While crucial to the accurate representation of Earth's climate in numerical modelling efforts, most turbulent mixing in the atmosphere and oceans occurs below typical grid scales. The goal of this workshop is to bring together researchers with expertise in both atmospheric and oceanic turbulent processes, with the hope of improving our understanding and perhaps spawning new approaches to the representation of unresolved mixing processes. Invited talks will span the range from canonical flows in their most theoretically accessible form, to more realistic flows with a full range of complications, both physical and numerical. Specific topics for discussion will be:

•The nonlinear interactions between various forms of wave motion and the large-scale slowly-varying vortices. The former have been known to be adequately described by simplified "balance" equations for 60 years. It is also known that these approximations break down at much smaller scales, but how?

• The role of boundaries, both external and internal (e.g. mixing barriers, the tropopause), where local dynamics are poorly understood.

•Whether the (sub-)mesoscale dynamics can be explained in terms of stratified turbulence, the influence of boundaries or both.

• The mechanical energy budget in the ocean and the route to dissipation; the relative roles of loss of balance and boundaries.

• Anisotropy in rotating stratified turbulence, e.g. surface front formation, including higher-order balance; jets and their influence on the larger scales.

Recent experimental, numerical and theoretical progress on such topics justifies a wide ranging debate on these fundamental questions.