  In the Ocean, thermohaline intrusions and interleaving layers occur within
the water mass fronts with horizontal temperature and salinity gradients, which
provide an important horizontal mixing mechanism. Here we report a new type of
thermohaline intrusion which is driven by the horizontal temperature and
salinity gradients in the fluid layers at adjacent depths due to the different
double diffusive mixing rates in the vertical direction. Once established, the
intrusion layers share similar behaviors as those found within the gradient
regions. Such intrusion process generates extra horizontal heat and salinity
fluxes towards the cold and fresh side, but transfer density anomaly towards
the warm and salty side. These findings greatly extend the circumstance where
thermohaline intrusions may be observed.
