We present an extratropical cyclone case study over the North Atlantic focusing on the role of atmospheric gravity waves (GW) in the generation of strong vertical shear and (clear-air) turbulence (CAT), as well as their impact on tracer distribution in the lowermost stratosphere. Our findings suggest that GW related processes should be considered as a key for upper troposphere lower stratosphere (UTLS) transport and mixing, and as an important candidate for the interpretation of CAT in the UTLS.