  We investigate the Meissner currents of interacting bosons subjected to a
staggered artificial gauge field in a three-leg ribbon geometry, realized by
spin-tensor--momentum coupled spin-1 atoms in a 1D optical lattice. By
calculating the current distributions using the state-of-the-art density-matrix
renormalization-group method, we find a rich phase diagram containing
interesting Meissner and vortex phases, where the currents are mirror symmetric
with respect to the {\color{red}middle leg} (i.e., they flow in the same
direction on the two boundary legs opposite to that on the middle leg), leading
to the spin-tensor type Meissner currents, which is very different from
previously observed chiral edge currents under uniform gauge field. The
currents are uniform along each leg in the Meissner phase and form
vortex-antivortex pairs in the vortex phase. Besides, the system also support a
polarized phase that spontaneously breaks the mirror symmetry, whose ground
states are degenerate with currents either uniform or forming vortex-antivortex
pairs. We also discuss the experimental schemes for probing these phases. Our
work provides useful guidance to ongoing experimental research on synthetic
flux ribbons and paves the way for exploring novel many-body phenomena therein.
