Barotropic

Barotropic describes a fluid state in which density depends only on pressure, so isopycnals and isobars coincide and there is no thermal-wind shear: the geostrophic velocity is depth-independent. A barotropic ocean stores no available potential energy in tilted density surfaces, so flow changes are driven by the free-surface pressure gradient and the bottom. The barotropic mode carries fast, depth-uniform adjustments such as the barotropic tide and storm surge, in contrast to the slower baroclinic modes that hold most of the eddy kinetic energy. Sverdrup balance describes the barotropic wind-driven interior transport.