Abstract Carbon system data from five expeditions over the time period of 1991 to 2005 in the central Arctic Ocean are evaluated with respect to the partial pressure of carbon dioxide in the surface waters. Nearly all waters were undersaturated with values typically below 300 μatm. In the areas occupied during several expeditions the variability is substantial, making it unrealistic to produce a coherent pCO 2 map. The potential oceanic uptake of CO 2 in the Arctic Ocean is evaluated as the difference in calculated total dissolved inorganic carbon at equilibrium with the atmosphere and that measured. The uptake capacity as computed from the under-saturation of the surface waters, although not homogenous across the separate basins, is on average 13 ± 3 g C m − 2 within the surface mixed layer of the central Arctic Ocean. The uptake capacity is dependent on several variables and processes, many likely to change as the Arctic environment responds to different climate forcings. For instance, the projected decrease in summer sea ice cover allows for air–sea equilibrium resulting in an estimated potential increase in CO 2 uptake of 1.3 ± 0.3 Tg C year − 1 . Other factors influencing the uptake capacity of the surface mixed layer that are discussed in this contribution are changes in the depth of the surface mixed layer, temperature and primary production, all impacting the partial pressure of CO 2.