Relating North Atlantic Deep Water transport to ocean bottom pressure variations as a target for satellite gravimetry missions

Abstract. The Atlantic Meridional Overturning Circulation (AMOC) is a salient feature of the climate system, observed for its strength and variability with a wide range of offshore installations and expensive sea-going expeditions. Satellite-based measurements of mass changes in the Earth system, such as from the Gravity Recovery and Climate Experiment (GRACE) mission, may help monitor these transport variations at large scale, by measuring associated changes in ocean bottom pressure (OBP) at the boundaries of the Atlantic remotely from space. However, as these signals are mainly confined to the continental slope and small in magnitude, their detection using gravimentry will likely require specialised approaches. Here we use the output of a fine-resolution (1/20°) regional ocean model to assess the connection between OBP signals at the western boundary of the North and South Atlantic. We find that North Atlantic Deep Water (NADW) transports in the ~1–3-km depth range can be reconstructed using spatially averaged OBP signals with correlations of 0.75 (0.72) for the North (South) Atlantic and root-mean-square errors of ~1 Sverdrup on monthly to interannual time scales. We further create a synthetic dataset containing only OBP signals due to NADW transport anomalies at the western boundary, which can be included in dedicated satellite gravimetry simulations to assess the AMOC detection capabilities of future mission scenarios and to develop specialised recovery strategies that are needed to track those weak signatures in the time-variable gravity field.