Nearly all regions of the global ocean are unstable to baroclinic instability, a process that converts available potential energy stored in sloping isopycnals into the mesoscale eddies that dominate the ocean's kinetic energy. However, the details of the local shear and stratification can give rise to distinct “flavours” of baroclinic instability, with important consequences for the structure of the growing perturbations. Here, we present a new atlas of baroclinic instability in the global ocean based upon a simple framework for categorizing baroclinic instability in terms of a small set of non-dimensional parameters that capture the competing effects of the baroclinic shear, the barotropic potential vorticity gradient, and surface buoyancy gradients. Within this framework, different regions of parameter space represent different flavours of baroclinic instability. Hydrographic temperature and salinity profiles are used to form a new monthly global dataset of baroclinic instability types in the ocean

The atlas allows a detailed examination of the central role of isopycnal tilting (changing isopycnal slope with depth) in baroclinic instability. In particular, we show that a net change in isopycnal slope over the water column will induce a “gradient beta-effect” --- a depth-independent potential vorticity gradient due to vortex stretching. Like the topographic beta-effect, the gradient beta-effect can reinforce or oppose the planetary vorticity gradient.  Unlike topographic beta, however, the gradient beta-effect will vary in time due to seasonal changes in stratification. We show how the gradient beta effect modifies the permitted flavours of baroclinic instability, and discuss the resulting patterns of regional and seasonal variability.