  We present tensor-to-scalar ratio forecasts for GreenPol, a hypothetical
ground-based B-mode experiment aiming to survey the cleanest regions of the
Northern Galactic Hemisphere at five frequencies between 10 and 44 GHz. Its
primary science goal would be to measure large-scale CMB polarization
fluctuations at multipoles $\ell \lesssim 500$, and thereby constrain the
primordial tensor-to-scalar ratio. The observations for the suggested
experiment would take place at the Summit Station (72deg N, 38deg W) on
Greenland, at an altitude of 3216 m above sea level. In this paper we simulate
various experimental setups, and derive limits on the tensor-to-scalar ratio
after CMB component separation using a Bayesian component separation
implementation called Commander. When combining the proposed experiment with
Planck HFI observations for constraining polarized thermal dust emission, we
find a projected limit of r<0.02 at 95 % confidence for the baseline
configuration. This limit is very robust with respect to a range of important
experimental parameters, including sky coverage, detector weighting, foreground
priors etc. Overall, GreenPol would have the possibility to provide deep CMB
polarization measurements of the Northern Galactic Hemisphere at low
frequencies.
