Temporal variability of the anthropogenic CO2 storage in the Irminger Sea

Abstract

The anthropogenic CO2 (Cant) estimates from cruises spanning more than two decades (1981-2006) in the Irminger Sea area of the North Atlantic Subpolar Gyre reveal a large variability in the Cant storage rates. During the early 1990's, the Cant storage rates (2.3±0.6 molCm-2 yr -1) doubled the average rate for 1981-2006 (1.1±0.1 molCm -2 yr-1), whilst a remarkable drop to almost half that average followed from 1997 onwards. The Cant storage evolution runs parallel to chlorofluorocarbon-12 inventories and is in good agreement with Cant uptake rates of increase calculated from sea surface p CO2 measurements. The contribution of the Labrador Seawater to the total inventory of Cant in the Irminger basin dropped from 66% in the early 1990s to 49% in the early 2000s. The North Atlantic Oscillation shift from a positive to a negative phase in 1996 led to a reduction of air-sea heat loss in the Labrador Sea. The consequent convection weakening accompanied by an increase in stratification has lowered the efficiency of the northern North Atlantic CO 2 sink. © Author(s) 2008.