Recent models of mercury (Hg) storage in the circumpolar north applied a single Hg to carbon (C) ratio (RHgC) to estimate Hg storage in the circumpolar north, which does not account for spatial variability in Hg storage within and between regions. Using the Hudson Bay Lowlands (HBL) as a case study region, we: 1) assess the use of RHgC to estimate Hg storage in comparison to analytically measured and modelled Hg storage, and 2) assess the inclusion of spatial variability in Hg concentrations during the upscaling process. We collected 50 peat cores from the HBL and measured for total Hg (THg) using a Milestone DMA-80 (n=980) and C content using an Elementar Vario. For each core we calculated C storage (kg m-2), mean RHgC, and THg storage (mg m-2). We applied mean C and Hg storage to the total peatland area, and used landcover classification to estimate Hg storage in bogs, fens, and permafrost features. In the HBL (a 372,000 km2 peatland) estimates of THg storage derived from a region-specific RHgC ratio (3.27 Gg THg) compared well to estimates calculated through direct measurements of THg (3.09�0.49 Gg THg). However, applying non-region specific RHgC values used in global models would estimate ~43.7 Gg Hg, 10x higher than region specific estimates. Within-region variation increased the Hg estimate to 3.64�0.83 Gg THg, with bogs storing larger amounts of THg than fens or permafrost features. Next steps include mapping variability in peat depth, and modelling Hg concentrations using climate, vegetation, and Hg deposition variables.