The code for the isoneutral mixing schemes have undergone some restructuring in MOM3 to account for the additional options of biharmonic_rm (Section 34.1.8), and the possibility of using nonconstant diffusivities (Section 34.2). Additional streamlining of the code to help speed up the schemes have been implemented as well. In summary, although there are major changes in the MOM2 versus MOM3 code for isoneutral mixing, these changes do not reflect any bugs in the MOM2 code.