Multi-technique geodetic study of the evolution of the Greenland ice sheet and associated Earth deformations : what uncertainties on the ice mass balances ?

• Main Author: Sanchez, Ana
• Other Authors: Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Paris Cité, Laurent Métivier, Marianne Greff
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Greenland; Ice mass balance; GRACE; GNSS; Firn model; SMB; Groenland; Bilan de masse de glace; Modèle de compaction de neige; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ice Sheet
• Online Access: https://theses.hal.science/tel-04391019; https://theses.hal.science/tel-04391019/document; https://theses.hal.science/tel-04391019/file/va_Sanchez_Ana.pdf

The evolution of the Greenland Ice Sheet (GIS) is an important indicator of climate changes and driver of global mean sea level rise. Nonetheless, generating error-free GIS ice mass balance remains a challenge, leading to major uncertainties in projecting future sea-level rise. We propose to combine various geodetic measurements to improve our knowledge of the spatial and temporal evolution of the GIS. In particular, we aim at reconciling ice mass balance estimates derived from satellite altimetry and time variable space gravity measurements over the 2003-2009 and 2011-2015 periods, by comparing the predicted induced ground deformation with regional observations of GNSS velocities. We first infer GIS mass variations using two of the well-established methods, compare results and seek reconciliation. On one hand, we use volume variations over the ice sheet derived from satellite altimetry (ICESat-1 and CryoSat-2) and digital elevation models generated from multiple satellite archives for peripheral glaciers. We combine these datasets with three different firn models, describing the evolving near-surface density, to convert volume change to mass. On the other hand, we use variations of the gravity field in space and time, measured by the GRACE satellite mission, to infer mass variations at a coarse spatial resolution. We show that the volume-mass conversion, through a range of firn models corrections, generates large uncertainties on the GIS mass balance derived from altimetry observations. Comparisons between the altimetry and GRACE-based model methods to infer ice mass balance reveal large disparity, we find a total mass balance in Greenland between -195.6 Gt/yr and -242.5 Gt/yr for the years 2003-2008 and between -165.5 Gt/yr and -249 Gt/yr for the years 2011-2015. Thus we invert, and estimate a mass balance and obtain -167 Gt/yr for the period 2003-2008 and -243 Gt/yr for the period 2011-2015. These results are consistent with previous estimates. We then model the Earth's elastic deformation induced by the ...