No abstract

No abstract

Since June, 2018, the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) is extending the 15-year monthly mass change record of the GRACE mission, which ended in June 2017. The GRACE-FO instrument and flight system performance has improved over GRACE. Better attitude solutions and enhanced pointing performance result in reduced fuel consumption and gravity range rate post-fit residuals. One accelerometer requires additional calibrations due to unexpected measurement noise. The GRACE-FO gravity and mass change fields from June 2018 through December 2019 continue the GRACE record at an equivalent precision and spatiotemporal sampling. During this period, GRACE-FO observed large interannual terrestrial water variations associated with excess rainfall (Central US, Middle East), drought (Europe, Australia), and ice melt (Greenland). These observations are consistent with independent mass change estimates, providing high confidence that no intermission biases exist from GRACE to GRACE-FO, despite the 11-month gap. GRACE-FO has also successfully demonstrated satellite-to-satellite laser ranging interferometry. Plain Language Summary Mass change is a fundamental climate system indicator and provides an integrated global view of how Earth's water cycle and energy balance are evolving. The Gravity Recovery and Climate Experiment (GRACE) mission monitored mass changes every month from 2002 through 2017. Since June 2018, GRACE Follow-On (GRACE-FO) continues this data record, tracking and monitoring changes in ice sheets and glaciers, near-surface and underground water storage, as well as changes in sea level and ocean currents. GRACE-FO instruments have been successfully calibrated and are providing new monthly mass change observations at a consistent spatial resolution and data quality with GRACE. Since its launch, GRACE-FO has measured record land water storage changes in 2018 and 2019 in response to extreme heat waves and droughts over Europe and Australia, as well as to extreme rainfall events over the United States and Middle East. In the summer of 2019, GRACE-FO measured record-level Greenland mass loss rates. A novel laser ranging interferometer was successfully demonstrated on GRACE-FO, laying the groundwork for improved future satellite gravity observations.

el; of Silurian soils as a result of pedoturbat i o~~, effectively mcreasing the average depth of soil CO, proiluction.Our results (Table 1) ~m p l y that atmospheric CO-, decllneil 1~y a factor of 10 from the Late S i h r i a n to the Early Permian, closely follow~ng (Fig. 4 ) a decline precllctecl hi; theoretical carbon lnais balance models (1). T h e largest decrease, hetween the Late Sil~lrian a11il Late Devonian. coincides with a of rapid evolution and diversificatlon of the terrestrial ecosystem (18).Estimates of atmospheric C02 levels from separated, time-equivalent ~-7aleosols are consistent, suggertlng that a coherent record of changing atlnospheric chem~stry is yreserl-eii In the ancient soil recorJ. REFERENCES AND NOTES1 R A Berner Science 261, 68 (1 993) At?? J SCI 294 56 (1 994) 2 T J Crowley and G R North, Paleoc!~~rato!ogy (Oxford UI?I\/ Press, Oxford, 1991) 3 R A Berner and R Ralswell, Geochim. Cosmochlm. Acta 47. 855 11983) L R. I

No abstract