  Protoplanetary disks are known to posses a stunning variety of substructure
in the distribution of their mm~sized grains, predominantly seen as rings and
gaps (Andrews et al. 2018), which are frequently interpreted as due to the
shepherding of large grains by either hidden, still-forming planets within the
disk (Zhang et al. 2018) or (magneto-)hydrodynamic instabilities (Flock et al.
2015). The velocity structure of the gas offers a unique probe of both the
underlying mechanisms driving the evolution of the disk, the presence of
embedded planets and characterising the transportation of material within the
disk, such as following planet-building material from volatile-rich regions to
the chemically-inert midplane, or detailing the required removal of angular
momentum. Here we present the radial profiles of the three velocity components
of gas in upper disk layers in the disk of HD 163296 as traced by 12CO
molecular emission. These velocities reveal significant flows from the disk
surface towards the midplane of disk at the radial locations of gaps argued to
be opened by embedded planets (Isella et al. 2016, 2018, Teague et al. 2018,
Pinte et al. 2018), bearing striking resemblance to meridional flows, long
predicted to occur during the early stages of planet formation (Szulagyi et al.
2014, Morbidelli et al. 2014, Fung & Chiang 2016, Dong et al. 2019). In
addition, a persistent radial outflow is seen at the outer edge of the disk,
potentially the base of a wind associated with previously detected extended
emission (Klaassen et al. 2013).
