The three-dimensional dynamics of equatorially asymmetric thermohaline flow are investigated using an ocean general circulation model in a highly idealized configuration with no wind forcing and nearly fixed surface density. Small asymmetries in surface density lead to strongly asymmetric meridional overturning patterns, with deep water formed in the denser (northern) hemisphere filling the abyss. The poleward deep transport in the lighter hemisphere implies that the deep zonal-mean zonal pressure gradient reverses across the equator. Density along the eastern boundary and the zonally averaged density are nearly symmetric about the equator except at very high latitudes; the Southern Hemisphere western boundary thermocline, in contrast, is balanced by weaker upwelling and is hence broader than its northern counterpart. This pattern is explained through the spinup of the asymmetric circulation from a symmetric one, the timescale of which is set through advection by the mean deep western boundary cu... Abstract The three-dimensional dynamics of equatorially asymmetric thermohaline flow are investigated using an ocean general circulation model in a highly idealized configuration with no wind forcing and nearly fixed surface density. Small asymmetries in surface density lead to strongly asymmetric meridional overturning patterns, with deep water formed in the denser (northern) hemisphere filling the abyss. The poleward deep transport in the lighter hemisphere implies that the deep zonal-mean zonal pressure gradient reverses across the equator. Density along the eastern boundary and the zonally averaged density are nearly symmetric about the equator except at very high latitudes; the Southern Hemisphere western boundary thermocline, in contrast, is balanced by weaker upwelling and is hence broader than its northern counterpart. This pattern is explained through the spinup of the asymmetric circulation from a symmetric one, the timescale of which is set through advection by the mean deep western boundary cu...