Changes in ventilation and anthropogenic carbon in the Nordic Seas and Arctic Ocean
The Greenland Sea has changed from a rather homogeneous and relatively well-ventilated water column in early 1980s, to a two-layer situation in the 2000s. The trend in AOU is here negative (positive) for the upper/intermediate (deep) waters, indicating stronger (reduced) ventilation. The changes in Cant inventory in the main Nordic Seas basins from 1982 to 1990s (mean) are very minor, and clearly below the atmospheric increase in CO2, while the mean inventories in the 2000s are significantly larger than the 1990s and markedly faster than the atmospheric change over the same period.
In the Arctic Ocean there is a significant negative trend in mean age in the waters connected to the Atlantic layer, being clearest closer to the inflow regions, indicating stronger advective ventilation of these layers. This ventilation signal gets progressively weaker along the circulation path of the boundary current. The inventory of Cant increased with 47–64% from 1987 to 2015 (Eurasian Basin), while an increase of 38% was seen in the Makarov Basin, from 1991 to 2015.