Rapid variability of Antarctic Bottom Water transport inferred from GRACE

Air-ice-ocean interactions near Antarctica leads to formation of the densest waters on Earth. These waters convect and spread to fill the global abyssal oceans. The heat and carbon storage capacity of these waters, combined with their abyssal residence times that often exceed centuries, makes this circulation pathway the most efficient sequestering mechanism on Earth. Yet monitoring this pathway has proven challenging due to the nature of the formation processes and the depth of the circulation. The Gravity Recovery and Climate Experiment (GRACE) gravity mission is providing a time-series of ocean mass redistribution, and offers a transformative view of the abyssal circulation. Here we use the GRACE measurements to infer, for the first time, a twelve-year time-series of Antarctic Bottom Water export into the South Pacific. We find this export highly variable, with a standard deviation of 1.49~Sv and a decorrelation timescale of less than one month. A significant trend is undetectable.