Seasonal and Interannual Variability of the Wind‐Driven Component of the Atlantic Meridional Overturning Circulation Transport at the Equator

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) transport across the equator varies from seasonal to interannual timescales. Using ECCO v4r4 state estimates (1992–2017), the 26‐year mean transport is 12.8 Sv (1 Sv = 10 ⁶  m ³  s ⁻¹ ). The seasonal cycle peaks in February and reaches its minimum in August, with an amplitude of ∼8.5 Sv. The interior cross‐equatorial transport east of 37°W follows the Sverdrup balance on interannual timescales, correlating with the zonally integrated wind‐stress curl ( r  = 0.86). In contrast, the western boundary current changes include local compensating flows to interior wind‐driven transport and potentially contributions from extratropical regions that propagates equatorward along the boundary. Sensitivity experiments with a three‐layer primitive‐equation model show that remote extratropical forcing, rather than local equatorial wind, dominates interannual variability of the wind‐driven component of the equatorial AMOC transport.