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, 203W and 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 2000 m was 0.95 mol m yr. Half of this input corresponds to a direct uptake of atmospheric CO (0.48 mol m 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 mol m yr), whereas the Labrador Sea Water contributes only 15% (0.07$0.04 mol m 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 50mol 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. 2001 Elsevier Science Ltd. All rights reserved.