  Combining ocean model data and in-situ Lagrangian data, I show that an array
of surface drifting buoys tracked by a Global Navigation Satellite System
(GNSS), such as the Global Drifter Program, could provide estimates of global
mean sea level (GMSL) and its changes, including linear decadal trends. For a
sustained array of 1250 globally distributed buoys with a standardized design,
I demonstrate that GMSL decadal linear trend estimates with an uncertainty less
than 0.3 mm yr$^{-1}$ could be achieved with GNSS daily random error of 1.6 m
or less in the vertical direction. This demonstration assumes that controlled
vertical position measurements could be acquired from drifting buoys, which is
yet to be demonstrated. Development and implementation of such measurements
could ultimately provide an independent and resilient observational system to
infer natural and anthropogenic sea level changes, augmenting the on-going tide
gauge and satellites records.
