Long-term (1977-1997) measurements of carbon dioxide in the Eastern North Atlantic: Evaluation of anthropogenic input

Abstract

From 1977to 1997CO

parameters were measured in the Eastern North Atlantic Ocean. A data set of 12 cruises carried out between 373N and 473N, 203Wand the Iberian Peninsula coast, were used to estimate the anthropogenic carbon (C

) based on a back-calculation technique, with the aim of evaluating its temporal evolution in that 20-year period. The rate of change of the integrated C

down to 2000m was 0.95 molm yr . Half of this input corresponds to a direct uptake of atmospheric CO

(0.48 molm yr ), while the other half enters by advection. The C

advected by the Mediterranean Water (MW) is the most important contributor to the total C

advected into the area, representing 59% (0.27$0.09 molm yr ), whereas the Labrador Sea Water contributes only 15% (0.07$0.04 molm yr ). The particular formation mechanism of MW explains its high content of advected C

. When MW is formed in the Gulf of CaH diz, 85% of Central Water is entrained by sinking of the Mediterranean Over#ow Water. Central Waters have about 50 mol kg of C

; thus this entrainment represents 0.07GtC yr , which is about 26% of the C

transported by the thermohaline circulation in the North Atlantic.