## 3 Results
The linear trend of mass variations derived from \(C_{20}\) estimates in TN14 is more negative, with its absolute value more than 50% larger than those from \(C_{20}\) estimates provided by TN07, TN11, and GFZ. Compared with \(C_{20}\) estimates from TN11, TN14-provided \(C_{20}\) estimates modified the linear trend of mass variations over the GrIS and the AIS by \(-1.9\pm 0.1\) and \(-11.4\pm 0.5\) Gt/yr, respectively, during the period from August 2002 to July 2016 (Table 3). GFZ-published \(C_{20}\) estimates and those in TN11 have very similar impacts on the linear trend of mass variations over each ice sheet, i.e., over the AIS, the difference between the two mass trends is 0.7 Gt/yr. We then examine the influence of \(C_{30}\) from GRACE RL05, RL06, and GSFC on mass variations over both ice sheets (experiment 3). As shown in Figure 4, the mass change time series caused by \(C_{30}\) from GRACE RL05, RL06, and GSFC are generally consistent with each other over ice sheets during the common study period, except those from CSR-published \(C_{30}\) in GRACE RL05 show some differences during the end of the GRACE mission. If selecting the study period from March 2012 to July 2016, the annual amplitudes of mass change time series corresponding to \(C_{30}\) from GRACE RL05 and RL06 data are 35 and 228 Gt, respectively, for the GrIS and the AIS, as compared to 27 and 175 Gt for those from SLR-based \(C_{30}\) terms in TN14 from GSFC. From Figure 4, it can be seen that the \(C_{30}\)-caused mass change time series show a negative linear trend over the GrIS before 2012 but a positive trend after 2012. Over the AIS, a positive linear trend can be observed before 2012 but a negative trend after 2012. As provided in Table 4, the mean value of linear trends of mass change time series caused by \(C_{30}\) from GRACE RL06 is \(-1.5\pm 0.5\) and \(9.7\pm 3.1\) Gt/yr, respectively, for the GrIS and the AIS during the period from August 2002 to February 2012. It correspondingly becomes \(1.7\pm 2.0\) and \(-10.6\pm 12.2\) Gt/yr during the time span from March 2012 to July 2016. It is noteworthy that \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & & \multicolumn{6}{c}{**Mass Change Caused by GEOC**} \\ \cline{3-10}  & & \multicolumn{2}{c}{**RL05**} & \multicolumn{6}{c}{**RL06**} \\ \cline{3-10}
**2002.08–2016.07** & \multicolumn{3}{c}{**SW**} & \multicolumn{3}{c}{**SUN11**} & \multicolumn{3}{c}{**SUN14**} & \multicolumn{3}{c}{**SV**} \\ \cline{3-10}  & & **Trend** & **Annual** & **Trend** & **Annual** & **Trend** & **Annual** & & \\  & & **[Gt/yr]** & **Amp.** & **[Gt/yr]** & **Amp.** & **[Gt/yr]** & **[Gt/yr]** & **Amp.** & **Trend** & **[Gt/yr]** & **Annual** \\  & & & & & & & & & **Amp.** \\  & CSR & & & \(-6.7\pm\) & & \(-7.0\pm\) & & & & \\  & CSR & & & \(0.2\) & & \(36.4\) & \(-7.0\pm\) & & & \\  & GFZ & \(-2.6\pm\) & \(25.8\) & & \(-7.1\pm\) & & \(37.2\) & \(-7.5\pm\) & & \\  & GFZ & \(0.2\) & & \(0.2\) & & \(0.2\) & & \(0.2\) & & \\  & JPL & & & \(-6.8\pm\) & & \(36.4\) & \(-7.2\pm\) & & \\  & CSR & & & \(35.8\pm\) & & \(10.0\) & & \(169.0\) & \(39.4\pm 1.0\) & & \\  & GFZ & \(13.1\pm\) & \(122.1\) & & \(37.5\pm\) & & \(185.1\) & & \(40.0\pm\) & \\  & GFZ & \(0.8\) & & \(0.9\) & & \(0.9\) & & \(173.4\) & \(42.6\pm 0.9\) & \\  & JPL & & & \(36.3\pm\) & & \(108.0\) & & \(38.7\pm\) & & \\  & & & & \(1.0\) & & \(1.0\) & & \(169.0\) & \(40.6\pm 1.0\) & \\ \hline \end{tabular}
\end{table} 
Table 2: The linear trend and annual amplitude (Amp.) of mass change time series caused by GEOC or degree one terms over the GrIS and the AIS during the time span from August 2002 to July 2016, using degree one terms corresponding to GRACE RL05 and RL06 data published by CSR, GFZ, and JPL. the impact of \(C_{30}\) replacement on ice sheet mass variations derived from each data processing center differs after March 2012. Those differences modify the mass trend of the AIS by 16.3, 9.6, and 5.6 Gt/yr, respectively, for GRACE RL06 data published by CSR, GFZ, and JPL.