The stability of an asymmetric slice of the Gulf Stream

The Gulf Stream plays an important role in the meridional overturning circulation in the North Atlantic, one of the primary mechanism by which the warm, salty water can move from low to high latitudes. It also provides closure to the North Atlantic subtropical gyre circulation as a western boundary current and makes Western European countries much warmer by transporting warm water across the ocean.

Observational data of the Gulf Stream (along the Oleander line, between New Jersey and Bermuda) has found that its stream-wise velocity skews to the right with increasing depth. This has motivated our development of an idealized model of a laterally skewed Gulf Stream jet that is surface trapped overlying a flat bottom. The nonlinear evolution of this unstable asymmetric jet is investigated using the Oceananigans.jl library for multiple values of a skewness parameter. The results show that the maximum growth rate has a nonlinear dependency on the skewness parameter, though weak and strong skew tend to be stabilizing and destabilizing, respectively.