Fixes issue in ekman limiter for KPP

Applies the ekman limiter for stabilizing buoyancy forcing only.

src/shared/cvmix_kpp.F90

@@ -1466,7 +1466,10 @@ subroutine cvmix_kpp_compute_OBL_depth_low(Ri_bulk, zw_iface, OBL_depth,    &
     ! Since depth gets more negative as you go deeper, that translates into
     ! OBL_depth = max(abs(computed depth), abs(Ekman depth), abs(M-O depth))
     if (CVmix_kpp_params_in%lEkman) then
-      if (Coriolis.eq.cvmix_zero) then
+      ! Column is stable if surf_buoy > 0
+      lstable = (surf_buoy.gt.cvmix_zero)
+
+      if (Coriolis.eq.cvmix_zero .and. .not. lstable) then !should not apply in unstable conditions
         ! Rather than divide by zero, set Ekman depth to ocean bottom
         Ekman = abs(zt_cntr(nlev))
       else