Streamflow and water quality have changed over the last several decades across the circumpolar north in response to altered precipitation regimes, increasing air temperatures, degrading permafrost, vegetation shifts, and land disturbance. Specifically, reported shifts in dissolved organic carbon (DOC) fluxes and concentrations vary greatly in direction and magnitude, likely due to complex spatial and temporal heterogeneity in terrestrial and aquatic processes. Resolving factors responsible for these changes, and their relative importance, is critical to understanding and quantifying how mobilization, chemical transformations and biological uptake will affect future DOC export. To address this need, Environment and Climate Change Canada has identified improved predictions of DOC in the Mackenzie River Basin as a priority objective within the newly introduced National Water Quality Model. The first phase of this program is to evaluate current numerical models that describe DOC dynamics, particularly across varying scales of interest where both lateral and vertical processes interact as water transits from headwaters to the great Arctic rivers. Here, we 1) present a conceptual model of carbon cycling processes across scales, 2) compare current numerical models representing northern DOC with this conceptual model, and 3) use long-term discharge and water quality datasets to present a comparative analysis of both trends and transport dynamics of DOC and streamflow from headwaters to major rivers in the Canadian pan-Arctic. Our findings highlight the importance of scale and provide a framework for DOC modelling in cold regions, as anticipated changes in local processes impacting aquatic loading may be overwhelmed by landscape-scale dynamics.