  We investigate the non-Markovianity of continuous variable Gaussian quantum
channels through the evolution of an operational metrological quantifier,
namely the Gaussian interferometric power, which captures the minimal precision
that can be achieved using bipartite Gaussian probes in a black-box phase
estimation setup, where the phase shift generator is \emph{a priori} unknown.
We observe that the monotonicity of the Gaussian interferometric power under
the action of local Gaussian quantum channels on the ancillary arm of the
bipartite probes is a natural indicator of Markovian dynamics; consequently,
its breakdown for specific maps can be used to construct a witness and an
effective quantifier of non-Markovianity. In our work, we consider two
paradigmatic Gaussian models, the damping master equation and the quantum
Brownian motion, and identify analytically and numerically the parameter
regimes that give rise to non-Markovian dynamics. We then quantify the degree
of non-Markovianity of the channels in terms of Gaussian interferometric power,
showing in particular that even nonentangled probes can be useful to witness
non-Markovianity. This establishes an interesting link between the dynamics of
bipartite continuous variable open systems and their potential for optical
interferometry. The results are an important supplement to the recent research
on characterization of non-Markovianity in continuous variable systems.
