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Antarctica is one of the most rapidly mass changing areas with poor ground observation data on Earth. Considering the dominant uncertainty in Glacial Isostatic Adjustment (GIA) effects for the Antarctic Ice Sheet (AIS) mass balance, we analyze mass change patterns of Antarctica qualitatively using a statistics-based blind source separation method named Independent Component Analysis (ICA). We extract the 6 leading independent components using gravimetric data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and GRACE Follow-On (GRACE-FO) mission. The results show that the whole continental mass changes can be effectively separated into several spatial patterns that could be dominated by different physical processes. Although the hidden independent physical processes cannot be completely separated, some significant signals such as glacial melting components, snow accumulation components, periodic climatic components, and GIA effects could be determined without introducing any external information. We also found that the time period of the employed data sets has a direct impact on ICA results. This suggested that some impacts of extreme events, such as rapid increases of snowfall in the late 2000s might cause dramatic changes spatially and temporally. In general, ICA provides a special view for a better understanding of AIS mass changes and specific regional researches.

How to cite: Shi, T., Fukuda, Y., Doi, K., and Okuno, J.: GRACE/GRACE-FO observed Mass change patterns of Antarctica extracted by ICA method, GRACE/GRACE-FO Science Team Meeting 2020, online, 27–29 Oct 2020, GSTM2020-49, https://doi.org/10.5194/gstm2020-49, 2020.

The Ice Mass Balance Intercomparison Exercize  (IMBIE) was initiated in 2011 with the intent of better reconciling the various reports  on the Greenland ice sheet (GrIS)  and Antarctic ice sheet (AIS) mass balance during the 2000’s. The focused study was funded and promoted by both ESA and NASA to better understand the origins of  contradictory results using space observations for a 20 year-long period: 1990-2010. Here we review some of the main results of phase I and II of IMBIE and the strength of the GRACE mission results.  For 20-year long trends (2002-2021) trends are influenced by glacial isostatic adjustment (GIA) in Greenland, but with more profound consequence for Antarctica. IMBIE-I determined a mass balance trend for 1992-2011: -142 ± 49 and -71 ± 83 Gt/yr, for GrIS and AIS, respectively.  IMBIE-II was open to a wider sampling of international  investigative teams and the results for GrIS over 1992-2018 changed to -150 ± 13 Gt/yr. Most notably the 1-sigma formal errors reported in IMBIE-II were 25% of those reported in the earlier IMBIE-I study for GrIS. For Antarctica the most notable contrast in results was the total value of the trend over 1992-2017 (IMBIE-II) in contrast 1992-2011 (IMBIE-I) (-109 ± 56 vs -71 ± 83 Gt/yr, respectively). The loss estimate for AIS rose by 67% and the error also reduced by about 33%. Glacial isostatic adjustment (GIA) estimates for Antarctica cluster around + 54 Gt/yr (meaning their correction adds to the negativity of the mass balance result for GRACE and GRACE-FO).  The East Antarctica Ice Sheet (EAIS) has trend errors for the estimate 1992-2017 (IMBIE-II) that continue to dwarf the uncertainty: +5 ± 46 Gt/yr. Beneath EAIS, GIA is also most uncertain and models have the greatest spread. We discuss the general plan for IMBIE-III that is currently forming.

How to cite: Ivins, E. and Shepherd, A.: The Prominent Role of GRACE in the Series of IMBIE Studies: Future Plans and Prominent Issues, GRACE/GRACE-FO Science Team Meeting 2020, online, 27–29 Oct 2020, GSTM2020-63, https://doi.org/10.5194/gstm2020-63, 2020.