Ageostrophic Instability and Mixing in a Dense Overflow

Larry Pratt, Stefan Smith, Karl Helfrich
We will discuss a number of aspects of ageostrophic instability in two-layer systems, with specific applications to deep channel flows such as that of the Denmark Strait. The work touches on the extension to two layers of Ripa's Theorem, including a geometric interpretation, linear stability analysis and finite amplitude simulations using a numerical model. Among other things, we attempt to explain the 2-4 day oscillations detected in the approach flow to the Denmark Strait sill.