Short-term variations in atmospheric CO2 at Ny-Ålesund, Spitsbergen, during spring and summer

Abstract

Results from the continuous measurements of atmospheric carbon dioxide performed at Ny-Ålesund, Spitsbergen are presented. The results are discussed with an emphasis on day-today variations during spring and early summer. During all years studied, significant negative anomalies (“dips”), lasting for several days, have been observed in the data from late May through July. The timing coincides with a draw down of dissolved carbon dioxide and nutrients in the surface waters of the North Atlantic observed by others. By using 3-dimensional trajectories, we follow the history of the air arriving in Ny-Ålesund, and show that the air, depleted in CO2 , had been in contact with these waters. Combining the trajectories with a box model yields a simple Lagrangian model, and we demonstrate that the timing and magnitude of the dips are consistent with the degree of CO2 saturation of the sea during April to mid-June. In late June and July, the model indicates that a significant portion of the dips must have other causes, e.g., CO2 uptake in the terrestrial biosphere further south.