investgated this problem concerning possible phase lag due to periodic loading (Tang et al. 2020, Liu et al. 2017). Notably, Bevis et al. (2012) show a very good correlaton between the global periodic loading (air mass + ice mass) and the global displacement, but it cannot be excluded that a more local-scale study might instead show delays in the Earth’s response, especially in areas in which the lithosphere is weaker. In this work we will compare the response to sinusoidal forcings of several Earth models with diferent lithospheric parameters, varying the thickness, rigidity, rheology and load size. We