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The Gravity Recovery and Climate Experiment (GRACE) space gravity mission has been one of the most successful missions ever, impacting the disciplines of hydrology, geophysics, oceanography and cryospheric science. For the first time, it was possible to quantify changes in broad-scale water resources, measure directly the mass loss of ice sheets in polar regions, observe the mass increase of the oceans due to polar melting and watch the process of uplift and subsidence of continents due to melting of ice sheets over the past 20,000 years. The key instrumental observation that makes all this possible was the inter-satellite measurement of change in distance between the two GRACE satellies, flying in tandem orbits at 300-500 km altitude above Earth. Decommissioned in 2017, the GRACE mission was succeeded by the GRACE Follow On mission which was launched in May 2018. We have developed software at the Research School of Earth Sciences to use the instrument measurements (so-called ’Level-1B data’) to estimate changes in mass on Earth. In this presentation I will take the lid off the black box of data processing and show the incredible feats of engineering that make it possible, describe how it works and highlight some of the strengths and weaknesses of analysis from the GRACE and GRACE Follow On missions. Results from GRACE Follow On allow us to compare the state of the current drought compared to the end of the Millenium Drought in 2009 and show the concerning increase in mass loss in Antarctica, especially in the Totten Glacier region near Australia’s Casey Station. |
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