Mass loss of the Greenland ice sheet from GRACE time-variable gravity measurements

Abstract

The Gravity Recovery and Climate Experiment (GRACE) satellite data is used to estimate the rate of ice mass variability over Greenland. To do this, monthly GRACE level 2 Release-04 (RL04) data from three different processing centers, Center for Space Research (CSR), German Research Center for Geosciences (GFZ) and Jet Propulsion Laboratories (JPL) were used during the period April 2002 to February 2010. It should be noted that some months are missing for all three data sets. Results of computations provide a mass decrease of −163 ± 20 Gigaton per year (Gt/yr) based on CSR-RL04 data, −161 ± 21 Gt/yr based on GFZ-RL04 data and −84 ± 26 Gt/yr based on JPL RL04.1. The results are derived by the application of a nonisotropic filter whose degree of smoothing corresponds to a Gaussian filter with a radius of 340 km. Striping effects in the GRACE data, C20 effect, and leakage effects are taken into the consideration in the computations. There is some significant spread of the results among different processing centers of GRACE solutions; however, estimates achieved in this study are in agreement with the results obtained from alternative GRACE solutions.

GRACE-derived ice-mass loss spread over Greenland

“…GRACE level 2 RL04 data was used in the computations. There is a good agreement between Khan et al (2010) and Joodaki's and Nahavandchi's (2012) results.…”

“…In this study, we use non-isotropic filters, since the GRACE noise structure mainly manifests itself as near north-south "stripes" and has a nonisotropic nature. We use the Kusche et al (2009) decorrelation and smoothing method to correct monthly GRACE RL05 gravity models, as done in Joodaki and Nahavandchi (2012). The filtered gravity coefficients are archived by the International Centre for Global Earth Models (ICGEM) and are publicly available at http://icgem.gfz-potsdam.de/ ICGEM/.…”

“…The leakage-in signal has to be reduced from the region of interest. We use results from Joodaki and Nahavandchi (2012) to estimate leakage effects. In this approach, we use only GRACE results to delineate the leakage effects rather than additional information from sources such as remote sensing or global hydrological models.…”

“…Due to the presence of non-isotopic noise structure in the real, unconstrained GRACE gravity field solutions, a filtering technique based on a non-isotropic filter is applied (See e.g. Joodaki and Nahavandchi 2012). We compare the ice mass change and spread in different years and discuss the impact of our results on the ice mass loss spread within different regions in Greenland.…”

Inverting GRACE gravity data for local climate effects

“…Since we focus here on the demonstration of the applicability of our novel method to the inversion of GRACE models, we restrict our attention to one example of a GRACE data set. It is certainly known Unauthenticated Download Date | 5/9/18 6:04 PM that different data sets can yield different results (see, e.g., Joodaki and Nahavandchi (2012) for a study of the Greenland ice sheet).…”