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We present the first year-long subpolar trans-Atlantic set of surface seawater CO₂ fugacity (<i>f</i>CO₂^sw) data. The data were obtained aboard the MV <i>Nuka Arctica</i> in 2005 and provide a quasi-continuous picture of the <i>f</i>CO₂^sw variability between Denmark and Greenland. Complementary real-time high-resolution data of surface chlorophyll-<i>a</i> (chl-<i>a</i>) concentrations and mixed layer depth (MLD) estimates have been collocated with the <i>f</i>CO₂^sw data. Off-shelf <i>f</i>CO₂^sw data exhibit a pronounced seasonal cycle. In winter, surface waters are saturated to slightly supersaturated over a wide range of temperatures. Through spring and summer, <i>f</i>CO₂^sw decreases by approximately 60 &mu;atm, due to biological carbon consumption, which is not fully counteracted by the <i>f</i>CO₂^sw increase due to summer warming. The changes are synchronous with changes in chl-<i>a</i> concentrations and MLD, both of which are exponentially correlated with <i>f</i>CO₂^sw in off-shelf regions.