Decadal Changes in Ventilation and Anthropogenic Carbon in the Nordic Seas

Abstract

We evaluate the decadal evolution of ventilation and anthropogenic carbon (Cant) in the Nordic Seas between 1982 and the 2010s. Ventilation changes on decadal timescale are identified by evaluating decadal changes in mean ages and apparent oxygen utilization in each of the four main basins of the Nordic Seas (the Greenland and Iceland Seas, and the Norwegian and Lofoten Basins). The ages are derived from the transient time distribution approach, based on the transient tracers chlorofluorocarbon-12 (CFC-12) and sulfur hexafluoride (SF6). The different decades show different phases in ventilation, with the 2000s being overall better ventilated than the 1990s in all basins. For the Greenland Sea, we also show that the 2010s are better ventilated than the 2000s, with a clear shift in hydrographic properties. The evolution of concentrations and inventory of Cant is linked to the ventilation state. The deep waters get progressively older over the analyzed period, which is connected to the increased fraction of deep water from the Arctic Ocean.

Decadal Changes in Ventilation and Anthropogenic Carbon in the Nordic Seas