Significance of secular trends of mass variations determined from GRACE solutions

• Published in: Journal of Geodynamics
• Language: English
• Published: Elsevier 2011
• Subjects: GRACE; filtering; mass variation; glacial isostatic adjustment; global hydrology models; Canada; Roland; Turnes; Fennoscandia; Fennoscandian
• Online Access: http://hdl.handle.net/2262/55785; https://doi.org/10.1016/j.jog.2009.09.029

Abstract Since 2002 the Earth's gravity field is globally observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission. The GRACE monthly gravity field solutions, available from several analysis centres, reflect mass variations in the atmosphere, hydrosphere and geosphere. Due to correlated noise contained in these solutions, it is, however, first necessary to apply an appropriate filtering technique. The resulting, smoothed time series are applied not only to determine variations with different periodic signatures (e.g., seasonal, short and medium-term), but to derive long-periodic mass variations and secular trends as well. As the GRACEmonthly solutions always show the integral effect of all mass variations, for separation of single processes, like the GIA (Glacial isostatic adjustment)- related mass increase in Fennoscandia, appropriate reduction models (e.g. from hydrology) are necessary. In this study we show for the example of the Fennoscandian uplift area that GRACE solutions from different analysis centres yield considerably different secular trends. Furthermore, it turnes out that the inevitable filtering of the monthly gravity field models affects not only the amplitudes of the signals, but also their spatial resolution and distribution such as the spatial form of the detected signals. It also becomes evident that the determination of trends has to be performed together with the determination of periodic components. All periodic terms which are really contained in the data, and only such, have to be included. The restricted time span of the available GRACE measurements, however, limits the separation of long-periodic and secular signals. It is shown that varying the analysis time span affects the results considerably. Finally, a reduction of hydrological signals from the detected integral secular trends using global hydrological models (WGHM, LaDWorld, GLDAS) is attempted. The differences among the trends resulting from different models illustrate that the state-of-the art hydrology models are not suitable for this purpose as yet. Consequently, taking the GRACE monthly gravity field solutions from one centre, choosing a single filter and applying an insufficiently reliable reduction model leads sometimes to a misinterpretation of considered geophysical processes. Therefore, one has to be cautious with the finalinterpretation of the results. correspondance: Corresponding author. (Steffen, Holger) [e-mail] (Steffen, Holger) Institut fur Erdmessung--> , Leibniz Universitat Hannover--> , Schneiderberg 50--> , D?30167 Hannover--> - GERMANY (Steffen, Holger) Now at: Department of Geoscience--> , University of Calgary--> , 2500 University Drive NW--> , Calgary--> , AB T2N 1N4--> - CANADA (Steffen, Holger) Institut fur Erdmessung--> , Leibniz Universitat Hannover--> , Schneiderberg 50--> , D?30167 Hannover--> - GERMANY (Steffen, Holger) Helmholtz-Zentrum Potsdam--> , Deutsches GeoForschungsZentrum ? GFZ--> , Telegrafenberg--> , D?14473 Potsdam--> - GERMANY (Petrovic, Svetozar) Institut fur Erdmessung--> , Leibniz Universitat Hannover--> , Schneiderberg 50--> , D?30167 Hannover--> - GERMANY (Muller, Jurgen) Helmholtz-Zentrum Potsdam--> , Deutsches GeoForschungsZentrum ? GFZ--> , Telegrafenberg--> , D?14473 Potsdam--> - GERMANY (Schmidt, Roland) Now at: Astrium GmbH--> , Robert-Koch-Str.1--> , D?81633 Munchen--> - GERMANY (Schmidt, Roland) Helmholtz-Zentrum Potsdam--> , Deutsches GeoForschungsZentrum ? GFZ--> , Telegrafenberg--> , D?14473 Potsdam--> - GERMANY (Wunsch, Johann) Helmholtz-Zentrum Potsdam--> , Deutsches GeoForschungsZentrum ? GFZ--> , Telegrafenberg--> , D?14473 Potsdam--> - GERMANY (Barthelmes, Franz) Helmholtz-Zentrum Potsdam--> , Deutsches GeoForschungsZentrum ? GFZ--> , Telegrafenberg--> , D?14473 Potsdam--> - GERMANY (Kusche, Jurgen) Now at: Institute for Geodesy and Geoinformation--> , University of Bonn--> , Nu?allee 17--> , D?53115 Bonn--> - GERMANY (Kusche, Jurgen) CANADA GERMANY