A "Mode Water" is a particular type of water mass characterized by its vertical homogeneity. There are two general varieties in the world ocean: Subtropical Mode Waters and Subpolar Mode Waters. The vertical homogeneity of a Mode Water is acquired by the process of deep vertical convection in winter. The low vertical density gradient imparted to the water column by convection persists laterally as the general circulation carries the Mode Water away from the formation zone....