Carbon dioxide characteristics of water masses in the northern North Atlantic Ocean

Accurate measurements of total dissolved carbon dioxide (TCO2) together with other tracers (Θ, S, O2, and nutrients) have been carried out during a hydrographic survey of a zonal section between Ireland and Greenland and a number of sections in the Iceland Basin. The resulting data, with > 1300 TCO2 data points, have allowed the determination of the TCO2 signature of the water masses in the northern North Atlantic Ocean in terms of seven water types. The structure of TCO2 and dissolved phosphate and nitrate appears to be well correlated with the apparent oxygen utilization. This indicates that ageing of the water types, by mineralization of organic matter, is more important for the observed TCO2 structure than differences in the preformed TCO2 when the water types were formed. The overturning of water in the “oceanic conveyor belt” will support meridional TCO2 transport. This transport was estimated at 0.16 • 10−1 mol s−1 (−0.06 Gt a−1 C) from the differences of TCO2 content between the northward flowing Surface and Sub-Polar Mode water and the southward flowing deep Iceland-Scotland and Denmark Strait Overflow Waters.