Study on the inter-annual hydrology-induced deformations in Europe using GRACE and hydrological models

Artur Lenczuk,Janusz Bogusz,Anna Klos,Wieslaw Kosek,Grzegorz Leszczuk

doi:10.1515/jag-2020-0017

Abstract

Abstract Earth’s crust deforms in various time and spatial resolutions. To estimate them, geodetic observations are widely employed and compared to geophysical models. In this research, we focus on the Earth’s crust deformations resulting from hydrology mass changes, as observed by GRACE (Gravity Recovery and Climate Experiment) gravity mission and modeled using WGHM (WaterGAP Global Hydrological Model) and GLDAS (Global Land Data Assimilation System), hydrological models. We use the newest release of GRACE Level-2 products, i. e. RL06, provided by the CSR (Center for Space Research, Austin) analysis center in the form of a mascon solution. The analysis is performed for the European area, divided into 29 river basins. For each basin, the average signal is estimated. Then, annual amplitudes and trends are calculated. We found that the eastern part of Europe is characterized by the largest annual amplitudes of hydrology-induced Earth’s crust deformations, which decrease with decreasing distance to the Atlantic coast. GLDAS largely overestimates annual amplitudes in comparison to GRACE and WGHM. Hydrology models underestimate trends, which are observed by GRACE. For the basin-related average signals, we also estimate the non-linear variations over time using the Singular Spectrum Analysis (SSA). For the river basins situated on the southern borderline of Europe and Asia, large inter-annual deformations between 2004 and 2009 reaching a few millimeters are found; they are related to high precipitation and unexpectedly large drying. They were observed by GRACE but mismodelled in the GLDAS and WGHM models. Few smaller inter-annual deformations were also observed by GRACE between 2002-2017 for central and eastern European river basins, but these have been also well-covered by the WGHM and GLDAS hydrological models.

Highlights

The GRACE (Gravity Recovery and Climate Experiment) twin satellites delivered changes in the Earth’s gravity field from 2002 until 2017. 15 years of global data coverage enabled many geodetic interpretations in terms of hydrology mass redistribution (e. g. [1, 8, 34, 36, 41, 50])
Annual amplitudes estimated for GRACE, Water GAP Global Hydrological Model (WGHM) and Global Land Data Assimilation System (GLDAS) Noah are similar to each other with no clear long-term trend being noticed
We showed the analysis of hydrologyinduced deformations over the European area

Summary

Introduction

The GRACE (Gravity Recovery and Climate Experiment) twin satellites delivered changes in the Earth’s gravity field from 2002 until 2017. 15 years of global data coverage enabled many geodetic interpretations in terms of hydrology mass redistribution (e. g. [1, 8, 34, 36, 41, 50]). Authors focused mainly on seasonal signals being similar to each other or reduced once GRACE-observed or hydrologically-modeled values are removed from GPS displacements [12, 15, 23, 24]. Han [16], Pan et al [26], Tiwari et al [42], or Wu et al [45] pointed that hydrology loading affects Earth’s crust deformations in the seasonal scale and in the inter-annual scale. These inter-annual deformations driven by hydrology changes are present in the GPS displacements. If this is the case, they may affect GPS station velocities and their uncertainties if not accounted for

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Results

Conclusion