High-resolution vertical pCO2 profiles from two Greenlandic fjords during sea-ice breakup

This dataset contains vertical profiles of partial pressure of CO₂ (pCO₂) collected in two Greenlandic fjords during the period of sea-ice breakup. The data were gathered to investigate fine-scale vertical variability in surface-water pCO₂ and its influence on air-sea CO₂ exchange in stratified Arctic coastal environments. Measurements were obtained using high-resolution profiling sensors deployed from small vessels, resolving vertical pCO₂ structure within the upper few meters of the water column. Young Sound (2017) profiles were measured using a Contros HydroC® CO₂ sensor following Henson et al. (2024, JGR: Biogeosciences). Meanwhile, Tasiilaq Bay (2025) profiles were measured using an EGM5 sensor following Sejr et al. (2011, Tellus B). Complementary micrometeorological flux measurements were conducted to assess air-sea CO₂ exchange under spatially and temporally heterogeneous conditions, and compare with water-side measurments. These observations reveal strong vertical and temporal variability in pCO₂ during the transition from ice-covered to open-water conditions, challenging the assumption of homogeneous surface layers and linear gradients typically used in bulk flux models. The dataset provides a valuable resource for improving CO₂ flux estimates in Arctic fjords and for evaluating gas-exchange parameterizations under stratified and rapidly changing conditions. These data are discussed in the submitted manuscript: Henson et al. (in review). “Sea ice melt drives vertical pCO₂ variability modulating air-sea gas exchange.”