Inert tracers in 2d turbulence
Garrett, C. (1983). Dynamics of Atmospheres and Oceans, 7, 265-277
Consider an initially very small patch of tracer.
3 regimes:
L<LS, spreads diffusively, k=ks
LS<L<LL, filamented
LL<L, spreads diffusively, k=kl
Lengthscales:
  LS=Ö(ks/g)
  LL= Ö(kl/g)