Presentation Information
[ACG68-P02]Estimation of GIA-induced vertical land motion from GNSS observation in Greenland
*Shuntaro Hata1, Jun'ichi Okuno1,2,3, Yusuke Suganuma1,2 (1.National Institute of Polar Research, 2.The Graduate University for Advanced Studies, (SOKENDAI), 3.Joint Support-Center for Data Science Research, Research Organization of Information and Systems)
Keywords:
GIA,RSL,GNSS
As a consequence of the rapid warming trend in the Arctic, the Greenland Ice Sheet has experienced accelerated mass loss over the past two decades and is currently one of the major contributors to the global sea level rise. Concurrently, glacial isostatic adjustment (GIA), a response of the solid Earth to the deglaciation, has been observed across Greenland. Time series of crustal deformation from the Greenland GNSS network (GNET) indicate uplift rates of up to 17.5 mm a-1. The observed uplift is a sum of viscoelastic deformation, and elastic deformation which instantly respond to current surface mass change. To accurately project the regional relative sea level change, it is important to separate both elastic and viscoelastic components from observed uplift. However, the discrepancy remains in the previous studies based on modelling approaches. An improved understanding of the spatial variability of GIA is therefore essential for accurate projection of regional relative sea level change. In this study, we aim to estimate the current elastic and GIA uplift rate through updated GNET time series analysis until 2024.
We analyzed GNET observation data of 55 stations over Greenland. The antenna coordinates were estimated by using CSRS-PPP (Canadian spatial reference system precise point positioning) service. We also used the daily coordinates distributed by Nevada University (Blewitt et al., 2018) for stations where original RINEX data is unavailable. From the daily coordinates of each antenna, the interannual trend and seasonal variation phase were estimated using a least-squares approach. Among the analyzed GNET stations, 53 stations (96%) showed clear bedrock uplift in 2008-2024 period, ranging from 1.2 to 17.6 mm a-1. The highest bedrock uplift rate was observed at KUAQ station, located near Kangerlussuaq Glacier in Southeastern Greenland. Most of GNET stations showed seasonal subsidence with peaks around May-July.
Seasonal variations in the GNSS time series were compared with combined surface load estimates derived from atmospheric pressure changes in Copernicus Arctic Regional Reanalysis (CARRA1) and surface mass variations observed by Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on. A linear relationship was found between monthly stacked merged loads and relative GNSS heights, indicating a rough estimate of the elastic uplift to a given mass loss around the stations. Elastic components during the study period were converted from GRACE-derived annual mass loss rates and removed from the observed vertical displacements to estimate the viscoelastic GIA component at each station. The resulting GIA-induced uplifts were spatially heterogeneous across Greenland. Although most estimates were within the same order of magnitude as prior studies, several stations showed discrepancies from previous studies. Despite the simplicity of the approach, our results broadly agree with previous studies, demonstrating the potential of this method. However, to precisely constrain the GIA uplift rate, a detailed analysis of each station is needed.
We analyzed GNET observation data of 55 stations over Greenland. The antenna coordinates were estimated by using CSRS-PPP (Canadian spatial reference system precise point positioning) service. We also used the daily coordinates distributed by Nevada University (Blewitt et al., 2018) for stations where original RINEX data is unavailable. From the daily coordinates of each antenna, the interannual trend and seasonal variation phase were estimated using a least-squares approach. Among the analyzed GNET stations, 53 stations (96%) showed clear bedrock uplift in 2008-2024 period, ranging from 1.2 to 17.6 mm a-1. The highest bedrock uplift rate was observed at KUAQ station, located near Kangerlussuaq Glacier in Southeastern Greenland. Most of GNET stations showed seasonal subsidence with peaks around May-July.
Seasonal variations in the GNSS time series were compared with combined surface load estimates derived from atmospheric pressure changes in Copernicus Arctic Regional Reanalysis (CARRA1) and surface mass variations observed by Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on. A linear relationship was found between monthly stacked merged loads and relative GNSS heights, indicating a rough estimate of the elastic uplift to a given mass loss around the stations. Elastic components during the study period were converted from GRACE-derived annual mass loss rates and removed from the observed vertical displacements to estimate the viscoelastic GIA component at each station. The resulting GIA-induced uplifts were spatially heterogeneous across Greenland. Although most estimates were within the same order of magnitude as prior studies, several stations showed discrepancies from previous studies. Despite the simplicity of the approach, our results broadly agree with previous studies, demonstrating the potential of this method. However, to precisely constrain the GIA uplift rate, a detailed analysis of each station is needed.