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arXiv · 2605.29142

Density and sea level changes weaken the Atlantic Meridional Overturning Circulation through ocean bottom pressure

Qianjiang Xing·Shane Elipot·William E. Johns·Bablu Sinha·Jules Kajtar·Adam T. Blaker·Tillys Petit·Ben I. Moat·David A. Smeed
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Abstract

Observations from the RAPID array at 26.5$^\circ$N indicate a linear decline in the Atlantic Meridional Overturning Circulation (AMOC) over the past two decades, linked to contrasting boundary changes: a weakening western-boundary contribution that is partly compensated by strengthening at the eastern boundary. Yet it remains unclear whether this partial compensation reflects a basin-wide adjustment or a regional feature, and what processes drive it. Here we use a high-resolution ocean model to investigate the spatial structure and underlying mechanisms of the AMOC change across the mid-latitude North Atlantic. The model reproduces a meridionally coherent decline in western-boundary deep overturning transport together with a partially compensating strengthening at the eastern boundary, consistent with observations at 26.5$^\circ$N. These opposing trends arise from a vertically coherent ocean bottom pressure trend shaped by two competing drivers: rising coastal sea level and decreasing interior density. Through geostrophic balance, this mechanism produces partial boundary compensation across latitudes, yielding a basin-wide AMOC decline throughout the mid-latitude North Atlantic.

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Qianjiang Xing, Shane Elipot, William E. Johns, Bablu Sinha, Jules Kajtar, Adam T. Blaker, Tillys Petit, Ben I. Moat, David A. Smeed. 2026-05-27. Density and sea level changes weaken the Atlantic Meridional Overturning Circulation through ocean bottom pressure. https://arxiv.org/abs/2605.29142

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