The Seasonality of Global Land and Ocean Mass and the Changing Water Cycle

The global water cycle is generally viewed as the cycling of water masses among the land, ocean, and atmosphere. This cycling predominantly occurs at the annual time scale and between land and ocean, constituting the seasonal global water cycle. NASA's Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On missions can directly observe the seasonal global water cycle and describe the changes in its intensity. We present seasonal amplitudes of the global land water and ocean mass anomalies between 04/2002 and 11/2020. We find that the average seasonal amplitude is 17.0 +/- 0.6 mm sea level equivalent (SLE), and its interannual variability (sigma = 1.1 mm SLE) is comparable to the long-term trends in the land and ocean masses. We investigate two periods of rapid amplification and deamplification during which the amplitude changed as much as 29%, and find that changes in hydroclimatology in certain land regions modulate the seasonal global water cycle.