ABSTRACT The Marine20 radiocarbon (¹⁴C) age calibration curve, and all earlier marine ¹⁴C calibration curves from the IntCal group, must be used extremely cautiously for the calibration of marine ¹⁴C samples from polar regions (outside ∼ 40ºS–40ºN) during glacial periods. Calibrating polar ¹⁴C marine samples from glacial periods against any Marine calibration curve (Marine20 or any earlier product) using an estimate of ${\rm{\Delta R}}$ , the regional ¹⁴C depletion adjustment, that has been obtained from samples in the recent (non-glacial) past is likely to lead to bias and overconfidence in the calibrated age. We propose an approach to calibration that aims to address this by accounting for the possibility of additional, localized, glacial ¹⁴C depletion in polar oceans. We suggest, for a specific polar location, bounds on the value of ${\rm{\Delta }}{{\rm{R}}_{20}}\left( {\rm{\theta }} \right)$ during a glacial period. The lower bound ${\rm{\Delta R}}_{20}^{{\rm{Hol}}}$ may be based on ¹⁴C samples from the recent non-glacial (Holocene) past and corresponds to a low-depletion glacial scenario. The upper bound, ${\rm{\Delta R}}_{20}^{{\rm{GS}}}$ , representing a high-depletion scenario is found by increasing ${\rm{\Delta R}}_{20}^{{\rm{Hol}}}$ according to the latitude of the ¹⁴C sample to be calibrated. The suggested increases to obtain ${\rm{\Delta R}}_{20}^{{\rm{GS}}}$ are based upon simulations of the Hamburg Large Scale Geostrophic Ocean General Circulation Model (LSG OGCM). Calibrating against the Marine20 curve using the upper and lower ${\rm{\Delta }}{{\rm{R}}_{20}}$ bounds provide estimates of calibrated ages for glacial ¹⁴C samples in high- and low-depletion scenarios which should bracket the true calendar age of the sample. In some circumstances, users may be able to determine which depletion scenario is more appropriate using independent paleoclimatic or proxy evidence.